FKBP1A and prostate carcinoma: Osman et al. (2009) reported that rapamycin induced rapid activation of TGF-β-Smad signaling in rat mesangial cells. Another study also reported that rapamycin further augmented SBE4-luc activation in prostate cancer cells (van der Poel, 2004). Shihab et al. (2004) found that rapamycin increased TGF-β expression in a rat model. Moreover, rapamycin can endow constitutive TGFβ signaling in monkey kidney COS-1 cells through binding to its intracellular receptor FKBP12, which inhibits TGFβ type I receptor phosphorylation (Chen et al., 1997).