Asciminib stands out as the superior tyrosine kinase inhibitor to combine with anti-CD20 monoclonal antibodies for the treatment of CD20+ Philadelphia-positive B-cell precursor acute lymphoblastic leukemia in preclinical models.

Philadelphia chromosome-positive B-cell precursor acute lymphoblastic leukemia (Ph+ BCPALL) is a high-risk acute lymphoblastic leukemia subtype characterized by the presence of BCR::ABL1 fusion gene. Tyrosine kinase inhibitors (TKIs) combined with chemotherapy are established as the first-line treatment. Additionally, rituximab (RTX), an anti-CD20 monoclonal antibody (mAb) is administered in adult BCP-ALL patients with ≥20% of CD20+ blasts. In this study, we observed a marked prevalence of CD20 expression in patients diagnosed with Ph+ BCP-ALL, indicating a potential widespread clinical application of RTX in combination with TKIs. Consequently, we examined the influence of TKIs on the antitumor effectiveness of anti-CD20 mAbs by evaluating CD20 surface levels and conducting in vitro functional assays. All tested TKIs were found to uniformly downregulate CD20 on leukemic cells, diminishing the efficacy of RTX-mediated complement-dependent cytotoxicity. Interestingly, these TKIs displayed varied effects on NK cell-mediated antibody-dependent cytotoxicity and macrophage phagocytic function. While asciminib demonstrated no inhibition of effector cell functions, dasatinib notably suppressed the anti-CD20-mAb-mediated NK cell cytotoxicity and macrophage phagocytosis of BCP-ALL cells. Dasatinib and ponatinib also decreased NK cell degranulation in vitro. Importantly, oral administration of dasatinib, but not asciminib, compromised NK cell activity within patients' blood, determined by ex vivo degranulation assay. Our results indicate that asciminib might be preferred over other TKIs for combination therapy with anti-CD20 mAbs.

Concomitant inhibition of the thioredoxin system and nonhomologous DNA repair potently sensitizes Philadelphia-positive lymphoid leukemia to tyrosine kinase inhibitors.

Breakpoint cluster region-Abelson (BCR::ABL1) gene fusion is an essential oncogene in both chronic myeloid leukemia (CML) and Philadelphia-positive (Ph+) B-cell acute lymphoblastic leukemia (B-ALL). While tyrosine kinase inhibitors (TKIs) are effective in up to 95% of CML patients, 50% of Ph+ B-ALL cases do not respond to treatment or relapse. This calls for new therapeutic approaches for Ph+ B-ALL. Previous studies have shown that inhibitors of the thioredoxin (TXN) system exert antileukemic activity against B-ALL cells, particularly in combination with other drugs. Here, we present that peroxiredoxin-1 (PRDX1), one of the enzymes of the TXN system, is upregulated in Ph+ lymphoid as compared to Ph+ myeloid cells. PRDX1 knockout negatively affects the viability of Ph+ B-ALL cells and sensitizes them to TKIs. Analysis of global gene expression changes in imatinib-treated, PRDX1-deficient cells revealed that the nonhomologous end-joining (NHEJ) DNA repair is a novel vulnerability of Ph+ B-ALL cells. Accordingly, PRDX1-deficient Ph+ B-ALL cells were susceptible to NHEJ inhibitors. Finally, we demonstrated the potent efficacy of a novel combination of TKIs, TXN inhibitors, and NHEJ inhibitors against Ph+ B-ALL cell lines and primary cells, which can be further investigated as a potential therapeutic approach for the treatment of Ph+ B-ALL.

Integrated modeling of the Nexin-dynein regulatory complex reveals its regulatory mechanism.

Cilia are hairlike protrusions that project from the surface of eukaryotic cells and play key roles in cell signaling and motility. Ciliary motility is regulated by the conserved nexin-dynein regulatory complex (N-DRC), which links adjacent doublet microtubules and regulates and coordinates the activity of outer doublet complexes. Despite its critical role in cilia motility, the assembly and molecular basis of the regulatory mechanism are poorly understood. Here, using cryo-electron microscopy in conjunction with biochemical cross-linking and integrative modeling, we localize 12 DRC subunits in the N-DRC structure of Tetrahymena thermophila. We also find that the CCDC96/113 complex is in close contact with the DRC9/10 in the linker region. In addition, we reveal that the N-DRC is associated with a network of coiled-coil proteins that most likely mediates N-DRC regulatory activity.

Integrated modeling of the Nexin-dynein regulatory complex reveals its regulatory mechanism.

Cilia are hairlike protrusions that project from the surface of eukaryotic cells and play key roles in cell signaling and motility. Ciliary motility is regulated by the conserved nexin-dynein regulatory complex (N-DRC), which links adjacent doublet microtubules and regulates and coordinates the activity of outer doublet complexes. Despite its critical role in cilia motility, the assembly and molecular basis of the regulatory mechanism are poorly understood. Here, utilizing cryo-electron microscopy in conjunction with biochemical cross-linking and integrative modeling, we localized 12 DRC subunits in the N-DRC structure of Tetrahymena thermophila . We also found that the CCDC96/113 complex is in close contact with the N-DRC. In addition, we revealed that the N-DRC is associated with a network of coiled-coil proteins that most likely mediates N-DRC regulatory activity.