急性白血病患者线粒体DNA D-loop区突变的临床研究

目的:研究急性白血病(AL)患者线粒体DNA(mtDNA)D-loop区突变及其与AL发病的关系。方法:提取38例初治AL患者骨髓单个核细胞mtDNA,对mtDNA D-loop区序列进行PCR扩增,通过正反向直接测序对PCR扩增产物基因序列进行检测,将测序结果与剑桥标准序列和有关数据库进行对照。结果:AL患者mtDNA D-loop区突变率为71.1%(27/38),在102个位点共发现了324个碱基改变,最常见的碱基置换是T-C(26.9%)和C-T(20.1%),其次是A-G(16.7%),其中57个为突变位点,发现一个新的突变类型nt150C-CT;急性淋巴细胞白血病和急性非淋巴细胞白血病患者的突变差异无统计学意义(P0.05);有和无mtDNA D-loop区突变患者的无事件生存率亦差异无统计学意义(P=0.894)。结论:AL患者中存在mtDNA D-loop区高频突变,mtDNA D-loop区的突变可能与AL的发生有关。     

三氧化二砷诱导白血病患者线粒体DNA的非编码区基因突变

三氧化二砷（As2O3）促白血病细胞分化和凋亡的作用机制至今尚不完全明了。线粒体基因（mt-DNA）是细胞核外遗传物质，其非编码区（D-loop区）包括重链复制起点等重要序列，对编码区有影响。mt-DNA缺乏组蛋白保护及损伤修复系统，其突变率比核基因高10—100倍。白血病细胞的D-loop区存在突变，但As2O3对白血病细胞mt-DNA的影响还不清楚。本研究就As2O3对白血病细胞D-100p区的影响进行了初步研究。     

mtDNA Cyt-b、 ATPase6在浸润性乳腺癌中的突变及意义

目的 检测线粒体DNA (mtDNA) Cyt-b、ATPase6在浸润性乳腺癌组织和癌旁组织的突变情况,寻找特异性位点.方法 采用PCR结合基因测序方法,对延边朝鲜族地区浸润性乳腺癌患者(30例)的癌组织及癌旁组织进行mtDNA Cyt-b、ATPase6基因测序,对照人线粒体DNA剑桥修定序列,分析其突变情况.结果 在研究对象的乳腺癌mtDNA中共发现Cyt-b基因区有6个高突变发生率位点,即A15326G、C14766T、G15301A、G15043A、T14783C、C15402T,其中A15326G、C14766T突变率最高;而ATPase6基因区共发现3个高突变发生率位点,即C8673T、A8729G、T8955C,其中C8673T、A8729G突变率最高.结论 mtDNA Cyt-b、mtDNA ATPase6高突变发生位点可为浸润性乳腺癌的诊断及乳腺癌细胞线粒体功能评价提供有价值的参考.     

线粒体突变及不稳定在胃癌中的研究

目的 探讨线粒体突变及不稳定在胃癌发生、发展中的作用.方法 利用激光显微切割技术分离胃癌组织及其切缘的正常组织,应用变性高效液相色谱DHPLC对胃癌线粒体D-loop调控区D-loop-(CA)n进行突变筛查及测序分析,同时进行线粒体D-loop非编码区(CA)n重复序列的不稳定(mtMSI)检测.结果 胃癌组织样本中D-loop-(CA)n调控区基因突变率为50.8％ (31/61),正常组织均未见有序列改变.29.5％ (18/61)发生线粒体重复序列(CA)n的不稳定.18例线粒体不稳定(mtMSI)中有16.4％(10/61)同时发生D-loop点突变,有8例同时存在核不稳定(nMSI-H).结论 胃癌mtDNA异常参与了肿瘤的发生、发展.     

