The Mechanism of Combination using mTORC1/2 Inhibitor and Imatinib to Suppress Cell Proliferation of Ph +ALL Cell Line

【Abstract】 Objective To investigate the anti-leukemia effect and mechanism of mTORC1/2 inhibitor PP242 combined with imatinib (IM) on the proliferation of Ph⁺ acute lymphoblastic leukemia (ALL) cell line SUP-B15. Methods SUP-B15 cell line was treated with PP242, imatinib (IM), or PP242 plus IM for 72 h, IC₅₀ values (the concentration of drug required to kill 50% of the cells) and the combination index (CI ) of synergistic cytotoxicity was determined using MTT methods. The expressions of PI3K/Akt/mTOR and apoptosis associated proteins were examined by Western blot test. Results The IC₅₀ value of IM alone was (1.50±0.09) μmol/L, however, the IC₅₀ values were (0.81±0.030) μmol/L, (0.36±0.140) μmol/L and (0.02±0.002) μmol/L combined with 20 nmol/L, 30 nmol/L and 50 nmol/L of PP242, and the CI values were 0.764, 0.545 and 0.507, indicating two drugs had highly synergistic effect on anti-proliferation in the SUP-B15 cell line. The expressions of p-Akt, p-4EBP1, p-elF4E, p-cAbl, p-mTOR and p-P70 were down-regulated significantly in a dose-dependent and time-dependent manner after PP242 treatment．Compared with PP242 or IM alone, the down-regulation of PI3K/Akt/mTOR signaling pathway and the up-regulation of the apoptosis associated proteins (bax and cleaved caspase-3) were more significant in the combination of two drugs. Conclusion The combination of IM and PP242 could increase the inhibition of PI3K/Akt/mTOR signaling pathway and apoptosis mediated by bax and caspase-3 in SUP-B15 cell line.