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Drug resistance is a major hurdle in oncology. Responses of acute myeloid leukaemia (AML) patients to cytarabine (Ara-C)-based therapies are often short lived with a median overall survival of months. Therapies are under development to improve outcomes and include targeting the eukaryotic translation initiation factor (eIF4E) with its inhibitor ribavirin. In a Phase II clinical trial in poor prognosis AML, ribavirin monotherapy yielded promising responses including remissions; however, all patients relapsed. Here we identify a novel form of drug resistance to ribavirin and Ara-C. We observe that the sonic hedgehog transcription factor glioma-associated protein 1 (GLI1) and the UDP glucuronosyltransferase (UGT1A) family of enzymes are elevated in resistant cells. UGT1As add glucuronic acid to many drugs, modifying their activity in diverse tissues. GLI1 alone is sufficient to drive UGT1A-dependent glucuronidation of ribavirin and Ara-C, and thus drug resistance. Resistance is overcome by genetic or pharmacological inhibition of GLI1, revealing a potential strategy to overcome drug resistance in some patients.

The Bcl-2 family of proteins controls a critical step in commitment to apoptosis by regulating permeabilization of the mitochondrial outer membrane (MOM). The family is divided into three classes: multiregion proapoptotic proteins that directly permeabilize the MOM; BH3 proteins that directly or indirectly activate the pore-forming class members; and the antiapoptotic proteins that inhibit this process at several steps. Different experimental approaches have led to several models, each proposed to explain the interactions between Bcl-2 family proteins. The discovery that many of these interactions occur at or in membranes as well as in the cytoplasm, and are governed by the concentrations and relative binding affinities of the proteins, provides a new basis for rationalizing these models. Furthermore, these dynamic interactions cause conformational changes in the Bcl-2 proteins that modulate their apoptotic function, providing additional potential modes of regulation.

Bax, a member of the Bcl-2 family of proteins, has been shown to accelerate apoptosis induced by growth factor withdrawal, gamma-irradiation, and the chemotherapeutic agent, etoposide. The mechanism by which Bax promotes apoptosis is poorly understood. Bax forms homodimers which have been suggested to act as accelerators or inducers of cell death. However, the requirement for homodimerization of Bax to promote cell death remains unclear. We performed site-directed mutagenesis of the BH1, BH2, and BH3 in Bax to determine the regions of Bax required for homodimerization and to define the role of Bax homodimers in cell death induced by chemotherapy drugs. Bax proteins expressing alanine substitutions of the highly conserved amino acids glycine 108 (G108) in BH1, tryptophan 158 (W158) in BH2, and glycine 67 and aspartic acid 68 (GD67-68) in BH3 as well as deletion of the most conserved amino acids in BH1 (Delta102-112) and BH2 (Delta151-159) and deletion of BH3 (Delta63-71) maintained their ability to accelerate chemotherapy-induced cell death. Immunoprecipitation studies revealed that Bax with deletions in BH1 and BH2 still associated with wild-type Bax while deletion of BH3 disrupted Bax homodimerization. These results demonstrate that Bax does not require the conserved regions of homology, BH1, BH2, or BH3, to accelerate chemotherapy-induced cell death. Furthermore, our results established BH3 as a region required for Bax homodimerization in mammalian cells and demonstrate that monomeric forms of Bax are active in accelerating cell death induced by chemotherapy agents.

Human Bcl-2 is located in multiple intracellular membranes when expressed in MDCK and Rat-1/myc cells. We restricted expression to the endoplasmic reticulum or mitochondria by exchanging the Bcl-2 carboxy-terminal insertion sequence for an equivalent sequence from cytochrome b5 or ActA, respectively. MDCK cells are protected from serum deprivation-induced apoptosis by both wild-type Bcl-2 and the mutant targeted to mitochondria but not by the mutant targeted to endoplasmic reticulum. In contrast, when expressed in Rat-1/myc cells, the Bcl-2 mutant located at the endoplasmic reticulum is more effective than that targeted to mitochondria. In MDCK cells both mutants bind Bax as effectively as wild-type, demonstrating that Bax binding is not sufficient to prevent apoptosis.

Introduction: Multiple studies have shown that tyrosine kinase inhibitor (TKI), usually imatinib (IM), can be successfully discontinued in chronic myeloid leukemia (CML) patients, achieving a 40-50% treatment free remission (TFR) rate. However, the remaining 60% of patients require reintroduction of TKI therapy. We have designed this study to answer the question if a second generation TKI, i.e. dasatinib, should be used after failing the first attempt of TKI discontinuation with IM. This prospective study attempts to evaluate whether the use of dasatinib after failure of a 1st attempt of TKI discontinuation with IM could improve TFR rate after a 2nd attempt of TKI discontinuation. Methods and materials: This is a prospective clinical trial (BMS CA180-543, Clinicaltrial.gov NCT#02268370) including all major CML centers across Canada (n=12). The primary objective is to determine the proportion of patients who remain in molecular remission (defined as maintaining ≥MR4.0) after dasatinib discontinuation following achieving ≥MR4.5. The present study has 3 phases: 1) IM discontinuation phase, 2) dasatinib rechallenge phase, 3) dasatinib discontinuation phase. A total of 135 patients is planned to be enrolled over 18-24 months. Key inclusion criteria include: 1) CML in chronic phase (CP), 2) total duration of IM therapy of minimum of 3 years, 3) total duration of MR4.5 or deeper response over 2 years with 2 consecutive confirmed MR4.5 or deeper response at the central lab with 3 months interval. Key exclusion criteria include prior allogeneic stem cell transplant or prior accelerated or blastic phase CML. Molecular recurrence was defined as an increase in BCR-ABL transcript level above MR4.0, on at least two consecutive occasions, or a single increase in BCR-ABL transcript level above MR3.0. Dasatinib is started at a dose of 100mg daily once molecular recurrence is confirmed. Results: The study was launched on March 2015. As of June 22 2016, 110 patients were entered into screening phase of whom 16 patients were not qualified due to 1) fluctuating transcripts (n=8) or 2) consent withdrawal (n=8). Two patients withdrew consent after losing their molecular response following IM discontinuation before starting dasatinib. Finally 75 patients were enrolled into IM discontinuation phase with 17 additional patients on screening in awaiting enrollment (Figure A). Of 67 patients evaluable for molecular relapse, 21 patients (31.3%) lost molecular response defined as loss of major molecular response (MMR; n=18) and loss of MR4 on 2 consecutive tests (n=3). The 6-month relapse free survival (RFS) rate was estimated as 58.0% (42.1-71.0%), while TFR rate using loss of MMR as an event was 64.7% (48.7-76.7%) at 6 months (Figure B) Of 21 patients who lost molecular response, 20 patients underwent dasatinib rechallenge phase, 14 of which were treated with dasatinib for at least 1 month and evaluated at least once with monthly BCR-ABL transcript monitoring (Figure C). Twelve patients achieved MMR at a median time of 56 days. The median time to achieve MR4.5 was 84 days. The incidence of MMR and MR4.5 at 3 months was 100% each (Figure D). Cox's proportional hazard regression model suggested strong correlation of RFS with total duration of IM therapy prior to IM discontinuation (p=0.001), duration of MR4 maintenance (p=0.004) or MR4.5 maintenance (p=0.006) prior to IM discontinuation, but not with time to achieve MR4 (p=0.289) or MR4.5 (p=0.330). Recursive partitioning method also defined the best cutoff for those variables: The group treated with IM for over 8.9 years (n=35) had RFS rate 81.1% vs 21.0% in those treated for less than 8.9 years (n=32; p Conclusion: Preliminary results of this Canadian TKI discontinuation trial show a RFS rate of 58-65% after IM discontinuation in CP-CML patients who attained MR4.5 for over 2 years, similar to other TKI discontinuation studies. Dasatinib can be safely administered in CML patients who lost molecular response after IM discontinuation with 100% of MMR rate at 3 months. Prolonged duration of IM treatment, or duration of MR4/MR4.5 maintenance with IM therapy could predict the chance of TFR success, but not time to achievement of MR4/MR4.5. Disclosures Bence-Bruckler: Lundbeck: Membership on an entity's Board of Directors or advisory committees. Savoie:Amgen: Consultancy; Celgene: Consultancy; Pfizer: Consultancy; BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy; Lundbeck: Consultancy. Busque:Pfizer: Honoraria, Speakers Bureau; BMS: Honoraria, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau. Delage:BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding. Laneuville:BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Paladin: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Liew:BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Xenocostas:Janssen Inc.: Research Funding. Kamel-Reid:BMS: Research Funding. Leber:BMS Canada: Honoraria, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Background : We previously presented that selected quality of life (QOL) domains in MDS patients are impaired compared with age-matched controls and most impacted by hemoglobin (Hgb) level, transfusion dependence, frailty and comorbidity in an initial cohort of 236 patients from a Canadian MDS registry (Buckstein R. et al, Abstract 699, ASH 2012 and Abstract 2500, ASH 2009). The optimal Hgb threshold associated with improved QOL may vary according to health states that may fluctuate for any given patient. With longer follow up and greater sample size, we now examine the impact of Hgb levels on QOL in transfusion dependent (TD) versus independent (TI) patients and according to IPSS-R risk scores. Methods:Since 2008, we have prospectively assessed QOL in all patients registered in the Canadian national MDS registry using the instruments EORTC QLQ-C30, FACT-F, global fatigue scale (GFS) and EQ-5D, at enrollment and every 4-6 months. These QOL data are paired with disease specific and laboratory information at the same time intervals. Each patient could provide multiple QOL measurements at different time points. Clinically significant score differences were considered 10 points for the EORTC, 0.08 for the EQ-5D and 4 for the FACT F. General linear regression analysis was applied to search for a significant relationship between physical and social functioning, dyspnea, fatigue and QOL with Hgb, according to transfusion dependence, IPSS and IPSS-R measured categorically. To account for multiple comparisons among 5 Hgb categories, Bonferroni adjusted p-value < .01 was considered statistically significant. Results: 689 patients from 15 Canadian sites completed their first QOL assessment at a median time of 7.8 (IQR 2.7-23) months from MDS diagnosis. The median time from MDS diagnosis to death or last follow-up was 2.5 years (IQR 1.2-4.9). The median Hgb at enrollment was 100 g/L (IQR 86-113) and the distribution of risk scores included: very low (13%); low (35%); intermediate (28%); high (15%); and very high (10%). 27% of patients were TD at enrollment and 54% were TD at any time. The median number of QOL assessments per patient completed was 3 (IQR 2-6) with 547 patients completing at least 2, 424 at least 3 and 335 at least 4 serial QOL measurements at a median time interval of 17 weeks (IQR 13-25). When examined by Hgb thresholds, mean physical functioning, dyspnea, fatigue (QLQ-C30 and GFS) and global QOL improved with increasing Hgb. QOL symptom and function scores were clinically and statistically significantly superior in TI versus TD patients (table 1). The optimal discriminating Hgb threshold for improved symptom and function scores was 100 g/L for patients that were TI or with IPSS-R very low, low and intermediate risk MDS; and 90 g/L for high and very high risk disease (table 2). No discriminating threshold was found in TD patients. Conclusions: In the largest reported serial cross sectional population based assessment of QOL in MDS patients, we confirm that higher Hgb and transfusion independence have significant impact on QOL, symptoms and self-reported function and should be considered important surrogate endpoints for clinical improvement. Disclosures Buckstein: Novartis: Honoraria; Celgene: Honoraria, Research Funding. Wells:Janssen: Honoraria, Other: Advisory Board; Celgene: Honoraria, Other: advisory board; Novartis: Honoraria, Other: advisory board; Alexion: Honoraria, Other: Advisory board. Zhu:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Geddes:Celgene: Other: Advisory Board, Research Funding. Sabloff:Gilead: Research Funding; Novartis Canada: Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Lundbeck: Research Funding. Leber:BMS Canada: Honoraria, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Keating:Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees. Storring:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Yee:Novartis Canada: Membership on an entity's Board of Directors or advisory committees, Research Funding. Leitch:Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. St-Hilaire:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis Canada: Membership on an entity's Board of Directors or advisory committees. Nevill:Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Shamy:Celgene: Honoraria, Other: Advisory board; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Kumar:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Delage:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding.

