Novel curcumin analogs to overcome EGFR-TKI lung adenocarcinoma drug resistance and reduce EGFR-TKI-induced GI adverse effects

Curcumin (1) down-regulates the expression as well as phosphorylation of epidermal growth factor receptor (EGFR) in lung adenocarcinoma cells expressing gefitinib-resistant EGFR. Thirty-seven newly synthesized curcumin analogues including dimethoxycurcumin (2, DMC) were evaluated for their effects on EGFR expression as well as phosphorylation in two gefitinib-resistant lung adenocarcinoma cell lines, CL1-5 (EGFR^wt) and H1975 (EGFR^L858R+T790M). Based on the identified structure-activity relationships, methoxy substitution at C-3′, C-4′, or both positions favored inhibitory activity (compounds 1, 2, 5, 8-15, 17, 36), while compounds with more polar substituents were generally less active in both cell lines. Compound 36 with a fluorine substituent at C-6′ and its protonated counterpart 2 did not lose activity, suggesting halogen tolerance. In addition, a conjugated linker was essential for activity. Among all evaluated curcumin derivatives, compound 2 showed the best inhibitory effects on both wild-type and mutant EGFR by efficiently inducing gefitinib-insensitive EGFR degradation. Compound 23 also reduced gefitinib-induced gastrointestinal damage in the non-transformed intestinal epithelial cell line IEC-18.