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

我们以往的研究表明，复制错误(RER)在铬酸盐肺癌中的频率很高，DNA错配修复基因hMLH1的表达失活与微卫星高不稳定性表型密切相关。我们推测铬酸盐肺癌的致癌过程：hMLH1蛋白→的抑制、遗传不稳定性→、癌相关基因的异常。为了早期发现肺癌，我们于1982年在日本德岛对83名铬酸盐工业工人进行了支气管活检。我们检测了铬酸盐作业工人中3例异型增生和14例鳞状化生的支气管中hMLH蛋白的表达，以及重型S…中2例原位癌、3例异型增生和7例鳞状化生的支气管中hMLH蛋白的表达。采用催化信号放大系统(DAKO Co.，Carpinteria，CA)方法对福尔马林固定的石蜡包埋组织切片中hMLH1进行免疫组织化学染色。应用抗hMLH1的小鼠单抗(克隆G 168-728，BD Biosciences Pharmingen，加利福尼亚州圣地亚哥)，稀释1：300，组织切片在48℃下孵育2个过夜。在显微镜下，我们评估了每个高倍视野至少200个肿瘤细胞，这些细胞在所有视野中染色更多。核染色频率分为无(0%)、少(35%)、中度(35%)、弥漫性(70%)。结果铬酸盐作业工人无核2例，少核8例，中核5例，弥漫核2例。重度吸烟者中度吸烟组5例，弥漫性吸烟组7例。无组、弱组和中度组均为hMLH蛋白“抑制”组，铬酸盐作业工人的抑制率(88%)显著高于重度吸烟者(42%)。结论DNA错配修复hMLH功能障碍参与了铬酸盐肺癌的早期癌变过程。较少

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