Dani Maria Angela C, Dani Sergio U, Lima Silmara P G, Martinez Alfredo, Rossi Benedito M, Soares Fernando, Zago Marco A, Simpson Andrew J G
Department of Genetics, Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
Genet Mol Res. 2004 Sep 30;3(3):395-409.
Levels of mtDNA(4977) deletions (DeltamtDNA(4977)) have been found to be lower in tumors than in adjacent non-tumoral tissues. In 87 cancer patients, DeltamtDNA(4977) was detected by multiplex polymerase chain reaction (PCR) amplification in 43 (49%) of the tumors and in 74 (85%) of the samples of non-tumoral tissues that were adjacent to the tumors. DeltamtDNA(4977) deletions were detected in 24% of the breast tumors, 52% of the colorectal tumors, 79% of the gastric tumors, and 40% of the head and neck tumors as compared with 77, 83, 100, and 90% of the adjacent respective non-tumoral tissues at the same DNA template dilution. Based on limiting dilution PCR of 16 tumors and their adjacent non-tumoral tissues, it was found that the amount of DeltamtDNA(4977) was 10- to 100-fold lower in the tumor than in the respective control non-tumoral tissues. Real-time PCR experiments were performed to quantify the number of DeltamtDNA(4977) deletions per cell, by determining the mitochondrial-to-nuclear DNA ratio. In all of the cases of breast, colorectal, gastric, and head and neck cancer the proportion of DeltamtDNA(4977) in tumors was lower than that of the respective non-tumoral tissue. Traces of DeltamtDNA(4977) in tumors were apparently due to contamination of tumor tissue with surrounding non-tumoral tissue, as evidenced by tumor microdissection and in situ PCR techniques, suggesting that tumors are essentially free of this mutation. Although the metabolic effect of DeltamtDNA(4977) may be minimal in normal (non-tumor) tissue, in tissue under stress, such as in tumors, even low levels of DeltamtDNA(4977) deletions may be intolerable.
已发现肿瘤组织中线粒体DNA（4977）缺失（DeltamtDNA(4977)）的水平低于相邻的非肿瘤组织。在87例癌症患者中，通过多重聚合酶链反应（PCR）扩增在43例（49%）肿瘤组织以及74例（85%）与肿瘤相邻的非肿瘤组织样本中检测到DeltamtDNA(4977)。在相同DNA模板稀释度下，与相应的相邻非肿瘤组织（分别为77%、83%、100%和90%）相比，24%的乳腺肿瘤、52%的结肠直肠肿瘤、79%的胃肿瘤以及40%的头颈肿瘤中检测到DeltamtDNA(4977)缺失。基于对16例肿瘤及其相邻非肿瘤组织进行的极限稀释PCR，发现肿瘤组织中DeltamtDNA(4977)的量比相应的对照非肿瘤组织低10至100倍。通过测定线粒体与核DNA的比率，进行实时PCR实验以量化每个细胞中DeltamtDNA(4977)缺失的数量。在所有乳腺癌、结肠直肠癌、胃癌和头颈癌病例中，肿瘤组织中DeltamtDNA(4977)的比例均低于相应的非肿瘤组织。肿瘤组织中微量的DeltamtDNA(4977)显然是由于肿瘤组织被周围非肿瘤组织污染所致，肿瘤显微切割和原位PCR技术证明了这一点，这表明肿瘤基本上不存在这种突变。尽管DeltamtDNA(4977)在正常（非肿瘤）组织中的代谢影响可能很小，但在处于应激状态的组织中，如肿瘤组织，即使是低水平的DeltamtDNA(4977)缺失也可能无法耐受。
