No abstract

PAX5 is the main target of somatic mutations in acute B lymphoblastic leukemia (B-ALL). We analyzed 153 adult and child B-ALL harboring karyotypic abnormalities at chromosome 9p, to determine the frequency and the nature of PAX5 alterations. We found PAX5 internal rearrangements in 21% of the cases. To isolate fusion partners, we used classic and innovative techniques (rolling circle amplification-rapid amplification of cDNA ends) and single nucleotide polymorphism-comparative genomic hybridization arrays. Recurrent and novel fusion partners were identified, including NCoR1, DACH2, GOLGA6, and TAOK1 genes showing the high variability of the partners. We noted that half the fusion genes can give rise to truncated PAX5 proteins. Furthermore, malignant cells carrying PAX5 fusion genes displayed a simple karyotype. These data strongly suggest that PAX5 fusion genes are early players in leukemogenesis.

Pediatric acute myeloid leukemia (AML) is a rare disease whose prognosis is highly variable according to factors such as chromosomal abnormalities. Recurrent genomic rearrangements are detected in half of pediatric AML by karyotype. NUcleoPorin 98 (NUP98) gene is rearranged with 31 different fusion partner genes. These rearrangements are frequently undetected by conventional cytogenetics, as the NUP98 gene is located at the end of the chromosome 11 short arm (11p15). By screening a series of 574 pediatric AML, we detected a NUP98 rearrangement in 22 cases (3.8%), a frequency similar to CBFB-MYH11 fusion gene (4.0%). The most frequent NUP98 fusion gene partner is NSD1. These cases are homogeneous regarding their biological and clinical characteristics, and associated with bad prognosis only improved by bone marrow transplantation. We detailed the biological characteristics of these AML by exome sequencing which demonstrated few recurrent mutations (FLT3 ITD, WT1, CEBPA, NBPF14, BCR and ODF1). The analysis of the clonal structure in these cases suggests that the mutation order in the NUP98-rearranged pediatric AML begins with the NUP98 rearrangement leading to epigenetic dysregulations then followed by mutations of critical hematopoietic transcription factors and finally, activation of the FLT3 signaling pathway.

Ibrutinib, obinutuzumab plus venetoclax demonstrate synergy in pre-clinical models of mantle-cell lymphoma (MCL). OAsIs (NCT02558816), a single-arm multi-center prospective phase I/II trial, aimed to determine the maximum tolerated dose (MTD) of venetoclax in combination with fixed doses of ibrutinib and obinutuzumab, in relapsed MCL patients. At the venetoclax MTD, extension cohorts were opened for relapsed and untreated patients. Safety and efficacy were secondary objectives. Minimal residual disease (MRD) was assessed by allele-specific oligonucleotide-quantitative polymerase chain reaction (ASO-qPCR). Between Oct 14, 2015 to May 29, 2018, forty-eight patients were enrolled. No dose limiting toxicity (DLT) was reported, and venetoclax at 400mg per day was chosen for extension. Eighteen (75%) relapsed and 8 (53%) untreated patients experienced grade 3/4 adverse events (AEs). The complete response rate assessed by positron-emission tomography at the end of cycle 6 was 67% in relapsed and 86.6% in untreated patients. MRD clearance for evaluable patients was seen in 71.5% of relapsed (10 out of 14) and 100% of untreated MRD-evaluable patients (n=12), at the end of three cycles. The median follow-up (mFU) for relapsed patients was 17 months (range, 10 to 35). The 2-years PFS was 69.5% (95% CI, 52.9- 91.4%) and 68.6% (95% CI, 49.5- 95.1%) for OS. The mFU was 14 months (range, 5 to 19) for untreated patients, the 1-year PFS was 93.3% (95% CI, 81.5- 100%). Obinutuzimab, ibrutinib and venetoclax combination is well tolerated and provides high response rates including at the molecular level in relapsed and untreated MCL patients.