A mouse model for assessing mTOR kinase-independent role and off-target effect of mTOR kinase inhibitors [III]
mTOR is a serine/threonine kinase with a crucial role in regulating fundamental cellular processes and is an attractive anticancer target. Multiple clinical trials of mTOR kinase inhibitors such as AZD2014 that suppress both mTORC1 and mTORC2 are ongoing, but their specificity and toxicity features remain a concern. We have developed an inducible kinase-dead D2338A mTOR mouse knock-in model and show that it is useful to study the kinase-independent function of mTOR and for assessing the off-target effects of mTOR kinase inhibitors. We found that while the mTOR KI mice in hematopoietic system displayed similar phenotypes to that of mTOR KO mice, they have significantly prolonged survival time than the KO mice. Whereas AZD2014 was mostly on-target in suppressing mTOR kinase activity, mimicking that seen in KI stem cells in transcriptome analysis, off-target genes in KI cells induced by AZD2014 including Ahnak2, Emp1, Lilrb4, Tpsb2, and Cma1 were detected. Our studies reveal kinase-independent function of mTOR in hematopoiesis and presents a mouse model for precisely assessing specificity of mTOR kinase inhibitors. Stringent test of drugs with such mouse models in the preclinical setting may provide useful information guiding the safety and efficacy of related clinical trials. Overall design: Comparative gene expression profiling analysis of RNA-seq data for mTOR WT HSCs and 0.01% DMSO-treated mTOR WT HSCs.