E-cadherin is synthesized as a precursor and then undergoes cleavage by proprotein convertases. This processing is essential for E-cadherin maturation and cell adhesion. Loss of cell adhesion causes detachment-induced apoptosis- anoikis. Anoikis can be inhibited despite loss of cell-matrix interactions by preserving E-cadherin mediated cell-cell adhesion. Conversely, acute loss of E-cadherin sensitizes cells to apoptosis by unknown post-translational mechanisms. In response to drug treatment of breast cancer cells, our analysis revealed that two independent modifications of E-cadherin inhibit its cell surface transport. Firstly, O-linked beta-N-acetylglucosamine (O-GlcNAc) modification of the cytoplasmic domain retains E-cadherin in the endoplasmic reticulum. Secondly, incomplete processing by proprotein convertases arrests E-cadherin transport late in the secretory pathway. We demonstrated these E-cadherin modifications (detected by specific lectins and antibodies) do not affect binding to α-catenin, β-catenin or γ-catenin. However, E-cadherin binding to Type I gamma phosphatidylinositol phosphate kinase (PIPKIγ), a protein required for recruitment of E-cadherin to adhesion sites, was blocked by O-GlcNAc glycosylation (O-GlcNAcylation). Consequently, E-cadherin trafficking to the plasma membrane was inhibited. However, deletion mutants that cannot be O-GlcNAcylated continued to bind PIPKIγ, traffic to the cell surface and delayed apoptosis, confirming the biological significance of the modifications and PIPKIγ binding. Thus, O-GlyNAcylation of E-cadherin accelerated apoptosis. Furthermore, cell stress induced inactivation of proprotein convertases, inhibited E-cadherin maturation further exacerbating apoptosis. The modifications of E-cadherin by O-GlcNAcylation and lack of pro-region processing represent novel mechanisms for rapid regulation of cell surface transport of E-cadherin in response to intoxication.

Apoptosis is an essential process for the development of all multi-cellular organisms, and Bcl-2 family proteins critically regulate most pathways of apoptosis at the level of mitochondria. Bid is a pro-apoptotic member of the Bcl-2 family proteins that regulates the integrity of the Mitochondrial Outer Membrane (MOM) by activating other Bcl-2 family members. Upon induction of apoptosis, Bid is cleaved and the active fragment, tBid binds to the MOM to potently induce cell death. However, the mechanism by which the two cleaved fragments of Bid separate to form tBid is contentious, and so is the nature of the interactions between tBid and other Bcl-2 family members.We have developed an in vitro fluorescent assay system to elucidate the mechanism of activation of tBid using recombinant proteins and either isolated mitochondria or biomimetic liposomes. Single cysteine mutants of Bid were created, and labelled with an environment sensitive fluorescent thiol-reactive dye to study the individual steps of tBid binding to the MOM and its interactions with pro- and anti-apoptotic proteins.We propose a mechanism by which cleaved Bid first binds to the MOM, the two cleaved fragments separate and then tBid undergoes a conformational change at the membrane to achieve its active form. Once active at the MOM, tBid adopts further distinct conformations when interacting with either Bax or Bcl-XL. The relative ratio of different conformers of tBid at the MOM is manipulated by the dynamic interactions between different Bcl-2 binding partners.These results offer a broad but simple model for the activation mechanism of tBid. It is possible that additional interactions of tBid with binding partners in a cell can further add to this model. Our results suggest that conformational changes of tBid at the MOM modulate specific apoptotic functions.

The role of passenger domains in protein targeting was examined by fusing previously characterized targeting motifs to different protein sequences. To compare the targeting requirements for a variety of subcellular compartments, targeting of the fusion proteins was examined for endoplasmic reticulum, mitochondria and peroxisomes in vitro and in yeast. Although most passenger domains were only partially passive to translocation, motif-dependent targeting via motifs positioned at either end of one passenger domain (gPA) was demonstrated for all of the subcellular compartments tested. The data presented extend earlier suggestions that translocation competence is an intrinsic property of the passenger protein. However, the properties that determine protein targeting are not mutually exclusive for the compartments tested. Therefore, although the primary determinant of specificity is the targeting motif, our results suggest that translocation competence of the targeted protein augments the fidelity of transport.

Overexpression of antiapoptotic proteins including Bcl-XL and/or Bcl-2 contributes to tumor initiation, progression, and resistance to therapy by direct interactions with proapoptotic BH3 proteins. Release of BH3 proteins from antiapoptotic proteins kills some cancer cells and sensitizes others to chemotherapy. Binding of Bcl-XL and Bcl-2 to the BH3 proteins Bad, Bid, and the three major isoforms of Bim was measured for fluorescent protein fusions in live cells using fluorescence lifetime imaging microscopy and fluorescence resonance energy transfer. In cells the binding of the proteins at mitochondria is similar to the results from in vitro measurements. However, mutations in the BH3 region of Bim known to inhibit binding to Bcl-XL and Bcl-2 in vitro had much less effect in MCF-7 cells. Moreover, the BH3 mimetic ABT-737 inhibited Bad and Bid but not Bim binding to Bcl-XL and Bcl-2. Thus, the selectivity of ABT-737 also differs markedly from predictions made from in vitro measurements.

While there is a clear connection between apoptosis and autophagy, the mechanisms that regulate the interaction have been difficult to identify. The initial clue to the link was the observation that Bcl-2 was located at the endoplasmic reticulum (ER), where it could prevent some forms of apoptosis and also bind to the autophagy regulatory protein Beclin-1. However, both of these enigmatic observations have been united with the discovery of the nutrient-deprivation autophagy factor-1 (NAF-1) protein. As an ER-localized protein that enhances the interaction of Bcl-2 and Beclin-1 and that also binds to the pro-apoptotic protein Bik, NAF-1 is perfectly placed to be a central regulator of the switch between autophagy and apoptosis.

Inhibiting apoptosis is widely accepted as a necessary step in the transition from normal to cancer cells, and most cancer therapies exert their effects by indirectly reversing this process. Commitment to apoptosis is caused by permeabilisation of the outer mitochondrial membrane – a process regulated by the binding between different members of the Bcl-2 family. Furthermore, Bcl-2 family members also bind to the endoplasmic reticulum, where they modify processes such as the unfolded-protein response and autophagy that also cause or modify different types of cell death. With the growing understanding of the importance of the Bcl-2 family as crucial regulators of the decision to initiate apoptosis, much effort has been directed at developing small molecules that modify function by directly binding to Bcl-2 proteins. Preclinical experiments have confirmed that these agents kill cancer cells and overcome chemotherapy resistance. Two of these drugs are in the initial stages of clinical development (ABT-263 and obatoclax), and early results show clinical efficacy at tolerable doses. Important questions for the future include the role of these drugs as monotherapy versus combination therapy with other anticancer drugs, and the related issue of the relative toxicity to cancerous versus normal cells.

