Anti-Proliferation Effect of Theasaponin E(1) 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 E(1) (TSE(1)), which was isolated from green tea (Camellia sinensis) seeds, has been proposed to be an effective compound for tumor treatment. However, studies on whether TSE(1) 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 TSE(1) 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 TSE(1) could inhibit cell proliferation and suspension sphere formation in ALDH+ cells. Our data suggests that TSE(1) 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 TSE(1)-mediated inhibition of ALDH+ cells and possible drug applications on the disease.