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Medulloblastoma is the most common malignant brain tumor in children. Even if current treatment dramatically improves the prognosis, survivors often develop long-term treatment-related sequelae. The current radiotherapy standard for medulloblastoma is craniospinal irradiation with a boost to the primary tumor site and to any metastatic sites. Proton therapy (PT) has similar efficacy compared to traditional photon-based radiotherapy but might achieve lower toxicity rates. We report on our multi-centric experience with 43 children with medulloblastoma (median age at diagnosis 8.7 years, IQR 6.6, M/F 23/20; 26 high-risk, 14 standard-risk, 3 ex-infant), who received active scanning PT between 2015 and 2021, with a focus on PT-related acute-subacute toxicity, as well as some preliminary data on late toxicity. Most acute toxicities were mild and manageable with supportive therapy. Hematological toxicity was limited, even among HR patients who underwent hematopoietic stem-cell transplantation before PT. Preliminary data on late sequelae were also encouraging, although a longer follow-up is needed.

Simple Summary Here, a case of neuroblastoma (NB) carrying a high-grade amplification of six loci besides MYCN is described. Since the patient had a very poor outcome, we postulated that these DNA co-amplifications might have a synergistic effect in increasing NB cell proliferation. In order to verify this hypothesis, we analyzed in silico the impact of high expression of the genes located within the amplifications on the NB patients’ outcome using a large dataset integrating three different platforms. These analyses disclosed that high expression of the TSSC1 gene was the most significantly associated with reduced overall survival of NB patients, suggesting that it may have a potential prognostic role in NB in both MYCN amplified and MYCN not amplified tumors. Further studies on TSSC1 interactions and functioning could lead to possible focused therapies for high-risk NB patients. Abstract We observed a case of high-risk neuroblastoma (NB) carried by a 28-month-old girl, displaying metastatic disease and a rapid decline of clinical conditions. By array-CGH analysis of the tumor tissue and of the metastatic bone marrow aspirate cells, we found a high-grade amplification of six regions besides MYCN on bands 2p25.3–p24.3. The genes involved in these amplifications were MYT1L, TSSC1, CMPK2, RSAD2, RNF144A, GREB1, NTSR2, LPIN1, NBAS, and the two intergenic non-protein coding RNAs LOC730811 and LOC339788. We investigated if these DNA co-amplifications may have an effect on enhancing tumor aggressiveness. We evaluated the association between the high expression of the amplified genes and NB patient’s outcome using the integration of gene expression data of 786 NB samples profiled with different public platforms from patients with at least five-year follow-up. NB patients with high expression of the TSSC1 gene were associated with a reduced survival rate. Immunofluorescence staining on primary tumor tissues confirmed that the TSSC1 protein expression was high in the relapsed or dead stage 4 cases, but it was generally low in NB patients in complete remission. TSSC1 appears as a putative new oncogene in NB.

BCOR is a gene that encodes for an epigenetic regulator involved in the specification of cell differentiation and body structure development and takes part in the noncanonical polycomb repressive complex 1. This review provides a comprehensive summary of BCOR’s involvement in oncology, illustrating that various BCOR aberrations, such as the internal tandem duplications of the PCGF Ub-like fold discriminator domain and different gene fusions (mainly BCOR–CCNB3, BCOR–MAML3 and ZC3H7B–BCOR), represent driver elements of various sarcomas such as clear cell sarcoma of the kidney, primitive mesenchymal myxoid tumor of infancy, small round blue cell sarcoma, endometrial stromal sarcoma and histologically heterogeneous CNS neoplasms group with similar genomic methylation patterns known as CNS-HGNET-BCOR. Furthermore, other BCOR alterations (often loss of function mutations) recur in a large variety of mesenchymal, epithelial, neural and hematological tumors, suggesting a central role in cancer evolution.

To evaluate cystic dynamics in two pediatric low grade gliomas during proton beam therapy (PBT) by weekly MRI and in the follow up (FU) time. Early late toxicity was also reported. Both solid and cystic tumor’s components were drown in weekly MRI performed during proton radiation and in the FU phase. P1 case was a multiple partially resected 5 yo girl with hypothalamic pylocitic Astrocytoma no-responding after second line of chemotherapy, who acutely lost visual acuity due to cystic tumor’s progression. P2 case was a 13 yo boy with progressive mesencephalic pylocitic Astrocytoma previously treated with multi-agents chemotherapy and several surgeries. After cystic drainage both were treated with PBT at 54 Gy GCE. During proton therapy # 7 MRI for P1 and # 6 MRI for P2 patient were performed and didn’t shown cyst growth which required intervention; P1 developed two episodes of severe acute headache and both developed partial alopecia. In P1 patient both cystic and solid component progressively reduced (cyst/solid-1w +2/-15%, cyst/solid-2w -9/-22%, cyst/solid-3w -17/-28%, cyst/solid-4w -18/-38%, cyst/solid-5w -30/-43%, cyst/solid-6w -34/-44%, cyst/solid-1FU -43/-50%, cyst/solid-2FU -51/-63%). In P2 patient only cyst part progressively increased (cyst/solid-2w +7/-4%, cyst/solid-3w +36/-10%, cyst/solid-4w +58/-12%, cyst/solid-5w +73/-15%, cyst/solid-6w +90/-15%, cyst/solid-7w +94/-16%, cyst/solid-1FU +126/-37%, cyst/solid-2FU -18/-45%). P2 had transient cyst growth after PT with significant volume reduction on the second FU. After 10 months of median FU, no late side effects were noted however P1 improved visual acuity.

Introduction: Rhabdomyosarcoma is a soft tissue malignant musculoskeletal tumor frequent in children. Biliary duct localization is extremely rare, but it is the most common cause of malignant obstructive jaundice in pediatric patients. Methods: This report describes a series of 10 patients under 18 years of age with biliary tract rhabdomyosarcoma who were enrolled, from 1979 to 2004, in 3 consecutive Italian pediatric cooperative protocols that had been drawn up by the Soft Tissue Sarcoma Committee of the Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP). Results: Considering initial and delayed surgery, tumor resection was achieved in 7 cases, 3 complete with free margins (2 liver transplants) and 4 with microscopic residual disease. Chemotherapy was given to all patients and radiotherapy to 3. At present, 5 patients survive in complete remission 90-200 months after diagnosis while 4 died of disease progression or relapse and 1 of liver transplant-related complications. Conclusions: Better outcomes in this series were associated with the feasibility of conservative surgery due to the favorable location of the tumor, in particular in the common bile duct. Chemotherapy and radiotherapy might obviate the need for demolitive surgery or liver transplant, which were linked to worse outcomes in our series.

L-Asparaginase (L-Asp) is an enzyme that catalyzes the hydrolysis of L-asparagine to L-aspartic acid, and its depletion induces leukemic cell death. L-Asp is an important component of treatment regimens for Acute Lymphoblastic Leukemia (ALL). Sensitivity to L-Asp is due to the absence of L-Asparagine synthetase (ASNS), the enzyme that catalyzes the biosynthesis of L-asparagine. ASNS gene is located on 7q21.3, and its increased expression in ALLs correlates with L-Asp resistance. Chromosome 7 monosomy (-7) is a recurrent aberration in myeloid disorders, particularly in adverse-risk Acute Myeloid Leukemias (AMLs) and therapy-related myeloid neoplasms (t-MN), that leads to a significant downregulation of the deleted genes, including ASNS. Therefore, we hypothesized that -7 could affect L-Asp sensitivity in AMLs. By treating AML cell lines and primary cells from pediatric patients with L-Asp, we showed that -7 cells were more sensitive than AML cells without -7. Importantly, both ASNS gene and protein expression were significantly lower in -7 AML cell lines, suggesting that haploinsufficiency of ASNS might induce sensitivity to L-Asp in AMLs. To prove the role of ASNS haploinsufficiency in sensitizing AML cells to L-Asp treatment, we performed siRNA-knockdown of ASNS in AML cell lines lacking -7, and observed that ASNS knockdown significantly increased L-Asp cytotoxicity. In conclusion, -7 AMLs showed high sensitivity to L-Asp treatment due to low expression of ASNS. Thus, L-Asp may be considered for treatment of AML pediatric patients carrying -7, in order to improve the outcome of adverse-risk AMLs and t-MN patients.

