Anticancer Effect of Enterococcus faecium, Isolated from Vaginal Fluid, on Ovarian Cancer Cells

Background: Given the association between cervicovaginal microbiota and OVC, we investigated the effect of E. faecium CM on OVC (Caov-4) cells. Methods: CM was obtained from the bacterium E. faecium isolated from the vagina of healthy women. The Caov-4 cells were treated with varying concentrations of CM that comprised co-cultured bacteria with 0.2, 0.5, 1, 1.5, and 2 OD for 12, 24, and 48 h. The apoptosis and growth of cancer cells were evaluated by DAPI staining, flow cytometry, and DNA laddering assay. Moreover, the expression of PTEN, BAX, BCL2, and AKT1 genes were analyzed using real-time PCR. Results: The CM at a concentration of 0.5 OD from the cultured bacteria and incubation time of 48 h showed the highest negative effect on the viability of cancer cells. The CM treatment increased DNA fragmentation and also induced apoptosis in Caov-4 cells. Interestingly, CM could decrease the expression of proapoptotic genes were less, while antiapoptotic genes were more than 5-FU in the presence of CM. Conclusion: CM of human-derived E. faecium could have an anticancer effect on OVC cells in a concentration- and time-dependent manner. This study demonstrated that E. faecium secretes anticancer substances into the CM, which could directly affect the viability and apoptosis of cancer cells.