The dysregulation of apoptosis is a key step in developing tumours, and mediates resistance to cancer therapy. Many different signals for cell death converge on permeabilization of the outer mitochondrial membrane, which is controlled by the Bcl-2 family of proteins. The importance of this step is becoming increasingly relevant as the first generation of small molecules that inhibit the interaction of Bcl-2 family proteins enters clinical trials as anticancer agents. The Bcl-2 family can be divided into three classes: BH3-only proteins that are activated by various forms of cellular stress, Bax and Bak proteins that mediate mitochondrial membrane permeabilization, and inhibitory proteins such as Bcl-2 and Bcl-XL. The recently proposed embedded together model emphasizes the fact that many of the regulatory interactions between different classes of Bcl-2 family members occur at intracellular membranes, and binding to membranes causes conformational changes in the proteins that dictate functions in a dynamic manner. Within this context, recent results indicate that Bcl-XL functions as a dominant-negative Bax, a concept that resolves the paradox of similar structures but opposite functions of Bcl-XL and Bax. We have also shown that the conformational change that allows Bax to insert into the outer mitochondrial membrane is the rate-limiting step in the multistep process of Bax activation. Nevertheless, investigating the structure of activated Bax or Bak as monomers and as components of the oligomeric structures that mediate membrane permeabilization is the focus of ongoing research (and controversy) at many laboratories worldwide.

Apoptosis or programmed cell death is a conserved process that serves to remove excess, damaged or infected cells in all multi-cellular organisms. Dysregulation in apoptosis can elicit important pathological conditions such as cancer and degenerative diseases. Bcl-2 family proteins critically regulate most pathways of apoptosis at the level of mitochondria. In addition to the protein-protein interactions among the Bcl-2 family members, the interaction of Bcl-2 family members with the mitochondrial outer membrane (MOM) are also very important for the execution of apoptosis. Considerable evidence supports that the composition of OMM mediates the translocation of the pro-apoptotic activator tBID to the OMM, and the subsequent activation of the pore-forming protein Bax at MOM to induce apoptosis. We have carried out a systematic study on the effect of different lipids, such as cardiolipin, monolysocardiolipin, cholesterol, and ceramide, using an in vitro system of liposomes to study MOM permeabilization.

Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder maintained by cancer stem cells. To target this population, we investigated the mechanism of action of BMS-214662, developed as a farnesyl transferase inhibitor (FTI) and unique in inducing apoptosis in these cells. By contrast, a related congener and equally effective FTI, BMS-225975 does not induce apoptosis, indicating a novel mechanism of action. BMS-214662 significantly and selectively induced apoptosis in primitive CD34+38− CML compared with normal cells. Apoptosis proceeded via the intrinsic pathway: Bax conformational changes, loss of mitochondrial membrane potential, generation of reactive oxygen species, release of cytochrome c, and caspase-9/3 activation were noted. Up-regulation of protein kinase Cβ (PKCβ), down-regulation of E2F1, and phosphorylation of cyclin A–associated cyclin-dependent kinase 2 preceded these changes. Cotreatment of CML CD34+ and CD34+38− cells with PKC modulators, bryostatin-1, or hispidin markedly decreased these early events and the subsequent apoptosis. None of these events was elicited by BMS-214662 in normal CD34+ cells or by BMS-225975 in CML CD34+ cells. These data suggest that BMS-214662 selectively elicits a latent apoptotic pathway in CML stem cells that is initiated by up-regulation of PKCβ and mediated by Bax activation, providing a molecular framework for development of novel therapeutics.

The eukaryotic translation initiation factor eIF4E is elevated in 30% of malignancies including M4/M5 subtypes of acute myeloid leukemia (AML). The oncogenic potential of eIF4E arises from its ability to bind the 7-methyl guanosine (m7G) cap on mRNAs, thereby selectively enhancing eIF4E-dependent nuclear mRNA export and translation. We tested the clinical efficacy of targeting eIF4E in M4/M5 AML patients with a physical mimic of the m7G cap, ribavirin. Among 11 evaluable patients there were 1 complete remission (CR), 2 partial remissions (PRs), 2 blast responses (BRs), 4 stable diseases (SDs), and 2 progressive diseases (PDs). Ribavirin-induced relocalization of nuclear eIF4E to the cytoplasm and reduction of eIF4E levels were associated with clinical response. Lack of response or relapse coincided with continued or renewed nuclear localization of eIF4E. This first clinical study to target eIF4E in human malignancy demonstrates clinical activity and associated molecular responses in leukemic blasts. This trial is registered at ClinicalTrials.gov (NCT00559091).

Apoptosis is an essential process for the development of all multi-cellular organisms, and Bcl-2 family proteins critically regulate most pathways of apoptosis at the level of mitochondria. Bid is a pro-apoptotic member of Bcl-2 family proteins that regulates the integrity of OMM (Outer Mitochondrial Membrane). Upon induction of apoptosis, Bid is cleaved into a p15 and a p7 fragment, a complex that is held together by strong non-covalent interactions. The separated p15 fragment, also known as tBid (truncated Bid) is a potent inducer of cell death, however, the mechanism of the fragments' separation and activation of Bid to tBid is unknown. The focus of this work was to develop an in vitro fluorescent assay system to elucidate the mechanism of activation of Bid using a recombinant liposomal system bearing physiological relevance along with isolated mitochondria. Single cysteine mutants of Bid were created, and labelled with fluorescent thiol-reactive molecules to study the individual steps of the activation of Bid. Using size exclusion chromatography, FCS (Fluorescent Correlation Spectroscopy), and FRET (Forster Resonance Energy Transfer), it was quantitatively determined that the two cleaved fragments of Bid spontaneously separate upon binding to the membrane without any additional post-translational modifications. After the initial binding to the membrane, p15 fragment undergoes a conformational change to adopt its active form. Taking together, we found that the activation of Bid is a two step process encompassing the separation of the cleaved fragments and a conformational change in the membrane.

Lymphomatoid granulomatosis (LG) is an uncommon but potentially fatal disease. The disease primarily involves the lungs; however, skin, renal, and central nervous system (CNS) are seen in varying proportions. Neurological involvement occurs in one third of the patients, and confers a worse prognosis. The use of radiotherapy to treat CNS involvement in LG has not been well studied. We report a case of a 33-year-old man with multiple CNS lesions treated successfully with radiotherapy and review 6 other cases in the literature using similar treatment. These cases support the use of radiotherapy for CNS involvement in LG.

Summary Oblimersen sodium plus rituximab was evaluated in relapsed/refractory B-cell non-Hodgkin lymphoma (NHL) patients. Oblimersen was administered as a continuous intravenous infusion at a daily dose of 3 mg/kg/d for 7 d on alternate weeks for 3 weeks. Rituximab was given at a weekly dose of 375 mg/m2 for six doses. Patients with stable disease or objective response were allowed to receive a second course of treatment. The overall response rate (ORR) was 42% with 10 complete responses (CR) and eight partial responses (PR). Twelve (28%) patients achieved a minimal response or stable disease. Among the 20 patients with follicular lymphoma the ORR was 60% (eight CR, four PR). Three of the responders were refractory to prior treatment with rituximab, and two of the responses occurred in patients who had failed an autologous stem cell transplant. Median duration of response was 12 months. Most toxicities were low grade and reversible. In conclusion, oblimersen sodium can be safely combined with rituximab. The combination appears to be most beneficial in patients with indolent NHL and warrants further investigation in a large randomized trial.

Familial platelet disorder with propensity to myeloid malignancy (FPD/AML) is an autosomal dominant syndrome characterized by platelet abnormalities and a predisposition to myelodysplasia (MDS) and/or acute myeloid leukemia (AML). The disorder, caused by inherited mutations in RUNX1, is uncommon with only 14 pedigrees reported. We screened 10 families with a history of more than one first degree relative with MDS/AML for inherited mutations in RUNX1. Germ- line RUNX1 mutations were identified in 5 pedigrees with a 3:2 predominance of N-terminal mutations. Several affected members had normal platelet counts or platelet function, features not previously reported in FPD/AML. The median incidence of MDS/AML among carriers of RUNX1 mutation was 35%. Individual treatments varied but included hematopoietic stem cell transplantation from siblings before recognition of the inherited leukemogenic mutation. Transplantation was associated with a high incidence of complications including early relapse, failure of engraftment, and posttransplantation lymphoproliferative disorder. Given the small size of modern families and the clinical heterogeneity of this syndrome, the diagnosis of FPD/AML could be easily overlooked and may be more prevalent than previously recognized. Therefore, it would appear prudent to screen young patients with MDS/AML for RUNX1 mutation, before consideration of sibling hematopoietic stem cell transplantation.

SummaryIn normal circumstances, the Bcl-2 family dutifully governs when cells die. However, the rules of engagement between the pro- and antiapoptotic family members are still contested, and how Bax is transformed from a cytosolic monomer to an outer mitochondrial membrane-permeabilizing oligomer is unclear. With fluorescence techniques and an in vitro system, the combination of tBid and Bax produced dramatic membrane permeabilization. The membrane is not a passive partner in this process beause membranes are required for the protein-protein interactions to occur. Simultaneous measurements of these interactions revealed an ordered series of steps required for outer membrane permeabilization: (1) tBid rapidly binds to membranes, where (2) tBid interacts with Bax, causing (3) Bax insertion into membranes and (4) oligomerization, culminating in (5) membrane permeabilization. Bcl-XL prevents membrane-bound tBid from binding Bax. Bad releases tBid from Bcl-XL, restoring both tBid binding to Bax and membrane permeabilization.