DNA聚合酶β基因启动子在食管癌组织中的突变分析

目的:研究人食管癌组织、癌旁组织及其远端正常黏膜组织中DNA聚合酶β(DNA polymerase beta,polβ)基因启动子的突变情况.方法:采用聚合酶链反应(PCR)、DNA序列分析技术对25例食管癌患者手术切除的病变标本进行DNA pol β基因启动子序列检测,并利用DNASIS、OMIGA等软件分析测序数据.结果:25例中,食管癌组织、癌旁组织和正常黏膜组织中DNA polβ基因启动子发生突变者分别为8、6、5例,三组问突变率差异无统计学意义.在三组标本中共有35个突变点(癌组织包括18个突变点,癌旁组织包括9个突变点,正常黏膜组织8个突变点),25个点在polβ核心启动子区域,其中,-37位C→A突变出现8次;.-5位G→T突变出现7次;29位T→C突变出现2次;-19位出现C的缺失和插入C突变各1次.结论:DNA polβ基因启动子突变可能与食管癌的发生和发展有关.     

糖尿病与线粒体ND1点突变的关系

目的探讨湖北省线粒体基因的热点突变区域ND1点突变(3243,3316,3394,3593)与老年2型糖尿病的关系。方法采用聚合酶链反应-限制性片段长度多态性法对无血缘关系的134例老年糖尿病患者及152例正常对照个体的血细胞线粒体DNA进行突变分析。结果病例组中3316G→A点突变率为3·7%,3394T→C点突变发生率为3·0%,而对照组3316和3394的突变率分别为0·66%和0,3394组间差异比较均有显著性(P<0·05)。病例组中3593点突变发生率为0·75%,对照组未见该突变,两组间差异无显著性。未发现3243的突变。结论线粒体DNA3394T→C突变与老年线粒体糖尿病的发生与发展有关,并起着重要作用。     

抑癌基因Mxi1在白血病细胞中突变的研究

目的分析Mxi1基因突变在白血病发病中的作用.方法利用逆转录-聚合酶链反应(RT-PCR)、单链构象多态性(SSCP)分析及DNA序列分析技术检测26例初治急性白血病患者、30名健康对照者和2种髓系白血病细胞株(KG1、K562)Mxi1基因表达及突变情况.结果RT-PCR显示所有标本中均可检测到Mxi1基因的表达,在11.5%(3/26)初治急性白血病患者和KG1细胞株中发现四处错义突变,发生突变的3例患者均于确诊后5个月内死亡.结论首次在急性白血病细胞中发现Mxi1基因突变,提示Mxi1基因的突变可能与白血病的发病和预后有关.     

抑癌基因Mxil在白血病细胞中突变的研究

目的：分析Mxil基因突变在白血病发病中的作用。方法：利用逆转录-聚合酶链反应（RT-PCR）、单链构象多态性（SSCP）分析及DNA序列分析技术检测26例初治急性白血病患者、30名健康对照者和2种髓系白血病细胞株（KG1、K562）Mxil基因表达及突变情况。结果：RT—PCR显示所有标本中均可检测到Mxil基因的表达，在11．5％（3／26）初治急性白血病患者和KG1细胞株中发现四处错义突变，发生突变的3例患者均于确诊后5个月内死亡。结论：首次在急性白血病细胞中发现Mxil基因突变，提示Mxil基因的突变可能与白血病的发病和预后有关。     

先天性心脏病相关PITX2c基因新突变研究

目的:研究先天性心脏病(congenital heart disease,CHD)相关PITX2c基因的新突变。方法:收集150例CHD患者和200名正常对照者的外周静脉血标本,使用DNA纯化试剂盒分离基因组DNA。使用DNA聚合酶扩增PITX2c基因的编码区和剪接位点,应用DNA测序试剂盒在DNA分析仪上对扩增片段进行测序。将所测序列与GenBank数据库中的PITX2c基因序列进行比对以发现PITX2c基因突变。使用在线程序MUSCLE分析突变氨基酸的保守性,分别应用MutationTaster和PolyPhen-2分析突变氨基酸的致病性。结果:在1例散发性CHD患者发现了1个新的PITX2c基因杂合错义突变,即p.S101G突变,突变率约为0.67%。该错义突变不存在于200名正常对照者。跨物种PITX2c蛋白之氨基酸序列对比显示第101位的丝氨酸在进化上完全保守,致病性预测显示所发现的PITX2c基因变异是致病性突变。结论:本研究揭示了CHD相关PITX2c基因新突变,对于制定新的CHD防治策略具有潜在的意义。     

