Inhibition of PAI-1 Limits Tumor Angiogenesis Regardless of Angiogenic Stimuli in Malignant Pleural Mesothelioma.

Malignant pleural mesothelioma (MPM) is an aggressive malignant tumor that secretes various angiogenic factors. The main inhibitor of plasminogen activators, PAI-1 (SERPINE1), has been implicated in tumor progression and angiogenesis, and high PAI-1 expression has been associated with poor prognosis in MPM patients. In this study, we examined the antiangiogenic effects of PAI-1 inhibition in MPM. We administered the PAI-1 inhibitor, SK-216, to orthotopic mouse models in which MPM cells expressing high levels of VEGF (VEGFA) or bFGF (FGF2) were intrapleurally transplanted. SK-216 administration reduced tumor weights and the degree of angiogenesis in intrapleural tumors, irrespective of their angiogenic expression profiles. In addition, a combination of SK-216 and the chemotherapeutic agent cisplatin significantly reduced tumor weights compared with monotherapy, prolonging the survival of animals compared with cisplatin treatment alone. Furthermore, SK-216 inhibited migration and tube formation of cultured human umbilical vein endothelial cells induced by various angiogenic factors known to be secreted by MPM. These findings suggest that PAI-1 inactivation by SK-216 may represent a general strategy for inhibiting angiogenesis, including for the treatment of MPM. Cancer Res; 76(11); 3285-94. ©2016 AACR.