Although Bcl-XL and Bax are structurally similar, activated Bax forms large oligomers that permeabilize the outer mitochondrial membrane, thereby committing cells to apoptosis, whereas Bcl-XL inhibits this process. Two different models of Bcl-XL function have been proposed. In one, Bcl-XL binds to an activator, thereby preventing Bax activation. In the other, Bcl-XL binds directly to activated Bax. It has been difficult to sort out which interaction is important in cells, as all three proteins are present simultaneously. We examined the mechanism of Bax activation by tBid and its inhibition by Bcl-XL using full-length recombinant proteins and measuring permeabilization of liposomes and mitochondria in vitro. Our results demonstrate that Bcl-XL and Bax are functionally similar. Neither protein bound to membranes alone. However, the addition of tBid recruited molar excesses of either protein to membranes, indicating that tBid activates both pro- and antiapoptotic members of the Bcl-2 family. Bcl-XL competes with Bax for the activation of soluble, monomeric Bax through interaction with membranes, tBid, or t-Bid-activated Bax, thereby inhibiting Bax binding to membranes, oligomerization, and membrane permeabilization. Experiments in which individual interactions were abolished by mutagenesis indicate that both Bcl-XL–tBid and Bcl-XL–Bax binding contribute to the antiapoptotic function of Bcl-XL. By out-competing Bax for the interactions leading to membrane permeabilization, Bcl-XL ties up both tBid and Bax in nonproductive interactions and inhibits Bax binding to membranes. We propose that because Bcl-XL does not oligomerize it functions like a dominant-negative Bax in the membrane permeabilization process., Author Summary During development and under stress, cells can become committed to die via programmed cell death (apoptosis). In most cases, the permeabilization of the outer mitochondrial membrane is a key component of this commitment. The membrane permeablization step is both positively and negatively regulated by members of the Bcl-2 family of proteins. One member of this protein family with only a BH3 region, such as tBid, activates another family member, Bax, causing it to form large complexes that generate membrane-spanning pores, hence making the membrane permeable. Antiapoptotic members of the Bcl-2 family, such as Bcl-XL, are structurally similar to Bax but inhibit the membrane permeabilization process by an unknown mechanism. Two mutually exclusive models have been proposed to explain how the Bcl-2 family is operating: one states that Bcl-XL binds to tBid, thereby preventing Bax activation, while the second suggests that Bcl-XL binds directly to activated Bax. It has been difficult to sort out which interaction is important in cells, where multiple members of all three protein families are present simultaneously. Here, we describe an in vitro system containing the three recombinant proteins and the use of mutagenesis to selectively remove individual interactions. We show that Bcl-XL inhibits Bax by competing with it for binding to membranes, tBid, and activated Bax. Because Bcl-XL does not form pores, it inhibits apoptosis by acting as if it is a dominant-negative version of Bax., Bcl-XL and Bax are structurally similar members of the Bcl-2 family of cell-death-related proteins, and they compete for binding to membranes, as well as to Bcl-2 family member tBid and activated Bax. Unlike Bax, Bcl-XL is unable to oligomerize and form pores in membranes, so it inhibits membrane permeabilization--a key step during commitment to apoptosis--by functioning like a dominant-negative Bax.

Cutaneous T-cell lymphomas are a type of indolent non-Hodgkin's lymphoma where patients with limited skin disease can be successfully treated with a variety of skin-directed, systemic, and immunomodulating therapies, whereas durable remissions are difficult to achieve in patients with tumor, erythrodermic, or systemic disease. We describe a patient with cutaneous T-cell lymphoma and malignant cells constituting 99% of her peripheral blood lymphocytes who had a sustained complete response after an HLA-matched sibling allogeneic stem cell transplantation. We also review the current literature regarding both autologous and allogeneic stem cell transplantations for advanced stages of cutaneous T-cell lymphoma, discuss the importance of the graft-versus-tumor immunomodulatory effect in successful transplantations, and suggest that allogeneic stem cell transplantation deserves further consideration and study as a potential treatment for selected patients who are younger and at high risk.

Photobleaching is a fluorophore-damaging process that commonly afflicts single-molecule fluorescence studies. It becomes an especially severe problem in fluorescence fluctuation experiments when studying slowly diffusing particles. One way to circumvent this problem is to use beam scanning to decrease the residence time of the fluorophores in the excitation volume. We report a systematic study of the effects of circular beam scanning on the photobleaching of fluorescent particles as observed in single-photon excitation fluorescence fluctuation experiments. We start by deriving a simple expression relating the average detected fluorescence to the photobleaching cross section of the fluorophores. We then perform numerical calculations of the spatial distribution of fluorescent particles in order to understand under which conditions beam scanning can prevent the formation of a photobleaching hole. To support these predictions, we show experimental results obtained for large unilamellar vesicles containing a small amount of the fluorescent lipophilic tracer DiD. We establish the required scanning radius and frequency range in order to obtain sufficient reduction of the photobleaching effect for that system. From the detected increase in fluorescence upon increase in scanning speed, we estimate the photobleaching cross section of DiD.

Introduction: Transfusional hemosiderosis is common in myelodysplastic syndromes (MDS). There are multiple retrospective analyses demonstrating a survival benefit associated with iron chelation therapy (ICT) in lower risk, transfusion dependent (TD) MDS patients. However, these studies are limited by their retrospective nature, potential for bias and by the use of risk scores at diagnosis rather than at the onset of TD. Since January 2012 the Canadian MDS Registry has prospectively collected disease and patient-related data on MDS patients including comorbidity (Charlson and MDS-CI), frailty (Rockwood clinical frailty scale) and disability [Lawton Brody Instrumental Activities of Daily Living (sIADL)]. We compared characteristics and clinical outcomes of lower risk TD MDS patients who received ICT to non chelated TD patients, adjusting for MDS and patient-related factors. Methods: Only patients who remained International Prognostic Scoring System (IPSS) low or intermediate (int)-1 risk at the time of first TD were included with MDS and patient-related factors analyzed at first TD rather than at MDS diagnosis or registry enrollment. Univariate and multivariate Cox proportional hazard models were used to determine significant predictive factors for overall survival (OS) and the model with the highest R2 was selected. Results: 219 Low (n=69)/Int-1 (n=149) risk MDS patients at the time of first TD were included. Median age was 73 [interquartile range (IQR 65,80)] with a median time from diagnosis until TD of 7 months (IQR 1,28). 60% were male with a median ECOG of 1 and median blast of 3% (IQR 1,4). By WHO classification, 39% and 37% had unilineage and multilineage dysplasia respectively, 11% CMML and 13% had excess blasts. By IPSS-revised (R), very low, low, intermediate, high and very high risk groups were 12%, 34%, 38%, 15% and 0.5%, respectively. Seventy (32%) patients received ICT with desferrioxamine (n=6), deferasirox (n=56) or both (n=8). At the time of first TD, chelated patients were younger, had higher ferritins and had lower IPSS-R risk scores (Table 1). Importantly, frailty, comorbidity, and disability scores did not differ. At a median follow up of 2.7 (IQR 2.2-3.3) years from diagnosis, OS was 6.1(IQR 4.5-7.5) years. OS was significantly improved among MDS patients treated with ICT as compared to those without (median 8.62 vs. 4.38 years, respectively, p = 0.0005, Figure 1.) By univariate analysis, age, ICT, IPSS, IPSS-R, MDS-CI, frailty, karyotype, time from diagnosis until TD, and disability were associated with improved OS. By multivariate analysis, ICT, age at TD and IPSS-R at TD were independently predictive of OS (Table 2). Conclusions: Adjusting for patient and disease related factors at the time of TD, ICT remains predictive of improved OS in patients with low/int-1 risk MDS who become TD. The adjustment for patient-related factors and analysis from TD rather than MDS diagnosis, diminishes the impact of selection bias that may have favored ICT patients in past analyses and lends additional support to the role for ICT in lower risk MDS. | Factors at Time of TD Median (IQR) | Without Iron Chelation (n=149) | With Iron Chelation (n=70) | p-value | | --------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------- | ------------------------------------------------------------------- | ------- | | Age (y) | 75 (67,81) | 69 (62,75) | 0.0008 | | Ferritin (ug/L) | 664 (346,1118) n=92 | 1201 (883,1691) n=44

