Glioblastomas are lethal cancers defined by angiogenesis and pseudopalisading necrosis. Here, we demonstrate that these histological features are associated with distinct transcriptional programs, with vascular regions showing a proneural profile, and hypoxic regions showing a mesenchymal pattern. As these regions harbor glioma stem cells (GSCs), we investigated the epigenetic regulation of these two niches. Proneural, perivascular GSCs activated EZH2, whereas mesenchymal GSCs in hypoxic regions expressed BMI1 protein, which promoted cellular survival under stress due to downregulation of the E3 ligase RNF144A. Using both genetic and pharmacologic inhibition, we found that proneural GSCs are preferentially sensitive to EZH2 disruption, whereas mesenchymal GSCs are more sensitive to BMI1 inhibition. Given that glioblastomas contain both proneural and mesenchymal GSCs, combined EZH2 and BMI1 targeting proved more effective than either agent alone both in culture and in vivo, suggesting that strategies that simultaneously target multiple epigenetic regulators within glioblastomas may be effective in overcoming therapy resistance caused by intratumoral heterogeneity.
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We thank PTC Therapeutics for providing PTC209 and PTC596, as well as performing measurement of drug levels. We thank E.P. Sulman (MD Anderson Cancer Center) and A.W. Boyd (Queensland Institute of Medical Research) for subtype-characterized GSCs (PN11, PN23, PN-JK2, PN-MMK1, MES20, MES28 and MES-MN1). We would like to thank N. DeWitt for editorial assistance, as well as the Cleveland Clinic Lerner Research Institute imaging core and proteomics core service teams. We also thank members of J.N.R.'s lab for input about the manuscript. Finally, we would like to thank our funding sources: the National Institutes of Health grants CA203101 (L.K.); CA183510 (T.E.M.); CA217065 (R.C.G.); CA217066 (B.C.P.); CA043703 (J.S.B.-S.); CA169117, CA184090, NS091080 and NS099175 (S.B.); CA197718, CA154130, CA169117, CA171652, NS087913 and NS089272 (J.N.R.); the Peter D. Cristal Chair, the Kimble Family Foundation, the Ferry Foundation, the Jerry Kaufman GBM Research Fund, and CA217956 (A.E.S.); the General Program of the National Natural Science Foundation of China (81572891) (X.J.); Canadian Institutes of Health Research Banting Fellowship (S.C.M.).
J.N.R. received an honorarium from PTC Therapeutics as an advisory board member.
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Jin, X., Kim, L., Wu, Q. et al. Targeting glioma stem cells through combined BMI1 and EZH2 inhibition. Nat Med 23, 1352–1361 (2017). https://doi.org/10.1038/nm.4415
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