Kaddour Chabane

High DNA Methyltransferase DNMT3B Levels: A Poor Prognostic Marker in Acute Myeloid Leukemia

It has been recently shown that DNA methyl transferase overexpression is correlated with unfavourable prognosis in human malignancies while methylation deregulation remains a hallmark that defines acute myeloid leukemia (AML). The oncogenic transcription factor EVI1 is involved in methylation deregulation and its overexpression plays a major role for predicting an adverse outcome. Moreover, the identification of DNMT3A mutations in AML patients has recently been described as a poor prognostic indicator. In order to clarify relationship between these key actors in methylation mechanisms and their potential impact on patient outcomes, we analysed 195 de novo AML patients for the expression of DNMT3A, 3B (and its non-catalytic variant 3BNC) and their correlations with the outcome and the expression of other common prognostic genetic biomarkers (EVI1, NPM1, FLT3ITD/TKD and MLL) in adult AML. The overexpression of DNMT3B/3BNC is (i) significantly correlated with a shorter overall survival, and (ii) inversely significantly correlated with event-free survival and DNMT3A expression level. Moreover, multivariate analysis showed that a high expression level of DNMT3B/3BNC is statistically a significant independent poor prognostic indicator. This study represents the first report showing that the overexpression of DNMT3B/3BNC is an independent predictor of poor survival in AML. Its quantification should be implemented to the genetic profile used to stratify patients for therapeutical strategies and should be useful to identify patients who may benefit from therapy based on demethylating agents.

The Durable Clearance of the T315I BCR-ABL Mutated Clone in Chronic Phase Chronic Myelogenous Leukemia Patients on Omacetaxine Allows Tyrosine Kinase Inhibitor Rechallenge

PURPOSE The onset of a BCR-ABLT315I mutation during the course of chronic myelogenous leukemia (CML) on tyrosine kinase inhibitors (TKIs) usually results in poor survival, and therapeutic options remain few in the absence of any allogeneic donor. PATIENTS AND METHODS We have investigated the affect of subcutaneous omacetaxine (OMA, or homo-harringtonine) cycles on unmutated and T315I-mutated BCR-ABL transcripts in a series of 8 TKI-resistant chronic-phase CML patients and we have addressed the question of whether the administration of OMA could resensitize patients to TKIs. Patients were regularly monitored for total disease burden and for BCR-ABLT315I transcripts using a new quantitative sensitive technique (sensitivity threshold, 0.05%), for up to 27 cycles of OMA. RESULTS Overall, patients demonstrated hematologic, cytogenetic, or molecular improvement. An initial rapid decline and a sustained disappearance of T315I-mutated transcripts were observed in 50% of patients, after a median of 10.5 cycles (range, 3-27 cycles) of OMA. As the unmutated leukemic burden reduction was modest, 2 patients were submitted to nilotinib after 9 months of sustained BCR-ABLT315I transcripts negativity on OMA and mutated transcripts remained undetectable after a median follow-up of 12 months on nilotinib challenge. CONCLUSION We suggest that OMA (ie, a non-targeted therapy) might provide a better disease control allowing the disappearance of the mutated clone probably elicited by the clone deselection after TKI release, and/or a preferential activity of OMA on the T315I-mutated cells through unknown mechanisms. These observations suggest that OMA could allow a safe TKI rechallenge in patients with resistant chronic-phase CML.

Longitudinal studies of SRC family kinases in imatinib- and dasatinib-resistant chronic myelogenous leukemia patients

This report aims to more accurately define the frequency of the involvement of SRC Family Kinases (SFKs) in imatinib- and dasatinib-resistant CML patients. Clinical samples were analysed during in vivo treatment. We confirmed the high frequency of SFKs involvement in Tyrosine kinase inhibitor-resistant CML (52% of the cases) and even further in progressive disease and blast crises (60% of the cases). The SFKs deregulation is also observed in patients harboring BCR-ABL mutations. In T315I and F317L mutated patients, CML-resistance appears to be promoted by SFKs kinase protein reactivation once the BCR-ABL mutated clone has decreased on Omacetaxine.

Pegylated IFN-α2a combined to imatinib mesylate 600 mg daily can induce complete cytogenetic and molecular responses in a subset of chronic phase CML patients refractory to IFN alone or to imatinib 600 mg daily alone

This phase I/II study was designed to demonstrate the tolerance and the efficacy of a combination of pegylated interferon-α 2a to Imatinib mesylate (IM) 600mg daily in cytogenetically IM-resistant but in CHR chronic phase CML patients. The combination was generally well tolerated in the 15 evaluable patients. A significant reduction of the Ph1(+) BM metaphases was observed in these poor prognosis patients, with 2 long-term CCyR including 2 MMR. After a median follow-up of 43 months, 93% of patients are alive. The addition of PegIFNα2a to IM600 is feasible, and able to overcome resistance within this context.

Molecular characterization and follow-up of five CML patients with new BCR–ABL1 fusion transcripts

We report five chronic myeloid leukaemia (CML) patients in whom we identified and characterized undescribed BCR–ABL1 fusion transcripts. We investigated the precise features of the molecular rearrangements and the minimal residual disease follow‐up for these five patients. Three resulted from new rearrangements between the BCR and ABL1 sequences (the breakpoints being located within BCR exon 13 in two cases and within BCR exon 18 in one case). The other two cases revealed a complex e8‐[ins]‐a2 fusion transcript involving a third partner gene, PRDM12 and SPECC1L, respectively. Moreover, single nucleotide polymorphism‐array analysis performed in the latter two cases showed copy number alterations shared by the two patients, thus identifying genes that were deleted during rearrangement and suggesting their potential role in CML pathogenesis. Interestingly, we highlight that the prognosis of alterations, such as the presence of an e8a2 transcript or the deletion of various genes, which have been controversial, may be definitively erased by the introduction of tyrosine kinase inhibitors (TKIs).

Detection of twelve nucleotides insertion in the BCR-ABL kinase domain in an imatinib-resistant but dasatinib-sensitive patient with bi-phenotypic acute leukemia.

Although targeted inhibition of BCR-ABL by imatinib (IM) is an effective therapy for patients with Philadelphia chromosome-positive leukemias, a minority of patients, most of them in advanced phase, acquire mutations in the BCR-ABL kinase domain (KD) leading to relapse.[1][1]–[5][2] These