TGFB1 and cancer: Such dynamic interplay between non-cancer stem cells and cancer stem cells has now been observed in a number of in vitro models and early paracrine signaling cues involved in this crosstalk involve HIFα (hypoxia inducible factors’ α subunits), sonic hedgehog, TGFβ1 (transforming growth factor beta 1), and nodal/activin to name some described from pancreatic cancer stem cell niche models or, importantly, prostaglandin E2-induced repopulation of the tumor following chemotherapy treatment from the slowly cycling CSC as shown in patient-derived xenotransplanted bladder cancer [27, 45, 46].