Abstract 3707: The multitargeted kinase inhibitor dasatinib induces DNA damage, Hippo pathway engagement and senescence in lung cancer cell lines that possess kinase-inactivating BRAF mutations

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death. Therapies that target specific genetic aberrations are very effective in a subset on NSCLC. An effective approach for discovering novel therapeutic targets is to characterize responsive tumors. In this regard, we discovered a novel, kinase-inactivating BRAF mutation in the tumor of a patient with a marked and durable response to the multi-targeted kinase inhibitor dasatinib. Likewise, dasatinib induces senescence in NSCLC cells with endogenous kinase-inactivating BRAF mutations (KIBRAF). To identify the mechanism underlying this effect, we used reverse phase protein array, Western blotting and gene expression analysis on NSCLC cell lines with KIBRAF or WTBRAF incubated with dasatinib. We found that ATM, ATR, Rad 51, pH2AX, CDC6, CHEK1 (Chk1), pLATS and TAZ, were differentially regulated in mutant vs. WT cell lines. Quantitative real-time PCR analysis revealed that CHEK1, TAZ and TAZ's downstream targets were decreased following incubation with dasatinib in KIBRAF cells. Overexpression of CHEK1 or TAZ in KIBRAF NSCLC cells resulted in dasatinib resistance and decreased dasatinib-induced senescence. Given the differential effect on CHEK1 and pH2AX, we studied the effect of dasatinib on DNA damage using the COMET assay and found that dasatinib induces a significant increase in COMET-positive KIBRAF NSCLC cells. These data suggest that the inhibition of Chk1 along with inhibition of Hippo pathway results in the dasatinib sensitivity in NSCLC with KIBRAF. Citation Format: Banibrata Sen, Shaohua Peng, Tuhina Mazumdar, Lauren A. Byers, Humam Kadara, Faye M. Johnson. The multitargeted kinase inhibitor dasatinib induces DNA damage, Hippo pathway engagement and senescence in lung cancer cell lines that possess kinase-inactivating BRAF mutations. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3707. doi:10.1158/1538-7445.AM2014-3707