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SARS-CoV-2; Hematological malignancies SARS-CoV-2; Neoplasias hematológicas SARS-CoV-2; Neoplasies hematològiques Optics COMMIT (COVID-19 Unmet Medical Needs and Associated Research Extension) COVID-19 RFP program by GILEAD Science, United States, Grant/Award Number: Project 2020-8223.

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Simple Summary Mitotane is the only approved drug for the treatment of advanced adrenocortical carcinoma and for postoperative adjuvant therapy. It is known that mitotane destroys the adrenal cortex impairing steroidogenesis, although its exact molecular mechanism is still unclear. However, confounding factors affecting in vitro experiments could reduce the relevance of the studies. In this review, we explore in vitro studies on mitotane effects, highlighting how different experimental conditions might contribute to the controversial findings. On this basis, it may be necessary to re-evaluate the experiments taking into account their potential confounding factors such as cell strains, culture serum, lipoprotein concentration, and culture passages, which could hide important molecular results. As a consequence, the identification of novel pharmacological molecular pathways might be used in the future to implement personalized therapy, maximizing the benefit of mitotane treatment while minimizing its toxicity. Abstract Mitotane is the only approved drug for the treatment of advanced adrenocortical carcinoma and is increasingly used for postoperative adjuvant therapy. Mitotane action involves the deregulation of cytochromes P450 enzymes, depolarization of mitochondrial membranes, and accumulation of free cholesterol, leading to cell death. Although it is known that mitotane destroys the adrenal cortex and impairs steroidogenesis, its exact mechanism of action is still unclear. The most used cell models are H295-derived cell strains and SW13 cell lines. The diverging results obtained in presumably identical cell lines highlight the need for a stable in vitro model and/or a standard methodology to perform experiments on H295 strains. The presence of several enzymatic targets responsive to mitotane in mitochondria and mitochondria-associated membranes causes progressive alteration in mitochondrial structure when cells were exposed to mitotane. Confounding factors of culture affecting in vitro experiments could reduce the significance of any molecular mechanism identified in vitro. To ensure experimental reproducibility, particular care should be taken in the choice of culture conditions: aspects such as cell strains, culture serum, lipoproteins concentration, and culture passages should be carefully considered and explicated in the presentation of results. We aimed to review in vitro studies on mitotane effects, highlighting how different experimental conditions might contribute to the controversial findings. If the concerns pointed out in this review will be overcome, the new insights into mitotane mechanism of action observed in-vitro could allow the identification of novel pharmacological molecular pathways to be used to implement personalized therapy.

In recent years, the digital polymerase chain reaction has received increasing interest as it has emerged as a tool to provide more sensitive and accurate detection of minimal residual disease. In order to start the process of data alignment, we assessed the consistency of the BCR-ABL1 quantification results of the analysis of 16 RNA samples at different levels of disease. The results were obtained by two different laboratories that relied on The Qx100/Qx200 Droplet Digital PCR System (Bio-Rad) and Quant Studio 3D dPCR System (Thermofisher) platforms. We assessed the compatibility between the estimated values by linear regression, Bland–Altman bias-plot, and Mann–Whitney nonparametric test. The results confirmed the compatibility of the measures, allowing us tocompute an ‘alignment factor’ (AF), equal to 1.41, which was further validated by a different series of experiments. We conclude that the performed measurements by the two laboratories are comparable, and also equalized through the introduction of an alignment factor.

Myeloproliferative neoplasms are chronic myeloid cancers divided in Philadelphia positive and negative. The JAK2 V617F is the most common mutation in Philadelphia negative patients and results in a constitutive activation of the JAK/STAT pathway, conferring a proliferative advantage and apoptosis inhibition. Recent studies identified a functional crosstalk between the JAK/STAT and mTOR pathways. The identification of an effective therapy is often difficult, so the availability of new therapeutic approaches might be attractive. Previous studies showed that curcumin, the active principle of the Curcuma longa, can suppress JAK2/STAT pathways in different type of cancer and injuries. In this study, we investigated the anti‐proliferative and pro‐apoptotic effects of curcumin in JAK2 V617F‐mutated cells. HEL cell line and cells from patients JAK2 V617F mutated have been incubated with increasing concentrations of curcumin for different time. Apoptosis and proliferation were evaluated. Subsequently, JAK2/STAT and AKT/mTOR pathways were investigated at both RNA and protein levels. We found that curcumin induces apoptosis and inhibition of proliferation in HEL cells. Furthermore, we showed that curcumin inhibits JAK2/STAT and mTORC1 pathways in JAK2 V617F‐mutated cells. This inhibition suggests that curcumin could represent an alternative strategy to be explored for the treatment of patients with myeloproliferative neoplasms.

