Abstract B12: Rapamycin-induced miR-21 promotes the survival of mTORC1 hyperactivated cells in tuberous sclerosis complex models

Abstract

Abstract Background: Tuberous sclerosis complex (TSC) is a multisystem, hamartomatous disease associated with tumors of the brain, skin and kidney, as well as progressive cystic lung destruction characteristic of lymphangioleiomyomatosis (LAM). TSC is caused by mutations in TSC1 or TSC2, resulting in hyperactive mechanistic Target of Rapamycin (mTOR) 1 signaling. Rapamycin and related rapalogs inhibit mTORC1 activity and stabilize tumors in TSC patients, but tumor progression proceeds at pretreatment rates following cessation of therapy. MicroRNA repress target gene expression and are commonly dysregulated in cancers. In previously published work, we identified a group of rapamycin responsive miRNA, rapa-miRs. Surprisingly the most upregulated rapa-miRs, miR-21 in particular, are known pro-survival oncogenic miRNA (oncomiRs). We hypothesize that inhibiting miR-21 and downstream targets may lead to more complete and durable responses to mTORC1 inhibitors. Methods: We utilized qRT-PCR to determine the kinetics of miR-21 induction with rapamycin in various cell types and in mouse xenografts. Mimics and inhibitors were used to determine the functional consequences of miR-21 in TSC2-null cells. Expression profiling was used to identify miRNA target genes. Bioinformatics and network analysis approaches were implemented to identify biological relationships between the miR-21 targets. Results: Our initial screens identified miR-29b, -21, -24, -221, -106a and -199a as candidate rapa-miRs. Rapamycin induced miR-21 greater than 1.5 fold in diverse cell lines and in mouse xenografts. We have identified pro-cell death targets, PPIF, TP53BP2 and PDCD4, which are negatively regulated by miR-21 upon rapamycin treatment. Network analysis using the Consolidated Interactome (CI) revealed that rapa-miRs inhibit multiple key pro-apoptotic targets. These data suggest that rapa-miRs regulate proteins critical for cell fate determination and survival in response to rapamycin treatment. Conclusions: Rapamycin induces pro-survival oncomiR, miR-21, which may be a valuable target for therapeutic intervention in TSC. Citation Format: Hilaire C. Lam, Harilaos Filippakis, Katherine A. Cottrill, Alicia Llorente Lope, Damir Khabibullin, Carmen Priolo, Barbara Ogorek, Stephen Y. Chan, Ana Pereira, Elizabeth P. Henske. Rapamycin-induced miR-21 promotes the survival of mTORC1 hyperactivated cells in tuberous sclerosis complex models. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr B12.