// Daniela Bressanin 1,* , Camilla Evangelisti 2,* , Francesca Ricci 3 , Giovanna Tabellini 4 , Francesca Chiarini 2 , Pier Luigi Tazzari 3 , Fraia Melchionda 5 , Francesca Buontempo 1 , Pasqualepaolo Pagliaro 3 , Andrea Pession 5 , James A. McCubrey 6 , Alberto M. Martelli 1,2 1 Department of Human Anatomy, University of Bologna, Bologna, Italy; 2 Institute of Molecular Genetics, National Research Council-Rizzoli Orthopedic Institute, Bologna, Italy; 3 Immunohaematology and Transfusion Center, Policlinico S.Orsola-Malpighi, Bologna, Italy; 4 Department of Biomedical Sciences and Biotechnology, University of Brescia, Brescia, Italy; 5 Paediatric Oncology and Hematology Unit Lalla Seragnoli, University of Bologna, Bologna, Italy; 6 Department of Microbiology & Immunology, School of Medicine, East Carolina University, Greenville, NC, USA. * Denotes equal contribution Correspondence: Alberto M. Martelli, email: // Keywords : acute leukemia, targeted therapy, signal transduction modulators, PI3K/PDK1, vertical inhibition Received : August 01, 2012, Accepted : August 04, 2012, Published : August 09, 2012 Abstract T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignant hematological disorder arising in the thymus from T-cell progenitors. T-ALL mainly affects children and young adults, and remains fatal in 20% of adolescents and 50% of adults, despite progress in polychemotherapy protocols. Therefore, innovative targeted therapies are desperately needed for patients with a dismal prognosis. Aberrant activation of PI3K/Akt/mTOR signaling is a common event in T-ALL patients and portends a poor prognosis. Preclinical studies have highlighted that modulators of PI3K/Akt/mTOR signaling could have a therapeutic relevance in T-ALL. However, the best strategy for inhibiting this highly complex signal transduction pathway is still unclear, as the pharmaceutical companies have disclosed an impressive array of small molecules targeting this signaling network at different levels. Here, we demonstrate that a dual PI3K/PDK1 inhibitor, NVP-BAG956, displayed the most powerful cytotoxic effects against T-ALL cell lines and primary patients samples, when compared with a pan class I PI3K inhibitor (GDC-0941), an allosteric Akt inhibitor (MK-2206), an mTORC1 allosteric inhibitor (RAD-001), or an ATP-competitive mTORC1/mTORC2 inhibitor (KU-63794). Moreover, we also document that combinations of some of the aforementioned drugs strongly synergized against T-ALL cells at concentrations well below their respective IC 50 . This observation indicates that vertical inhibition at different levels of the PI3K/Akt/mTOR network could be considered as a future innovative strategy for treating T-ALL patients.

T-Acute Lymphoblastic Leukemia (T-ALL) remains a subgroup of pediatric ALL, with a lower response to standard chemotherapy. Some recent studies established the fundamental role of epigenetic aberrations such as DNA hypermethylation, to influence patients’ outcome and response to chemotherapy. Moreover, L-asparaginase is an important chemotherapeutic agent for treatment of ALL and resistance to this drug has been linked toASNSexpression, which can be silenced through methylation. Therefore, we tested whether the sensitivity of T-ALL cell lines towards L-asparaginase is correlated to the epigenetic status ofASNSgene and whether the sensitivity can be modified by concurrent demethylating treatment. Hence we treated different T-ALL cell lines with L-asparaginase and correlated different responses to the treatment withASNSexpression. Then we demonstrated that theASNSexpression was dependent on the methylation status of the promoter. Finally we showed that, despite the demethylating effect on theASNSgene expression, the combined treatment with the demethylating agent Decitabine could synergistically improve the L-asparaginase sensitivity in those T-ALL cell lines characterized by hypermethylation of theASNSgene. In conclusion, this preclinical study identified an unexpected synergistic activity of L-asparaginase and Decitabine in the subgroup of T-ALL with lowASNSexpression due to hypermethylation of theASNSpromoter, while it did not restore sensitivity in the resistant cell lines characterized by higherASNSexpression.

