Proteasome inhibition overcomes ALK-TKI resistance in ALK-rearranged/TP53 mutant NSCLC via Noxa expression

2020 
Purpose:In ALK-rearranged non-small cell lung cancer (NSCLC), impacts of concomitant genetic alterations on targeted therapies with ALK-tyrosine kinase inhibitors (ALK-TKIs) have not yet well understood. Here, we investigated genetic alterations related to ALK-TKI resistance using clinico-genomic data and explored effective therapies to overcome the resistance in preclinical models through the identification of underlying molecular mechanisms. Experimental Design:We used integrated clinical and next-generation sequencing data generated in a nationwide lung cancer genome screening project (LC-SCRUM-Japan). ALK-rearranged NSCLC cell lines expressing wild-type or mutant TP53 were used to evaluate cellular apoptosis induced by ALK-TKIs. Results:In 90 ALK-rearranged NSCLC patients who were treated with a selective ALK-TKI, alectinib, TP53 co-mutated patients showed significantly worse progression-free survival (PFS) than TP53 wild-type patients [median PFS, 11.7 months (95% CI, 6.3-not reached [NR]) vs. NR (23.6-NR); p=0.0008; hazard ratio, 0.33 (95% CI, 0.17-0.65)]. ALK-rearranged NSCLC cell lines which lost p53 function were resistant to alectinib-induced apoptosis, but a proteasome inhibitior, ixazommib markedly induced apoptosis in the alectinib-treated cells by increasing the expression of a pro-apoptotic protein, Noxa which bound to an anti-apoptotic protein, Mcl-1. In subcutaneous tumor models, combination of ixazomib and alectinib prominently induced tumor regression and apoptosis even though the tumors were generated from ALK-rearranged NSCLC cells with non-functional p53. Conclusions:These clinical and preclinical results indicate concomitant TP53 mutations reduce the efficacy of alectinib for ALK-rearranged NSCLC and the combined use of a proteasome inhibitor with alectinib is a promising therapy for ALK-rearranged/TP53-mutated NSCLC.
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