Sui Guoping, Zhou Shaoyu, Wang Jean, Canto Marcia, Lee Edward E, Eshleman James R, Montgomery Elizabeth A, Sidransky David, Califano Joseph A, Maitra Anirban
Department of Pathology, Johns Hopkins University School of Medicine, Washington, DC.
Mol Cancer. 2006 Dec 13;5:73. doi: 10.1186/1476-4598-5-73.
Somatic mutations of mitochondrial DNA (mtDNA) are common in many human cancers. We have described an oligonucleotide microarray ("MitoChip") for rapid sequencing of the entire mitochondrial genome (Zhou et al, J Mol Diagn 2006), facilitating the analysis of mtDNA mutations in preneoplastic lesions. We examined 14 precancerous lesions, including seven Barrett esophagus biopsies, with or without associated dysplasia; four colorectal adenomas; and three inflammatory colitis-associated dysplasia specimens. In all cases, matched normal tissues from the corresponding site were obtained as germline control. MitoChip analysis was performed on DNA obtained from cryostat-embedded specimens.
A total of 513,639 bases of mtDNA were sequenced in the 14 samples, with 490,224 bases (95.4%) bases assigned by the automated genotyping software. All preneoplastic lesions examined demonstrated at least one somatic mtDNA sequence alteration. Of the 100 somatic mtDNA alterations observed in the 14 cases, 27 were non-synonymous coding region mutations (i.e., resulting in an amino acid change), 36 were synonymous, and 37 involved non-coding mtDNA. Overall, somatic alterations most commonly involved the COI, ND4 and ND5 genes. Notably, somatic mtDNA alterations were observed in preneoplastic lesions of the gastrointestinal tract even in the absence of histopathologic evidence of dysplasia, suggesting that the mitochondrial genome is susceptible at the earliest stages of multistep cancer progression.
Our findings further substantiate the rationale for exploring the mitochondrial genome as a biomarker for the early diagnosis of cancer, and confirm the utility of a high-throughput array-based platform for this purpose from a clinical applicability standpoint.
线粒体DNA（mtDNA）的体细胞突变在许多人类癌症中很常见。我们已经描述了一种用于对整个线粒体基因组进行快速测序的寡核苷酸微阵列（“线粒体芯片”）（Zhou等人，《分子诊断杂志》2006年），这有助于分析癌前病变中的mtDNA突变。我们检查了14个癌前病变，包括7例伴有或不伴有相关发育异常的巴雷特食管活检标本；4例大肠腺瘤；以及3例炎症性结肠炎相关发育异常标本。在所有病例中，均获取了相应部位的匹配正常组织作为种系对照。对从冷冻切片包埋标本中获得的DNA进行线粒体芯片分析。
在14个样本中总共对513,639个mtDNA碱基进行了测序，其中490,224个碱基（95.4%）由自动基因分型软件进行了分型。所有检查的癌前病变均显示至少有一处体细胞mtDNA序列改变。在这14例病例中观察到的100处体细胞mtDNA改变中，27处为非同义编码区突变（即导致氨基酸改变），36处为同义突变，37处涉及非编码mtDNA。总体而言，体细胞改变最常涉及COI、ND4和ND5基因。值得注意的是，即使在没有发育异常的组织病理学证据的情况下，在胃肠道癌前病变中也观察到了体细胞mtDNA改变，这表明线粒体基因组在多步骤癌症进展的最早阶段就易受影响。
我们的发现进一步证实了探索线粒体基因组作为癌症早期诊断生物标志物的理论依据，并从临床适用性的角度证实了基于高通量阵列平台用于此目的的实用性。