The proteasome inhibitor bortezomib is a new targeted treatment option for refractory or relapsed acute lymphoblastic leukemia (ALL) patients. However, a limited efficacy of bortezomib alone has been reported. A terminal pro-apoptotic endoplasmic reticulum (ER) stress/unfolded protein response (UPR) is one of the several mechanisms of bortezomib-induced apoptosis. Recently, it has been documented that UPR disruption could be considered a selective anti-leukemia therapy. CX-4945, a potent casein kinase (CK) 2 inhibitor, has been found to induce apoptotic cell death in T-ALL preclinical models, via perturbation of ER/UPR pathway. In this study, we analyzed in T-and B-ALL preclinical settings, the molecular mechanisms of synergistic apoptotic effects observed after bortezomib/CX-4945 combined treatment. We demonstrated that, adding CX-4945 after bortezomib treatment, prevented leukemic cells from engaging a functional UPR in order to buffer the bortezomib-mediated proteotoxic stress in ER lumen. We documented that the combined treatment decreased pro-survival ER chaperon BIP/Grp78 expression, via reduction of chaperoning activity of Hsp90. Bortezomib/CX-4945 treatment inhibited NF-kappa B signaling in T-ALL cell lines and primary cells from T-ALL patients, but, intriguingly, in B-ALL cells the drug combination activated NF-kappa B p65 pro-apoptotic functions. In fact in B-cells, the combined treatment induced p65-HDAC1 association with consequent repression of the anti-apoptotic target genes, Bcl-xL and XIAP. Exposure to NEMO (IKK gamma)-binding domain inhibitor peptide reduced the cytotoxic effects of bortezomib/ CX-4945 treatment. Overall, our findings demonstrated that CK2 inhibition could be useful in combination with bortezomib as a novel therapeutic strategy in both T-and B-ALL.

It has been shown previously that the suppression of tumor immunosurveillance may be a mechanism by which tumors resist immune detection and elimination. In this study, we evaluated the role of the immunoregulatory natural killer T (NKT) cells in the biology of immunosurveillance of osteosarcoma. The K7M2 mouse osteosarcoma cell line was implanted orthotopically into wild-type and NKT cell–deficient CD1d knockout (KO) BALB/c mice, and mice were monitored for growth of primary tumors. Further, we examined the role of CD4+ and/or CD8+ cells by depleting the cells in vivo and measuring CTL activity in vitro. We also asked the role of interleukin (IL)-4 receptor α (IL-4Rα)-signal transducer and activator of transcription 6 (STAT6) signaling, including IL-13, and transforming growth factor β (TGF-β) by using gene-disrupted mice or treating mice with cytokine antagonists. We were surprised to find a high rate of rejection of osteosarcoma primary tumors in 88% (14 of 16) of CD1d KO mice compared with syngeneic wild-type BALB/c mice that showed rejection of tumor in

Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) induces selective apoptosis in a variety of tumors, including most cell lines derived from Ewing’s sarcoma family of tumors, an aggressive sarcoma that afflicts children and young adults. To determine the in vivo efficacy of TRAIL receptor agonists in Ewing’s sarcoma family of tumors, mice with orthotopic xenografts were treated with anti-TRAIL-R2 monoclonal antibody or TRAIL/Apo2L in a model that can identify effects on both primary tumors and metastases. Administration of either agonist slowed tumor growth in 60% of animals and induced durable remissions in 11 to 19% but did not alter the incidence of metastatic disease. Response rates were not improved by concurrent doxorubicin treatment. Cells recovered from both TRAIL receptor agonist–treated and nontreated tumors were found to be resistant to TRAIL-induced death in vitro unless pretreated with interferon (IFN) γ. This resistance coincided with a selective down-regulation of TRAIL receptor expression on tumor cells. In vivo treatment with IFNγ increased tumor expression of TRAIL receptors and caspase 8, but did not increase the antitumor effect of TRAIL receptor agonists on primary tumors. However, IFNγ treatment alone or in combination with a TRAIL receptor agonist significantly decreased the incidence of metastatic disease and the combination of TRAIL receptor agonist therapy with IFNγ-mediated impressive effects on both primary tumors and metastatic disease. These data demonstrate that in vivo growth favors TRAIL resistance but that TRAIL receptor agonists are active in Ewing’s sarcoma family of tumors and that the combination of TRAIL receptor agonists with IFNγ is a potent regimen in this disease capable of controlling both primary and metastatic tumors.

Despite expression of tumor-associated or tumor-specific antigens by most tumors, evasion of protective T-cell immunity is the rule rather than the exception. Understanding whether tumor immune escape primarily represents T-cell neglect, anergy/tolerance, or quantitative limits of an existent immune response is central to developing new strategies to enhance antitumor immunity. The authors studied the immune response to MB49, a tumor that naturally expresses HY. Immune surveillance was effective following low-dose tumor inocula, since normal female mice showed a diminished incidence and slower growth rate of MB49 compared with T-cell-depleted female mice and male mice. Following high-dose tumor inoculation, females developed large, progressive tumors but continued to demonstrate immune responses to class I and class II restricted HY epitopes. The HY reactive T cells remained capable of executing HY immune responses since T cells adoptively transferred from MB49-bearing animals mediated accelerated HY skin graft rejection compared with those taken from naive mice. Thus, MB49 does not induce immune tolerance to HY but rather escapes immune surveillance largely due to quantitative limits of the immune response. Treatment of tumor-bearing animals with rhIL7 significantly increased the number of T cells responding to HY but did not alter tumor growth rate. These results demonstrate that escape from immune surveillance does not necessarily imply immune tolerance to tumor antigens and that immunotherapy need not overcome tumor-induced tolerance per se, and suggest that substantial opportunities remain in tumor-bearing hosts to amplify weak but persistent antitumor immune responses.

Polo-like kinases (PLKs) and Aurora kinases (AKs) act as key cell cycle regulators in healthy human cells. In cancer, these protein kinases are often overexpressed and dysregulated, thus contributing to uncontrolled cell proliferation and growth. T-cell acute lymphoblastic leukemia (T-ALL) is a heterogeneous malignancy arising in the thymus from T-cell progenitors. Primary chemoresistant and relapsed T-ALL patients have yet a poor outcome, therefore novel therapies, targeting signaling pathways important for leukemic cell proliferation, are required. Here, we demonstrate the potential therapeutic effects of BI6727, MK-5108, and GSK1070916, three selective inhibitors of PLK1, AK-A, and AK-B/C, respectively, in a panel of T-ALL cell lines and primary cells from T-ALL patients. The drugs were both cytostatic and cytotoxic to T-ALL cells by inducing G2/M-phase arrest and apoptosis. The drugs retained part of their pro-apoptotic activity in the presence of MS-5 bone marrow stromal cells. Moreover, we document for the first time that BI6727 perturbed both the PI3K/Akt/mTORC2 and the MEK/ERK/mTORC1 signaling pathways, and that a combination of BI6727 with specific inhibitors of the aforementioned pathways (MK-2206, CCI-779) displayed significantly synergistic cytotoxic effects. Taken together, our findings indicate that PLK1 and AK inhibitors display the potential for being employed in innovative therapeutic strategies for improving T-ALL patient outcome.

Background. The aim oi this phase I study was to define the maximum tolerated dose (MTD) of thiotepa (TT), administered with busulfan (BU) 480 mg/m 2 and etoposide 2,400 mg/m 2 , followed by autologous bone marrow transplantation (ABMT) or peripheral blood stem cell transplantation (APBSCT) support in children with solid tumors either disseminated at diagnosis or after relapse. Procedure. Nineteen patients, between 2 and 16 years of age, received a high-dose chemotherapy regimer including escalating doses of TT starting from 150 mg/m 2 . Subsequent dose escalation was determined by a modified Fibonacci scheme. Whenever one patient at one dosage level showed a grade III or grade IV reversible toxicity, additional patients were admitted (one by one) up to a maximum number of 6. Upon observing grade III or IV reversible toxicity in two or more systems, in 3 of the 6 patients, no further escalation was performed, and the corresponding dosage was taken as the MTD. WHO criteria were adopted to assess grade of toxicity. Results. All patients had hematological recovery ; and neutrophils and platelet engraftment were observed after median times of 12 and 29 days from stem cell infusion, respectively. The MTD of TT was determined to be 750 mg/m 2 . At this level. 3 of 6 patients experienced grad III mucositis and/or grade III gastrointestinal toxicity. No patient died of treatment-related toxicity. Conclusions. A dose of 750 mg/m 2 TT is the MTD when it is associated with BU 480 mg/m 2 and etoposide 2,400 mg/m 2 . This ablative regimen represents a feasible and tolerable combination for high-dose chemotherapy followed by hematopoietic stem cell rescue (HSCRI. Phase II studies in children with poor-prognosis solid tumors are required to evaluate the effectiveness of this treatment.

© 2014 Macmillan Publishers Limited All rights reserved, Constitutively active phosphoinositide 3-kinase (PI3K) signaling is a common feature of T-cell acute lymphoblastic leukemia (T-ALL), where it upregulates cell proliferation, survival and drug resistance. These observations lend compelling weight to the application of PI3K inhibitors in the therapy of T-ALL. Here, we have analyzed the therapeutic potential of the pan-PI3K inhibitor NVP-BKM120 (BKM120), an orally bioavailable 2,6-dimorpholino pyrimidine derivative, which has entered clinical trials for solid tumors, on both T-ALL cell lines and patient samples. BKM120 treatment resulted in G2/M phase cell cycle arrest and apoptosis, being cytotoxic to a panel of T-ALL cell lines and patient T lymphoblasts, and promoting a dose- and time-dependent dephosphorylation of Akt and S6RP. BKM120 maintained its pro-apoptotic activity against Jurkat cells even when cocultured with MS-5 stromal cells, which mimic the bone marrow microenvironment. Remarkably, BKM120 synergized with chemotherapeutic agents currently used for treating T-ALL patients. Moreover, in vivo administration of BKM120 to a subcutaneous xenotransplant model of human T-ALL significantly delayed tumor growth, thus prolonging survival time. Taken together, our findings indicate that BKM120, either alone or in combination with chemotherapeutic drugs, may be an efficient treatment for T-ALLs that have aberrant upregulation of the PI3K signaling pathway., This work was supported by a grant from MIUR FIRB 2010 (RBAP10447J_003) to AMM and by grants PTDC/SAU-OBD/104816/2008 and PTDC/SAU-ONC/122428/2010 from Fundação para a Ciência e a Tecnologia (FCT), Portugal, to JTB. ILA received a postdoctoral fellowship (SFRH/BPD/63920/2009) from FCT. FL was supported by Special Project AIRC 5x1000 n. 9962 and Progetto di rilevante Interesse Nazionale, PRIN 2010.

