Mutant GT198 in angiogenesis as a common origin of human prostate and bladder cancers

Prostate and bladder cancers are common cancers in men. It has been speculated that the high concomitant incidence of the two cancers is due to a potential shared cause underlying both cancers. In this report, we have identified a common cause of human prostate and bladder cancers as the mutant oncoprotein GT198 (PSMC3IP). GT198 is a DNA repair factor and a steroid hormone receptor coactivator. GT198 has been previously shown to be mutated in angiogenic pericyte stem cells in solid tumor microenvironment. GT198 is also a direct protein target of chemo drugs paclitaxel and doxorubicin. Here we show, the GT198 gene is mutated with protein overexpression in tumor stroma of human prostate and bladder cancers. Affected stromal cells include angiogenic blood vessel pericyte stem cells, and vascular smooth muscle cell lineages including myofibroblasts in prostate and smooth muscle cells in bladder. In prostate cancers, GT198+ tumor stromal cells are associated with early stages of cancer with lower Gleason scores. In bladder cancers, the presence of angiogenesis and GT198+ stroma are associated with better progression-free survival in docetaxel-treated patients. Together, our evidence suggests that angiogenic pericyte stem cells are initial lesions producing a mutant stroma carrying GT198 somatic mutations. Subsequently, mutant myofibroblasts promote adenocarcinomas in prostate and mutant smooth muscle cells promote urothelial carcinomas in bladder. Chemo drugs targeting to GT198 is more effective in early stages of cancers with GT198+ stromal cells. This study supports oncoprotein GT198 as a common cause and a drug target in human prostate and bladder cancers.