线粒体DNA3537A→G、4824A→G、5351A→G突变与2型糖尿病的相关性研究

目的研究T2DM患者线粒体ND1基因3537A→G和ND2基因4824A→G、5351A→G突变与T2DM的相关性。方法应用PCR-RFLP技术检测145例T2DM和334例正常对照者（NC）线粒体DNA（mtDNA）3537A→G、4824A→G、5351A→G突变情况。结果NC组mtDNA4824A→G突变率高于T2DM组（P＜0．05）。3537A→G及5351A→G突变率在两组中无统计学差异（P〉0．05）。结论mtDNA4824A→G突变可能为T2DM患病的保护因素。3537A→G及5351A→G突变可能与T2DM不相关。     

Study on the mutations in the D-loop region of mitochondrial DNA in cervical carcinoma

Background  Study on genesis and development of tumor is mainly concentrated on gene mutation in nucleus. But in recent years, the role of mitochondrial DNA (mtDNA) mutation in tumor genesis has been given more attention, which is the only extra-nucleus DNA in cells of higher animals. Carcinoma of the uterine cervix is a common tumor in gynecology. There are few reports of mtDNA mutation in this area. The focus of this study was to investigate the mitochondrial DNA mutation in tumor tissues of cervical carcinomas patients and their relationship to tumorigenesis and tumor development. Methods  The D-loop region of 24 cervical carcinomas together with the adjacent normal tissues were amplified by PCR and sequenced. Results  Among the 24 cervical carcinomas, 30 mutations were identified with the mutations rate of 37.5% (9/24).There were eight microsatellite instabilities among the mutations and 13 new polymorphisms which were not reported previously in the GeneBank. Conclusions  The D-loop region of mitochondrial DNA is a highly polymorphoric and mutable region and the mutations rate is relatively high in patients with cervical carcinomas. Daozhen Chen and Huiying Zhan contributed equally to this work.     

Analysis of mitochondrial DNA in 104 patients with myelodysplastic syndromes

OBJECTIVE: To determine the frequency and spectrum of somatic mutations of mitochondrial DNA (mtDNA) in bone marrow of patients with myelodysplastic syndrome (MDS). MATERIALS AND METHODS: Analysis included 104 patients with MDS (24 refractory anemia, 32 refractory anemia with ringed sideroblasts, 34 refractory anemia with excess of blasts, 7 refractory anemia with excess of blasts in transformation to acute leukemia, and 7 chronic myelo-monocytic leukemia), 3 patients with acute myeloid leukemia from MDS, and 36 patients with myeloproliferative disease (23 chronic myeloid leukemia, 9 polycythemia vera, 4 idiopathic myelofibrosis). Mutation scanning was performed using heteroduplex analysis with denaturing high-performance liquid chromatography (dHPLC). The entire mitochondrial genome was amplified in 67 overlapping polymerase chain reaction fragments carefully optimized regarding DNA melting profiles. Abnormal dHPLC findings were confirmed by DNA sequencing. RESULTS: Heteroplasmic mtDNA mutations, mostly transitions, were identified in 56% of MDS and 44% of myeloproliferative disorders patients. In MDS, mutation frequency increased with age and more-advanced disease. Mutational spectra showed no hot spots and were similar in different types of MDS. Heteroplasmic mutations generally did not represent known polymorphisms, and about half of them affected conserved amino acids or nucleotides. Mutations were less frequent in protein encoding genes (50 per 10(6) base pairs) than other mitochondrial genes (transfer RNAs, ribosomal RNAs, and control region; about 80 per 10(6) base pairs). CONCLUSIONS: As mitochondria often show ultrastructural abnormalities in MDS, including pathological iron accumulation, mitochondrial dysfunction may contribute to MDS pathology. We found a high frequency of acquired mtDNA mutations in MDS. However, their functional importance remains unclear, considering that genotype correlates poorly with phenotype in mitochondrial diseases. The clonally expanded mtDNA mutations in MDS support the concept of age-related damage to mtDNA in hematopoietic stem cells.     