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive neoplastic disorder arising from T-cell progenitors. T-ALL accounts for 15% of newly diagnosed ALL cases in children and 25% in adults. Although the prognosis of T-ALL has improved, due to the use of polychemotherapy schemes, the outcome of relapsed/chemoresistant T-ALL cases is still poor. A signaling pathway that is frequently upregulated in T-ALL, is the phosphatidylinositol 3-kinase/Akt/mTOR network. To explore whether Akt could represent a target for therapeutic intervention in T-ALL, we evaluated the effects of the novel allosteric Akt inhibitor, MK-2206, on a panel of human T-ALL cell lines and primary cells from T-ALL patients. MK-2206 decreased T-ALL cell line viability by blocking leukemic cells in the G(0)/G(1) phase of the cell cycle and inducing apoptosis. MK-2206 also induced autophagy, as demonstrated by an increase in the 14-kDa form of LC3A/B. Western blotting analysis documented a concentration-dependent dephosphorylation of Akt and its downstream targets, GSK-3 alpha/b and FOXO3A, in response to MK-2206. MK-2206 was cytotoxic to primary T-ALL cells and induced apoptosis in a T-ALL patient cell subset (CD34(+)/CD4(-)/CD7(-)), which is enriched in leukemia-initiating cells. Taken together, our findings indicate that Akt inhibition may represent a potential therapeutic strategy in T-ALL.

The mammalian target of rapamycin (mTOR) serine/threonine kinase is the catalytic subunit of two multi-protein complexes, referred to as mTORC1 and mTORC2. Signaling downstream of mTORC1 has a critical role in leukemic cell biology by controlling mRNA translation of genes involved in both cell survival and proliferation. mTORC1 activity can be down-modulated by upregulating the liver kinase B1/AMP-activated protein kinase (LKB1/AMPK) pathway. Here, we have explored the therapeutic potential of the anti-diabetic drug, metformin (an LKB1/AMPK activator), against both T-cell acute lymphoblastic leukemia (T-ALL) cell lines and primary samples from T-ALL patients displaying mTORC1 activation. Metformin affected T-ALL cell viability by inducing autophagy and apoptosis. However, it was much less toxic against proliferating CD4(+) T-lymphocytes from healthy donors. Western blot analysis demonstrated dephosphorylation of mTORC1 downstream targets. Unlike rapamycin, we found a marked inhibition of mRNA translation in T-ALL cells treated with metformin. Remarkably, metformin targeted the side population of T-ALL cell lines as well as a putative leukemia-initiating cell subpopulation (CD34(+)/CD7(-)/CD4(+)) in patient samples. In conclusion, metformin displayed a remarkable anti-leukemic activity, which emphasizes future development of LKB1/AMPK activators as clinical candidates for therapy in T-ALL.

The mammalian Target Of Rapamycin (mTOR) serine/threonine kinase belongs to two multi-protein complexes, referred to as mTORC1 and mTORC2. mTOR-generated signals have critical roles in leukemic cell biology by controlling mRNA translation of genes that promote proliferation and survival. However, allosteric inhibition of mTORC1 by rapamycin has only modest effects in T-cell acute lymphoblastic leukemia (T-ALL). Recently, ATP-competitive inhibitors specific for the mTOR kinase active site have been developed. In this study, we have explored the therapeutic potential of active-site mTOR inhibitors against both T-ALL cell lines and primary samples from T-ALL patients displaying activation of mTORC1 and mTORC2. The inhibitors affected T-ALL cell viability by inducing cell-cycle arrest in G(0)/G(1) phase, apoptosis and autophagy. Western blot analysis demonstrated a Ser 473 Akt dephosphorylation (indicative of mTORC2 inhibition) and a dephosphorylation of mTORC1 downstream targets. Unlike rapamycin, we found a marked inhibition of mRNA translation in T-ALL cell lines treated with active-site mTOR inhibitors. The inhibitors strongly synergized with both vincristine and the Bcl-2 inhibitor, ABT-263. Remarkably, the drugs targeted a putative leukemia-initiating cell sub-population (CD34(+)/CD7(-)/CD4(-)) in patient samples. In conclusion, the inhibitors displayed remarkable anti-leukemic activity, which emphasizes their future development as clinical candidates for therapy in T-ALL.

