Trichosanthes kirilowii tuber extract induces G2/M phase arrest via inhibition of tubulin polymerization in HepG2 cells

Trichosanthes kirilowii tuber is one of most popular herbal plant of East Asia, which has been prescribed for patients with diabetes, rigorous coughing, breast abscesses, and cancer-related symptoms.Aim of the studyTo investigated the anticancer properties of the methanol extract of Trichosanthes kirilowii tuber (TKE), focusing on cell cycle arrest and microtubule instability in HepG2 cells.Materials and MethodsCell growth and death were checked using a CCK-8 assay and a LDH release assay respectively. Cell cycle was analyzed by FACS after PI staining. Immunofluorece, western blot, real-time PCR for tubulin were performed.ResultsTKE treatment inhibited cell growth at around 25 μg/mL of IC50 in a CCK-8 assay and a LDH release assay, but did not result in cell death. We found that TKE induced cell cycle arrest at the G2/M phase in a time-dependent manner. However, an immunofluorescence assessment of beta-tubulin revealed a dramatically reduced amount of polymerized tubulin after TKE treatment. Furthermore, TKE treatment radically decreased the polymerized portion of soluble tubulin in a dose-dependent manner, as did colchicine; the effects, however, were opposite to those of paclitaxel in comparative analysis of polymerized to soluble tubulin. We also found that TKE treatment moderately affected α-tubulin protein production, but not that of β-tubulin and its gene expression using a Western assay and real-time PCR.ConclusionsAnticancer mechanisms of TKE linked to the inhibition of tubulin polymerization, through which it exerts cell cycle arrest at the G2/M phase in the HepG2 cell line.