Rho kinase and matrix metalloproteinase inhibitors cooperate to inhibit angiogenesis and growth of human prostate cancer xenotransplants

The purpose of this study was to determine the effects of inhibitors of Rho kinase (ROK) and matrix metalloproteinases (MMPs) on angiogenesis and tumor growth and to evaluate ROK activity in human prostate cancer PC3 cells and endothelial cells (HUVECs). Vacuolation by endothelial cells and lumen formation, the earliest detectable stages of angiogenesis, were inhibited by the ROK inhibitor Wf-536. Combining Wf-536 with the MMP inhibitor Marimastat greatly enhanced in vitro inhibition of endothelial vacuolation, lumen and cord formation, and VEGF- and HGF-stimulated endothelial sprout formation from aorta. Inhibition of sprout formation by the two inhibitors was synergistic. Both agents inhibited migration of HUVECs. The regulatory subunit (MYPT1) of the myosin phosphatase was phosphorylated in PC3 cells and HUVECs, and phosphorylation of MYPT1 and the myosin regulatory light chain was reduced by Wf-536, providing direct evidence of ROK activity. Early treatment of immuno-incompetent mice bearing xenotransplants of PC3 cells with a combination of Wf-536 plus Marimastat with or without Paclitaxel, significantly inhibited tumor growth, prevented tumor growth escape after discontinuation of Paclitaxel, and increased survival.