INTRODUCTION Patients with myelodysplastic syndrome (MDS) frequently receive red blood cell (RBC) transfusions to alleviate symptoms of fatigue and improve well-being, yet their experiences of transfusion have not been previously characterized. The aim of this qualitative study was to explore the changes in well-being that patients with MDS experience with RBC transfusion and hence, to inform the selection of Quality of Life (QoL) tools for future studies in this transfused patient population. METHODS: An applied qualitative approach was used for the study. Adult patients with MDS receiving chronic RBC transfusions at two hematology/oncology outpatient clinics between August 1, 2013 and March 31, 2014 were invited to participate in a 10-20 minute semi-structured interview. Patients were excluded if they could not provide informed consent. Interviews elicited information pertaining to: side effects and benefits of transfusion therapy; the patient's experience of anemia and fatigue prior to, during, and after transfusion; and the impact of transfusion on their QoL. Interviews were recorded, transcribed, and analyzed using QSR's NVivo 10 software. Standard techniques of qualitative content analysis were used. Two researchers independently reviewed all transcripts to identify and develop codes to categorize information from the interviews. The coding scheme was applied to the interview information, compared for agreement with discrepancies resolved and refined using consensus. The final version of the coding scheme was applied to all transcripts by one researcher. Informational content of the data within each code were reviewed and interpreted to form summative statements. Statements were grouped, organized and summarized under 3 major themes: participant experience of fatigue, impact of RBC transfusion, and side effects of transfusion. The study was approved by the local research ethics board and informed consent was obtained from all participants. RESULTS: 12/16 (75%) of patients approached consented to participant in the study (median age: 77; IQR, 72, 80 years; 2 female). Participant experience of fatigue: All participants reported experiencing fatigue, which significantly impacted their activities of daily living. Severity of fatigue prior to transfusion varied between participants, and for two participants' levels of fatigue also varied between transfusions. Impact of RBC transfusion: Time to recovery from fatigue varied between participants, ranging an improvement noted during the transfusion to 24 hours post-transfusion. Although transfusion did not alleviate symptoms of fatigue completely, participants reported improved appetite and decreased lethargy. One participant reported having a better frame of mind post-transfusion. Effect of transfusion on symptom relief varied between participants, ranging from several days to three weeks. Side effects of transfusion: Four participants reported side effects accompanying some transfusions, which included: confusion described as "heaviness in the head", headache, rise in temperature, itchiness/rash, epistaxis, and/or lightheadedness. Side effects were short-lived and not severe. In addition to the patient derived findings reported above, we identified 4 challenges to performing this qualitative study in the MDS population: MDS affects an aging population with several comorbidities, which may further compromise well-being; patients live sedentary lifestyles, which may impede their ability to assess subtle changes in well-being; caregiver presence during the interview can impact the patient perspective; and, the timing of interviews can affect the quality of data depending on the participant's level of fatigue. CONCLUSION: Results of this study reveal that the experiences of patients who receive RBC transfusion are diverse and are not consistent between consecutive transfusion episodes. Considering the findings, an appropriate QoL tool for use in this population should be short and quick to complete, disease specific, have an emphasis on fatigue and should have a short recall period to capture transient changes in well-being. Disclosures Leber: Celgene Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees.

INTRODUCTION: A randomized crossover design is an efficient way to compare two treatment approaches as patients serve as their own control minimizing between patient variability; however, for the crossover design to be valid the patients disease must be stable during observation period. A crossover design was considered for exploring the age of transfused red cells on quality of life (QoL) in patients with myelodysplastic syndrome (MDS). To determine if this design would be appropriate, a chart review of patients with MDS requiring transfusion was performed. Stable disease was defined by transfusion interval and pre-transfusion hemoglobin. METHODS: Adult patients scheduled for transfusion at two hematology/oncology outpatient clinics (one in an academic hospital center and one at a cancer center) were screened for eligibility. Inclusion criteria included: a diagnosis of MDS; ≥18 years; diagnosed and followed for at least six months. Data were abstracted from electronic health records and charts of eligible patients between the dates of January 1 and June 30, 2013. Information pertaining to hospital admissions, infection, red blood cell (RBC) product utilization, and hematology laboratory test results were captured. Additional information pertaining to the age of RBCs transfused was retrieved from the Transfusion Registry for Utilization, Surveillance, and Tracking database. Data abstraction and entry were 100% verified using source documents. The study was approved by the local research ethics board and informed consent was not required. The primary outcome was proportion of stable patients who received more than 4 transfusions during the 6 months observation period. The criteria for stability were peer reviewed by clinicians who treat MDS patients and included: 1) quartiles 1 and 3 around the median number of days between transfusion episodes was ≤7 days; and, 2) quartiles 1 and 3 around the median pre-RBC transfusion hemoglobin (Hb) count was ≤10g/L. Patient's disease was not considered to be stable if the patient was admitted to hospital for an MDS or co-morbidity related issue within the past 6 months or, if there was severe infections within the past 6 months. Data were analyzed descriptively. Means and standard deviations were reported for continuous variables along with medians and interquartile ranges (IQRs) where appropriate. Proportions were used to describe categorical variables RESULTS: 21/52 (40.4%) of patients screened were eligible for the study (mean age: 79.52 ± 6.03 years; 6 female). Most patients (17/21; 81%) had at least one comorbid illness. Patients experienced a median of 5 transfusion episodes (IQR, 2, 12) over 6 months. The median age of RBCs transfused was 24 days (IQR, 20, 31). 14 patients had at least 4 transfusion episodes during this time and were included in the stability assessment. 2/14 patients had unstable disease: one patient had a median of 11 days between transfusion episodes (IQR, 4.25, 20); another patient had a median pre-transfusion Hb of 91.5 g/L (IQR, 79.75, 97.5) and was considered not stable since quartile 1 exceeded 10g/L. None of the patients had severe infections or were admitted to hospital for MDS or other co-morbid illnesses. Hence 12/14 (85.7%) of patients were considered stable. CONCLUSION: This study introduces a novel approach to assessing clinical stability in transfused patients with MDS. While the criteria for assessing stability were peer reviewed, this approach requires further validation. More than half of patients with MDS in our study (12/21) were considered clinically stable. This approach, once validated, can be used to define stable MDS patients if research using a crossover design is being considered. Disclosures Leber: Novartis Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Background Bcl-2 and Bcl-XL are anti-apoptotic paralogues that inhibit apoptosis elicited by a wide variety of stimuli, and play critical roles in cancer development and resistance to treatment. Many clinical studies have indicated that expression of these anti-apoptotic proteins in tumours is associated with poor prognosis. It has therefore been assumed that in cells the essential difference between Bcl-2 and Bcl-XL involves regulation of expression and that they are otherwise functionally similar. To examine this issue, we have compared the function of the proteins and of mutants of Bcl-2 and Bcl-XL specifically targeted to different subcellular sites. Methods We generated clones of the human breast cancer line MCF-7 stably expressing known amounts of Bcl-2, or Bcl-XL as determined by quantitative immunoblotting. Clones expressing equivalent amounts of wild-type and mutants of Bcl-2 and Bcl-XL with subcellular localization restricted to the cytoplasm, endoplasmic reticulum or outer mitochondrial membrane were studied in both MCF-7 and Rat-1 fibroblasts. In MCF-7 cells we measured the functional activities of these proteins in preventing apoptosis induced by four different agents (doxorubicin, ceramide, thapsigargin, TNF-α). Etoposide and low serum were used to compare the effect of Bcl-2, Bcl-XL and mutants located at the endoplasmic reticulum on induction of apoptosis in fibroblasts. Results We noted both qualitative and quantitative differences in the functional activity of these two anti-apoptotic proteins in cells: Bcl-2 localized to the endoplasmic reticulum inhibits apoptosis induced by ceramide and thapsigargin but not by doxorubicin or TNFα, while Bcl-XL at the endoplasmic reticulum is active against all four drugs. In fibroblasts Bcl-2 localized to the ER did not prevent cell death due to etoposide whereas Bcl-XL in the same location did. Finally in MCF-7 cells, Bcl-XL is approximately ten times more active than Bcl-2 in repressing apoptosis induced by doxorubicin. This difference can be manifest as a large difference in clonal survival. Conclusion When examined in the same cellular context, Bcl-2 and Bcl-XL differ substantially in the potency with which they inhibit apoptosis, mediated in part by differences in the inhibition of specific subcellular pathways.

New approaches in the treatment of chronic B lymphocytic leukemia (B-CLL) have led to improved clinical response rates. In this setting there is a need to evaluate novel therapeutic approaches that aim to eradicate minimal residual B-CLL cells following an initial favorable response. The use of tumor lysate-pulsed dendritic cells (DC) represents a potentially important development in the field of cancer vaccination. B-CLL is ideally suited for DC-based vaccination since tumor cells are readily available (peripheral blood) and both known (tumor idiotype) and unknown antigens can be exploited to stimulate immune responses. In the current study we have evaluated the ability to stimulate in vitro autologous immune reactivity against target B-CLL cells using autologous DCs pulsed with B-CLL tumor lysate. Enhanced specific T cell IFN-gamma expression was detected in 9 of 14 patients evaluated. These responses were specific with increased levels of IFN-gamma mRNA measurable in T-cells stimulated with NC-DCs and not unpulsed DCs or DCs pulsed with normal B cell lysate. CTLs demonstrating increased levels of IFN-gamma mRNA also lysed autologous B-CLL targets cells in an MHC class 1-restricted manner by (51)chromium release assay. Priming target leukemic cells with CD40 ligand and IL-4 enhanced CTL killing. The effector CTL displayed negligible toxicity against NK susceptible target cells K-562 and spared CD19(+)CD5(-) normal B cells in cytotoxicity assays. The specificity of the CTL response was confirmed by blocking HLA class I molecules and cold target inhibition assays.

Bcl-2 inhibits apoptosis by regulating the release of cytochrome c and other proteins from mitochondria. Oligomerization of Bax promotes cell death by permeabilizing the outer mitochondrial membrane. In transfected cells and isolated mitochondria, Bcl-2, but not the inactive point mutants Bcl-2-G145A and Bcl-2-V159D, undergoes a conformation change in the mitochondrial membrane in response to apoptotic agonists such as tBid and Bax. A mutant Bcl-2 with two cysteines introduced at positions predicted to result in a disulfide bond that would inhibit the mobility of alpha5-alpha6 helices (Bcl-2-S105C/E152C) was only active in a reducing environment. Thus, Bcl-2 must change the conformation to inhibit tBid-induced oligomerization of integral membrane Bax monomers and small oligomers. The conformationally changed Bcl-2 sequesters the integral membrane form of Bax. If Bax is in excess, apoptosis resumes as Bcl-2 is consumed by the conformational change and in complexes with Bax. Thus, Bcl-2 functions as an inhibitor of mitochondrial permeabilization by changing conformation in the mitochondrial membrane to bind membrane-inserted Bax monomers and prevent productive oligomerization of Bax.

