VK3-OCH3 is an analog of vitamin K3 that that has antiproliferative activities in vitro. It preferentially decreases proliferation of IMR-32, LA-N-1, NB-39, and SK-N-SH neuroblastoma cells (IC50s = 2.43, 1.55, 10.69, and 3.45 μM, respectively) compared with non-cancerous HUVEC and HDF cells (IC50s = 26.24 and 87.11 μM, respectively). It increases heme oxygenase-1 (HO-1) and caveolin-1 levels, induces apoptosis, and halts the cell cycle at the G2/M phase in IMR-32 cells. VK3-OCH3 also inhibits protein-tyrosine phosphorylase (PTPase) activity (IC50 = 57.2 μM in a cell-free assay), induces protein-tyrosine phosphorylation in Hep3B hepatoma cells when used at a concentration of 50 μM, and inhibits the growth of Hep3B cells (IC50 = 8.6 μM).