Abstract 14683: Everolimus Prevents Vascular Smooth Muscle Cell Proliferation by Repressing Cell Cycle-Dependent Telomerase Activation
BACKGROUND: Telomerase activation induces mitogenic stimulation of vascular smooth muscle cells during neointima formation. In the present study, we investigated the hypothesis that telomerase constitutes a key downstream target for the anti-proliferative activity of everolimus, frequently used as a platform for drug-eluting coronary stents to prevent restenosis after coronary artery angioplasty.
METHODS AND RESULTS: Using a series of molecular approaches, we first demonstrate that everolimus inhibits telomerase activity and telomerase reverse transcriptase (TERT) expression in VSMC through an Ets-1-dependent inhibition of TERT promoter activity. Transcriptional repression of TERT by everolimus confers anti-proliferative activity in VSMC, since the inhibition of VSMC proliferation in vitro and neointima formation in vivo by everolimus are lost in mice overexpressing a TERT transgene. The inhibition of TERT-dependent VSMC proliferation by everolimus occurred in the absence of telomere shortening but rather as a result of a G1-S phase arrest of the cell cycle. Although everolimus failed to inhibit phosphorylation of the retinoblastoma protein as the key gatekeeper or cell cycle transition, it potently repressed its downstream target genes including MCM 7, PCNA and Cyclin A. In chromatin immunoprecipitation assay we further demonstrate that TERT induces E2F binding to the promoters of these S phase genes and histone acetylation, effects that are potently inhibited by everolimus and mediate its antiproliferative activity in VSMC.
CONCLUSIONS: These results characterize telomerase as a previously unrecognized target for the antiproliferative activity of everolimus. In addition, our studies identify a novel mitogenic pathway in VSMC, which depends on the epigenetic modification of chromatin at S phase gene promoters by TERT.
Author Disclosures: J. Aono: None. E. Ruiz-Rodriguez: None. H. Qing: None. E.B. Heywood: None. K.L. Jones: None. D. Bruemmer: None.
- © 2014 by American Heart Association, Inc.