Recent findings have highlighted that constitutively active phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling is a common feature of T-cell acute lymphoblastic leukemia (T-ALL), where it upregulates cell proliferation, survival, and drug resistance. These observations lend compelling weight to the application of PI3K/Akt/mTOR inhibitors in the therapy of T-ALL. Here, we have analyzed the therapeutic potential of the novel dual PI3K/mTOR inhibitor NVP-BEZ235, an orally bioavailable imidazoquinoline derivative, which has entered clinical trials for solid tumors, on both T-ALL cell lines and patient samples. NVP-BEZ235 was cytotoxic to a panel of T-ALL cell lines as determined by MTT assays. NVP-BEZ235 treatment resulted in cell cycle arrest and apoptosis. Western blots showed a dose- and time-dependent dephosphorylation of Akt and mTORC1 downstream targets in response to NVP-BEZ235. Remarkably, NVP-BEZ235 targeted the side population of both T-ALL cell lines and patient lymphoblasts, which might correspond to leukemia-initiating cells, and synergized with chemotherapeutic agents (cyclophosphamide, cytarabine, dexamethasone) currently used for treating T-ALL patients. NVP-BEZ235 reduced chemoresistance to vincristine induced in Jurkat cells by coculturing with MS-5 stromal cells, which mimic the bone marrow microenvironment. NVP-BEZ235 was cytotoxic to T-ALL patient lymphoblasts displaying pathway activation, where the drug dephosphorylated eukaryotic initiation factor 4E-binding protein 1, at variance with rapamycin. Taken together, our findings indicate that longitudinal inhibition at two nodes of the PI3K/Akt/mTOR network with NVP-BEZ235, either alone or in combination with chemotherapeutic drugs, may be an efficient treatment of those T-ALLs that have aberrant upregulation of this signaling pathway for their proliferation and survival. Cancer Res; 70(20); 8097–107. ©2010 AACR.

Pediatric early T-cell precursor leukemia with NF1 deletion and high-sensitivity in vitro to tipifarnib

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Primary tumors developing in immunocompetent hosts escape immunosurveillance by acquiring immune evasive properties. This raises the prospect that metastases derived from such tumors will also evade immunity. To investigate whether immune surveillance plays a role in preventing metastases, we studied a murine model which mimics the clinical progression of osteosarcoma: primary tumor growth in the lower extremity, amputation, minimal residual disease followed by the development of overt metastases. K7M2 implants readily escaped immune surveillance since normal BALB/c mice, T cell deficient SCID and T/NK cell deficient SCID-bg mice showed no difference in the rate of growth of primary osteosarcomas. However, both SCID and SCID-bg mice had higher rates of metastases than immunocompetent mice. Similarly, immune reconstitution following transfer of naive T cells to SCID or SCID-bg mice did not impact primary tumor growth, but significantly diminished metastatic recurrence. T cells in osteosarcoma bearing mice produced IFNgamma in response to tumor and IFNgamma production by immune reconstituting T cells was required to prevent metastases. These results demonstrate an important role for T cell based immune surveillance in preventing metastases, even when metastases develop from tumors that adeptly evade immunosurveillance. The results further suggest that T cell depleting cancer therapies may eliminate beneficial immune responses and that immune reconstitution of lymphopenic cancer patients could prevent metastatic recurrence of solid tumors.

Trisomy 11 is uncommon in pediatric acute myeloid leukemia (AML) and molecular studies of AML with trisomy 11 in adult patients have recently revealed high incidence of partial tandem duplication (PTD) of the MLL gene. We report the first case of trisomy 11 and MLL-PTD in a 3 months old girl with AML, the immunophenotype of bone marrow aspirate documented blast cells positive for CD34, CD33, AntiHLA DR, CD117, and MPO Figure 1. Interphase FISH analysis with MLL probe revealed a MLL triple signal (a) and with a centromeric probe confirmed trisomy 11 (b). Direct sequencing confirmed the MLL PTD with in-frame fusion of exons 6 and exon 2(c). Figure 1. Interphase FISH analysis with MLL probe revealed a MLL triple signal (a) and with a centromeric probe confirmed trisomy 11 (b). Direct sequencing confirmed the MLL PTD with in-frame fusion of exons 6 and exon 2(c).