XIAP and cancer: We have showed that TGF-β3 induces XIAP-dependent degradation of PTEN [9]: since TGF-β1 and TGF-β2 also increase XIAP levels in cancer cells, but through mechanisms different from TGF-β3 [6], we hypothesized that, compared to TGF-β3, these isoforms would differently regulate XIAP-induced degradation of PTEN.