HYPOTHESIS: Intracellular copper levels have been reported to correlate with tumor pathogenesis and affect the sensitivity of cancer cells to cytotoxic chemotherapy. We hypothesized that intracellular copper levels may affect the sensitivity of oral cancer cells to curcumin.
METHODS: We analysed the correlation between intracellular copper levels and response to curcumin treatment in a panel of OSCC cell lines derived from oral cancer patients. Exogenous copper was supplemented in curcumin insensitive cell lines to observe the effect of copper on curcumin-mediated inhibition of cell viability and migration, as well as induction of oxidative stress and apoptosis. Protein markers of cell migration and oxidative stress were also analysed using Western blotting.
RESULTS: Concentrations of curcumin which inhibited 50% OSCC cell viability (IC50) was reduced up to 5 times in the presence of 250 µM copper. Increased copper level in curcumin-treated OSCC cells was accompanied by the induction of intracellular ROS and increased level of Nrf2 which regulates oxidative stress responses in cells. Supplemental copper also inhibited migration of curcumin-treated cells with enhanced level of E-cadherin and decreased vimentin, indications of suppressed epithelial-mesenchymal transition. Early apoptosis was observed in combined treatment but not in treatment with curcumin or copper alone.
CONCLUSION: Supplement of copper significantly enhanced the inhibitory effect of curcumin treatment on migration and viability of oral cancer cells. Together, these findings provide molecular insight into the role of copper in overcoming insensitivity of oral cancer cells to curcumin treatment, suggesting a new strategy for cancer therapy.
METHODS: Cell proliferation, migration, TUNEL assay, western blotting, time-lapse confocal microscopy analyses, chorioallantoic membrane assay, and a xenograft BALB/c nude mouse system were used in this study. Chemical fingerprinting of AC-3E was established using LC-MS.
RESULTS: AC-3E attenuated T47D breast cancer cell activity by deregulating the PI3K/Akt/mTOR signaling pathway and key cell-cycle mediators, and inducing apoptosis. AC-3E also effectively inhibited tube-like structures of endothelial cells, blood vessel branching and microvessel formation ex vivo and in vivo. Significant preventive and therapeutic effects against T47D mammary tumor growth of AC-3E was observed comparable or superior to tamoxifen treatment in xenograft BALB/c nude mice. Dehydroeburicoic acid (2) was characterized as the main chemical constituent in AC-3E against breast cancer.
CONCLUSION: This study suggests that AC-3E extracts can be employed as a double-barreled approach to treat human ER+ breast cancer by attacking both cancer cells and tumor-associated blood vessel cells.