Carcinogenesis mechanism of lung cancer of the chromate industrial workers with chromate exposure -Relationship between DNA mismatch repair hMLH gene and gene instability-

背景我们的前期研究表明，铬酸盐肺癌中的复制错误（RER）频率很高，DNA错配修复基因hMLH 1表达的失活与微卫星高不稳定性表型密切相关。推测铬酸盐肺癌的发生过程为：hMLH 1蛋白的抑制→基因的不稳定→癌相关基因的异常。在这项研究中，我们研究了hMLH蛋白的表达在癌前病变的支气管活检标本铬酸盐工人和重度吸烟者没有chromate exposure.Material and methodsTo检测肺癌在早期阶段，我们进行了活检的支气管为83铬酸盐工业工人在德岛，日本，在1982年。我们检测了hMLH蛋白在铬酸盐工人中3例不典型增生和14例鳞状上皮化生的支气管中的表达，以及在重金属工人中2例原位癌、3例不典型增生和7例鳞状上皮化生的支气管中的表达。 ...更多信息 使用催化信号放大系统（DAKO Co.，Carpinteria，CA）方法。应用针对hMLH 1的小鼠单克隆抗体（克隆G168 -728，BD Biosciences Pharmingen，San Diego，CA），1：300稀释，并将组织切片在48 ℃下孵育2过夜。在显微镜下，我们评估了每个高倍视野中至少200个肿瘤细胞，这些细胞在所有视野中染色更多。结果无核染色组2例，核染色不足组8例，核染色中等组5例，核染色弥漫组2例。重度吸烟者中中度组5例，弥漫组7例。根据hMLH蛋白表达水平的不同，将hMLH蛋白表达水平分为无抑制、低抑制和中度抑制三组，其中嗜铬工人的抑制率（88%）明显高于重度吸烟者（42%）。少

BackgroundOur previous studies have revealed that the frequency of replication error (RER) in chromate lung cancer is very high and that the inactivation of DNA mismatch repair gene hMLH1 expression strongly correlated with the microsatellite high instability phenotype. We speculate the carcinogenesis process of chromate lung cancer: the repression of hMLH1 protein→the genetic instability→the abnormality of cancer-related genes. In this study, we examined the expression of hMLH protein in pre-malignant lesions of the bronchial biopsy specimens from chromate workers and heavy smokers without chromate exposure.Material and methodsTo detect lung carcinoma at an early stage, we performed biopsies of the bronchus for 83 chromate industry workers in Tokushima, Japan, in 1982. We examined the expression of hMLH protein in the bronchi of 3 dysplasia and 14 squamous metaplasia in the chromate workers and in the bronchi of 2 carcinoma in situ, 3 dysplasia and 7 squamous metaplasia in the heavy s … More mokers without chromate exposure.Immunohistochemical staining for hMLH1 in formalin-fixed, paraffin-embedded tissue sections was performed using the Catalyzed Signal Amplification system (DAKO Co., Carpinteria, CA) method. Mouse monoclonal antibodies to hMLH1 (clone G 168-728, BD Biosciences Pharmingen, San Diego, CA) were applied, diluted 1: 300, and tissue sections were incubated 2 overnight at 48C. Under microscopy, we evaluated at least 200 tumor cells per high power field, which were more stained in all fields. The frequency of nuclear staining was scored as none (0%), scant (<35%), moderate (>=35%,70%<=), and diffuse (>70%).ResultsThere were 2 cases in none group, 8 cases in scant group, 5 cases in moderate group and 2 cases in diffuse group in the chromate workers. On the other hand, there were 5 cases in moderate group and 7 cases in diffuse group in the heavy smokers. We classified none, scant and moderate groups as "repression" of hMLH protein.The repression rate of the chromate workers (88%) was significantly higher than that of the heavy smokers (42%).ConclusionWe speculate that dysfunction of DNA mismatch repair hMLH involve early stage of carcinogenesis of chromate lung cancer. Less