Abstract
Improved therapies are greatly needed for non-small cell lung cancer (NSCLC) that does not harbor targetable kinase mutations or translocations. We previously demonstrated that NSCLC cells that harbor kinase-inactivating BRAF mutations (KIBRAF) undergo senescence when treated with the multitargeted kinase inhibitor dasatinib. Similarly, treatment with dasatinib resulted in a profound and durable response in a patient with KIBRAF NSCLC. However, no canonical pathways explain dasatinib-induced senescence in KIBRAF NSCLC. To investigate the underlying mechanism, we used 2 approaches: gene expression and reverse phase protein arrays. Both approaches showed that DNA repair pathways were differentially modulated between KIBRAF NSCLC cells and those with wild-type (WT) BRAF. Consistent with these findings, dasatinib induced DNA damage and activated DNA repair pathways leading to senescence only in the KIBRAF cells. Moreover, dasatinib-induced senescence was dependent on Chk1 and p21, proteins known to mediate DNA damage-induced senescence. Dasatinib also led to a marked decrease in TAZ but not YAP protein levels. Overexpression of TAZ inhibited dasatinib-induced senescence. To investigate other vulnerabilities in KIBRAF NSCLC cells, we compared the sensitivity of these cells with that of WTBRAF NSCLC cells to 79 drugs and identified a pattern of sensitivity to EGFR and MEK inhibitors in the KIBRAF cells. Clinically approved EGFR and MEK inhibitors, which are better tolerated than dasatinib, could be used to treat KIBRAF NSCLC. Our novel finding that dasatinib induced DNA damage and subsequently activated DNA repair pathways leading to senescence in KIBRAF NSCLC cells represents a unique vulnerability with potential clinical applications.