Curcumin Lowers Erlotinib Resistance in Non-Small Cell Lung Carcinoma Cells With Mutated EGF Receptor

Non-small cell lung cancer (NSCLC) patients with activating mutations in the epidermal growth factor receptor (EGFR) are responsive to erlotinib, an EGFR-tyrosine kinase inhibitor (EGFR-TKI). However, patients with secondary somatic EGFR mutations are resistant to EGFR-TKI treatment. In this study, we investigated the effect of curcumin on the tumor growth of erlotinib-resistant NSCLC cells. Cell proliferation was determined by MIT assay. Apoptosis was examined using TUNEL staining. Protein expression of genes was determined by Western blot. Tumor growth was assessed in a xenograft mouse model. Results showed that erlotinib had a stronger effect on the induction of apoptosis in erlotinib-sensitive PC-9 cells but showed a weaker effect on erlotinib-resistant H1975 and H1650 cells than cisplatin and curcumin. Furthermore, curcumin significantly increased the cytotoxicity of erlotinib to erlotinib-resistant NSCLC cells, enhanced erlotinib-induced apoptosis, downregulated the expressions of EGFR, p-EGFR, and survivin, and inhibited the NF-kappa B activation in erlotinib-resistant NSCLC cells. The combination of curcumin and erlotinib exhibited the same effects on apoptosis as the combination of curcumin and cisplatin in erlotinib-resistant NSCLC cells. Moreover, the combined treatment of curcumin and erlotinib significantly inhibited tumor growth of erlotinib-resistant NSCLC cells in vivo. Our results indicate that curcumin is a potential adjuvant for NSCLC patients during erlotinib treatment.