结直肠癌DNA错配修复蛋白的表达及临床病理学意义

The expression of DNA mismatch repair proteins in colorectal carcinoma and clinical pathological significance

目的探讨错配修复蛋白在结直肠癌中的表达及临床病理学意义。方法采用免疫组织化学法,对55例结直肠癌组织标本进行MLH1、MSH2、MSH6、PMS2四种错配修复蛋白检测,同时观察其与临床病理学参数关系。采用real-time PCR法对其中10例进行鼠类肉瘤病毒癌基因(KRAS)第2号外显子和鼠类肉瘤滤过性毒菌致癌基因同源体B1(BRAF)基因第15号外显子突变检测。结果 55例患者中50例四种蛋白均阳性表达,为微卫星稳定(MSS),5例患者蛋白表达有缺失,提示为高频微卫星不稳定(MSI-H),缺失率为9.09%,其中4例MLH1、PMS2联合缺失,1例MSH2、MSH6联合缺失;MSI-H患者肿瘤多发生在右半结肠,与MSS患者相比差异显著(P=0.01),其中3例为黏液癌或伴黏液分化癌,均无淋巴结转移;10例行KRAS及BRAF突变检测的病例中,6例存在KRAS基因突变,1例存在BRAF基因突变且表现为MLH1、PMS2表达联合缺失。结论 MSI-H结直肠癌患者多发生在右半结肠,这类患者有以黏液癌或伴有黏液分化癌多见及淋巴结转移少见为特征的趋势;MSI-H与MSS患者相比,在年龄、性别、肿块大小、肿瘤分级及分期方面无显著差异;发现散发性结直肠癌中具有微卫星不稳定的病例,结合其他检测可进一步指导临床用药,为新的治疗方案提供理论依据。

Objective To discuss the expression of DNA mismatch repair proteins in colorectal carcinoma and their clinical pathological significances. Methods A total of 55 colorectal carcinoma cases（CRCs） were studied. The expressions of MLH1, MSH2, MSH6 and PMS2 were detected by immunohistochemistry（IHC）, and their relationships with clinical pathological figures were investigated. Real-time PCR was used to detect the mutations in exon 2 of KRAS gene and exon 15 of BRAF gene in 10 cases. Results 50 from 55 cases expressed the four proteins, indicating MSS. The deficiency expression of MMR proteins was detected in the remaining 5 cases, with negative MLH1 and PMS2 in 4 cases and negative MSH2 and MSH6 in 1 case. They were MSI-H. MSI-H cases tended to occur in the right colon, and there was significant difference in comparison with patients with MSS（P = 0.01）. There were 3 cases of mucinous adenocarcinoma or with mucus differentiation carcinoma in 5 MSI-H cases. The metastasis of lymph node wasn＇t found in these 5 cases. KRAS and BRAF mutations were detected in 10 cases. KRAS mutation was found in 6 cases. BRAF mutation was detected in one case, which showed the deficiency of MLH1 and PMS2. Conclusions Colorectal carcinoma patients with MSI-H tended to occur in the right colon, had the trend of mucinous carcinoma or accompanied by mucus secretion and less lymph node metastasis. But more cases are needed to confirm this. There were no significant differences between MSI-H and MSS in the patients＇ age, sex, tumor size, tumor grade and stage. MSI cases were found in the sporadic colorectal carcinoma by IHC of four kinds of DNA mismatch repair proteins. Combined with other detections（such as the mutations of KRAS and BRAF genes）, it could further guide the application of drugs in clinical therapy, and provide theory basis for new treatment（such as immunotherapy）.