错配修复蛋白表达缺失在结直肠癌中的意义

目的检测结直肠癌组织中错配修复（MMR）蛋白表达情况,探究错配修复缺陷（dMMR）与患者临床病理特征的相关性及其对预后的影响。 方法回顾性收集2019年1月至2021年5月于攀枝花市中心医院就诊且行根治术治疗的214例结直肠癌患者临床资料及病理组织标本进行研究。采用免疫组织化学染色法和免疫印迹法分别检测临床肿瘤组织、对应癌旁正常组织中MMR蛋白（hMSH2、hMSH6、hMLH1、hPMS2）的表达情况,任一蛋白表达缺失则判定为dMMR。分析MMR蛋白表达与患者临床病理特征的相关性;Pearson检验结直肠癌组织中四种MMR蛋白表达缺失的相关性;绘制Kaplan-Meier生存曲线,分析dMMR对患者预后生存的影响。 结果（1）四种MMR蛋白阳性染色均主要分布于细胞核中,呈棕黄色或棕褐色。结直肠癌组织中dMMR发生率为15.4%（33/214）,显著高于对应癌旁正常组织的3.3%（7/214）,差异有统计学意义（χ²=18.642,P<0.001）。hMLH1蛋白表达缺失25例,hPMS2 20例,hMSH2 12例,hMSH6 9例;MMR蛋白常协同表达缺失,以hMLH1/hPMS2协同缺失为主。（2）dMMR与肿瘤位置有关,多位于右半结肠;错配基因功能正常（pMMR）患者则多位于直肠和左半结肠,表现为高-中分化腺癌。hMLH1表达缺失多为中-低分化腺癌,与肿瘤直径、分化程度和TNM分期密切相关;hMSH2表达缺失与肿瘤直径密切相关;hPMS2表达缺失与分化程度、TNM分期及浸润深度密切相关;hMSH6表达缺失与肿瘤形态密切相关（均P<0.05）。（3）结直肠癌组织中四种MMR蛋白表达缺失呈正相关关系,以hMLH1/hPMS2、hMSH2/hMSH6协同表达缺失最为显著（P<0.05）。（4）dMMR患者的术后累积总生存率为84.8%,显著高于pMMR患者的61.3%,差异有统计学意义（Log-rank χ²=2.985,P=0.043）。 结论结直肠癌组织中dMMR发生率高于癌旁正常组织,在右半结肠癌患者中比例更高,以hMLH1/hPMS2协同表达缺失较为多见;dMMR患者预后更好。dMMR对于判断结直肠癌临床恶性程度、选择治疗方案及预测患者预后有重要意义。

Significance of mismatched repair protein expression loss in colorectal cancer

ObjectiveTo detect the expression of mismatch repair (MMR) protein in colorectal cancer, and to explore the correlation between deficient mismatch repair (dMMR) and clinicopathological features and its impact on the prognosis of patients. MethodsThe clinical data and pathological tissue samples of 214 patients with colorectal cancer undergoing radical surgery in Panzhihua City Central Hospital from January 2019 to May 2021 were collected retrospectively. Immunohistochemical staining and Western blotting were used to detect the expression of MMR proteins (hMSH2, hMSH6, hMLH1 and hPMS2) in clinical tumor tissues and corresponding adjacent normal tissues respectively, and the loss of any protein expression was determined as dMMR. The correlation between MMR protein expression and clinicopathological features was analyzed. Pearson correlation analysis was used to test the correlation between the loss of expression of four MMR proteins in colorectal cancer. Kaplan-Meier survival curve was drawn to analyze the influence of dMMR on the prognosis and survival of patients. Results(1) The positive staining of the four MMR proteins were mainly distributed in the nucleus, showing brownish yellow or brown signals. dMMR was found in 33 (15.4%) of 214 colorectal cancer patients, which was significantly higher than 3.3% (7/214) of the corresponding adjacent normal tissues, and the difference was statistically significant (χ²=18.642, P<0.001). HMLH1 protein expression was lost in 25 cases, hPMS2 in 20 cases, hMSH2 in 12 cases and hMSH6 in 9 cases. MMR proteins were often co-expressed deletion, mainly in hMLH1/hPMS2. (2) dMMR was associated with tumor location, which was more common in the right colon cancer patients. And proficiency of MMR (pMMR) patients were more likely to be located in the rectum and left colon, presenting as high-medium differentiated adenocarcinoma. The loss of hMLH1 expression was mostly in medium-low differentiated adenocarcinoma, which was closely related to tumor diameter, degree of differentiation and TNM stage. The loss of hMSH2 expression was closely related to tumor diameter, while the loss of hPMS2 expression to the degree of differentiation, TNM stage and the depth of muscular invasion, and the loss of hMSH6 expression to tumor morphology (all P<0.05). (3) There was positive correlation between the expression loss of four MMR proteins in colorectal cancer tissues, and the co-expression deletion of hMLH1/hPMS2 and hMSH2/hMSH6 were the most significant (P<0.05). (4) The cumulative overall survival rate of dMMR patients was 84.8%, which was significantly higher than that of pMMR patients (61.3%), and the difference was statistically significant (Log-rank χ²=2.985, P=0.043). ConclusionsThe incidence of dMMR in colorectal cancer tissues is higher than that in normal adjacent tissues, the proportion of dMMR is higher in the right colon cancer patients, and the co-expression deletion of hMLH1/hPMS2 is more common. dMMR is closely related to the clinicopathological features of patients, and the prognosis may be better, which has important guiding significance for the judgment of clinical malignant degree of colorectal cancer, the selection of treatment plan, and the prediction of prognosis of patients.