Abstract 4657: Selective inhibitors epigenetically modify and eradicate tumor-initiating stem-like cells through downregulating microRNA 22-mediated TET induction and apoptosis

Tumor-initiating stem-like cells (TICs) are a minor population in bulk tumors that play a critical role in tumor recurrence and therapy-resistance. We previously showed that a key stemness marker Nanog is upregulated that regulates self-renewal and pluripotency of embryonic stem cells and TICs. We demonstrated that alcohol-mediated activation of Toll-like receptor 4 (TLR4) by endotoxin resulted in increased expression of pluripotency stem cell transcription factor NANOG that metabolically reprograms tumor-initiating stem-like cells (TICs: cancer stem cells) via inhibition of oxidative phosphorylation and activation of fatty acid oxidation in our recently accepted Cell Metabolism paper. Discovery of a drug that specifically targets TICs would be a vital goal for cancer therapy. To identify selective TIC inhibitors, we conducted a high throughput screening of an FDA-approved drug library using combination of Nanog promoter-GFP-based screening with viability-based screening and their combination screening of each hit compound. Our high-throughput screening identified the best combination of repurposed FDA-approved drugs: all-trans retinoic acid (ATRA) and the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) that repressed NANOG and induces apoptosis of TICs. Treatment of ATRA inhibits self-renewal ability in vitro. To specifically target the CD133 (+) population, we encapsulated ATRA into nanoparticles conjugated with CD133 antibody using biodegradable poly(D,L-lactide-co-glycolide) (PLGA) polymer. The combination treatment significantly inhibited tumor growth compared to single drug treatments while the ATRA or SAHA monotherapy groups did not reduce or even promoted tumor growth. The combination of ATRA with SAHA specifically induces apoptosis of TICs. Targeting of TICs by NANOG antagonism increases drug susceptibility in tumor-bearing mice and achieves ∼90% tumor growth suppression. RNA-seq analysis identified that ATRA+SAHA treatment reduced expression of MicroRNA-22 (miR-22), leading to induction of PTEN and ten-eleven translocation enzymes (TET2), which demethylates DNA. PTEN induction promoted P-FOXO3A and induced BIM, leading to induction of apoptosis. The combined treatment Induced TET1/2 to demethylate p53-binding sites of NANOG promoter, leading to downregulation of NANOG. Taken together, combination treatment of ATRA with SAHA may serve as a novel avenue for HCC treatment. Novel combination of repurposed drugs is cost-effective therapeutic strategy to target microRNA for eradication of TICs, leading to inhibition of metastasis and recurrence. Citation Format: Chia-Lin Chen, Suresh Swaminathan, Ameya Kirtane, Jayanth Panyam, Keigo Machida. Selective inhibitors epigenetically modify and eradicate tumor-initiating stem-like cells through downregulating microRNA 22-mediated TET induction and apoptosis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4657.