Dasatinib induces DNA damage and activates DNA repair pathways leading to senescence in non-small cell lung cancer cell lines with kinase-inactivating BRAF mutations

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.