Our previous studies clearly demonstrated that a combination of
WP 631 and Epo B has higher activity against
ovarian cancer cells than either of these compounds used separately. In order to fully understand the exact mechanism of action in combination, we assessed effects on the cell cycle of SKOV-3 cells. We evaluated three control points essential for
WP 631 and Epo B action to determine which cell cycle-regulating
proteins (CDK1/
cyclin B complex,
EpCAM or
HMGB1) mediate activity. The effects of the
drug on the cell cycle were measured based on the nuclear
DNA content using flow cytometry. Expression of cell cycle-regulating genes was analyzed using real-time PCR. It was discovered that
WP 631, at the tested concentration, did not affect the SKOV-3 cell cycle. Epo B caused significant G2/M arrest, whereas the
drug combination induced stronger apoptosis and lower mitotic arrest than Epo B alone. This is very important information from the point of view of the fight against
cancer, as, while mitotic arrest in Epo B-treated cells could be overcame after DNA damage repair, apoptosis which occurs after mitotic slippage in combination-treated cells is irreversible. It clearly explains the higher activity of the
drug combination in comparison to Epo B alone. Epo B acts via the CDK1/
cyclin B complex and has the ability to inhibit CDK1, which may be a promising strategy for
ovarian cancer treatment in the future. The
drug combination diminishes
EpCAM and
HMGB1 expression to a greater degree than either
WP 631 and Epo B alone. Owing to the fact that the high expression of these two
proteins is a poor prognostic factor for
ovarian cancer, a decrease in their expression, observed in our studies, may result in improved efficacy of
cancer therapy. The presented findings show that the combination of
WP 631 and Epo B is a better therapeutic option than either of these drugs alone.