PPARγ agonists regulate the expression of stemness and differentiation genes in brain tumour stem cells

BACKGROUND: Brain tumour stem cells (BTSCs) are a small population of cancer cells that exhibit self-renewal, multi-drug resistance, and recurrence properties. We have shown earlier that peroxisome proliferator-activated receptor gamma (PPAR gamma) agonists inhibit the expansion of BTSCs in T98G and U87MG glioma. In this study, we analysed the influence of PPAR gamma agonists on the expression of stemness and differentiation genes in BTSCs. METHODS: The BTSCs were isolated from T98G and DB29 glioma cells, and cultured in neurobasal medium with epidermal growth factor+basic fibroblast growth factor. Proliferation was measured by WST-1 (4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2 H-5-tetrazolio]-1,3-benzene disulphonate) and 3H thymidine uptake assays, and gene expression was analysed by quantitative reverse-transcription PCR and Taqman array. The expression of CD133, SRY box 2, and nanog homeobox (Nanog) was also evaluated by western blotting, immunostaining, and flow cytometry. RESULTS: We found that PPAR gamma agonists, ciglitazone and 15-deoxy-Delta(12,14) -ProstaglandinJ2, inhibited cell viability and proliferation of T98G- and DB29-BTSCs. The PPAR gamma agonists reduced the expansion of CD133(+) BTSCs and altered the expression of stemness and differentiation genes. They also inhibited Sox2 while enhancing Nanog expression in BTSCs. CONCLUSION: These findings highlight that PPAR gamma agonists inhibit BTSC proliferation in association with altered expression of Sox2, Nanog, and other stemness genes. Therefore, targeting stemness genes in BTSCs could be a novel strategy in the treatment of glioblastoma. British Journal of Cancer (2012) 106, 1702-1712. doi:10.1038/bjc.2012.161 www.bjcancer.com Published online 24 April 2012 (C) 2012 Cancer Research