Suppression of EphB4 improves the inhibitory effect of mTOR shRNA on the biological behaviors of ovarian cancer cells by down-regulating Akt phosphorylation.

The aim of the present study was to examine the effects of suppression of EphB4 and/or mTOR on the biological behaviors of ovarian cancer cells, and the potential regulatory pathways. Antisense EphB4 vectors and shRNA vectors targeting mammalian target of rapamycin (mTOR) were constructed and transfected into A2780 and SKOV3 cells (two ovarian cancer cell lines). The effects of the antisense EphB4 vectors and the shRNA vectors on the proliferation, apoptosis and invasion of ovarian cancer cells were measured, and the expression of EphB4, mTOR and Akt detected. The results showed that transfection with mTOR shRNA could inhibit growth, induce apoptosis, and reduce invasive ability of ovarian cancer cells, which was accompanied by downregulation of EphB4, mTOR and Akt. The inhibitory effects on cell growth caused by mTOR shRNA alone were weaker than those by antisense pEGFP-C1-EphB4. In the antisense pEGFP-C1-EphB4-transfected cells, it was found that EphB4 knockdown could decrease the mTOR expression and slightly reduce the Akt phosphorylation. Significant suppressive effects on cell growth were observed in cells co-transfected with antisense pEGFP-C1-EphB4 and mTOR shRNA. In co-transfection group, the expression levels of EphB4, mTOR and Akt were distinctly lower than those in other groups. It was concluded that suppression of EphB4 may inhibit the growth of ovarian cancer cells by downregulation of the PI3K/Akt/mTOR pathway, and reverse Akt phosphorylation induced by mTOR shRNA. Inhibition of EphB4 and mTOR combined may cooperatively suppress the biological behaviors of ovarian cancer cells.