Julie Quessada

Myeloid/lymphoid neoplasms with tyrosine kinase rearrangements (MLN-TKs) are rare clonal eosinophilias driven by PDGFRA, PDGFRB and other kinase fusions, highly sensitive to tyrosine kinase inhibitors. Their detection remains challenging, particularly for cryptic PDGFRA rearrangements. We performed a large multicenter real-world validation of the generic quantitative RT-PCR assay (gPDGFR), which detects 3′ PDGFRA/PDGFRB overexpression independently of fusion partner. A total of 231 consecutive patients with hypereosinophilia from 12 French centers were analyzed, and assay robustness was further assessed in an independent heterogeneous cohort of 102 tyrosine kinase inhibitor (TKI)-treated patients. Twenty-two PDGFR-rearranged cases (14 PDGFRA-r, 8 PDGFRB-r) were identified. The assay demonstrated 100% sensitivity and 100% negative predictive value. For PDGFRA, positive predictive value and specificity reached 100%. In contrast, PDGFRB overexpression showed lower specificity due to borderline false-positive cases, underscoring the need for confirmatory testing. In selected patients, longitudinal gPDGFR kinetics paralleled fusion-specific RT-qPCR, supporting its use for molecular follow-up when dedicated assays are unavailable, although it does not provide quantitative measurable residual disease assessment. Overall, gPDGFR represents a robust, partner-independent first-line screening strategy that can be readily integrated into routine diagnostic workflows to enable timely identification of patients eligible for targeted therapy.

Myeloid/lymphoid neoplasms with tyrosine kinase rearrangements (MLN-TK) are rare clonal eosinophilias driven by PDGFRA, PDGFRB and other kinase fusions, highly sensitive to tyrosine kinase inhibitors. Their detection remains challenging, particularly for cryptic PDGFRA rearrangements. We performed a large multicenter real-world validation of the generic quantitative RT-PCR assay (gPDGFR), which detects 3′ PDGFRA/PDGFRB overexpression independently of fusion partner. A total of 231 consecutive patients with hypereosinophilia from 12 French centers were analyzed, and assay robustness was further assessed in an independent heterogeneous cohort of 102 TKI-treated patients. Twenty-two PDGFR-rearranged cases (14 PDGFRA-r, 8 PDGFRB-r) were identified. The assay demonstrated 100% sensitivity and 100% negative predictive value. For PDGFRA, positive predictive value and specificity reached 100%. In contrast, PDGFRB overexpression showed lower specificity due to borderline false-positive cases, underscoring the need for confirmatory testing. In selected patients, longitudinal gPDGFR kinetics paralleled fusion-specific RT-qPCR, supporting its use for molecular follow-up when dedicated assays are unavailable, although it does not provide quantitative measurable residual disease assessment. Overall, gPDGFR represents a robust, partner-independent first-line screening strategy that can be readily integrated into routine diagnostic workflows to enable timely identification of patients eligible for targeted therapy.

T-cell acute lymphoblastic leukemia (T-ALL) is a malignant proliferation of T-cell progenitors originating in the thymus. T-ALL is a heterogenous disease involving the dysregulation of various oncogenes/tumor-suppressor (TS) genes. Loss of the TS gene phosphatase and TENsin homolog (PTEN) is a recurrent alteration, which is often associated with a mature T-ALL subgroup expressing a T-cell receptor. Herein, we used a single-cell RNA-sequencing approach to investigate the impact of the absence of PTEN on pathological development of mouse thymocytes. First, our differential gene expression analysis of tumor cells vs physiologic cells uncovers an ectopic expression, in leukemic cells, of the gene encoding Bex1. Then, to determine the relevance of our observation in humans, we queried a public RNA-sequencing database from the TARGET-TCGA (Therapeutically Applicable Research to Generate Effective Treatments–The Cancer Genome Atlas) project. We show that BEX1, BEX2, and BEX5 genes are ectopically expressed in T-ALL samples and we further found that ectopic BEX expression is mainly restricted to the T-ALL subgroup overexpressing TAL1 oncogene. Proximity ligation assays demonstrated the nuclear colocalization of brain-expressed X-linked 1/2 (BEX1/2) proteins with T-cell acute lymphocytic leukemia protein 1 (TAL1) in T-ALL cells. To investigate their functional role, we generated Jurkat cells with a triple knockout of BEX1, BEX2, and BEX5 using CRISPR–CRISPR-associated protein 9. This genetic inactivation led to reduced cell proliferation, a loss of histone H3 lysine 4 monomethylation (H3K4me1) marks notably at genomic regions enriched for E-box motifs, and dysregulation of several TAL1 target genes. Collectively, our findings suggest that BEX1 and BEX2 may contribute to human T-ALL oncogenesis by acting as cofactors within the TAL1 complex.

