Hyperactivated mTORC1 downregulation of FOXO3a/PDGFR?/AKT cascade restrains tuberous sclerosis complex-associated tumor development.

ABSTRACT: Hyperactivation of mammalian target of rapamycin complex 1 (mTORC1), caused by loss-of-function mutations in either the TSC1 or TSC2 gene, leads to the development of tuberous sclerosis complex (TSC), a benign tumor syndrome with multiple affected organs. mTORC1-mediated inhibition of AKT constrains the tumor progression of TSC, but the exact mechanisms remain unclear. Herein we showed that loss of TSC1 or TSC2 downregulation of platelet-derived growth factor receptor ? (PDGFR?) expression was mediated by mTORC1. Moreover, mTORC1 inhibited PDGFR? expression via suppression of forkhead box O3a (FOXO3a)-mediated PDGFR? gene transcription. In addition, ectopic expression of PDGFR? promoted AKT activation and enhanced proliferation and tumorigenic capacity of Tsc1- or Tsc2-null mouse embryonic fibroblasts (MEFs), and vice versa. Most importantly, rapamycin in combination with AG1295, a PDGFR inhibitor, significantly inhibited growth of TSC1/TSC2 complex-deficient cells in vitro and in vivo. Therefore, downregulated FOXO3a/PDGFR?/AKT pathway exerts a protective effect against hyperactivated mTORC1-induced tumorigenesis caused by loss of TSC1/TSC2 complex, and the combination of rapamycin and AG1295 may be a new effective strategy for TSC-associated tumors treatment.

SUBMITTER: Wang L 

PROVIDER: S-EPMC5589626 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature