OPN3 and cancer: Immunocytochemistry with anti-tubulin antibody and Hoechst 33342 showed the misalignment of chromosomes at the equatorial plane in cancer cells treated with RAB3GAP1 siRNA (19/33 cells, 57.8%), while no abnormal alignment was observed in cancer cells treated with OPN3 siRNA (0/26 cells, 0%) or scrambled RNA (0/31 cells, 0%) (Fig. 5a).