Mutations In D-loop Region Research Articles

Screening of the gene mutation in D-loop region of mitochondrial DNA in oral squamous cell carcinoma

To investigate the gene mutation in D-loop region of mitochondrial DNA (mtDNA) in oral squamous cell carcinoma (OSCC) tissue and to explore the role of the gene mutation in D-loop region in the OSCC tumorigenesis. mtDNA was obtained from cancer, paracancerous and normal mucosa tissues of thirty patients with OSCC. The D-loop regions of mtDNA were amplified with PCR, sequencing and then analyzed by Chromas software and BLAST to identify the mutation site. Mutation in the D-loop region was found in eight cases, with the mutation rate of 27%. There were nine mutations totally, including one point mutation, two base deletions, three insertion mutations, three heterozygous mutations. In these mutations, base deletions were different from each other and heterozygous mutations had no same mutation form, while the three insertion mutations were same, the insertion of base C. One case had T/A heterozygous mutation and base C insertion at the same time. There were mutations in mtDNA D-loop in OSCC, but the relationship between occurrence of OSCC and mutation of mtDNA needs further study.

Mitochondrial DNA mutations in gastric endothelial cells induced by extract of helicobacter pylori in vitro

To investigate the relationship between the helicobacter pylori (HP) infection and the genetic instability of mitochondrial DNA (mtDNA) in human gastric adenocarcinoma epithelial cells (AGS). After treated with extracts of HP11638 (CagA+, VacA+) or Hp11638 mutant strain (CagA+, VacA-), AGS cells were collected, and mitochondrial DNA was extracted and Cox-I, Cox-II, Cox-III, ATPase6, ATPase8 and Cytb genes and the D-Loop region were amplified by PCR and then sequenced. The mutation rates of the mtDNA in AGS cells were correlated with the extracts of the two HP strains in a concentration- and time-dependent manner. But the mtDNA mutation rate in AGS cells treated with the HP11638 extract was higher than that treated with the Hp11638 mutant extract. Total of 616 mutations in D-Loop region were detected, including 489 point mutations, 81 insertions and 46 deletions. Among them, 70.9% (437/616) belonged to GC to AT and AT to GC transition. Seventeen out of 20 (85%) AGS cells treated with extract of HP had mutations in 303PolyC, 16184PolyC and 514CA regions of mtDNA D-Loop. No mutation was detected in Cox-I, Cox-II, Cox-III, ATPase6 and ATPase8 genes, three point mutations were found in the Cytb gene. HP can cause the accumulation of mutations in mtDNA, in particular, in the D-Loop region, and the VacA participated in the process.

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

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

Analysis of mitochondrial DNA mutations in D-loop region in thyroid lesions

Background Mitochondrial defects have been associated with various human conditions including cancers. Methods We analyzed the mutations at the mitochondrial DNA (mtDNA) in patients with different thyroid lesions. In particular, in order to investigate if the accumulation of mtDNA mutations play a role in tumor progression, we studied the highly variable main control region of mtDNA, the displacement-loop (D-loop) in patients with non-tumor nodular goiters, with benign thyroid adenomas, and with malignant thyroid carcinomas. Total thyroid tumor or goiter samples were obtained from 101 patients, matched with nearby normal tissue and blood from the same subject. Results Noticeably, mitochondrial microsatellite instability (mtMSI) was detected in 2 of 19 nodular goiters (10.53%), and 8 of 77 (10.39%) malignant thyroid carcinomas. In addition, 6 patients, including 5 (6.49%) with malignant thyroid carcinomas and 1 (5.26%) with nodular goiter, were found to harbor point mutations. The majority of the mutations detected were heteroplasmic. General significance Our results indicate that mtDNA alterations in the D-loop region could happen before tumorigenesis in thyroid, and they might also accumulate during tumorigenesis.