Chronic myeloid leukemia is a myeloproliferative neoplasm characterized by the presence of the Philadelphia chromosome that originates from the reciprocal translocation t(9, 22)(q34, q11.2) and encodes for the constitutively active tyrosine kinase protein BCR-ABL1 from the Breakpoint Cluster Region (BCR) sequence and the Abelson (ABL1) gene. Despite BCR-ABL1 being one of the most studied oncogenic proteins, some molecular mechanisms remain enigmatic, and several of the proteins, acting either as positive or negative BCR-ABL1 regulators, are still unknown. The Drosophila melanogaster represents a powerful tool for genetic investigations and a promising model to study the BCR-ABL1 signaling pathway. To identify new components involved in BCR-ABL1 transforming activity, we conducted an extensive genetic screening using different Drosophila mutant strains carrying specific small deletions within the chromosomes 2 and 3 and the gmrGal4,UAS-BCR-ABL1 4M/TM3 transgenic Drosophila as the background. From the screening, we identified several putative candidate genes that may be involved either in sustaining chronic myeloid leukemia (CML) or in its progression. We also identified, for the first time, a tight connection between the BCR-ABL1 protein and Rab family members, and this correlation was also validated in CML patients. In conclusion, our data identified many genes that, by interacting with BCR-ABL1, regulate several important biological pathways and could promote disease onset and progression.

Iron is crucial to satisfy several mitochondrial functions including energy metabolism and oxidative phosphorylation. Patients affected by Myelodysplastic Syndromes (MDS) and acute myeloid leukemia (AML) are frequently characterized by iron overload (IOL), due to continuous red blood cell (RBC) transfusions. This event impacts the overall survival (OS) and it is associated with increased mortality in lower-risk MDS patients. Accordingly, the oral iron chelator Deferasirox (DFX) has been reported to improve the OS and delay leukemic transformation. However, the molecular players and the biological mechanisms laying behind remain currently mostly undefined. The aim of this study has been to investigate the potential anti-leukemic effect of DFX, by functionally and molecularly analyzing its effects in three different leukemia cell lines, harboring or not p53 mutations, and in human primary cells derived from 15 MDS/AML patients. Our findings indicated that DFX can lead to apoptosis, impairment of cell growth only in a context of IOL, and can induce a significant alteration of mitochondria network, with a sharp reduction in mitochondrial activity. Moreover, through a remarkable reduction of Murine Double Minute 2 (MDM2), known to regulate the stability of p53 and p73 proteins, we observed an enhancement of p53 transcriptional activity after DFX. Interestingly, this iron depletion-triggered signaling is enabled by p73, in the absence of p53, or in the presence of a p53 mutant form. In conclusion, we propose a mechanism by which the increased p53 family transcriptional activity and protein stability could explain the potential benefits of iron chelation therapy in terms of improving OS and delaying leukemic transformation.

During the phase of proliferation needed for hematopoietic reconstitution following transplantation, hematopoietic stem/progenitor cells (HSPC) must express genes involved in stem cell self-renewal. We investigated the expression of genes relevant for self-renewal and expansion of HSPC (operationally defined as CD34+ cells) in steady state and after transplantation. Specifically, we evaluated the expression of ninety-one genes that were analyzed by real-time PCR in CD34+ cells isolated from (i) 12 samples from umbilical cord blood (UCB), (ii) 15 samples from bone marrow healthy donors, (iii) 13 samples from bone marrow after umbilical cord blood transplant (UCBT), and (iv) 29 samples from patients after transplantation with adult hematopoietic cells. The results show that transplanted CD34+ cells from adult cells acquire an asset very different from transplanted CD34+ cells from cord blood. Multivariate machine learning analysis (MMLA) showed that four specific gene signatures can be obtained by comparing the four types of CD34+ cells. In several, but not all cases, transplanted HSPC from UCB overexpress reprogramming genes. However, these remarkable changes do not alter the commitment to hematopoietic lineage. Overall, these results reveal undisclosed aspects of transplantation biology.

