Melanoma Immunology and Oncology Group, The Centenary Institute, University of Sydney, Camperdown, New South Wales, Australia; Melanoma Institute Australia, The University of Sydney, Sydney, New South Wales, Australia.
Systems Biology and Cancer Metabolism, Program for Quantitative Systems Biology, University of California Merced, Merced, California, USA.
J Invest Dermatol. 2020 Dec;140(12):2442-2454.e5. doi: 10.1016/j.jid.2020.02.042. Epub 2020 Apr 29.
The histone methylase EZH2 is frequently dysregulated in melanoma and is associated with DNA methylation and silencing of genes involved in tumor suppression. In this study, we used chromatin immunoprecipitation and sequencing to identify key suppressor genes that are silenced by histone methylation in constitutively active EZH2 mutant melanoma and assessed whether these regions were also sites of DNA methylation. The genes identified were validated by their re-expression after treatment with EZH2 and DNA methyltransferase inhibitors. The expression of putative EZH2 target genes was shown to be highly relevant to the survival of patients with melanoma in clinical datasets. To determine correlates of response to EZH2 inhibitors, we screened a panel of 53 melanoma cell lines for drug sensitivity. We compared RNA sequencing profiles of sensitive to resistant melanoma cells and performed pathway analysis. Sensitivity was associated with strong downregulation of IFN-γ and IFN-α gene signatures that were reversed by treatment with EZH2 inhibitors. This is consistent with EZH2-driven dedifferentiated invasive states associated with treatment resistance and defects in antigen presentation. These results suggest that EZH2 inhibitors may be most effectively targeted to immunologically cold melanoma to both induce direct cytotoxicity and increase immune responses in the context of checkpoint inhibitor immunotherapy.
组蛋白甲基转移酶 EZH2 在黑色素瘤中经常失调，与涉及肿瘤抑制的基因的 DNA 甲基化和沉默有关。在这项研究中，我们使用染色质免疫沉淀和测序来鉴定由组成性激活的 EZH2 突变黑色素瘤中组蛋白甲基化沉默的关键抑制基因，并评估这些区域是否也是 DNA 甲基化的位点。通过用 EZH2 和 DNA 甲基转移酶抑制剂处理后这些基因的重新表达来验证它们的存在。在临床数据集显示，假定的 EZH2 靶基因的表达与黑色素瘤患者的生存高度相关。为了确定对 EZH2 抑制剂反应的相关性，我们筛选了 53 种黑色素瘤细胞系对药物的敏感性。我们比较了敏感和耐药黑色素瘤细胞的 RNA 测序图谱，并进行了通路分析。敏感性与 IFN-γ 和 IFN-α 基因特征的强烈下调相关，这些特征可以通过 EZH2 抑制剂治疗逆转。这与 EZH2 驱动的去分化侵袭状态一致，这种状态与治疗抵抗和抗原呈递缺陷有关。这些结果表明，EZH2 抑制剂可能最有效地针对免疫冷黑色素瘤，以在检查点抑制剂免疫治疗的背景下诱导直接细胞毒性和增强免疫反应。
