TGFB1 and ovarian cancer: This hypothesis has support in the observations that senescent mesothelial cells lie in close proximity to ovarian cancer cells within a tumor [17] and that conditioned medium from these cells is capable of triggering the development of a senescence phenotype in primary epithelial ovarian cancer cells in vitro with GRO-1, HGF, and TGF-β1 as mediators [8].