BCR-ABL1 fusion transcript is the minimal residual disease marker in chronic myeloid leukemia, 2% of patients show unusual breakpoints generating atypical transcripts, not quantifiable by standardized real-time PCR (RT&ndash, PCR). Response monitoring is performed by non-quantitative NESTED PCR, useless for evaluating patients&rsquo, molecular remission, excluding them from treatment-free-remission protocols. Droplet digital PCR (ddPCR) is highly sensitive technology, allowing an absolute quantification independent of standard curves. Based on this, we have developed assays able to evaluate the molecular response in atypical patients. We designed new ddPCR-based molecular assays able to quantify atypical BCR-ABL1 transcripts, with a detection limit of 0.001%, validated in a cohort of 65 RNA from 11 patients. Fifty samples were identified congruently by ddPCR and NESTED PCR (40 positives and 10 negatives for atypical BCR&ndash, ABL1 transcript), while 11 positive samples were detected only by ddPCR. Our results highlight ddPCR usefulness, primarily when the BCR&ndash, ABL1/ABL1 level is less than 1.5% and NESTED PCR results are often inaccurate. Furthermore, we identified 3 patients who maintained a deep molecular response for at least one year, who could be considered good candidates for treatment-free remission approaches. Here, we describe a new promising molecular approach, highly sensitive, to monitor atypical BCR&ndash, ABL1 patients, paving the foundation to include them in treatment-free remission protocols.

Myelodysplastic syndromes (MDS) are hematological malignancies characterized by ineffective hematopoiesis and increased apoptosis in the bone marrow, which cause peripheral cytopenia. Mitochondria are key regulators of apoptosis and a site of iron accumulation that favors reactive oxygen species (ROS) production with detrimental effects on cell survival. Although the energy metabolism could represent an attractive therapeutic target, it was poorly investigated in MDS. The purpose of the study was to analyze how the presence of myelodysplastic hematopoiesis, iron overload and chelation impact on mitochondrial metabolism. We compared energy balance, OxPhos activity and efficiency, lactic dehydrogenase activity and lipid peroxidation in mononuclear cells (MNCs), isolated from 38 MDS patients and 79 healthy controls. Our data show that ATP/AMP ratio is reduced during aging and even more in MDS due to a decreased OxPhos activity associated with an increment of lipid peroxidation. Moreover, the lactate fermentation enhancement was observed in MDS and elderly subjects, probably as an attempt to restore the energy balance. The biochemical alterations of MNCs from MDS patients have been partially restored by the in vitro iron chelation, while only slight effects were observed in the age-matched control samples. By contrast, the addition of iron chelators on MNCs from young healthy subjects determined a decrement in the OxPhos efficiency and an increment of lactate fermentation and lipid peroxidation. In summary, MDS-MNCs display an altered energy metabolism associated with increased oxidative stress, due to iron accumulation. This condition could be partially restored by iron chelation.

Myeloproliferative neoplasms are divided into essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF). Although ruxolitinib was proven to be effective in reducing symptoms, patients rarely achieve complete molecular remission. Therefore, it is relevant to identify new therapeutic targets to improve the clinical outcome of patients. Bcl-xL protein, the long isoform encoded by alternative splicing of the Bcl-x gene, acts as an anti-apoptotic regulator. Our study investigated the role of Bcl-xL as a marker of severity of MPN and the possibility to target Bcl-xL in patients. 129 MPN patients and 21 healthy patients were enrolled in the study. We analysed Bcl-xL expression in leucocytes and in enriched CD34+ and CD235a+ cells. Furthermore, ABT-737, a Bcl-xL inhibitor, was tested in HEL cells and in leucocytes from MPN patients. Bcl-xL was found progressively over-expressed in cells from ET, PV and PMF patients, independently by JAK2 mutational status. Moreover, our data indicated that the combination of ABT-737 and ruxolitinib resulted in a significantly higher apoptotic rate than the individual drug. Our study suggests that Bcl-xL plays an important role in MPN independently from JAK2 V617F mutation. Furthermore, data demonstrate that targeting simultaneously JAK2 and Bcl-xL might represent an interesting new approach.

TO THE EDITOR: The Imatinib Suspension and Validation (ISAV) study1 is a multicenter trial of imatinib discontinuation (ID) among patients with chronic myeloid leukemia (CML) in undetectable deep molecular remission (U-DMR). After 12 months of follow-up, 48% of patients relapsed (total n = 107), with the majority of relapses occurring within the first 9 months. An inverse relationship between patient age and risk of relapse was also observed at this timepoint. Here we report the final results of ISAV after a median follow-up of 49 months, as well as the dynamics of leukemic tumor load as determined by digital polymerase chain reaction (dPCR) in nonrelapsed patients. This trial is registered at www.clinicaltrials.gov (NCT01578213). Eligible patients were 18 years and older and had CML, either in chronic or accelerated phase, with U-DMR of at least 18 months’ duration and at least...