Introduction The 12- and 24-mo results of the Evaluating Nilotinib Efficacy and Safety in clinical Trials–complete molecular response (ENESTcmr) trial showed that pts with CML-CP with minimal residual disease after ≥ 2 y on imatinib achieved deeper molecular responses with switch to nilotinib. Results from ENESTcmr with 36-mo follow-up will be presented. Methods Pts with Philadelphia chromosome–positive (Ph+) CML-CP who had achieved complete cytogenetic response (CCyR) but had detectable BCR-ABL after ≥ 2 y on imatinib were included. Pts (N = 207) were randomized 1:1 to continue the same dose of imatinib (400 or 600 mg once daily [QD]; n = 103) or switch to nilotinib 400 mg twice daily (BID; n = 104). Rates of major molecular response (MMR; BCR-ABL ≤ 0.1% according to the International Scale [IS]) and MR4.5 (BCR-ABLIS ≤ 0.0032%) were evaluated by real-time quantitative polymerase chain reaction (RQ-PCR). Confirmed undetectable BCR-ABL was measured by RQ-PCR with a sensitivity of ≥ 4.5 logs, confirmed with a sensitivity of at least 4 logs in the next sample. Predictors of response were evaluated by multivariate logistic regression. Pts receiving imatinib were allowed to cross over to nilotinib if they had not achieved confirmed undetectable BCR-ABL by 24 mo or if they experienced treatment failure or confirmed loss of undetectable BCR-ABL at any time. Results By 24 mo, 77% of pts in the nilotinib arm and 91% in the imatinib arm remained on study treatment. Discontinuation rates were comparable between arms during year 2; 7% and 5% of pts discontinued study treatment in the nilotinib and imatinib arms, respectively, between years 1 and 2. Three pts crossed over to nilotinib before 24 mo; the no. of pts who crossed over at or after 24 mo will be presented. By 24 mo, more pts in the nilotinib arm achieved confirmed undetectable BCR-ABL compared with imatinib (22.1% vs 8.7%; P = .0087; Table). Regardless of molecular response at study start, more pts in the nilotinib arm than the imatinib arm achieved MR4.5 by 24 mo. None of the pts in the imatinib arm who lacked MMR at study start achieved confirmed MR4.5 or confirmed undetectable BCR-ABL by 24 mo (vs 20.8% and 16.7% in the nilotinib arm, respectively). Twice as many pts achieved and maintained MR4.5 in 3 consecutive assessments in the nilotinib vs imatinib arm (n = 12 vs 6). Age, sex, BCR-ABL level at study start, duration of prior imatinib (≤ 36 mo vs > 36 mo), and prior interferon were analyzed as predictors of response in univariate and multivariate analyses. None of these was clearly predictive of achieving MR4.5 or undetectable BCR-ABL in multivariate logistic regression. No cases of progression to accelerated phase/blast phase were observed with 24 mo follow-up. Three pts in the imatinib arm had confirmed loss of CCyR vs 0 in the nilotinib arm. Conclusions Switching to nilotinib continues to induce deeper molecular responses in pts with minimal residual disease on long-term imatinib therapy. More pts achieved confirmed undetectable BCR-ABL in the nilotinib arm vs the imatinib arm, with the difference between arms increasing between 12 and 24 mo and notably marked in pts lacking MMR at study start. Maintenance of deeper molecular responses achieved with nilotinib therapy may enable more pts to benefit from treatment-free remission trials. Disclosures: Leber: novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau. Cervantes:Novartis: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau; Pfizer: Membership on an entity’s Board of Directors or advisory committees. Spector:Novartis: Honoraria, Research Funding. Lipton:Novartis: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bristol Myers Squibb: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Ariad: Equity Ownership, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau. Etienne:Pfizer: Membership on an entity’s Board of Directors or advisory committees; Bristol Myers Squibb: Consultancy, Membership on an entity’s Board of Directors or advisory committees; novartis: Consultancy, Membership on an entity’s Board of Directors or advisory committees; Ariad: Membership on an entity’s Board of Directors or advisory committees. Guerci-Bresler:Celgene: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Novartis : Honoraria, Membership on an entity’s Board of Directors or advisory committees; AMGEN: Honoraria. Forrest:Bristol Myers Squibb: Consultancy. Schwarer:Bristol Myers Squibb: Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau. Acharya:Novartis Healthcare Pvt. Ltd.: Employment. Collins:Novartis: Employment. Szczudlo:Novartis: Employment, Equity Ownership. Hughes:Araid: Consultancy, Honoraria; Bristol Myers Squib: Consultancy, Honoraria, Research Funding; Novarits: Consultancy, Honoraria, Research Funding; CSL: Research Funding.

Bax promotes cell death by permeabilizing mitochondrial outer membranes by an unresolved mechanism. However, in cells lacking the gene c-myc, membrane permeabilization by Bax is blocked by changes in the mitochondria that prevent Bax oligomerization. Drug-treated c-myc null cells and cells expressing Myc were used to map the topology of Bax in membranes prior to and after mitochondrial permeabilization. Chemical labeling of single cysteine mutants of Bax using a membrane bilayer impermeant cysteine-specific modifying agent revealed that Bax inserted both the 'pore domain' (helices alpha5-alpha6), and the tail-anchor (helix alpha9) into membranes prior to oligomerization and membrane permeabilization. Additional topology changes for Bax were not required in Myc-expressing cells to promote oligomerization and cytochrome c release. Our results suggest that unlike most pore-forming proteins, Bax membrane permeabilization results from oligomerization of transmembrane monomers rather than concerted insertion of the pore domains of a preformed oligomer.

The Bcl-2 family member Bax is an apoptosis-promoting protein that normally resides in an inactive state within the cytoplasm of healthy cells. Upon induction of apoptosis by diverse stimuli, Bax undergoes a conformational change and translocates to mitochondria, where it oligomerizes and forms pores that allow the release of cytochrome c and other cytotoxic factors. Protein-protein interactions between Bax and other Bcl-2 family members are strongly implicated in Bax activation, but a compelling case has recently been made for the involvement of lipids in this process as well. Here we report that purified Bax undergoes a reversible conformational change upon incubation with lipid vesicles in the absence of other proteins. This Bax-liposome interaction does not depend on a specific lipid composition. Changes in Bax conformation were observed by immunoprecipitation with the conformation-specific antibody 6A7, circular dichroism spectroscopy, and differential scanning calorimetry. Although liposomes induced Bax to become 6A7-reactive (a feature normally associated with the onset of apoptosis), the protein did not insert into membranes, become oligomeric, or form pores, clearly indicating that other triggers are required for Bax to achieve its final pro-apoptotic state. Indeed, the lipid-induced Bax conformational change is shown to be required for tBid-induced Bax oligomerization and pore formation, putting it upstream of tBid activity in this molecular pathway to Bax activation. These data demonstrate that Bax is sensitized to activation by transient interaction with lipid membrane surfaces and provide evidence that Bax activation proceeds in a stepwise fashion, with multiple triggers and potential levels of regulation.

Proteins of the Bcl-2 family are important regulators of cell fate. The role of these proteins in controlling mitochondrial apoptotic processes has been extensively investigated, although exact molecular mechanisms are incompletely understood. However, mounting evidence indicates that these proteins also function at the endoplasmic reticulum and other locations within the cell. Both pro- and anti-apoptotic Bcl-2 family members can regulate endoplasmic reticulum calcium, cellular pH and endoplasmic reticulum resident proteins. In this review, we discuss the activities and potential targets of Bcl-2 family members at the endoplasmic reticulum and other cellular locations.

Bcl-2 family proteins play a crucial role in the regulation of the permeabilization of the outer mitochondrial membrane (OMM), which is one of the main steps leading to cell death through apoptosis.To a first approximation, apoptosis is controlled by the balance between pro-apoptotic and anti-apoptotic Bcl-2 family proteins. Deregulation of this balance induces a dysfunction of the apoptosis process leading to different pathologies. The molecular mechanism leading to OMM permeabilization is not yet understood in details. This is in part because of the multiplicity and complexity of the molecular interactions involving Bcl-2 family proteins, since each of them can often interact with itself (homo-oligomerization), with other members of the family (hetero-oligomerization) and with the lipids of the OMM.Whereas in most studies ensemble methods have been used to study these proteins, we have used a single mobile particle detection method to characterize the distribution of different Bcl-2 family proteins on a population of large unilamellar liposomes, in order to better understand the interplay between different family members and lipid membranes during the process of membrane permeabilization. We used large unilamellar liposomes (∼ 200 nm in diameter) with a lipid composition mimicking that of mitochondrial membranes and fluorescently labeled recombinant proteins, which were imaged by confocal microscopy. The specific brightness of each particle detected in the images can then calculated for each separate emission channel.As a first application, we studied the distribution of Bax and Bid on a population of liposomes. These proteins are both pro-apoptotic, promoting pore formation in liposomes, and they are known to interact with one another. We measured the probability that a liposome carried Bax, Bid, or both proteins, allowing us to quantify their colocalization on the same liposome.

