The mammalian target of rapamycin (mTOR) controls cell growth and enlargement and has been found to be aberrant in a wide variety of malignancies. Allosteric mTOR inhibitors, which inhibit mTORC1 but not mTORC2, result in feedback activation of AKT signaling, which can attenuate their antitumor activity. AZD2014 is a second generation mTOR inhibitor that blocks activation of both mTORC1 and mTORC2, and activates apoptosis in cancer cells without activation of AKT signaling. Here, we investigated the therapeutic efficacy of everolimus and AZD2014 in lymphocytic leukemia cell line (L1210) and mouse xenograft model.
Cytotoxicity effect of AZD2014 and everolimus in L1210 cells was assessed after 24 and 48 h by using cell viability assays, clonogenic survival assays, and cell cycle analyses. Cell cycle, mTOR signal transduction pathway and the relative regulatory molecules were examined in mTOR inhibitor-treated L1210 cells by western blotting to detect protein expression. Then, the in vivo anti-leukemic effect of AZD2014 was assessed in L1210 cell-transplanted DBA/2 mice.
AZD2014 significantly inhibited L1210 cell proliferation with an IC50 of 100nM. In contrast, everolimus was a poor growth inhibitor of L1210 cells (IC50 > 200nM). Treatment with AZD2014 was more effective than RAD001 to down-regulate the levels of mTORC1 downstream effectors, including S6K1, 4EBP1,eIF4E and a significant decrease in protein levels of rictor, a component of mTORC2 protein.We also observed inhibition of mTORincreased G1 arrest by reducing cyclin D1 and CDK4 levels, which augmented growth-inhibitory effect of L1210 cells. In vivo, AZD2014 oral administration significantly inhibited the growth of L1210 cell xenograft in DBA/2 mice, and the mice survival was dramatically improved.
These data indicate that AZD2014 may be a better therapeutic agent than mTORC1 inhibitors to enhance the antitumor activity of lymphocytic leukemia both in vitro and under xenograft model in vivo conditions. Antitumor activity of AZD2014 was inhibited of both mTORC1 and mTORC2 activity and cell cycle arrest, leading to lymphocytic leukemia growth inhibition.
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All authors have declared no conflicts of interest.