Curcumin induces apoptosis through caspase dependent pathway in human colon carcinoma cells

Abstract

We investigated the apoptotic effects of curcumin in the colon carcinoma cell line SW480. Cells were treated with 40-200μM curcumin for 24, 48, and 72h, and the IC50 values were determined for each time interval. BrdU, caspase-3, and TUNEL staining results and the gene expression of FADD, CASP8, and CASP3 were evaluated. Curcumin treatments significantly inhibited cell proliferation and significantly induced apoptosis for 24, 48, and 72h. The proportion of BrdU-stained cells in the control groups were 58%, 57% and 61% and 28%, 27%, and 30% in the curcumin treatment groups at 24, 48, and 72h, respectively. The proportion of apoptotic cells was 28%, 29%, and 28% in the control groups and 59%, 61%, and 60% in the curcumin treatment groups at 24, 48, and 72h, respectively. As expected, caspase-3 staining also revealed a higher number of apoptotic cells in curcumin treatment groups at 24, 48, and 72h compared to controls. The proportion of Caspase-3-stained cells in the control groups were 23%, 25%, and 24% and 59%, 60%, and 62% in the curcumin treatment groups at 24, 48, and 72h, respectively. To prove caspase-3 staining results, FADD, CASP8, and CASP3 gene expressions were evaluated by real-time qPCR. Unlike the immunohistochemical results, no statistically significant upregulation was found at 24 and 48h, while relative gene expressions of FADD, CASP8, and CASP3 was significantly upregulated at 72h. The expression level increase was 0.88-, 1.19-, and 2.11-fold for FADD, 1.25-, 1.29-, and 1.59-fold for CASP8, and 1.33-, 1.46-, and 3.00-fold for CASP3 at 24, 48, and 72h, respectively. These results suggest that curcumin may be a potential protective or treatment agent against colon cancer; however, further studies on curcumin-rich diets and curcumin bioavailability are required.