Abstract
Curcumin and fenretinide are 2 well-known and promising chemotherapeutic compounds via various molecular mechanisms. However, the anticancer capacity of either curcumin or fenretinide is limited. This prompted us to examine the combined anticancer effects of curcumin and fenretinide. Our results demonstrate for the first time that there is synergistic anticancer effect of combined treatment with these 2 agents, leading to enhanced cytotoxicity and enhanced expression level of pro-apoptotic protein cleaved PARP in non-small cell lung cancer (NSCLC) cells while showed little toxicity to rat cardiomyoblast normal cells. The combination treatment was also demonstrated to inhibit lung carcinoma growth in vivo. Furthermore, we show that fenretinide or the ER stress inhibitor 4-PBA decreased curcumin-induced Glucose-regulated protein 78 (GRP78) upregulation, and produced a similar enhanced cytotoxic effect. In addition, GRP78 knockdown by siRNA also enhanced the cytotoxic effect of curcumin in A549 and H1299 cells. Our findings suggest that the 2 small molecules, when used in combination, can potentially be effective therapeutic agents for treating NSCLC, at least in part, by regulating endoplasmic reticulum (ER) chaperone protein GRP78.