Background: Acute myeloid leukemia is a heterogeneous hematological disease, characterized by karyotypic and molecular alterations. Mutations in IDH2 have a role in diagnosis and as a minimal residue disease marker. Often the variant allele frequency during follow up is less than 20%, which represents the limit of detection of Sanger sequencing. Therefore, the development of sensitive methodologies to identify IDH2 mutations might help to monitor patients&rsquo, response to therapy. We compared three different methods to identify and monitor IDH2 mutations in patients&rsquo, specimens. Methods: Performances of PNA-PCR clamping, droplet digital PCR and Sanger for IDH2 status identification were evaluated and compared in 96 DNA patients&rsquo, specimens. Results: In contrast with Sanger sequencing, our results highlighted the concordance between PNA clamping and digital PCR. Furthermore, PNA-PCR clamping was able to detect more mutated DNA with respect to Sanger sequencing that showed several false negatives independently from the allelic frequency. Conclusions: We found that PNA-PCR clamping and digital PCR identified IDH2 mutations in DNA samples with comparable results in a percentage significantly higher compared to Sanger sequencing. PNA-PCR clamping can be used even in laboratories not equipped for sophisticated analyses, decreasing cost and time for IDH2 characterization.

Acute myeloid leukemia is a genetically heterogeneous disease characterized by the accumulation of mutations in hematopoietic progenitor cells. For its heterogeneity, prognostic markers are very useful for therapeutic choice. The most important prognostic markers are age, white blood cell count, chromosomal alterations and gene mutations. Recent works have studied the prognostic significance of WT1 polymorphisms and mutations, highlighting the role of SNP rs16754 as a positive prognostic factor in AML patients. Nevertheless, the data are still unclear. To investigate the role of WT1 rs16754 polymorphism in AML, we designed a new tool for the detection using PNA directed PCR Clamping technology. Our data were able to establish a correlation between SNP rs16754 and the clinical outcome. Our results support the hypothesis that rs16754 polymorphism is an independent positive prognostic molecular marker that could be useful for therapeutic choice. In view of this, we described a novel assay faster, more sensitive and cheaper than DNA sequencing. The assay allows evaluating WT1 rs16754 polymorphism in diagnostic routine to improve prognostic information faster and without over-costing for diagnostic laboratories.

// Valentina Rosso 1 , Jessica Petiti 1 , Enrico Bracco 2 , Roberto Pedrola 1 , Francesca Carnuccio 1 , Elisabetta Signorino 1 , Sonia Carturan 1 , Chiara Calabrese 1 , Giada Bot-Sartor 1 , Michela Ronconi 1 , Anna Serra 1 , Giuseppe Saglio 1 , Francesco Frassoni 3 , Daniela Cilloni 1 1 Department of Clinical and Biological Sciences, University of Turin, Turin, Italy 2 Department of Oncology, University of Turin, Turin, Italy 3 Department of Pediatric Hemato-Oncology and Stem Cell, Cellular Therapy Laboratory, Institute G. Gaslini, Genova, Italy Correspondence to: Daniela Cilloni, email: daniela.cilloni@unito.it Keywords: CALR, PNA, MPN, PCR clamping, diagnostic assay Received: September 14, 2016 Accepted: December 15, 2016 Published: December 23, 2016 ABSTRACT The myeloproliferative neoplasms are chronic myeloid cancers divided in Philadelphia positive (Ph+), chronic myeloid leukemia, or negative: polycythemia vera (PV) essential thrombocythemia (ET), and primary myelofibrosis (PMF). Most Ph negative cases have an activating JAK2 or MPL mutation. Recently, somatic mutations in the calreticulin gene ( CALR ) were detected in 56–88% of JAK2/MPL -negative patients affected by ET or PMF. The most frequent mutations in CARL gene are type-1 and 2. Currently, CALR mutations are evaluated by sanger sequencing. The evaluation of CARL mutations increases the diagnostic accuracy in patients without other molecular markers and could represent a new therapeutic target for molecular drugs. We developed a novel detection assay in order to identify type-1 and 2 CALR mutations by PNA directed PCR clamping. Seventy-five patients affected by myeloproliferative neoplasms and seven controls were examined by direct DNA sequencing and by PNA directed PCR clamping. The assay resulted to be more sensitive, specific and cheaper than sanger sequencing and it could be applied even in laboratory not equipped for more sophisticated analysis. Interestingly, we report here a case carrying both type 1 and type2 mutations in CALR gene.

