错配修复基因hMSH2在散发性胰岛素瘤中的表达及临床意义

目的 探讨错配修复基因hMSH2在散发性胰岛素瘤发生中的作用,以及hMSH2表达能否作为胰岛素瘤良、恶性鉴别的标志物.方法 以取自50例散发性胰岛素瘤患者的55个肿瘤(良性40个,恶性15个)作为研究对象,用免疫组化方法检测hMSH2蛋白表达.提取显微切割组织DNA,用PCR-LOH方法测定hMSH2的杂合缺失.在3条染色体上选择6个微卫星位点,PCR法测定肿瘤组织有无微卫星不稳定(MSI).并与患者的临床、病理资料进行相关分析.结果 13%的散发性胰岛素瘤hMSH2蛋白表达下调.55个胰岛素瘤均未发生hMSH2基因杂合缺失.36%(20/55)的胰岛素瘤中发现高频MSI(MSI-H,即6个位点中至少2个位点发生(MSI).15个恶性肿瘤中有33%存在hMSH2表达下调,而40个良性肿瘤中hMSH2表达下调仅为5%(P=0.019).结论 错配修复基因hMSH2表达丢失或下降可能与胰岛素瘤的恶性程度相关.测定肿瘤中hMSH2表达下调可作为判断该肿瘤良、恶性的潜在标志物.

Expression and clinical implications of hMSH2 gene in sporadic insnlinomns

Objective To investigate the role of hMSH2 in the pathogenesis of sporadic insulinomas and to determine whether the expression of hMSH2 could be used to differentiate benign sporadic insulinomas from malignant ones. Methods Fifty-five sporadic insulinomas (40 benign and 15 malignant tumors) resected from 50 patients were obtained. Expression of hMSH2 was detected by immunohistochemistry staining. DNA was obtained from micradissected tissue. Loss of heterozygnsity (LOH) of hMSH2 gene was detected by PCR-LOH. 6 microsatellite markers were selected on 3 chromosomes, and microsatellite instability (MSI) status of tumor tissue were detected by PCR. The findings were analyzed in relation to the clinicopathological characteristics. Results Down-regulation of hMSH2 expression was found in 13% of 55 sporadic insulinomas. LOH of the hMSH2 gene was not present in 55 insulinomas. High frequency MSI (MSI-H, MSI occurred in at least 2 out of 6 sites) was present in 36% (20/55) of all the insulinomas. Down-regulation of hMSH2 expression was found in 33% of the 15 malignant tumors, while it was 5% in benign tumors (P < 0. 05). Conclusions Down-regulation of mismatch repair gene hMSH2 may be correlated with the degree of tumor malignancy. The expression of hMSH2 could be used as a potential marker for distinguishing benign insulinoma from malignant ones.