HPV E6 down-regulation and apoptosis induction of human cervical cancer cells by a novel lipid-soluble extract (PE) from Pinellia pedatisecta Schott in vitro

Aim of the study: To evaluate the cytotoxicity and apoptosis induction effects of a novel lipid-soluble extract (PE) from Pinellia pedatisecta Schott on CaSki, HeLa and HBL-100 cells. Particularly, the effect of PE on HPV E6 gene expression was tested, and the mechanism of its apoptosis induction effect was also studied. Materials and methods: Cell viability was measured by the MTT assay. DAPI staining and flow cytometric analysis (FCM) were used to identify apoptotic cells in PE-treated CaSki, HeLa, and HBL-100 cells. Expression of the HPV E6 gene in CaSki and HeLa cells was detected by real-time RT-PCR and western blot analysis. Apoptosis-associated genes were examined by RT-PCR and western blot analysis in CaSki cells. Results: PE inhibited the growth of CaSki and HeLa cells in a time- and dose-dependent manner, but it had no obvious inhibiting effect on HBL-100 cells except at a relatively high dose (500 mu g/mL). PE could induce apoptosis in CaSki and HeLa cells in a time-dependent manner but not in HBL-100 cells. HPV E6 mRNA and protein were decreased significantly by PE. Caspase-8, caspase-3, Bax, P53 and P21 mRNAs as well as proteins were increased while BcI-2 mRNA and protein were decreased significantly by 24 h of PE treatment. Conclusions: PE can function as a tumor suppressor by inducing apoptosis in human cervical cancer cells but it has little side effect on normal cells. It probably acts via mitochondria-dependent and death receptor-dependent apoptotic pathways. HPV E6 may be the key target of its action. (C) 2010 Elsevier Ireland Ltd. All rights reserved.