In most of the acute myeloid leukemia patients there is an aberrant tyrosine kinase activity. The prototype of Sprouty proteins was originally identified in Drosophila melanogaster as antagonists of Breathless, the mammalian ortholog of fibroblast growth factor receptor. Usually, SPRY family members are inhibitors of RAS signaling induced by tyrosine kinases receptors and they are implicated in negative feedback processes regulating several intracellular pathways. The present study aims to investigate the role of a member of the Sprouty family, Sprouty1, as a regulator of cell proliferation and growth in patients affected by acute myeloid leukemia. Sprouty1 mRNA and protein were both significantly down-regulated in acute myeloid leukemia cells compared to the normal counterpart, but they were restored when remission is achieved after chemotherapy. Ectopic expression of Sprouty1 revealed that it plays a key role in the proliferation and apoptotic defect that represent a landmark of the leukemic cells. Our study identified Sprouty1 as negative regulator involved in the aberrant signals of adult acute myeloid leukemia. Furthermore, we found a correlation between Sprouty1 and FoxO3a delocalization in acute myeloid leukemia (AML) patients at diagnosis, suggesting a multistep regulation of RAS signaling in human cancers.

Introduction. Discontinuation (D/C) of Imatinib or other TKIs in Chronic Myeloid Leukemia (CML) represents an important issue in the management of this disease. It is generally accepted that relapse develops (and treatment must be resumed) when patients (pts) lose Major Molecular Remission (MMR), i.e. when the amount of the BCR-ABL1 transcript, measured in peripheral blood by RT-PCR, exceeds 0.1 %. The Imatinib Suspension And Validation (ISAV) study, which started in 2011, enrolled pts with CML treated with Imatinib who showed no evidence of BCR-ABL1 transcript for at least 18 months before enrollment. Methods. A digital PCR (dPCR) for BCR-ABL1 was performed at the time of Imatinib D/C while a second dPCR was performed when non relapsed patients exited the study, 36 months later. dPCR experiments were performed by the QX200 system (BioRad) in the same lab and using the same methodology. The BCR-ABL1 fusion and ABL1 transcripts were quantified using DigiDrop P210 MasterMix and DigiDrop P210 Positive Control (Bioclarma), according to manufacturer's protocol. The target concentration in each sample was expressed as percentage of BCR-ABL1/ABL1. Results. A total of 107 pts were enrolled in the ISAV study. Relapses occurred in 54 pts (52%); among the 53 non relapsed pts, 41 (77%) presented at least one positive RT-PCR result following Imatinib D/C, and only 12 (23%) maintained PCR negativity throughout the duration of the study. Among the non-relapsed pts dPCR performed at treatment D/C showed positivity in 20.6% of cases (95% confidence interval [C.I.] 9-36%), while 91.1% of pts (95%, C.I. 80-97%) evaluated 36 months later showed a positive dPCR value, although no patient resumed treatment. The evaluation of non relapsed pts by dPCR showed that mean values at D/C were 0.00143% +/- 0.0006 (SE); when tested at study exit, the same pts showed average dPCR values of 0.0115 % +/- 0.002. This difference is statistically highly significant and corresponds to a change of approximately 1 log in the residual tumor burden: from 2x107 to 2x108 cells. There was no correlation between the results of RT-PCR performed during the study and the dPCR status at study exit: pts who tested negative by RT-PCR during the study were uniformly negative in dPCR at D/C but tested positive at study exit in 83.3% of cases; pts who showed at least on positive RT-PCR during the study showed positivity by dPCR in 25% at D/C and in 89.3% at study exit. Finally, half of the pts who tested negative by dPCR at study exit showed dPCR positivity when tested at the time of Imatinib D/C. Conclusions. These results show that during a three year period, the D/C of Imatinib led to the increase of approximately 1 log in the tumour burden of non-relapsed pts, although none of them lost MMR and resumed treatment. These data strongly indicate the need for a long-term monitoring of pts who D/C Imatinib; they also suggest that the functional status of residual CML cells rather than their number could represent the critical factor to predict the tumour load present after 3 years of Imatinib D/C. Disclosures Le Coutre: Incyte: Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Pfizer: Honoraria, Speakers Bureau; Bristol-Myers Squibb: Honoraria, Speakers Bureau. Elena:Novartis: Consultancy; Pfizer: Consultancy. Assouline:Abbvie: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria. Stagno:Incyte: Honoraria; Novartis: Honoraria; Pfizer: Honoraria; BMS: Honoraria. Iurlo:Novartis: Other: Speaker Honoraria; Incyte: Other: Speaker Honoraria; Pfizer: Other: Speaker Honoraria. Kim:Novartis: Research Funding; BMS: Research Funding; Pfizer: Research Funding; Takeda: Research Funding; Il-Yang co.: Research Funding. Fava:Pfizer: Honoraria; Novartis: Honoraria; Incyte: Honoraria; BMS: Honoraria. Gambacorti-Passerini:Bristol-Meyers Squibb: Consultancy; Pfizer: Honoraria, Research Funding.

