Figure 7. Role of TGF-β signaling in suppression of cell growth, Survivin expression and activation of Rb by antagonists of mTOR, Akt, PI3K and MEK in prostate epithelial cells.

The ability of the mTORC1 inhbitor rapamycin (A) and the mTORC1 and mTORC2 dual inhibitor Ku-0063794 (B) to inhibit growth of NRP-152 cells is revered by silencing Smads 2 and 3 (sh-S2+3) or by the TβRI/TβRII kinase dual inhibitor (TKDI), as assessed by cell growth after 6 days in GM3 medium. Although the Akt inhibitor MK2206 (0.5 µM) effectively represses LR3-IGF-I-induced cell growth in GM3 (C), TKDI reverses such suppression (D) as well as growth suppression (E) and Survivin suppression (F) by LY294002, rapamycin, U0126, MK2206 and Ku-0063794. D,E,F) Cells were plated in GM2.1 and pre-treated with TKDI or vehicle 4 h prior to treatment with the other kinase inhibitors. Cells were examined for cell growth after 5 days (by crystal violet staining) (D,E) or for expression of Survivin, XIAP, P-Smad3, P-Smad1/5/8, P-Rb, and ID-1 (by Western blot) after 24 h treatment (F). Data shown are the average of triplicate determinations ± S.E; Statistical significance (*p<0.01) was determined by two-way Anova.