Introduction: MDS is a disease of the elderly; yet, the impact of clinical frailty (an age-related vulnerability state created by a multidimensional loss of reserves) and patient-reported outcomes on overall survival (OS) are unknown. Rockwood et al. have developed a simple 9-point clinical frailty scale (CFS) that correlated highly with the risk of death, institutionalization, worsening health and hospital use (Rockwood K., CMAJ 2005). In a prospective, national MDS registry, participants have undergone annual evaluations with the following: (a) 3 geriatric physical performance tests, (b) Charlson (CCI) and Della Porta comorbidity index (DP-CCI) scores, (c) graded frailty using the Rockwood CFS, (d) disability assessments with the Lawton Brody SIADL, and (e) QOL using the EORTC QLQ C-30 and the EQ-5D. The results of these frailty assessments and the effects of these patient-related factors and reported outcomes on OS, in addition to the IPSS/revised IPSS, will be presented. Methods: Overall survival was measured from time to enrollment. Results from physical performance tests were divided into quintiles with higher scores indicating better performance. We used univariate and multivariable Cox proportional hazard model to determine significant predictive factors of overall survival (OS). The variables considered included age, IPSS, R-IPSS, ferritin, LDH, transfusion dependence, hemoglobin (hgb), ECOG, frailty, CCI and DP-CCI, grip strength, 4 M walk test, stand-sit test, modified short physical performance battery (SPPB), Lawton Brody SIADL, time from diagnosis and selected QOL domains including the EQ-5D summary score, EORTC physical functioning, dyspnea and fatigue scores. Results: 453 MDS patients (pts) have been consented and enrolled locally since January 2008 (n=231) and nationally since January 2012 (n=222). Median time from diagnosis was 5.8 mos (IQR 1.4-21). Median age was 73 y (range, 26-95 y), 65% were male and the R-IPSS scores were very low (14%), low (46%), intermediate (24%), high (10%) and very high (6%). Thirty-three % of pts were transfusion dependent at enrollment. Median CCI and DP-CCI scores were 1 (0-12) and 0 (0-6) respectively with 18% and 24% falling into the highest category scores. Median frailty scale score (n=346) was 3 (1-9) with 25% having scores indicating moderate (4-5) or severe (6-9) frailty. The CCI and DP-CCI strongly correlated (r=0.6; p< .0001) with each other, while frailty significantly but modestly correlated with them (r=0.3-0.35, p2, p=.03) and EORTC fatigue (p=.01) as summarized in Table 1 below. A frailty score > 3 predicted for worse survival (figure 1: 2 year OS 68.5% vs. 83.8%) and further refined survival within the R-IPSS categories (Figure 2). Frailty was also the single most predictive factor for OS from the start of azacitidine therapy (not shown). Conclusions: Patient-related factors such as frailty and comorbidity (that evaluate physiologic reserve and global fitness) should be considered in addition to traditional MDS prognostic indices. Abstract 165. Table. Independent Covariate Predictive factors at baseline Coefficient SE p -value HR 95% CI of HR R2 (%) Time from diagnosis (months) * 0.0335 0.1076 0.7557 1.034 0.837 1.277 17.29% R-IPSS (5 categories) Figure 1 Overall survival by Frailty (n=346) Figure 1. Overall survival by Frailty (n=346) Figure 2 Overall Survival by Frailty and R-IPSS Figure 2. Overall Survival by Frailty and R-IPSS Disclosures Buckstein: Celgene Canada: Research Funding. Wells:Celgene: Honoraria, Other, Research Funding; Novartis: Honoraria, Research Funding; Alexion: Honoraria, Research Funding. Leitch:Alexion: Honoraria, Research Funding; Novartis: Honoraria, Research Funding, Speakers Bureau; Celgene: Educational Grant Other, Honoraria, Research Funding. Shamy:Celgene: Honoraria, Other.

7025 Background: With 24 mo f/u, ENESTcmr demonstrated higher rates of stable, deep MRs with nilotinib (NIL) vs IM in pts on long-term (≥ 2 y) IM with residual disease. Here, we present 36-mo resul...

Acute promyelocytic leukemia (APL) has a favorable prognosis. Current therapy includes chemotherapy used in combination with all-trans-retinoic acid (ATRA). Although the differentiating effects of ATRA on promyelocytes have been well established, in vitro studies have shown that less-differentiated APL blasts (CD34(+)) demonstrate a variable responsiveness to ATRA. To assess the clinical relevance of this finding, we analyzed a cohort of 38 patients with t(15;17) and/or PML-RARalpha APL to determine the incidence and laboratory features of CD34(+) APL. Thirty-two percent (12/38) of cases were CD34(+). There was a difference in WBC at presentation between CD34(+) and CD34(-) cases (34.6 +/- 9.2, mean +/- standard error vs. 5.4 +/- 2.0, P = 0.009). Patients with CD34(+) APL demonstrated a micro/hypogranular phenotype (75%) (P = 0.001), co-expression of CD2(+) (83%) (P = 0.001), and the bcr3 isoform (100%) (P = 0.017). In contrast, CD34(-) cases demonstrated hypergranular morphology (65%), CD2(+) (15%), and the bcr1 isoform (50%). A high presenting WBC count (\G10 x 10(9)/L) was associated with an inferior overall survival (Log rank = 0.0047). Patients with CD34(+) APL demonstrated an incidence of early mortality of 50%. Despite a marked correlation between CD34 positivity and increased WBC count, overall survival of CD34(+) and CD34(-) cases did not differ significantly in our small cohort. Immunophenotypic analysis for CD34 expression should be included in future large APL trials to determine if detection of CD34(+) blasts represents an independent adverse prognostic factor.

Bcl-2 family protein including anti-apoptotic (Bcl-2) or pro-apoptotic (Bax) members can form ion channels when incorporated into synthetic lipid bilayers. This contrasts with the observation that Bcl-2 stabilizes the mitochondrial membrane barrier function and inhibits the permeability transition pore complex (PTPC). Here we provide experimental data which may explain this apparent paradox. Bax and adenine nucleotide translocator (ANT), the most abundant inner mitochondrial membrane protein, can interact in artificial lipid bilayers to yield an efficient composite channel whose electrophysiological properties differ quantitatively and qualitatively from the channels formed by Bax or ANT alone. The formation of this composite channel can be observed in conditions in which Bax protein alone has no detectable channel activity. Cooperative channel formation by Bax and ANT is stimulated by the ANT ligand atractyloside (Atr) but inhibited by ATP, indicating that it depends on the conformation of ANT. In contrast to the combination of Bax and ANT, ANT does not form active channels when incorporated into membranes with Bcl-2. Rather, ANT and Bcl-2 exhibit mutual inhibition of channel formation. Bcl-2 prevents channel formation by Atr-treated ANT and neutralizes the cooperation between Bax and ANT. Our data are compatible with a menage a trois model of mitochondrial apoptosis regulation in which ANT, the likely pore forming protein within the PTPC, interacts with Bax or Bcl-2 which influence its pore forming potential in opposing manners.

Bcl-2 is a key inhibitor of a broad range of apoptotic pathways, yet neither the mechanism of action nor the role of Bcl-2 subcellular localization are well understood. The subcellular localization of Bcl-2 includes the mitochondrial membrane as well as the contiguous membrane of the endoplasmic reticulum and nuclear envelope. Most studies suggest that the ability of Bcl-2 to confer cell survival is dependent upon its localization to the mitochondria. In this manuscript, we show that Bcl-2 targeted to the endoplasmic reticulum can inhibit Myc-, but not etoposide-induced apoptosis in the Rat-1 fibroblast cell line. By contrast, wild type Bcl-2 can inhibit apoptosis triggered by either death agonist. We further show both Myc and etoposide trigger disruption of mitochondrial membrane potential (MMP) and induce poly-ADP ribose polymerase (PARP) cleavage, but release of calcium was not evident. Bcl-2 abrogates apoptosis at or upstream of MMP depletion showing that Bcl-2 does not have to reside at the mitochondria to prevent apoptosis. These results further elucidate the biochemical events associated with Myc- and etoposide-induced apoptosis and significantly advance our understanding of Bcl-2 function.

We show here that the anti-apoptosis protein Bcl-2 potently inhibits p53-dependent transcriptional activation of various p53-responsive promoters in reporter gene co-transfection assays in human embryonic kidney 293 and MCF7 cells, without affecting nuclear accumulation of p53 protein. In contrast, Bcl-2(Deltatransmembrane (TM)), which lacks a hydrophobic membrane-anchoring domain, had no effect on p53 activity. Similarly, in MCF7 cells stably expressing either Bcl-2 or Bcl-2(DeltaTM), nuclear levels of p53 protein were up-regulated upon treatment with the DNA-damaging agents doxorubicin and UV radiation, whereas p53-responsive promoter activity and expression of p21(CIP1/WAF1) were strongly reduced in MCF7-Bcl-2 cells but not in MCF7-Bcl-2(DeltaTM) or control MCF7 cells. The issue of membrane anchoring was further explored by testing the effects of Bcl-2 chimeric proteins that contained heterologous transmembrane domains from the mitochondrial protein ActA or the endoplasmic reticulum protein cytochrome b5. Both Bcl-2(ActA) and Bcl-2(Cytob5) suppressed p53-mediated transactivation of reporter gene plasmids with efficiencies comparable to wild-type Bcl-2. These results suggest that (a) Bcl-2 not only suppresses p53-mediated apoptosis but also interferes with the transcriptional activation of p53 target genes at least in some cell lines, and (b) membrane anchoring is required for this function of Bcl-2. We speculate that membrane-anchored Bcl-2 may sequester an unknown factor necessary for p53 transcriptional activity.

