Mitochondrial DNA haplogroup confers genetic susceptibility to nasopharyngeal carcinoma in Chaoshanese from Guangdong, China

Nasopharyngeal carcinoma among the Bidayuh of Sarawak, Malaysia: History and risk factors

Nasopharyngeal carcinoma (NPC) is a cancer of the epithelial cells lining the nasopharynx. The incidence of NPC has a distinct geographical distribution, mainly affecting the Chinese population of Southern China. In Malaysia, this cancer is exceptionally prevalent among males. There is a high incidence rate of NPC among the Bidayuh natives in Sarawak, Malaysia. Other than epidemiology reports, there has not been an article describing plausible cancer risk factors contributing to NPC within this native group. Researchers are still trying to understand the reasons the Bidayuh and Southern Chinese are highly susceptible to NPC. This article discusses the risk factors of developing NPC: Epstein-Barr virus infection, genetic predisposition, diet, environmental exposure and tobacco smoking. There is a need to improve the understanding of the role of risk factors to identify new ways to prevent cancer, especially among high-risk groups.

Mitochondrial DNA haplogroups J and T increase the risk of glioma

The presence of different sets of mitochondrial polymorphisms generated by the accumulation of mutations in different maternal lineages has allowed differentiating mitochondrial haplogroups in human populations. These polymorphisms, in turn, may have effects at the phenotypic level, considering a possible contribution of these germinal mutations to the development of certain diseases such as cancer. The main goal of the present study is to establish a possible association between mitochondrial haplogroups and the risk of suffering glioma. Blood samples were obtained from 32 patients from Catalonia (Spain) diagnosed with different grades of glioma (II, III and IV), according to the World Health Organization. The mitochondrial genome was amplified and sequenced using MiSeq 2000 (Illumina). The HaploGrep tool implemented in mtDNA-Server v.1.0.5 was used for the identification of mitochondrial haplogroups. Data obtained in the present study was further pooled with data from previous European studies including glioma patients from Galicia (Spain) and Italy. Results for the Catalonian samples showed an association between individuals with haplogroup J and the increased risk of suffering glioma, with a significant increase of the frequency of individuals with this haplogroup (25%) regarding the general population (7%). Combining different sets of patients with European origin, it appears that individuals with haplogroups J and T have a significantly higher risk of suffering glioma (p < 0.001; OR: 2.407 and p = 0.007; OR: 1.82, respectively). This is the first study that establishes an association between different mitochondrial haplogroups and the risk of suffering glioma, highlighting the role of mitochondrial variants in this disease.

Targeting the signaling in Epstein-Barr virus-associated diseases: mechanism, regulation, and clinical study

Epstein–Barr virus-associated diseases are important global health concerns. As a group I carcinogen, EBV accounts for 1.5% of human malignances, including both epithelial- and lymphatic-originated tumors. Moreover, EBV plays an etiological and pathogenic role in a number of non-neoplastic diseases, and is even involved in multiple autoimmune diseases (SADs). In this review, we summarize and discuss some recent exciting discoveries in EBV research area, which including DNA methylation alterations, metabolic reprogramming, the changes of mitochondria and ubiquitin-proteasome system (UPS), oxidative stress and EBV lytic reactivation, variations in non-coding RNA (ncRNA), radiochemotherapy and immunotherapy. Understanding and learning from this advancement will further confirm the far-reaching and future value of therapeutic strategies in EBV-associated diseases.

Contribution of Mitochondrial DNA Variation to Chronic Disease in East Asian Populations

Mitochondria are the main producers of energy in eukaryotic cells. Mitochondrial dysfunction is associated with specific mitochondrial DNA (mtDNA) variations (haplogroups), and these variations can contribute to human disease. East Asian populations show enrichment of many mitochondrial haplogroups, including A, B, D, G, M7, M8, M9, N9, R9, and exhibit half of the known haplogroups of worldwide. In this review, we summarize the current research in the field of mtDNA variation and associated disease in East Asian populations and discuss the physiological and pathological relevance of mitochondrial biology. mtDNA haplogroups are associated with various metabolic disorders ascribed to altered oxidative phosphorylation. The same mitochondrial haplogroup can show either a negative or positive association with different diseases. Mitochondrial dynamics, mitophagy, and mitochondrial oxidative stress, ultimately influence susceptibility to various diseases. In addition, mitochondrial retrograde signaling pathways may have profound effects on nuclear-mitochondrial interactions, affecting cellular morphology, and function. Other complex networks including proteostasis, mitochondrial unfolded protein response and reactive oxygen species signaling may also play pivotal roles in metabolic performance.

Mitochondrial DNA Haplogroup N9a Negatively Correlates with Incidence of Hepatocellular Carcinoma in Northern China

Mitochondrial DNA (mtDNA) haplogroups are associated with various types of cancer; however, the molecular mechanisms by which mtDNA haplogroups affect primary hepatocellular carcinoma (HCC) are not known. In this study, we carried out a case-control study on 388 HCC patients and 511 geographically matched asymptomatic control subjects in northern China. We found that mtDNA haplogroup N9a and its diagnostic SNP, m.16257C > A, negatively correlated with the incidence of HCC in northern China (odds ratio [OR] 0.290, 95% confidence interval [CI] 0.123–0.685, p = 0.005), particularly in patients with infection of hepatitis B/C virus (HBV/HCV) (for haplogroup N9a: OR 0.213, 95% CI 0.077–0.590, p = 0.003; for m.16257C > A: OR 0.262, 95% CI 0.107–0.643, p = 0.003). However, mtDNA haplogroup N9a is not associated with clinical characteristics of HCC including serum alpha-fetoprotein (AFP) level and tumor size. In addition, cytoplasmic hybrid (cybrid) cells with N9a haplogroup (N9a10a and N9a1) had transcriptome profiles distinct from those with non-N9a (B5, D4, and D5) haplogroups. Gene set enrichment analysis (GSEA) showed that metabolic activity varied significantly between N9a and non-N9a haplogroups. Moreover, cells with haplogroup N9a negatively correlated with cell division and multiple liver cancer pathways compared with non-N9a cells. Although it is still unclear how N9a affects the aforementioned GSEA pathways, our data suggest that mtDNA haplogroup N9a is negatively correlated with the incidence and progression of HCC in northern China.

Mitochondria in cancer: in the aspects of tumorigenesis and targeted therapy

Mitochondria play pivotal roles in most eukaryotic cells, ranging from energy production to regulation of apoptosis. As sites of cellular respiration, mitochondria experience accumulation of reactive oxygen species (ROS) due to damage in electron transport chain carriers. Mutations in mitochondrial DNA (mtDNA) as well as nuclear DNA are reported in various cancers. Mitochondria have a dual role in cancer: the development of tumors due to mutations in mitochondrial genome and the generation of ROS. Impairment in the mitochondria-regulated apoptosis pathway accelerates tumorigenesis. Numerous strategies targeting mitochondria have been developed to induce the mitochondrial (i.e. intrinsic) apoptosis pathway in cancer cells. This review elaborates the roles of mitochondria in cancer with respect to mutations and apoptosis and discusses mitochondria-targeting strategies as cancer therapies to enhance the killing of cancer cells.

Female-specific association among I, J and K mitochondrial genetic haplogroups and cancer: A longitudinal cohort study

Recent studies highlighted the role of mitochondrial dysregulation in cancer, suggesting that the different mitochondrial haplogroups might play a role in tumorigenesis and risk of cancer development. Our aim is to investigate whether any mitochondrial haplogroups carried a significant higher risk of cancer development in a large prospective cohort of North American people. The haplogroup assignment was performed by a combination of sequencing and PCR-RFLP techniques. Our specific outcome of interest was the incidence of any cancer during follow-up period. Overall, 3222 participants were included in the analysis. Women having I, J, K haplogroup reported a significant higher incidence of cancer compared to people with other haplogroups (p < 0.0001), whilst in men non association was found. In the multivariate analysis, women having I, J, K mitochondrial haplogroup reported a 50% increased risk of cancer (HR = 1.50; 95%CI: 1.04-2.16; p = 0.03). This gender-linked association may be partly explained by the role of mitochondrial function in female-specific (e.g. BRCA-driven) oncogenesis, but further studies are needed to better understand this potential correlation. Our findings may have important implications for cancer epidemiology and prevention.

Overview of mitochondrial germline variants and mutations in human disease: Focus on breast cancer (Review)

High lactate production in cells during growth under oxygen-rich conditions (aerobic glycolysis) is a hallmark of tumor cells, indicating the role of mitochondrial function in tumorigenesis. In fact, enhanced mitochondrial biogenesis and impaired quality control are frequently observed in cancer cells. Mitochondrial DNA (mtDNA) encodes 13 subunits of oxidative phosphorylation (OXPHOS), is present in thousands of copies per cell, and has a very high mutation rate. Mutations in mtDNA and nuclear DNA (nDNA) genes encoding proteins that are important players in mitochondrial biogenesis and function are involved in oncogenic processes. A wide range of germline mtDNA polymorphisms, as well as tumor mtDNA somatic mutations have been identified in diverse cancer types. Approximately 72% of supposed tumor-specific somatic mtDNA mutations reported, have also been found as polymorphisms in the general population. The ATPase 6 and NADH dehydrogenase subunit genes of mtDNA are the most commonly mutated genes in breast cancer (BC). Furthermore, nuclear genes playing a role in mitochondrial biogenesis and function, such as peroxisome proliferators-activated receptor gamma coactivator-1 (PGC-1), fumarate hydratase (FH) and succinate dehydrogenase (SDH) are frequently mutated in cancer. In this review, we provide an overview of the mitochondrial germline variants and mutations in cancer, with particular focus on those found in BC.

