ABSTRACT

Drug resistance is one of the trademark features of Cancer Stem Cells (CSCs). We and others have recently shown that paucity of functional death receptors (DR4/5) on the cell surface of tumour cells is one of the major reasons for drug resistance, but their involvement in the context of in CSCs is poorly understood. By harnessing CSC specific cytotoxic function of salinomycin, we discovered a critical role of epigenetic modulator EZH2 in regulating the expression of DRs in colon CSCs. Our unbiased proteome profiler array approach followed by ChIP analysis of salinomycin treated cells indicated that the expression of DRs, especially DR4 is epigenetically repressed in colon CSCs. Concurrently, EZH2 knockdown demonstrated increased expression of DR4/DR5, significant reduction of CSC phenotypes such as spheroid formation in-vitro and tumorigenic potential in-vivo in colon cancer. TCGA data analysis of human colon cancer clinical samples shows strong inverse correlation between EZH2 and DR4. Taken together, this study provides an insight about epigenetic regulation of DR4 in colon CSCs and advocates that drug-resistant colon cancer can be therapeutically targeted by combining TRAIL and small molecule EZH2 inhibitors.

摘要

耐药性是癌症干细胞 (CSC) 的标志性特征之一。我们和其他人最近表明，肿瘤细胞表面缺乏功能性死亡受体 (DR4/5) 是耐药性的主要原因之一，但它们在 CSC 中的参与却知之甚少。通过利用盐霉素的 CSC 特异性细胞毒功能，我们发现了表观遗传调节剂 EZH2 在调节结肠 CSC 中 DR 表达中的关键作用。我们的无偏蛋白质组分析仪阵列方法随后对盐霉素处理的细胞进行 ChIP 分析表明 DR，尤其是 DR4 的表达在结肠 CSC 中受到表观遗传抑制。同时，EZH2 敲低显示 DR4/DR5 表达增加，CSC 表型如球体形成显着减少结肠癌的体外和体内致瘤潜力。人结肠癌临床样本的 TCGA 数据分析显示 EZH2 和 DR4 之间存在强负相关。总之，这项研究提供了关于结肠 CSC 中 DR4 的表观遗传调控的见解，并主张通过结合 TRAIL 和小分子 EZH2 抑制剂可以治疗靶向耐药性结肠癌。