Anti-Proliferation Effect of Theasaponin E1 on the ALDH-Positive Ovarian Cancer Stem-Like Cells.

Ovarian cancer has the highest mortality rate of all gynecological malignancies and the five-year death rate of patients has remained high in the past five decades. Recently, with the rise of cancer stem cells (CSCs) theory, an increasing amount of research has suggested that CSCs give rise to tumor recurrence and metastasis. Theasaponin E1 (TSE1), which was isolated from green tea (Camellia sinensis) seeds, has been proposed to be an effective compound for tumor treatment. However, studies on whether TSE1 takes effect through CSCs have rarely been reported. In this paper, ALDH-positive (ALDH+) ovarian cancer stem-like cells from two platinum-resistant ovarian cancer cell lines A2780/CP70 and OVCAR-3 were used to study the anti-proliferation effect of TSE1 on CSCs. The ALDH+ cells showed significantly stronger sphere forming vitality and stronger cell migration capability. In addition, the stemness marker proteins CD44, Oct-4, Nanog, as well as Bcl-2 and MMP-9 expression levels of ALDH+ cells were upregulated compared with the original tumor cells, indicating that they have certain stem cell characteristics. At the same time, the results showed that TSE1 could inhibit cell proliferation and suspension sphere formation in ALDH+ cells. Our data suggests that TSE1 as a natural compound has the potential to reduce human ovarian cancer mortality. However, more research is still needed to find out the molecular mechanism of TSE1-mediated inhibition of ALDH+ cells and possible drug applications on the disease.

3-Hydroxyterphenyllin, a natural fungal metabolite, induces apoptosis and S phase arrest in human ovarian carcinoma cells.

In the present study, we evaluated 3-Hydroxyter-phenyllin (3-HT) as a potential anticancer agent using the human ovarian cancer cells A2780/CP70 and OVCAR-3, and normal human epithelial ovarian cells IOSE-364 as an in vitro model. 3-HT suppressed proliferation and caused cytotoxicity against A2780/CP70 and OVCAR-3 cells, while it exhibited lower cytotoxicity in IOSE-364 cells. Subsequently, we found that 3-HT induced S phase arrest and apoptosis in a dose-independent manner. Further investigation revealed that S phase arrest was related with DNA damage which mediated the ATM/p53/Chk2 pathway. Downregulation of cyclin D1, cyclin A2, cyclin E1, CDK2, CDK4 and Cdc25C, and the upregulation of Cdc25A and cyclin B1 led to the accumulation of cells in S phase. The apoptotic effect was confirmed by Hoechst 33342 staining, depolarization of mitochondrial membrane potential and activation of cleaved caspase-3 and PARP1. Additional results revealed both intrinsic and extrinsic apoptotic pathways were involved. The intrinsic apoptotic pathway was activated through decreasing the protein levels of Bcl2, Bcl-xL and procaspase-9 and increasing the protein level of Puma. The induction of DR5 and DR4 indicated that the extrinsic apoptotic pathway was also activated. Induction of ROS and activation of ERK were observed in ovarian cancer cells. We therefore concluded that 3-HT possessed anti-proliferative effect on A2780/CP70 and OVCAR-3 cells, induced S phase arrest and caused apoptosis. Taken together, we propose that 3-HT shows promise as a therapeutic candidate for treating ovarian cancer.