iTorin1—An Active Site Inhibitor of mTOR, Suppresses Prostate Cancer Cell Growth Induced by Activated α2M-Macroglobulin Ligation of Cell Surface GRP78


In this study, we reported the effect of the ATP binding site competitive inhibitor Torin1 on activated α2-macroglobulin (α2M*)-induced cell proliferation and activation of mTORC1 and mTORC2 signaling in prostate cancer cells. Torin1 significantly inhibited α2M*-induced cellproliferation as measured by protein and DNA synthesis. Translational activity, a major cellular response in malignant cells,is coordinately regulated by the mTORC1-S6-kinaseand mTORC1-4EBP1 axes. Torin1 significantly inhibited α2M*- and insulin-induced activation of mTORC1 as determined by phosphorylation of S6-kinaseat Thr389 and 4EBP1 at Thr37/46 compared to untreated cells employing Raptor immunoprecipitates. Torin1 also significantly inhibited α2M*- and insulin-induced upregulation of p-AktT308 and p-AktS473 in prostate cancer cells. The effect was comparable to that of insulin employed as a positive control. Finally, Torin1 inhibited α2M*- and insulin-induced activation of mTORC2 kinase assayas measured by phosphorylation of Akt at Ser473 inRictor immunoprecipitates of prostate cancer cells.

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U. Misra and S. Pizzo, "iTorin1—An Active Site Inhibitor of mTOR, Suppresses Prostate Cancer Cell Growth Induced by Activated α2M-Macroglobulin Ligation of Cell Surface GRP78," Journal of Cancer Therapy, Vol. 4 No. 4A, 2013, pp. 74-85. doi: 10.4236/jct.2013.44A008.

Conflicts of Interest

The authors declare no conflicts of interest.


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