FIGURE 7.

Combinatory suppression of mTOR and PDK4 synergistically inhibits cell proliferation. a, NIH/3T3 cells transfected with PDK4 expression plasmids or control plasmids were treated with rapamycin for 48 h at the indicated concentrations. b, NIH/3T3 cells with shPDK4 or shScr were treated with rapamycin for 48 h at the indicated concentrations. c, PC3 cells were treated with various doses of rapamycin and DCA in a 96-well plate for 48 h. Isoboles for the combination of rapamycin with DCA were isoeffective (IC₅₀) for inhibition of proliferation of PC3. The dashed line indicates the zero interaction of the isobole. d, PC3 cells were treated with varying doses of Torin-1 and DCA in a 96-well plate for 48 h. e, cell lysates from NIH/3T3 treated with or without 10 mm DCA for 24 h were collected and analyzed by immunoblotting. f, schematic illustration of PDK4-CREB-RHEB-mTOR signaling cascade. PDK4 binds to CREB and prevents its degradation. The enhanced CREB consequently transactivates the expression RHEB and potentiates mTOR. Cell viability was assessed with MTT assay. Data are calculated as the mean ± S.E. *, p < 0.05; **, p < 0.01.