Department of Otolaryngology and Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Cell Cycle. 2012 Apr 15;11(8):1656-63. doi: 10.4161/cc.20120.
Anti-EGFR therapy is among the most promising molecular targeted therapies against cancer developed in the past decade. However, drug resistance eventually arises in most, if not all, treated patients. Emerging evidence has linked epigenetic changes, such as DNA methylation at CpG islands, to the development of resistance to multiple anticancer drugs. In addition, genes that are differentially methylated have increasingly been appreciated as a source of clinically relevant biomarker candidates. To identify genes that are specifically methylated during the evolution of resistance to anti-EGFR therapeutic agents, we performed a methylation-specific array containing a panel of 56 genes that are commonly known to be regulated through promoter methylation in two parental non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC) cell lines and their resistant derivatives to either erlotinib or cetuximab. We found that death-associated protein kinase (DAPK) was hypermethylated in drug-resistant derivatives generated from both parental cell lines. Restoration of DAPK into the resistant NSCLC cells by stable transfection re-sensitized the cells to both erlotinib and cetuximab. Conversely, siRNA-mediated knockdown of DAPK induced resistance in the parental sensitive cells. These results demonstrate that DAPK plays important roles in both cetuximab and erlotinib resistance, and that gene silencing through promoter methylation is one of the key mechanisms of developed resistance to anti-EGFR therapeutic agents. In conclusion, DAPK could be a novel target to overcome resistance to anti-EGFR agents to improve the therapeutic benefit, and further evaluation of DAPK methylation as a potential biomarker of drug response is needed.
抗 EGFR 治疗是过去十年中开发的最有前途的癌症分子靶向治疗之一。然而，在大多数（如果不是全部）接受治疗的患者中，最终都会出现耐药性。新出现的证据将表观遗传变化（如 CpG 岛的 DNA 甲基化）与对多种抗癌药物耐药性的发展联系起来。此外，差异甲基化的基因越来越被认为是临床相关生物标志物候选物的来源。为了确定在对抗 EGFR 治疗药物的耐药性发展过程中特异性甲基化的基因，我们进行了一项甲基化特异性阵列分析，其中包含了一组 56 个基因，这些基因通常被认为是通过启动子甲基化调节的，在两个亲本非小细胞肺癌（NSCLC）和头颈部鳞状细胞癌（HNSCC）细胞系及其对厄洛替尼或西妥昔单抗耐药的衍生系中。我们发现，在两个亲本细胞系产生的耐药衍生系中，死亡相关蛋白激酶（DAPK）高度甲基化。通过稳定转染将 DAPK 恢复到耐药的 NSCLC 细胞中，使细胞对厄洛替尼和西妥昔单抗重新敏感。相反，siRNA 介导的 DAPK 敲低诱导亲本敏感细胞产生耐药性。这些结果表明，DAPK 在西妥昔单抗和厄洛替尼耐药中都发挥重要作用，通过启动子甲基化导致基因沉默是产生抗 EGFR 治疗药物耐药性的关键机制之一。总之，DAPK 可能是克服抗 EGFR 药物耐药性以提高治疗效果的新靶点，需要进一步评估 DAPK 甲基化作为药物反应的潜在生物标志物。
