Cytotoxic and chemosensitization effects of Scutellarin from traditional Chinese herb Scutellaria altissima L. in human prostate cancer cells

Scutellaria altissima L. is a common traditional Chinese medicine used to treat inflammation in some countries. Scutellarin, an active major flavone glycoside isolated from the traditional Chinese medicine Scutellaria altissima L., has been shown to offer various beneficial biochemical effects on cerebrovascular diseases and inflammation. However, the antiproliferative effects of Scutellarin in prostate cancer and the underlying mechanism are not fully elucidated. In the present study, we aimed to ascertain whether Scutellarin inhibits cancer cell growth and to further explore the molecular mechanism. Scutellarin enhanced the sensitivity of prostate cancer cells to cisplatin. MTT assays revealed that cell viability was significantly decreased in the prostate cancer cells treated with Scutellarin. Flow cytometric analysis indicated that Scutellarin suppressed cell proliferation by promoting G2/M arrest and inducing apoptosis. We employed western blotting to delineate the underlying mechanisms involved in the G2/M arrest and apoptosis. Comet assay and γH2AX immunocytochemistry were used to detect levels of DNA damage in PC3 cells exposed to Scutellarin and/or cisplatin. Our data revealed that Scutellarin significantly induced prostate cancer cell apoptosis by activating the caspase cascade. An increase in the Bax/Bcl-2 ratio, depolarization of mitochondrial membrane potential and cell cycle arrest at G2/M phase were accompanied by the apoptosis induction. Additionally, Scutellarin altered the protein expression of cell cycle and apoptosis regulatory genes by downregulating Cdc2, cyclin B1 and Bcl-2 and upregulating caspase-3, caspase-9 and Bax in prostate cancer cells. Furthermore, Scutellarin sensitized PC3 cells to cisplastin treatment in a dose-dependent manner. Taken together, our data confirmed the cytotoxicity of Scutellarin against prostate cancer PC3 cells and provide new findings in regards to Scutellarin sensitizing prostate cancer cells to chemotherapy. Our findings suggest that Scutellarin has potential to be used as a novel antineoplastic therapeutic candidate for prostate cancer patients.