Keloid disease can be inhibited by antagonizing excessive mTOR signaling with a novel dual TORC1/2 inhibitor

Abstract

Keloid disease (KD) is a fibroproliferative lesion of unknown etiopathogenesis that possibly targets the PI3K/Akt/mTOR pathway. We investigated whether PI3K/Akt/mTOR inhibitor, Palomid 529 (P529), which targets both mammalian target of rapamycin complex 1 (mTORC-1) and mTORC-2 signaling, could exert anti-KD effects in a novel KD organ culture assay and in keloid fibroblasts (KF). Treatment of KF with P529 significantly (P < 0.05) inhibited cell spreading, attachment, proliferation, migration, and invasive properties at a low concentration (5 ng/mL) and induced substantial KF apoptosis when compared with normal dermal fibroblasts. P529 also inhibited hypoxia-inducible factor-1α expression and completely suppressed Akt, GSK3β, mTOR, eukaryotic initiation factor 4E-binding protein 1, and S6 phosphorylation. P529 significantly (P < 0.05) inhibited proliferating cell nuclear antigen and cyclin D and caused considerable apoptosis. Compared with rapamycin and wortmannin, P529 also significantly (P < 0.05) reduced keloid-associated phenotypic markers in KF. P529 caused tissue shrinkage, growth arrest, and apoptosis in keloid organ cultures and substantially inhibited angiogenesis. pS6, pAkt-Ser473, and mTOR phosphorylation were also suppressed in situ. P529 reduced cellularity and expression of collagen, fibronectin, and α-smooth muscle actin (substantially more than rapamycin). These pre-clinical in vitro and ex vivo observations are evidence that the mTOR pathway is a promising target for future KD therapy and that the dual PI3K/Akt/mTOR inhibitor P529 deserves systematic exploration as a candidate agent for the future treatment of KD.