OVCAR-5, OVCAR-3, OV-90, SKOV-3, and LP-9 cells a were grown to 80% confluence in 75 cm2 flasks (Corning, Sigma Aldrich) and cell extracts were collected. Cells were dislodged using a cell scraper and resuspended in 200 μl of RIPA buffer (1% Nonidet P-40, 1% sodium deoxycholate, 0.1% SDS, 0.15 M sodium chloride, 50 mM Tris- HCL and 1 mM EDTA, pH 8.0 with protease inhibitor) and spun at 7000 rpm (Eppendorf 5424 centrifuge) for 10 min and stored at −20°C. Equal amounts of protein were electrophoresed and transferred to PVDF membranes (GE Healthcare, Little Chalfont, England) as described previously . Proteins bands were detected with mouse monoclonal K5/6 antibody (1/200, clone D5/16 B4, Dako, Glostrup, Denmark) or K5 rabbit monoclonal antibody (1/5000, clone EPR1600Y, Abcam Ab75869, Melbourne, Vic, Australia) with anti-mouse or anti-rabbit IgG peroxidase-conjugated secondary antibodies, enhanced chemiluminescence, and autoradiography as described previously . β-actin mouse monoclonal antibody (1/10,000, clone AC-15, Sigma Aldrich A3854) was used as a loading control. Ovarian cancer tissue extracts prepared in RIPA buffer with high K5/6 and K5 immunostaining used as positive controls for the western blots.