Ide Takao, Kitajima Yoshihiko, Ohtaka Kazuma, Mitsuno Mayumi, Nakafusa Yuji, Miyazaki Kohji
Department of Surgery, Saga University Faculty of Medicine, Saga, Japan.
Oncol Rep. 2008 Jun;19(6):1571-6.
The loss of a DNA mismatch repair occurs in approximately 15% of sporadic colorectal cancer (CRC) and is usually caused by the lack of expression of the hMLH1 gene due to promoter methylation. Despite undergoing adjuvant 5-fluorouracil (5-FU) therapy after a curative surgical resection, some patients with advanced-stage CRC develop recurrence. In the present study, we investigated whether the hMLH1 mRNA expression or promoter methylation is a prognostic factor in CRC patients treated with adjuvant 5-FU. The hMLH1 mRNA expression levels were measured by quantitative reverse transcription PCR in cancer and normal epithelial cells that were obtained from 94 CRC patients using a laser capture microdissection. Then, the methylation status of the hMLH1 promoter in the CRC tissues was examined by methylation-specific PCR. The hMLH1 mRNA expression levels were significantly lower in the cancer cells than in the normal mucosa (p<0.01) and the hMLH1 mRNA expression levels in the cancer cells were significantly lower in the CRC tissues with methylated versus unmethylated hMLH1 (p<0.01) in the 94 patients. Among the 35 patients receiving adjuvant 5-FU, the disease-free survival rate was significantly better in the patients demonstrating a low hMLH1 mRNA expression in the cancer cells in comparison to that of the patients with a high hMLH1 mRNA expression (p<0.01). Moreover, a multivariate analysis revealed that hMLH1 mRNA expression was a significant independent prognostic factor for tumor recurrence in CRC patients treated with adjuvant 5-FU. However, hMLH1 methylation was not correlated with the survival in these 35 patients. These data suggest that the hMLH1 mRNA quantitation in colorectal cancer cells may be helpful for evaluating the prognosis of CRC patients receiving 5-FU-based adjuvant chemotherapy after a surgical resection.
DNA错配修复缺陷发生在约15%的散发性结直肠癌（CRC）中，通常是由于启动子甲基化导致hMLH1基因表达缺失所致。尽管在根治性手术切除后接受了辅助性5-氟尿嘧啶（5-FU）治疗，但一些晚期CRC患者仍会出现复发。在本研究中，我们调查了hMLH1 mRNA表达或启动子甲基化是否是接受辅助性5-FU治疗的CRC患者的预后因素。使用激光捕获显微切割技术从94例CRC患者中获取癌组织和正常上皮细胞，通过定量逆转录PCR测量hMLH1 mRNA表达水平。然后，通过甲基化特异性PCR检测CRC组织中hMLH1启动子的甲基化状态。癌细胞中的hMLH1 mRNA表达水平显著低于正常黏膜（p<0.01），在94例患者中，hMLH1甲基化的CRC组织中癌细胞的hMLH1 mRNA表达水平显著低于未甲基化的组织（p<0.01）。在35例接受辅助性5-FU治疗的患者中，癌细胞中hMLH1 mRNA表达低的患者无病生存率明显优于hMLH1 mRNA表达高的患者（p<0.01）。此外，多变量分析显示，hMLH1 mRNA表达是接受辅助性5-FU治疗的CRC患者肿瘤复发的显著独立预后因素。然而，hMLH1甲基化与这35例患者的生存率无关。这些数据表明，结直肠癌细胞中的hMLH1 mRNA定量可能有助于评估手术切除后接受基于5-FU的辅助化疗的CRC患者的预后。