Associations between cigarette smoking and mitochondrial DNA abnormalities in buccal cells

DNA alterations in mitochondria are believed to play a role in carcinogenesis and are found in smoking-related cancers. We sought to replicate earlier findings for the association of smoking with increased mitochondrial DNA (mtDNA) content in buccal cells and further hypothesized that there would be an increased number of somatic mtDNA mutations in smokers. Buccal cells and blood lymphocytes were studied from 42 healthy smokers and 30 non-smokers. Temporal temperature gradient electrophoresis screening and sequencing was used to identify mtDNA mutations. The relative mtDNA content was determined by real-time polymerase chain reaction. Assuming that mtDNA in lymphocytes represents the inherited sequence, it was found that 31% of smokers harbored at least one somatic mtDNA mutation in buccal cells with a total of 39 point mutations and 8 short deletions/insertions. In contrast, only 23% of non-smokers possessed mutations with a total of 10 point mutations and no insertions/deletions detected. mtDNA somatic mutation density was higher in smokers (0.68/10 000 bp per person) than in non-smokers (0.2/10 000 bp per person). There was a statistically significant difference in the pattern of homoplasmy and heteroplasmy mutation changes between smokers and non-smokers. Whereas non-smokers had the most mutations in D-loop region (70%), smokers had mutations in both messenger RNA encoding gene (36%) and D-loop region (49%). The mean ratio of buccal cells to lymphocytes of mtDNA content in smokers was increased (2.81) when compared with non-smokers (0.46). These results indicate that cigarette smoke exposure affects mtDNA in buccal cells of smokers. Additional studies are needed to determine if mitochondrial mutation assays provide new or complementary information for estimating cigarette smoke exposure at the cellular level or as a cancer risk biomarker.

Mitochondrial DNA mutations and mitochondrial DNA depletion in breast cancer

Somatic mutations in mitochondrial DNA (mtDNA) have been demonstrated in various tumors, including breast cancer. However, it still remains unclear whether the alterations in mtDNA are related to the clinicopathological features and/or the prognosis in the breast cancer. We analyzed somatic mutations in the D-loop region, the common 4,977-bp deletion, and the copy number of mtDNA in breast cancer and paired nontumorous breast tissues from 60 Taiwanese patients. We found that 18 of the 60 (30%) breast cancers displayed somatic mutations in mtDNA D-loop region. The incidence of the 4,977-bp deletion in nontumorous breast tissues (47%) was much higher than that in breast cancers (5%). The copy number of mtDNA was significantly decreased in 38 of the 60 (63%) breast cancers as compared to their corresponding nontumorous breast tissues (P = 0.0008). The occurrence of D-loop mutations was associated with an older onset age (>or=50 years old, P = 0.042), and tumors that lacked expressions of estrogen receptor and progesterone receptor (P = 0.024). Patients with mtDNA D-loop mutation and breast cancer had significantly poorer disease-free survival than those without mutation, when assessed by Kaplan-Meier curves and log-rank test (P = 0.005). Multivariate Cox regression analysis indicated that a D-loop mutation is a significant marker that is independent of other clinical variables and that it can be used to assess the prognosis of patients. Our findings suggest that somatic mutations in mtDNA D-loop can be used as a new molecular prognostic indicator in breast cancer.

Mutations in the mitochondrial DNA D-loop region are frequent in cervical cancer

BackgroundMitochondrial DNA (mtDNA) is known for high mutation rates caused by lack of protective histones, inefficient DNA repair systems, and continuous exposure to mutagenic effects of oxygen radicals. Alterations in the non-coding displacement (D) loop of mitochondrial DNA are present in many cancers. It has been suggested that the extent of mitochondrial DNA mutations might be useful in the prognosis of cancer outcome and/or the response to certain therapies. In order to investigate whether a high incidence of mutations exist in mitochondrial DNA of cervical cancer patients, we examined the frequency of mutations in the D-loop region in 19 patients of cervical cancer.ResultsMutations, often multiple, were detected in 18 of 19 (95%) patients. The presence of mutations correlated with Human Papilloma Virus (HPV) infection in these patients. Mutations were also detected in normal samples and lymphocytes obtained from cervical cancer patients, but their frequency of occurrence was much lower as compared to the cervical cancer tissues.ConclusionOur findings indicate that D-loop alterations are frequent in cervical cancers and are possibly caused by HPV infection. There was no association of mtDNA D-loop mutations with the histopathological grade and tumor staging.

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

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. 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. 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. Mutation in D-loop region plays a role in the genesis and development of gastric cancer.