Figure 6. The role of mTOR in PI3K/Akt and MEK/Erk pathways. Optimal concentration of LY294002, PD98059 or rapamycin was added into MSCs culture 1h before treated with PDGF-BB. LY294002 significantly inhibited PDGF-BB induced phosphorylation of Akt, and partly inhibited phosphorylation of mTOR, Thr389 and Ser371, while PD98059 inhibited phosphorylation of ERK1/2. In contrast, rapamycin, rapamycin combined with LY294002 (L+R) or rapamycin combined with PD98059 (P+R) could completely inhibit phosphorylation of mTOR, Thr389 and Ser371 (A). Different inhibitors were added 1, 6, 12 or 24h before treated with PDGF-BB. The CCK-8 test revealed that compared with LY294002 or PD98059, rapamycin revealed better Inhibited effect of PDGF-BB-induced viability of MSCs, while combination of LY294002 and PD98059 revealed similar effect with rapamycin. Results are mean ± SD from three independent experiments (B). Con: Control; N: None; A: AG1296; L: LY294002; P: PD98059; R: rapamycin; L+R: LY294002+ rapamycin; P+R: PD98059+ rapamycin.