Transglutaminase 2 enhances hepatocyte growth factor signaling to drive the mesothelioma cancer cell phenotype

Transglutaminase 2 (TG2) is an important mesothelioma cancer cell survival protein. However, the mechanism whereby TG2 maintains mesothelioma cell survival is not well understood. We present studies showing that TG2 drives hepatocyte growth factor (HGF)-dependent MET receptor signaling to maintain the aggressive mesothelioma cancer phenotype. TG2 increases HGF and MET messenger RNA and protein levels to enhance MET signaling. TG2 inactivation reduces MET tyrosine kinase activity to reduce cancer cell spheroid formation, invasion and migration. We also confirm that HGF/MET signaling is a biologically important mediator of TG2 action. Reducing MET level using genetic methods or treatment with MET inhibitors reduces spheroid formation, invasion and migration and this is associated with reduced MEK1/2 and ERK1/2. In addition, MEK1/2 and ERK1/2 inhibitors suppress the cancer phenotype. Moreover, MET knockout mesothelioma cells form 10-fold smaller tumors compared to wild-type cells and these tumors display reduced MET, MEK1/2, and ERK1/2 activity. These findings suggest that TG2 maintains HGF and MET levels in cultured mesothelioma cells and tumors to drive HGF/MET, MEK1/2, and ERK1/2 signaling to maintain the aggressive mesothelioma cancer phenotype.