VRK1 and hepatocellular carcinoma: Knocking down VRK1 expression reduced the size of all HCC cell colonies (P < 0.001), with the most dramatic effect on SK-Hep1 cells, which normally express the highest level of VRK1 (19.86% ± 0.27), and the smallest effect on Hep3B cells, which normally express the lowest levels of VRK1 (74.92% ± 6.98; Fig. 2E).