New techniques are on the horizon for the detection of small leukemic clones in both, acute leukemias and myeloproliferative disorders. A promising approach is based on digital polymerase chain reaction (PCR). Digital PCR (dPCR) is a breakthrough technology designed to provide absolute nucleic acid quantification. It is particularly useful to detect a low amount of target and therefore it represents an alternative method for detecting measurable residual disease (MRD). The main advantages are the high precision, the very reliable quantification, the absolute quantification without the need for a standard curve, and the excellent reproducibility. Nowadays the main disadvantages of this strategy are the costs that are still higher than standard qPCR, the lack of standardized methods, and the limited number of laboratories that are equipped with instruments for dPCR. Several studies describing the possibility and advantages of using digital PCR for the detection of specific leukemic transcripts or mutations have already been published. In this review we summarize the available data on the use of dPCR in acute myeloid leukemia and myeloproliferative disorders.

Background: Monitoring of BCR-ABL1 molecular levels is essential for the management of Chronic Myeloid Leukemia (CML) patients treated with Tyrosine Kinases Inhibitors (TKIs). Real Time Quantitative PCR (RT-qPCR) is currently the standard method for assessing molecular remission (MR) in patients with CML. Recently, droplet digital PCR (ddPCR) has emerged to provide a more accurate detection of minimal residual disease (MRD). In order to hypothesize the use of this new technology in the clinical practice, in the era of TKI discontinuation, we designed a multi-centric study to evaluate the potential value of ddPCR in diagnostic routine. Aims of the study were:1) the evaluation of the agreement between the measures obtained by ddPCR and RT-qPCR and 2) the assessment of the repeatability of the two methods. Methods: Total RNA was extracted from 37 CML patients using Maxwell 16 LEV simplyRNA Blood kit (Promega), following the manufacturer's instructions. Samples were divided in 5 groups based on molecular response (MR) as follow: group 1, MR Statistical analysis: Bland-Altman analysis was performed. For the measurement of the agreement we reported the bias, which is the mean of the difference between the methods, the 95% limits of agreement and the coefficient of variation. Residual variance and coefficients of repeatability (i.e. the upper limits of a prediction interval for the absolute difference between two measurements by the same method on the same item) were computed to achieve the second endpoint. An analysis of sensitivity on the labs was also carried out. All analyses were stratified by the level of disease. Results: A total of 370 measures were included in the analysis, 185 for ddPCR and 185 for RT-qPCR divided as follow: 50 for group 1 and for group 2, 90 for group 3, 4 and 5. In Table 1 we reported the median and interquartile range (IQR) for all levels of disease. Results of the Bland-Altman analysis are shown in Table 2. The coefficients of variation, which expresses the standard deviation as a percentage of the mean, were 2.35, 2.31, 1.10, 1.34, 39.12 in group 1, 2, 3, 4 and 5 respectively. The repeatability coefficients of ddPCR were smaller than qRT-PCR across all the levels of disease, showing a slightly better precision of ddPCR (Table 2). Conclusions: Higher coefficients of variation in group 1 and 2 were probably due to a greater heterogeneity of the patients. In fact, BCR-ABL1/ABL1 levels by RT-qPCR ranged between 1.43 and 6.94 and between 0.10 and 0.25 in group 1 and in group 2 respectively (Table 1). Sensitivity analysis showed that the high coefficient of variation in group 5 can be explained almost all by the variability observed in Lab B. Coefficient of repeatability of ddPCR was always smaller than RT-qPCR for all level of disease showing a slightly better precision. Our results showed that ddPCR has a good agreement with RT-qPCR and it is more precise to quantify BCR-ABL1 transcript levels, particularly for MR 4 and MR 4.5. Thus, ddPCR may be valuable in diagnostic routine. Disclosures Fava: Novartis: Honoraria; BMS: Honoraria; Pfizer: Honoraria; Incyte: Honoraria. Martino:Bio-Rad: Employment. Saglio:Ariad: Consultancy; Incyte: Consultancy; Pfizer: Consultancy; Jansen: Consultancy; Celgene: Consultancy; Novartis: Consultancy; BMS: Consultancy. Martinelli:Roche: Consultancy; BMS: Consultancy; Novartis: Consultancy; ARIAD: Consultancy; Pfizer: Consultancy. Pane:Novartis: Membership on an entity's Board of Directors or advisory committees, Other: research founding; Janssen: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees. Cilloni:Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees.

