Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University, Baltimore, Maryland, United States of America.
PLoS One. 2009 Aug 6;4(8):e6533. doi: 10.1371/journal.pone.0006533.
Mitochondrial DNA (mtDNA) mutations are reported in different tumors. However, there is no information on the temporal development of the mtDNA mutations/content alteration and their extent in normal and abnormal mucosa continuously exposed to tobacco smoke in lung cancer patients.
We examined the pattern of mtDNA alteration (mtDNA mutation and content index) in 25 airway mucosal biopsies, corresponding tumors and normal lymph nodes obtained from three patients with primary lung cancers. In addition, we examined the pattern of mtDNA mutation in corresponding tumors and normal lymph nodes obtained from eight other patients with primary lung cancers. The entire 16.5 kb mitochondrial genome was sequenced on Affymetrix Mitochip v2.0 sequencing platform in every sample. To examine mtDNA content index, we performed real-time PCR analysis.
The airway mucosal biopsies obtained from three lung cancer patients were histopathologically negative but exhibited multiple clonal mtDNA mutations detectable in the corresponding tumors. One of the patients was operated twice for the removal of tumor from the right upper and left lower lobe respectively within a span of two years. Both of these tumors exhibited twenty identical mtDNA mutations. MtDNA content increased significantly (P<0.001) in the lung cancer and all the histologically negative mucosal biopsies except one compared to the control lymph node.
CONCLUSIONS/SIGNIFICANCE: Our results document the extent of massive clonal patches that develop in lifetime smokers and ultimately give rise to clinically significant cancers. These observations shed light on the extent of disease in the airway of smokers traceable through mtDNA mutation. MtDNA mutation could be a reliable tool for molecular assessment of respiratory epithelium exposed to continuous smoke as well as disease detection and monitoring. Functional analysis of the pathogenic mtDNA mutations may be useful to understand their role in lung tumorigenesis.
线粒体 DNA（mtDNA）突变已在不同肿瘤中报道。然而，对于持续暴露于烟草烟雾的肺癌患者的正常和异常黏膜中 mtDNA 突变/含量改变的时间发展及其程度，尚无信息。
我们检查了 25 例气道黏膜活检、相应肿瘤和来自 3 例原发性肺癌患者的正常淋巴结中 mtDNA 改变（mtDNA 突变和含量指数）的模式。此外，我们还检查了来自另外 8 例原发性肺癌患者的相应肿瘤和正常淋巴结中 mtDNA 突变的模式。每个样本都在 Affymetrix Mitochip v2.0 测序平台上对整个 16.5 kb 线粒体基因组进行测序。为了检查 mtDNA 含量指数，我们进行了实时 PCR 分析。
从 3 例肺癌患者获得的气道黏膜活检在组织病理学上为阴性，但在相应的肿瘤中可检测到多个克隆 mtDNA 突变。其中一名患者在两年内两次接受手术切除右肺上叶和左肺下叶的肿瘤。这两个肿瘤都表现出 20 个相同的 mtDNA 突变。与对照淋巴结相比，肺癌和所有组织学上阴性的黏膜活检中的 mtDNA 含量均显著增加（P<0.001）。
结论/意义：我们的结果记录了终生吸烟者中大量克隆斑块的发展程度，最终导致临床上有意义的癌症。这些观察结果阐明了吸烟者气道中疾病的程度，通过 mtDNA 突变可以追踪到。mtDNA 突变可能是一种用于对持续吸烟暴露的呼吸道上皮进行分子评估以及疾病检测和监测的可靠工具。对致病性 mtDNA 突变的功能分析可能有助于了解它们在肺癌发生中的作用。