Sir, Swisher and colleagues propose that on occasion acute pancreatitis can precipitate thrombotic thrombocytopenic purpura (TTP).[1][1] We also recently observed a patient with acute pancreatitis subsequently complicated by TTP. A 23-year-old Caucasian male, otherwise fit and healthy (except for

Current models of the regulation of hematopoiesis postulate a combination of both factor-directed cell differentiation/survival acting through intracellular signaling pathways, and factor-independent differentiation along intrinsically set, default pathways. Recent reports have indicated that eosinophil/basophil (Eo-Baso) differentiation may represent one default pathway. Because of the strong modulating effect of all trans-retinoic acid (ATRA) on hematopoietic differentiation, we have investigated the role of ATRA in regulating Eo-Baso differentiation from pluripotent progenitors. Our results indicate that ATRA inhibits Eo-Baso maturation at early stages of lineage commitment. Because allergic responses may depend on the continued recruitment and differentiation of such inflammatory mediators, the ability to modulate this pathway may eventually prove to have a therapeutic role in allergic inflammation.

Background Chronic transfusion support plays a key role in survival and quality of life for patients with hematological disorders. However, transfusion-related iron overload (TRIO) is a significant cause of morbidity and mortality in these patients.Adequate iron overload (IO) screening and use of iron chelators, if necessary, is now standard practice in chronically transfused individuals such as hemoglobinopathy patients. Screening practices for IO for patients receiving multiple red blood cell (RBC) transfusions for other reasons (e.g. cancer) are unknown. Objective This two part study aimed to detect pediatric (Jaffer et al., 2012) and adult populations at risk for TRIO and to evaluate and compare current screening practices. Methods Children (≤ 18 years) and adults (> 18 years) receiving at least 1 RBC transfusion from January 1, 2008 to December 31, 2011 at a tertiary care academic institution were identified using a transfusion registry database. Only those receiving chronic RBC transfusions were included in the study. Chronic transfusion was defined as ≥20 units of RBC or ≥ 20 RBC transfusions dosed at 15ml/kg within 12 consecutive months where transfusions were not given in the setting of an operating room, trauma or surgical procedures, not given 7 days prior/post-surgical procedures and not all given in one day. An adjudicator resolved study inclusion ambiguity. The analysis excluded hemoglobinopathy patients. Medical records were reviewed to collect patient demographics, diagnosis, and to evaluate IO screening practices and frequency of iron chelation therapy. Results A total of 343 patients met the eligibility criteria: 27 pediatric and 316 adult patients, with mean ages of 8.1 years (SD 5.7) and 62 years (SD 12.6), respectively. Table 1 summarizes demographics, number of transfusions, and IO screening and results. Ferritin levels were checked for 12 (44%) pediatric and 227 (72%) adult patients: 2 (17%) pediatric and 30 (13%) adult patients had values 500 occurred in 71% of pediatric and 85% of adult patients, with an iron chelator reported in 1 adult. Total RBC transfusions ranged from 20 to 44 with a median of 26.5 for pediatrics and 20 to 176 with a median of 31 for adults. Conclusion Despite high rates of RBC transfusion, screening for TRIO was inconsistent. Although information regarding reasons for not screening for TRIO or not treating with chelation therapy was not collected, the possibilities include a lack of awareness of the risk of TRIO and lack of access to ferriscan and/or to oral iron chelator in Canada for conditions other than hemoglobinopathy and a select subset of MDS cases. Considering TRIO presents an additional, yet unidentified, co-morbidity of cancer therapy and that the therapy (e.g. anthracyclines) may potentiate the end organ effect of TRIO, it is vital to develop strategies to evaluate cancer patients at risk for TRIO and ensure they have access to appropriate iron chelation therapy. Research is needed to explore the comorbidities associated with failure to treat TRIO and to identify barriers to treatment so cancer patients can receive optimal care. Disclosures: Leber: Novartis Canada: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau. Heddle:Canadian Blood Services and Health Canada: Research Funding.

7053^ Background: The 12-mo results of ENESTcmr demonstrated that switching pts on IM with sustained BCR-ABL positivity to NIL leads to faster, deeper molecular responses (MRs)vs remaining on IM. These deeper molecular responses (MR4.5 [BCR-ABL ≤ 0.0032%IS] or greater) are a prerequisite to enter most treatment-free remission studies. Here, we report 24-mo f/u of ENESTcmr. Methods: Philadelphia chromosome–positive CML-CP pts (N = 207) who achieved a complete cytogenetic response, but had detectable BCR-ABL transcripts after ≥ 2 y on IM, were randomized to receive NIL 400 mg twice daily (BID; n = 104) or continue their IM dose (400/600 mg once daily [QD]; n = 103). Results: By 24 mo, significantly more pts achieved confirmed undetectable BCR-ABL (by RQ-PCR with ≥ 4.5 log sensitivity in 2 consecutive samples) with a switch to NIL vs continuing IM (22.1% vs 8.7%; P = .0087). The increase in the rate of undetectable BCR-ABL from mo 12 to 24 was higher for pts on NIL vs IM (9.6 vs 2.9 percentage points). In pts without MR4.5 at baseline (BL), MR4.5 was achieved by 24 mo in 42.9% vs 20.8% of pts (NIL vs IM; P = .0006). In pts without major molecular response (MMR; ≤ 0.1%IS) at BL, MR4.5 was achieved by 24 mo in 29.2% vs 3.6% of pts (P = .016). No progressions to accelerated phase/blast crisis or deaths occurred on study since the 12-mo f/u. Event-free survival at 24 mo was 96.6% vs 92.8% in the NIL and IM arms, respectively. Discontinuations due to adverse events occurred in 11.5% and 2.9% of pts in the NIL and IM arms. The NIL safety profile was consistent with prior switch studies. Conclusions: By 24 mo, significantly more pts achieved deeper responses (MR4.5and undetectable BCR-ABL) with switch to NIL vs remaining on IM, and the difference between arms in these endpoints increased between 12 and 24 mo. Clinical trial information: NCT00760877. [Table: see text]

Telomeres, the ends of eukaryotic chromosomes, are structural and functional units composed of proteins and repetitive DNA sequences. Telomeres protect the ends of chromosomes from DNA loss caused by incomplete replication of 3′ ends. The obligatory loss of terminal sequence with each cell division leads to telomere shortening, and is counteracted in germline cells by an enzymatic activity termed telomerase that resynthesizes telomeric DNA de novo. Telomere length and telomerase activity have been measured by several groups in both normal and malignant blood and marrow cells. Telomere length decreases with age in normal blood and bone marrow, despite the presence of a detectable telomerase activity. In most hematologic malignancies telomere length is short and telomerase activity is enhanced, compatible with the late activation of the enzyme in tumour development. The implications of these findings for tumour pathogenesis, diagnosis, and treatment are discussed.

Summary The above studies have begun to address the fundamental question of the mechanisms of bone marrow involvement and response to allergen challenge in allergic asthmatics. Further studies in this area should complement our investigations in human asthma — which suggest that a particular bias toward differentiation of Eo-Baso progenitors characterizes the atopic state — as well as our findings in the dog model of allergen-induced airway hyperresponsiveness, which indicate that the bone marrow responds to inhalation of allergen or corticosteroids. Taken in the context of previous indications that IgE and bronchial responsiveness may both be transferrable through bone marrow transplantation (log), these findings indicate a physiologic role for the bone marrow in allergic inflammation. Likewise, these concepts provide a basis for making certain predictions regarding management and novel therapeutic interventions in atopy and asthma.

PURPOSE To determine whether modifying the standard regimen of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) from full doses given every 3 weeks to one-third doses given weekly (chop) increases the received chemotherapy dose-intensity in elderly patients with advanced-stage intermediate-grade lymphoma. PATIENTS AND METHODS Consenting patients, age > or = 65 years who had acceptable cardiac, renal, and liver function and an Eastern Cooperative Oncology Group (ECOG) performance status less than 4, were stratified by bone marrow and performance status and randomized to receive standard CHOP or weekly chop. Drug doses were attenuated or escalated according to a defined dose-modification schedule. The primary outcome was average relative received dose-intensity. Secondary outcomes included response, progression-free and overall survival, toxicity, and performance status. RESULTS Nineteen patients were allocated to each group. No difference in received dose-intensity was seen. When dose-intensity was calculated for the first six cycles of therapy, average relative received dose-intensity was .92 with CHOP versus .89 with weekly chop (P = .5); when calculated for the first 18 weeks of therapy, values were .88 with CHOP versus .89 with weekly chop (P = .8). The complete response rate was 68% with CHOP versus 74% with weekly chop (P = .9). At 2 years, the progression-free survival rate was 57% with CHOP versus 46% with weekly chop (P = .16) and the survival rate was 74% with CHOP versus 51% with weekly chop (p = .05). More myelotoxicity was seen with CHOP. CONCLUSION We conclude that CHOP can be given in sufficient doses to elderly patients and that weekly chop does not increase received dose-intensity. Progression-free and overall survival are unlikely to be superior with weekly chop, and may be worse. CHOP should remain the standard against which new therapies for elderly patients with intermediate-grade lymphoma are compared.