RT Journal Article
SR Electronic
T1 Suppression of Feedback Loops Mediated by PI3K/mTOR Induces Multiple Overactivation of Compensatory Pathways: An Unintended Consequence Leading to Drug Resistance
JF Molecular Cancer Therapeutics
JO Mol Cancer Ther
FD American Association for Cancer Research
SP 2477
OP 2488
DO 10.1158/1535-7163.MCT-14-0330
VO 13
IS 11
A1 Rozengurt, Enrique
A1 Soares, Heloisa P.
A1 Sinnet-Smith, James
YR 2014
UL http://mct.aacrjournals.org/content/13/11/2477.abstract
AB The development of drug resistance by cancer cells is recognized as a major cause for drug failure and disease progression. The PI3K/AKT/mTOR pathway is aberrantly stimulated in many cancer cells and thus it has emerged as a target for therapy. However, mTORC1 and S6K also mediate potent negative feedback loops that attenuate signaling via insulin/insulin growth factor receptor and other tyrosine kinase receptors. Suppression of these feedback loops causes overactivation of upstream pathways, including PI3K, AKT, and ERK that potentially oppose the antiproliferative effects of mTOR inhibitors and lead to drug resistance. A corollary of this concept is that release of negative feedback loops and consequent compensatory overactivation of promitogenic pathways in response to signal inhibitors can circumvent the mitogenic block imposed by targeting only one pathway. Consequently, the elucidation of the negative feedback loops that regulate the outputs of signaling networks has emerged as an area of fundamental importance for the rational design of effective anticancer combinations of inhibitors. Here, we review pathways that undergo compensatory overactivation in response to inhibitors that suppress feedback inhibition of upstream signaling and underscore the importance of unintended pathway activation in the development of drug resistance to clinically relevant inhibitors of mTOR, AKT, PI3K, or PI3K/mTOR. Mol Cancer Ther; 13(11); 2477–88. ©2014 AACR.