Selective inhibition of endothelin receptor A as an anti-angiogenic and anti-proliferative strategy for human pancreatic cancer.

Endothelin-1 (ET-1) plays a major role in tumor proliferation and angiogenesis of various types of cancer acting through endothelin receptors A and B (ET(R)A and ET(R)B). The aim of this study was to analyze the ET-1/ET(R) system in human pancreatic cancer cell lines and to evaluate the effect of a selective endothelin A inhibitor in vitro and in vivo in an orthotopic mouse model. Three different human pancreatic cancer cell lines, MiaPaCa-2, AsPC-1, and Panc-1, were studied. We found that proliferation of human pancreatic carcinoma cells expressing ET(R)A was significantly reduced with a selective antagonist. Hypoxic conditions led to improved results compared to a normoxic environment (MiaPaCa-2: -53% vs. -18%; AsPC-1: -54% vs. -46%). Proliferation of ET(R)A negative Panc-1 cells was not decreased. In vivo, the selective ET(R)A inhibition resulted in reduced angiogenesis as measured by lower microvessel densities (MiaPaCa-2: -47%; AsPC-1: -55%). The blockade of ET(R)A decreased the volume (MiaPaCa-2: -87%; AsPC-1: -28%) and metastatic spread (MiaPaCa-2: -95.5%; AsPC-1: -27%) of receptor-positive tumors, thereby increasing survival in experimental pancreatic cancer. ET(R)A blockade did not show an effect on ET(R)A negative Panc-1 tumors. Therefore, targeting ET(R)A with a selective antagonist might provide a new approach to reducing proliferation and angiogenesis in human pancreatic cancer.