大肠癌细胞线粒体DNA D-环区的突变

目的研究线粒体DNAD-环区在大肠癌细胞中的突变情况。方法用PCR与直接测序相结合的方法．对比分析三株大肠癌细胞系和一例原代培养的正常肠上皮细胞的线粒体DNAD-环区的突变位点。结果三株大肠癌细胞系和正常肠上皮细胞的线粒体DNAD—环区均存在不同程度的点突变，其中72位C→T，73位A→G，16298位C→T，16519位T→C这4个突变位点在3株癌细胞和正常肠上皮细胞中均可检测到。在SW480和Lovo细胞中检测到16224位T—c、1631l位T—c两个相同的突变位点，在SW480和HT29中检测到114位C→T、498位C→T、16234位C→T 3个相同的突变位点．不同大肠癌细胞系中相同的突变位点考虑为细胞的特征性改变。结论大肠癌细胞线粒体DNAD-环区具有多态性和特征性突变，细胞特征性的突变可能与大肠癌患者的易感性有关。     

Mitochondrial DNA sequence variation in single cells from leukemia patients

A high frequency of mtDNA somatic mutation has been observed in many tumors as well as in aging tissues. In this study, we analyzed the mtDNA control region sequence variation in 3534 single normal cells and individual blasts from 18 patients with leukemia and 10 healthy donors, to address the mutation process in leukemic cells. We found significant differences in mtDNA sequence, as represented by the number of haplotypes and the mean number of cells with each nonaggregate haplotype in a population of cells, in patients compared to controls. Patients with similar clinical leukemia types, particularly acute myeloid leukemia (AML), did not show a uniform pattern of sequence variation in single blasts. Some patients at relapse presented a complex shift of major haplotypes in single cells. Four patients showed high frequencies of cells containing mutations 189, 260, 16150, and 16488, respectively, as a result of clonal expansion and could be considered as potential markers for their respective disease progression. To our knowledge, this is the first large-scale study of mtDNA variation in single malignant cells. Our results suggest that the somatic mutation process in leukemia is complex, leading to diverse levels of genetic alterations due to either intrinsic aspects of leukemia pathophysiology or chemotherapy effects.     

Mutations in the cardiac mitochondrial DNA control region associated with cardiomyopathy and aging

BACKGROUND: An age-dependent accumulation of point mutations in the noncoding control region of human mitochondrial D-loop has been found in cultured fibroblasts and muscle cells. Damage in mitochondrial DNA (mtDNA) coding genes and decreased bioenergetic generation have also been found in human cardiac tissues with aging and in cardiac disease. METHODS AND RESULTS: We analyzed cardiac mtDNA for the incidence and distribution of point mutations in the D-loop control region involved in mtDNA replication (from nucleotides 110 to 570) in 47 patients with cardiomyopathy and 40 subjects with no history of cardiac disease. The nucleotide changes in the control region were compared with changes in a cytb fragment of roughly the same size in controls and patients. Frequency and distribution of mutations in relation to age and cardiac disease were assessed. No significant accumulation of point mutations in the D-loop control region or in cytb was found as a function of age. However, mutations in important sites within the D-loop control region were present in 8 patients (17%). CONCLUSIONS: We found specific mutations at critical sites in the D-loop in cardiomyopathy that may play a role in cardiac pathogenesis. Age does not appear to be a factor in mutation accumulation.     