Simple Summary The diagnostic and clinical success of standardization of BCR-ABL1 p210 monitoring in chronic myeloid leukemia patients could be seen as a good example for further standardization of molecular monitoring in other gene rearrangements. In this review, we present the chronology of more than 20 years of scientific work that allowed to achieve this result. We believe that this paper will be useful for researchers who approach the chronic myeloid leukemia field. Abstract The introduction of tyrosine kinase inhibitors in 2001 as a targeted anticancer therapy has significantly improved the quality of life and survival of patients with chronic myeloid leukemia. At the same time, with the introduction of tyrosine kinase inhibitors, the need for precise monitoring of the molecular response to therapy has emerged. Starting with a qualitative polymerase chain reaction, followed by the introduction of a quantitative polymerase chain reaction to determine the exact quantity of the transcript of interest-p210 BCR-ABL1, molecular monitoring in patients with chronic myeloid leukemia was internationally standardized. This enabled precise monitoring of the therapeutic response, unification of therapeutic protocols, and comparison of results between different laboratories. This review aims to summarize the steps in the diagnosis and molecular monitoring of p210 BCR-ABL1, as well as to consider the possible future application of a more sophisticated method such as digital polymerase chain reaction.

The Wilms tumor gene WT1 is a useful marker of clonal hematopoiesis and it has been shown to be a good marker of residual disease and it reflects the response to therapy. Although myelofibrosis is characterized by mutations of JAK2 and calreticulin (CALR), these mutations are not useful to monitor response to therapy. In this study we demonstrated that in patients affected by myelofibrosis WT1 correlates with the International Prognostic Scoring System (IPSS) score at diagnosis. Furthermore WT1 is a good marker of response to JAK2 inhibitors especially for patients without blasts and for patients who develop anemia or thrombocytopenia not for progression but as therapy related toxicity. Finally, WT1 transcript reduction can mirror a benefit of therapy on the disease burden. This study demonstrated that WT1 is a good marker for monitoring the response to therapy in patients affected by myelofibrosis.

Meningioma 1 (MN1) gene overexpression has been reported in acute myeloid leukaemia (AML) patients and identified as a negative prognostic factor. In order to characterize patients presenting gene overexpression and to verify if MN1 transcript could be a useful marker for minimal residual disease detection, MN1 was quantified in 136 AML patients with different cytogenetic risk and in 50 normal controls. In 20 patients bearing a fusion gene transcript suitable for minimal residual disease quantitative assessment and in 8 patients with NPM1 mutation, we performed a simultaneous analysis of MN1 and the fusion-gene transcript or NPM1 mutation during follow-up. Sequential MN1 and WT1 analysis was also performed in 13 AML patients lacking other molecular markers. The data obtained show that normal cells consistently express low levels of MN1 transcript. In contrast, high levels of MN1 expression are present in 47% of patients with normal karyotype and in all cases with inv(16). MN1 levels during follow-up were found to follow the pattern of other molecular markers (fusion gene transcripts, NPM1 and WT1). Increased MN1 expression in the BM during follow up was always found to be predictive of an impending hematological relapse.

