Gain of chromosome 21 (Hsa21) is among the most frequent aneuploidies in leukemia. However, it remains unclear how partial or complete amplifications of Hsa21 promote leukemogenesis and why children with Down syndrome (i.e. trisomy 21) are particularly at risk of leukemia development. Here, we propose that RUNX1 isoform disequilibrium with RUNX1A bias is key to Down syndrome-associated myeloid leukemia (ML-DS). Starting with Hsa21-focused CRISPR-Cas9 screens, we uncovered a strong and specific RUNX1 dependency in ML-DS cells. Expression of the RUNX1A isoform is elevated in ML-DS patients, and mechanistic studies using murine ML-DS models and patient-derived xenografts (PDXs) revealed that excess RUNX1A synergizes with the pathognomonic Gata1s mutation during leukemogenesis by displacing RUNX1C from its endogenous binding sites and inducing oncogenic programs in complex with the MYC cofactor MAX. These effects were reversed by restoring the RUNX1A:RUNX1C equilibrium in PDXs in vitro and in vivo. Moreover, pharmacological interference with MYC:MAX dimerization using MYCi361 exerted strong anti-leukemic effects. Thus, our study highlights the importance of alternative splicing in leukemogenesis, even on a background of aneuploidy, and paves the way for the development of specific and targeted therapies for ML-DS, as well as for other leukemias with Hsa21 aneuploidy or RUNX1 isoform disequilibrium.
Aneuploidy is a hallmark of cancer, but its complex nature limits our understanding of how it drives oncogenesis. Gain of chromosome 21 (Hsa21) is among the most frequent aneuploidies in leukemia and is associated with markedly increased leukemia risk. Here, we propose that disequilibrium of the RUNX1 isoforms is key to the pathogenesis of trisomy 21 (i.e. Down syndrome)-associated myeloid leukemia (ML-DS). Hsa21-focused CRISPR-Cas9 screens uncovered a strong and specific RUNX1 dependency in ML-DS. Mechanistic studies revealed that excess of RUNX1A isoform - as seen in ML-DS patients - synergized with the pathognomonic Gata1s mutation in leukemogenesis by displacing RUNX1C from its endogenous binding sites and inducing oncogenic programs in complex with the MYC cofactor MAX. These effects were reversed by restoring the RUNX1A:RUNX1C equilibrium or pharmacological interference with MYC:MAX dimerization. Our study highlights the importance of alternative splicing in leukemogenesis, even on a background of aneuploidies, and opens new avenues for developing specific and targeted therapies.
Background: VTd is a standard of care for transplant-eligible newly diagnosed multiple myeloma (NDMM) patients. Daratumumab (DARA), a CD38 mAb, significantly reduced the risk of progression or death and improved complete response (CR) and minimal residual disease (MRD)-negative rates in relapsed refractory multiple myeloma or transplant-ineligible NDMM in phase 3 studies. Aims: We report the primary and final analysis of Part 1 of the CASSI-OPEIA trial for NDMM. Methods: In Part 1, transplant-eligible NDMM patients 18-65 years old were randomized 1:1 to VTd (6 28-day cycles [C; 4 pre-autologous stem cell transplantation {ASCT} induction, 2 post-ASCT consolidation] of V 1.3 mg/m 2 SC BIW Week [W] 1-2; T 100 mg PO QD; d 40-80 mg/week PO or IV W 1-4 C 1-2, W 1-3 C 3-6) ± DARA (16 mg/kg IV QW C 1-2, Q2W C 3-6). Melphalan 200 mg/m 2 was pre-ASCT therapy. The primary endpoint was the rate of post-consolidation stringent complete response (sCR) assessed at Day 100 post-ASCT. Part 2 (maintenance) is ongoing. Results: A cohort of 1085 patients (D-VTd, 543; VTd, 542) was randomized. The Day 100 post-ASCT sCR rate was significantly higher for the D-VTd arm versus the VTd arm (28.9% vs 20.3%; P = 0.0010; Table ). With 18.8-months median follow-up, progression-free survival (PFS) from first randomization favored D-VTd with a hazard ratio (HR) of 0.47 (95% CI, 0.33-0.67; P < 0.0001; Figure ). With median PFS not reached in either arm, 18-month PFS rates were 92.7% versus 84.6% for D-VTd versus VTd. Rates of ≥CR, ≥VGPR, and MRD negativity supported sCR results (Table ). Overall survival is immature with 46 deaths on study (D-VTd, 14; VTd, 32; HR, 0.43; 95% CI, 0.23-0.80). The most common (≥10%) grade 3/4 treatment-emergent adverse events (D-VTd/ VTd) were neutropenia (27.6%/14.7%), lymphopenia (17.0%/9.7%), stomatitis (12.7%/16.4%), and thrombocytopenia (11.0%/7.4%). In the D-VTd arm, infusion-related reactions occurred in 35.4% of patients. Summary/Conclusion: D-VTd in induction prior to and consolidation after ASCT improved depth of response (sCR, ≥CR, and MRD negativity) and PFS with acceptable safety. The favorable benefit-risk profile supports the use of D-VTd in transplant-eligible NDMM. CASSIOPEIA is the first study to demonstrate the clinical benefit of daratumumab plus standard of care in transplant-eligible NDMM patients.
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