Department of Experimental Pathology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Clin Cancer Res. 2010 Jan 15;16(2):398-409. doi: 10.1158/1078-0432.CCR-09-1677. Epub 2010 Jan 12.
Some 85% of lung cancers are smoking related. Here, we investigate the role of serine protease HtrA3 in smoking-related lung cancer.
We assess HtrA3 methylation and its corresponding expression in the human bronchial cell line BEAS-2B following cigarette smoke carcinogen treatment, in lung cancer cell lines and in primary lung tumors from light, moderate, and heavy smokers. We also show the effects of HtrA3 downregulation on MTT reduction and clonogenic survival with etoposide and cisplatin treatment and the corresponding effects of HtrA3 re-expression during treatment.
We show for the first time that HtrA3 expression is reduced or completely lost in over 50% of lung cancer cell lines and primary lung tumors from heavy smokers. Treatment of HtrA3-deficient cell lines with 5-aza-2'-deoxycytidine resulted in a dose-dependent increase in HtrA3 transcription. Further, sequence analysis of bisulfite-modified DNA from lung cancer cell lines and from primary lung tumors showed an increased frequency of methylation within the first exon of HtrA3 with a corresponding loss of HtrA3 expression, particularly in tumors from smokers. In BEAS-2B, treatment with the cigarette smoke carcinogen 4-(methylnitrosamino)-I-(3-pyridyl)-1-butanone resulted in HtrA3 downregulation with a corresponding increase in methylation. Additional studies indicate resistance to etoposide and cisplatin cytotoxicity as a functional consequence of HtrA3 loss. Finally, immunohistochemical analysis of primary lung tumors revealed a strong correlation between low HtrA3 expression and heavy smoking history.
Collectively, these results suggest that cigarette smoke-induced methylation of HtrA3 could contribute to the etiology of chemoresistant disease in smoking-related lung cancer.
约 85%的肺癌与吸烟有关。在这里，我们研究丝氨酸蛋白酶 HtrA3 在与吸烟相关的肺癌中的作用。
我们评估了香烟烟雾致癌物处理后人类支气管细胞系 BEAS-2B 中 HtrA3 甲基化及其相应表达，以及在肺癌细胞系和轻度、中度和重度吸烟者的原发性肺肿瘤中的表达。我们还展示了 HtrA3 下调对依托泊苷和顺铂处理的 MTT 减少和集落形成存活的影响，以及在治疗过程中 HtrA3 重新表达的相应影响。
我们首次表明，超过 50%的肺癌细胞系和重度吸烟者的原发性肺肿瘤中 HtrA3 表达降低或完全丢失。用 5-aza-2'-脱氧胞苷处理 HtrA3 缺陷细胞系，导致 HtrA3 转录呈剂量依赖性增加。此外，对肺癌细胞系和原发性肺肿瘤的亚硫酸氢盐修饰 DNA 的序列分析显示，HtrA3 第一外显子内的甲基化频率增加，相应的 HtrA3 表达丢失，特别是在吸烟者的肿瘤中。在 BEAS-2B 中，用香烟烟雾致癌物 4-(甲基亚硝氨基)-I-(3-吡啶基)-1-丁酮处理导致 HtrA3 下调，相应的甲基化增加。进一步的研究表明，HtrA3 缺失是导致依托泊苷和顺铂细胞毒性耐药的功能后果。最后，对原发性肺肿瘤的免疫组织化学分析显示，HtrA3 低表达与重度吸烟史之间存在很强的相关性。
综上所述，这些结果表明，香烟烟雾诱导的 HtrA3 甲基化可能导致与吸烟相关的肺癌中化学抗性疾病的病因。