To the Editor: Many anti‐cancer vaccination strategies have been tested in mice and humans in the attempt to eradicate leukemia cells 1. The vast majority of clinical trials are based on peptide vaccination which allows the induction of cellular response to specific tumor associated antigens 2. WT1(Wilms tumor‐1) gene is located on chromosome 11p13 and encodes a zinc finger transcription factor that plays an important role in cell growth and differentiation. WT1 was originally described as a tumor suppressor gene although many evidences demonstrated that it plays an oncogenic function in the setting of leukemia. WT1 protein represents an optimal tumor antigen since it is highly expressed in acute leukemias, myelodysplastic syndromes (MDS) and myeloproliferative neoplasms 3. By contrast, it is expressed at very low levels in normal hematopoietic progenitors. Expression of the WT1 protein is restricted to a limited set of tissues, including the gonads, uterus, kidney, and spleen.

Mutations of the BCR-ABL1 fusion gene represent a well established cause of resistance to tyrosine kinase inhibitors. Among the different mutations identified T315I is of particular concern since it is not effectively targeted by the majority of Tyrosine Kinase Inhibitors so far available. We developed a novel assay based on peptide nucleic acid (PNA) technology coupled to immunofluorescence microscopy (PNA-FISH) for the specific detection at a single cell level of BCR-ABL T315I mutation thus improving both, diagnostic resolution and the study of clonal prevalence. Furthermore we developed an additional method based on PNA directed PCR-clamping for the fast and easy detection of the mutation. The PNA directed PCR clamping allows to detect an amount of mutated template as low as 0.5 %. This method is highly sensitive, specific and cheap and could be applied even in laboratory not equipped for more sophisticated analysis. Furthermore, the PNA FISH method allows to identify a small amount of progenitor cells still present after therapy with specific inhibitors. We present here two different methods based on PNA for the detection of T315I useful for different purposes. PNA-FISH can be used to study clonal evolution. In addition, this method could help in the study of compound mutations being able to identify two different mutations in a single cell. PNA directed PCR clamping although not superior to sequencing can be applied worldwide even in laboratory not equipped to search for mutations.

Abstract 3732 Background: The BCR-ABL T315I mutation at the gatekeeper residue is frequent in advanced phases of chronic myeloid leukemia (CML) and is one of the main cause of resistance to Tyrosine Kinase Inhibitors (TKI) by disrupting important contact points between the drugs and the enzyme. Although this mutation can be detected by different techniques and at different levels of the mutated clone, the prognostic significance of the absolute amount of the mutated allele is widely unknown. The aim of the study was to develope a novel assay based on peptide nucleic acid (PNA) technology coupled to immuno-fluorescence microscopy (PNA-FISH) for the specific detection at a single cell level of T315I mutation thus improving both the diagnostic resolution and the knowledge on the behaviour of the mutated clone. Methods: We designed a fluorescently-labelled PNA probe, coupled to FISH technology, which allows to distinguish with a high degree of specificity between CD34+ progenitor stem cells harbouring T315I mutation or the wild type form of BCR-ABL. CD34+ cells were enriched from CML patients who were positive for T315I mutation, or from patients who lost T315I mutation after ponatinib treatment. In addition we tested CML patients without T315I mutation as control and BM samples from healthy donors to establish the specificity of the method. CD34+ progenitors cells were enriched by MACS and then cytospun onto slides and hybridized with human species-specific fluorescinated 15 base pairs (bp)-long oligo-PNA, specifically recognizing the BCR-ABL T315I sequence. Slides were analyzed by fluorescence confocal microscopy. Results: We found, with a rather wide variability occurring among patients, a percentage of mutated CD34+ cells ranging from 3 to 90%. In addition these data indicate that fluorescinated BCR-ABL T315I/PNA probe displays a very high specificity towards a single base-pair mismatch. Interestingly, when evaluating the presence of T315I positive cells collected from a patient who lost the mutation (evaluated by sequencing) after ponatinib therapy and acquired T317 mutation a small amount of T315I positive CD34+ cells were still present. This percent did not exceeded 2% of the total CD34+ cell population. Importantly, the lack of positivity detected in CD34 positive cells from CML patient without mutations or in 20 healthy subjects demonstrates a high specificity of this method. Conclusions: BCR/ABL T315I/PNA probe method displays high specificity and reliability in discriminating cell subpopulations harbouring the mutation. In addition, it allows to analyze the CD34+ population at the single cell level and to monitor the behaviour of the clone at the stem/progenitor cell level. This approach allows to monitor longitudinally the evolution of the mutated population over time, the response to specific drugs active against T315I mutants and to characterization the mutated stem/progenitor cell compartment in patients with CML. Disclosures: Saglio: Novartis: Consultancy, Speakers Bureau; BMS: Consultancy, Speakers Bureau; Pfizer: Consultancy.