Inhibition of cellular proliferation and induction of apoptosis by curcumin in human malignant astrocytoma cell lines

Nuclear factor (NF)-kappa B is known to control cellular proliferation and apoptosis. In malignant astrocytoma cells, it was reported that NF-kappa B was activated aberrantly and promoted their proliferation. Thus, inhibition of NF-kappa B activity is considered to be a promising therapeutic strategy for malignant astrocytoma. Recently, curcumin, the major constituent of turmeric, was reported to inhibit NF-kappa B activity. In this study, we investigated inhibitory effects of curcumin on NF-kappa B activity and cellular proliferation, and induction of apoptosis by curcumin in human malignant astrocytoma cell lines. Alteration of NF-kappa B activity in NP-2 human malignant astrocytoma cell line after treatment with curcumin was examined using electrophoretic mobility shift assay. Alterations of DNA synthesis and cellular growth in five human malignant astrocytoma cell lines after treatment with curcumin were examined using [H-3]thymidine incorporation assay and the trypan blue dye exclusion method, respectively. Induction of apoptosis by curcumin in NP-2 and NP-3 human malignant astrocytoma cell lines was examined by DNA-fragmentation analysis and morphological observation. We found that the NF-kappa B activity in NP-2 was significantly reduced by curcumin. The DNA synthesis and the cellular growth were inhibited by curcumin in dose-dependent manner in all the five malignant astrocytoma cell lines. Nuclear condensation and fragmentation, and DNA fragmentation were observed in both NP-2 and NP-3 after the treatment with curcumin. These results indicate that curcumin inhibits the cellular proliferation and induces apoptosis in human malignant astrocytoma cell lines. These results are considered to be resulted from the inhibition of NF-kappa B activity by curcumin.