Effects of curcumin on the AKT/mTOR signaling pathway in human melanoma cell lines A375 and C8161

Abstract

Objective To explore molecular mechanisms underlying the in vitro counteracting effect of curcumin on malignant melanoma. Methods Cultured A375 and C8161 human melanoma cells were cultivated in vitro, and randomly divided into several test groups and a control group to be treated with different concentrations of curcumin and dimethyl sulfoxide respectively for different durations. Then, methyl thiazolyl tetrazolium (MTT) assay, Transwell assay, flow cytometry and Western blot were performed to evaluate the effect of curcumin on the proliferation, invasion and cell cycle of, as well as expressions of AKT/mTOR signaling pathway-related proteins in A375 and C8161 cells respectively. Statistical analysis was carried out by using t test. Results MTT assay showed that the treatment with curcumin of 5 - 35 mg/L for 24 - 96 hours significantly inhibited the proliferation of both A375 and C8161 cells compared with that with dimethyl sulfoxide (all P< 0.001), and the inhibitory effect was in a dose-dependent manner within the range of 5 - 15 mg/L for A375 cells and within the range of 5 - 10 mg/L for C8161 cells, and in a time-dependent manner from 0 to 48 hours for both cells. After treatment for 24 hours, the 50% inhibitory concentration(IC50) of curcumin against A375 cells and C8161 cells was 10 mg/L and 5 mg/L respectively. Transwell assay demonstrated that the invasion of A375 and C8161 cells was significantly suppressed by 72-hour treatment with curcumin at 10 mg/L and 5 mg/L respectively (both P < 0.001). Flow cytometry showed that the cell cycle of A375 and C8161 cells was arrested at G2/M phase after 24-hour treatment with curcumin at 10 mg/L and 5 mg/L respectively, with significant differences in the proportion of A375 cells and C8161 cells in G2/M phase between the test group and control group (A375 cells: 35.00%±3.54% vs. 120.80%±7.46%, P < 0.001; C8161 cells: 19.33%±4.04% vs. 85.00%±9.53%, P < 0.001). Western blot revealed that the expressions of AKT/mTOR signaling pathway-related proteins were decreased in A375 and C8161 cells after 24-hour treatment with 10 mg/L and 5 mg/L curcumin respectively. Conclusion Curcumin can inhibit the proliferation and invasion of A375 and C8161 cells, likely by blocking cell cycle and inhibiting activation of the AKT/mTOR signaling pathway. Key words: Melanoma, experimental; Curcumin; Cell proliferation; Cell cycle; Signal transduction