Department of Surgery, University of Ulsan College of Medicine, Seoul, Korea.
J Cancer Res Clin Oncol. 2011 Oct;137(10):1571-80. doi: 10.1007/s00432-011-1036-7. Epub 2011 Aug 18.
Few efficient methylation markers of chemosensitivity have been discovered. The genome-wide analysis of methylation markers is needed to identify chemosensitive candidates to targeted therapy.
This study describes a two-step process to select chemosensitive candidates of methylation genes. A genome-wide screening of methylation genes was performed using a Beadarray and an in vitro chemosensitivity assay of 119 colorectal cancers (CRCs). Ten candidate genes identified during the initial screening were verified by biological utility assessment using cell viability assays of transfected CRC cells.
Five methylation genes related to sensitivity to bevacizumab regimens (RASSF1, MMP25, KCNQ1, ESR1, and GALR2) or cetuximab regimens (SCL18A2, GPX7, NID2, IGFBP3, and ALX4) were chosen during the first step. A viability assay revealed that GALR2-overexpressing HCT116 cells were significantly more chemosensitive to bevacizumab regimens than control cells (P = 0.022 and 0.019 for bevacizumab with FOLFIRI and FOLFOX, respectively), concurrently verified on a caspase-3 activity assay. GPX7- or ALX4-overexpressed RKO cells were significantly less viable to cetuximab regimens compared to control cells (GPX7: P = 0.027 each for cetuximab with FOLFIRI and FOLFOX; ALX4: P = 0.049 and 0.003 for cetuximab with FOLFIRI and FOLFOX, respectively), but caspase-3 activity was not prominent in GPX7-overexpressed RKO cells.
Two novel genes, GALR2 and ALX4, have been identified as chemosensitive methylation candidates to bevacizumab and cetuximab regimens, respectively. As our study did not include a clinical association study, the two candidates should be validated in large clinical cohorts, hopefully predicting responsive patients to targeted regimens.
尚未发现有效的化疗敏感性甲基化标志物。需要对甲基化标志物进行全基因组分析，以鉴定针对靶向治疗的化疗敏感候选物。
本研究描述了一种两步法来选择甲基化基因的化疗敏感候选物。使用 Beadarray 进行全基因组甲基化基因筛选，并对 119 例结直肠癌（CRC）进行体外化疗敏感性测定。在初始筛选过程中鉴定的 10 个候选基因通过转染 CRC 细胞的细胞活力测定进行生物学效用评估进行验证。
在第一步中选择了与贝伐单抗方案（RASSF1、MMP25、KCNQ1、ESR1 和 GALR2）或西妥昔单抗方案（SCL18A2、GPX7、NID2、IGFBP3 和 ALX4）相关的 5 个甲基化基因。细胞活力测定显示，与对照细胞相比，GALR2 过表达的 HCT116 细胞对贝伐单抗方案的化疗敏感性明显更高（贝伐单抗联合 FOLFIRI 和 FOLFOX 时分别为 P=0.022 和 0.019），同时在 caspase-3 活性测定中得到验证。与对照细胞相比，过表达 GPX7 或 ALX4 的 RKO 细胞对西妥昔单抗方案的活力明显降低（GPX7：贝伐单抗联合 FOLFIRI 和 FOLFOX 时分别为 P=0.027；ALX4：贝伐单抗联合 FOLFIRI 和 FOLFOX 时分别为 P=0.049 和 0.003），但 GPX7 过表达的 RKO 细胞中的 caspase-3 活性不明显。
鉴定出两个新基因 GALR2 和 ALX4 分别为贝伐单抗和西妥昔单抗方案的化疗敏感甲基化候选物。由于本研究未包括临床关联研究，因此这两个候选物应在大型临床队列中进行验证，有望预测对靶向方案有反应的患者。