Mutation in D-loop region of mitochondrial DNA in gastric cancer and its significance

AIM:To investigate the mutation in D-loop region of mitochondrial DNA in gastric cancer and its influence on the changes of reactive oxygen species (ROS) and cell cycle. METHODS: The D-loop region was amplified by PCR and sequenced.Reactive oxygen species and cell cycle were detected by flow cytometry in 20 specimens from gastric cancer and adjacent normal tissues.According to the sequence results,gastric cancer tissue was divided into mutation group and control group.Reactive oxygen species,apoptosis and proliferation in the two groups were compared. RESULTS:Among the 20 gastric cancer specimens, 18 mutations were identified in 7 patients,the mutation rate being 35%.There were four microsatellite instabilities in the mutations. No mutation was found in the adjacent tissues. Reactive oxygen species,apoptosis,and proliferation in the mutation group were all significantly higher than those in control group. CONCLUSION: Mutation in D-loop region plays a role in the genesis and development of gastric cancer.     

Amplification of mitochondrial DNA in acute myeloid leukaemia

There is a long-standing interest in the possible role of mitochondria in malignancy. We sought to discover whether amplification of mitochondrial DNA (mtDNA) occurred in leukaemia, and found it was often remarkably amplified in the blast cells of acute myeloid leukaemia (AML).
We used gene dosage experiments to quantify the amount of mtDNA relative to nuclear DNA. DNA extracted from peripheral blood leucocytes or bone marrow of healthy individuals or patients was simultaneously hybridized with a probe for the mitochondrial genome and a control probe for the renin gene on human chromosome 1. Comparative densitometric ratios of approximately 1 were obtained between the two signals in 20 normal control peripheral blood samples. In contrast, comparative ratios in the range of 2–50 were observed in 25 AML samples and 13 of these showed 8-fold or greater amplification of mtDNA relative to normal peripheral blood controls. An additional four cases of AML were investigated at both presentation and remission and showed 3–10-fold amplification of mtDNA at presentation, but no amplification when in clinical remission. 18 cases of chronic granulocytic leukaemia (CGL) were also studied in chronic phase and showed mtDNA dosage levels equivalent to normal peripheral blood controls. However, 8/9 CGL patients showed mtDNA amplification during transformation from chronic phase. We conclude that amplification of mtDNA is an invariable feature of acute myeloid leukaemia and that it may be a useful marker for detecting transformation of CGL.     

结直肠癌组织中线粒体DNA D-环区突变的研究

背景：近年线粒体DNA与肿瘤之间的相关性已成为新的研究热点，目前已在多种恶性肿瘤或癌前病变中检测到线粒体突变。目的：研究线粒体DNAD-环区在结直肠癌组织中的突变情况，探讨其在结直肠癌发生、发展中的作用。方法：以聚合酶链反应（PCR）扩增40例结直肠癌患者肿瘤组织和癌旁组织的线粒体DNAD-环区，扩增产物直接测序。结果：40例结直肠癌患者中，共发现50个D-环区多态性，其中2个为BLAST数据库中未记录的新多态性。14例患者存在线粒体DNAD-环区突变，突变率为35％，突变位点12个，其中9个点突变，2个微卫星不稳定，1个缺失。结论：结直肠癌组织线粒体DNAD-环区具有高度多态性和高突变率，可能与结直肠癌的发生、发展有关。     

Evaluating mitochondrial DNA in patients with breast cancer and benign breast disease

Purpose

To evaluate the role of mtDNA in breast cancer.

Methods

We carried out an investigation into the mtDNA major control region or D-loop region and an essential and the largest mtDNA protein-coding gene, NADH dehydrogenase subunit 5 (ND5), together with a mitochondrial haplogroup analysis in 64 patients with breast cancer (BC) and 54 patients with benign breast disease (BBD) as controls.

Results

Mutations in D-loop region were found in 10/64 or 15.6% of patients with BC and 14/54 or 25.9% of patients with BBD, while mutations in ND5 were detected in 6/64 or 9.4% of patients with BC and 5/54 or 9.3% of patients with BBD. In addition, in patients with BBD, mtDNA mutations were more likely to rise in D-loop region and the mutations were more likely to be heteroplasmic. However, in patients with BC, those with metastatic feature were less likely to carry mutations in D-loop region. Finally, we found haplogroup M has an increased risk of breast cancer compared with haplogroup N.

Conclusion

mtDNA mutation may play a role in early stage of tumorigenesis, and mitochondrial haplogroup can also modulate breast cancer occurrence.