T790M-Selective EGFR-TKI Combined with Dasatinib as an Optimal Strategy for Overcoming EGFR-TKI Resistance in T790M-Positive Non-Small Cell Lung Cancer

T790M mutation-selective EGFR tyrosine kinase inhibitors (EGFR-TKI) have demonstrated clinical benefits in non-small cell lung cancer (NSCLC) patients harboring T790M mutation, which is the major cause of resistance to EGFR-TKI. However, their efficacy is limited, possibly due to the emergence of apoptosis resistance in T790M-positive NSCLC. We previously identified Src family kinases as cooncogenic drivers along with T790M and found that the Src inhibitor dasatinib combined with an irreversible or a preclinical T790M-selective EGFR-TKI enhanced antitumor activity in T790M-positive cells. In the current study, we evaluated the efficacy of dasatinib combined with the clinically relevant T790M-selective EGFR-TKI ASP8273 or osimertinib in mutation-positive NSCLC with or without T790M mutation. A cell viability assay revealed that dasatinib had synergistic effects with these TKIs in T790M-positive cells and simultaneously inhibited Src, Akt, and Erk, which remained activated upon single-agent treatment. Dasatinib also increased the rate of apoptosis in T790M-positive cells induced by T790M-selective EGFR-TKIs, as determined by the Annexin-V binding assay; this was associated with downregulation of the antiapoptotic Bcl-2 family member Bcl-xL, a finding that was confirmed in mice bearing T790M-positive xenografts. Our results suggest that Bcl-xL plays a key role in the apoptosis resistance of T790M-positive NSCLC, and that dasatinib combined with clinically relevant T790M-selective EGFR-TKIs is potentially effective in overcoming resistance to first-generation EGFR-TKIs in NSCLC patients with acquired T790M. .