To evaluate the feasibility of using quercetin (Figure 1A) in the treatment of TKI-resistant NSCLCs, we examined the cytotoxic effects of quercetin on NSCLC cells, including A549 (wild-type EGFR), H1975 (EGFR L858R+T790M) and H1975-MS35 (EGFR L858R+T790M+C797S) cells. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.