The Inhibitory Effects And Mechanisms Of Theaflavin-3,3’-gallate On Human Ovarian Carcinoma Cells

Ovarian cancer is one of the most common and fatal gynecological cancers.Epidemiological studies have shown black tea consumption is associated with a linear decline in ovarian cancer risk.Black tea is widely consumed in the world.Theaflavins are unique black tea polyphenols which have multiple physiological activities.Recently,researchers emphasized on investigating the anti-cancer activity of theaflavins.However,the anti-ovarian cancer activity and mechanisms of theaflavins haven’t been studied yet.In this research,the inhibitory effect of four main theaflavin monomers on ovarian cancer was investigated.One of the four main theaflavin monomers was selected for further experiments.The main results are as follows:1.All the four main theaflavin monomers preferentially inhibited the viability of two ovarian cancer cells OVCAR-3 and A2780/CP70 compared with that of normal ovarian cells IOSE 364.All the four main theaflavin monomers had anti-tumor angiogenic activity and decreased the VEGF secretion of ovarian cancer cells.TF2A,TF2B and TF3 induced apoptosis of both ovarian cancer cells and enhanced the activity of Caspase-3/7,8 and 9.In general,TF2A,TF2B and TF3 showed similar anti-cancer effects and mechanisms on ovarian cancer cells.Meanwhile,some of the effects and mechanisms of TF1 were different from those of the other three theaflavin monomers.As the yield rate of TF3(using our lab’s previous extraction method)was much higher than that of TF2A and TF2B,respectively,TF3 was selected as the material for further experiments.2.TF3 dose-dependently decreased OVCAR-3 cells-induced angiogenesis,the expression of HIF-1α and the secretion of VEGF.According to the results of western blot assay and luciferase reporter assay,TF3 inhibited OVCAR-3 cells-induced angiogenesis via the Akt/mTOR/p70S6K/4E-BP1/HIF-1α/VEGF pathway and Akt/c-Myc/HIF-la/VEGF pathway.Wortmannin,an Akt inhibitor,enhanced the sensitivity of OVCAR-3 cells to TF3.On the contrary,overexpression of active Akt enhanced the resistance of OVCAR-3 cells to TF3.Notch-1/c-Myc/HIF-la/VEGF pathway was also involved in TF3-mediated inhibition of tumor angiogenesis.DAPT,a Notch inhibitor,enhanced the sensitivity of OVCAR-3 cells to TF3.Meanwhile,overexpression of NICD enhanced the resistance of OVCAR-3 cells to TF3.However,TF3 had little effect on the MAPK pathway.3.TF3 dose-dependently increased the apoptosis and the activity of Caspase-3/7,8 and 9,respectively,in OVCAR-3 cells.TF3 activated Chk2 in an ATM-independent manner,up-regulated the expression of Bax,down-regulated the expression of Bcl-xL and promoted the cleavage of PARP-1.Nevertheless,TF3 had little impact on the expression of p53,Bad,Bcl-2,Mcl-1 and Apaf-1.According to the result of siRNA transfection assay,TF3 mediated intrinsic apoptosis via activating Chk2,increasing the expression of Bax,reducing the expression of Bcl-xL and enhancing the activity of Caspase-3/7 and 9.In addition,TF3 induced extrinsic apoptosis through increasing the expression of two death receptors,Fas and DR5,and activating Caspase-8 in OVCAR-3 cells.4.TF3 induced G0/G1 cell cycle arrest in OVCAR-3 cells via increasing the expression of p27 and decreasing the expression of Cyclin D1,CDK4 and p-Rb.In conclusion,we proved TF3 reduced the viability,decreased tumor angiogenesis,induced apoptosis and caused G0/G1 cell cycle arrest in OVCAR-3 cells.Notch-1,Chk2 and p27 were identified as novel targets of TF3.This study provides novel perspectives and potential targets for the anti-cancer activity of TF3,suggesting that TF3 might serve as a potent anti-cancer agent.