We previously demonstrated that a reduced-intensity chemotherapy schedule can safely replace hyper-CVAD (cyclophosphamide-vincristine-doxorubicin [Adriamycin]-dexamethasone) cycle 1 when combined with imatinib in adults with Philadelphia-positive acute lymphoblastic leukemia. In the present randomized GRAAPH-2014 trial, we used nilotinib and addressed the omission of cytarabine (Ara-C) in consolidation. The primary objective was the major molecular response (MMR) rate measured by BCR::ABL1 quantification after cycle 4 (end of consolidation). All patients were eligible for allogeneic stem cell transplant (SCT), whereas those in MMR could receive autologous SCT, followed by 2-year imatinib maintenance in both cases. After the enrollment of 156 of 265 planed patients, the data and safety monitoring board decided to hold the randomization because of an excess of relapse in the investigational arm. Among the 155 evaluable patients, 76 received Ara-C during consolidation (arm A) and 79 did not (arm B). Overall, 133 patients (85%) underwent SCT, 93 allogeneic and 40 autologous. The noninferiority end point regarding MMR was reached with 71.1% (arm A) and 77.2% (arm B) of patients reaching MMR. However, the 4-year cumulative incidence of relapse was higher in arm B compared with arm A (31.3% [95% confidence interval {CI}, 21.1%-41.9%] vs 13.2% [95% CI, 6.7%-21.9%]; P = .017), which translated to a lower relapse-free survival. With a median follow-up of 3.8 years, 4-year overall survival was 79.0% (95% CI, 70.6%-89.3%) in arm A vs 73.4% (95% CI, 63.9%-84.4%) in arm B (P = .35). Despite a noninferior rate of MMR, more relapses were observed when ARA-C was omitted without impact on survival. ClinicalTrials.gov ID, NCT02611492.

Myeloproliferative neoplasms (MPN) are clonal hematopoietic stem cell-derived disorders characterized by uncontrolled proliferation of differentiated myeloid cells. Two main groups of MPN, BCR::ABL1-positive (Chronic Myeloid Leukemia) and BCR::ABL1-negative (Polycythemia Vera, Essential Thrombocytosis, Primary Myelofibrosis) are distinguished. For many years, cytomorphologic and histologic features were the only proof of MPN and attempted to distinguish the different entities of the subgroup BCR::ABL1-negative MPN. World Health Organization (WHO) classification of myeloid neoplasms evolves over the years and increasingly considers molecular abnormalities to prove the clonal hematopoiesis. In addition to morphological clues, the detection of JAK2, MPL and CALR mutations are considered driver events belonging to the major diagnostic criteria of BCR::ABL1-negative MPN. This highlights the preponderant place of molecular features in the MPN diagnosis. Moreover, the advent of next-generation sequencing (NGS) allowed the identification of additional somatic mutations involved in clonal hematopoiesis and playing a role in the prognosis of MPN. Nowadays, careful cytomorphology and molecular biology are inseparable and complementary to provide a specific diagnosis and to permit the best follow-up of these diseases.