Anti-tumor activity and acquired resistance mechanism of Dovitinib (TKI258) in RET rearranged lung adenocarcinoma

RET rearrangement is a newly identified oncogenic mutation in lung adenocarcinoma (LADC). Activity of dovitinib (TKI258), a potent inhibitor of FGFR, VEGFR, and PDGFR, in RET-rearranged LADC has not been reported. The aims of the study are to explore anti-tumor effects and mechanisms of acquired resistance of dovitinib in RET-rearranged LADC. Using structural modeling and in vitro analysis, we demonstrated that dovitinib induced cell cycle arrest at G0/G1 phase and apoptosis by selective inhibition of RET kinase activity and ERK1/2 signaling in RET-rearranged LC-2/ad cells. Strong anti-tumor effect of dovitinib was observed in LC-2/ad tumor xenograft model. To identify the acquired resistance mechanisms to dovitinib, LC-2/ad cells were exposed to increasing concentrations of dovitinib to generate LC-2/ad DR cells. Gene set enrichment analysis of gene expression and receptor tyrosine kinase assay revealed that Src, a central gene in focal adhesion , was activated in LC-2/ad DR cells. Saracatinib, a src kinase inhibitor, suppressed ERK1/2 phosphorylation and growth of LC-2/ad DR cells. Taken together, these findings suggest that dovitinib can be a potential therapeutic option for RET-rearranged LADC, in which acquired resistance to dovitinib can be overcome by targeting Src. To identify potential mechanisms of acquired resistance to dovitinib, we established LC-2/ad DR cells with acquired resistance to dovitinib by exposing LC-2/ad cells to increasing doses of dovitinib. LC-2/ad DR cells showed strong resistance to dovitinib (IC50> 3 μmol/L). Next, LC-2/ad and LC-2/ad DR cells were subjected to genome-wide gene expression profiling using cDNA microarray.