Ancestry and different rates of suicide and homicide in European countries: A study with population-level data

INTRODUCTION

There are large differences in suicide rates across Europe. The current study investigated the relationship of suicide and homicide rates in different countries of Europe with ancestry as it is defined with the haplotype frequencies of Y-DNA and mtDNA.

MATERIAL AND METHODS

The mortality data were retrieved from the WHO online database. The genetic data were retrieved from http://www.eupedia.com. The statistical analysis included Forward Stepwise Multiple Linear Regression analysis and Pearson Correlation Coefficient (R).

RESULTS

In males, N and R1a Y-DNA haplotypes were positively related to both homicidal and suicidal behaviors while I1 was negatively related. The Q was positively related to the homicidal rate. Overall, 60-75% of the observed variance was explained. L, J and X mtDNA haplogroups were negatively related with suicide in females alone, with 82-85% of the observed variance described.

DISCUSSION

The current study should not be considered as a study of genetic markers but rather a study of human ancestry. Its results could mean that research on suicidality has a strong biological but locally restricted component and could be limited by the study population; generalizability of the results at an international level might not be possible. Further research with patient-level data are needed to verify whether these haplotypes could serve as biological markers to identify persons at risk to commit suicide or homicide and whether biologically-determined ancestry could serve as an intermediate grouping method or even as an endophenotype in suicide research.

Mitochondrial DNA haplogroup K as a contributor to protection against thyroid cancer in a population from southeast Europe

We aimed to analyze the contribution of mitochondrial DNA (mtDNA) haplogroups of the mtDNA control region to thyroid cancer risk in a population from southeastern Europe consisting of 235 thyroid tumor patients, including 114 patients with thyroid follicular adenoma, 121 patients with papillary thyroid carcinoma, and 419 healthy controls. Binary logistic regression with adjustment for age and gender revealed that mtDNA haplogroup K was significantly associated with a protective role for thyroid cancer in the combined tumor group versus controls. These results indicate a potential role for mtDNA haplogroups as important candidate susceptibility markers for the patients with thyroid nodules.

Maternal genetic backgrounds contribute to the genetic susceptibility of tongue cancer patients in Hunan, central of China

Mitochondrial DNA (mtDNA) mutations played crucial roles on affecting the susceptibility to cancer. In this study, to investigate whether mitochondrial DNA mutations contributed to the genetic susceptibility of Chinese tongue cancer patients, mtDNA control regions of 105 Chinese tongue cancer patients were amplified and sequenced, the mutations were recorded by comparing with the revised Cambridge Reference Sequence (rCRS), which were attributed to certain mtDNA haplogroups based on the specific variations motif of each patients. The Miao Chinese group (a Chinese ethnic minority) from surrounding region has no essential difference with tongue cancer group, which was taken as the matched control group with principal component analysis by taking the haplogroups frequency of 105 tongue cancer individuals and 354 healthy individuals of eight groups from the similar geographic regions as input factors. This was supported by the smallest genetic distance between tongue cancer and Miao_2 groups. Further, the statistical analysis based on mtDNA variations of hypervariable sequence I (HVSI) indicated that 13 variations including 16,124, 16,148, 16,182C, 16,183C, 16,227, 16,266A, 16,249, 16,272, 16,291, 16,327, 16,335, 16,497, and 16,519 have significant differences between tongue cancer group and matched control group. Comparison of mtDNA haplogroups between tongue cancer and control groups indicated that mtDNA haplogroups C, F2*, and M10 have significant differences. It's worth noting that 16,327 and 16,291 was the defining variation of haplogroups C and F2*, respectively. Our results suggested that mitochondrial DNA may play a crucial role for the maternal genetic susceptibility of tongue cancer patients from Hunan, central of China.

Associations of mitochondrial haplogroups and mitochondrial DNA copy numbers with end-stage renal disease in a Han population

Mitochondrial DNA (mtDNA) is closely related to mitochondrion function, and variations have been suggested to be involved in pathogenesis of complex diseases. The present study sought to elucidate mitochondrial haplogroups and mtDNA copy number in end-stage renal disease (ESRD) in a Han population. First, the mitochondrial haplogroups of 37 ESRD patients were clustered into several haplogroups, and haplogroup A & D were taken as the candidate risk haplogroups for ESRD. Second, the frequencies of A and D were assessed in 344 ESRD patients and 438 healthy controls, respectively. Haplogroup D was found to be risk maker for ESRD in young subjects (<30 years) with an OR of 2.274. Finally, intracellular and cell-free mtDNA copy numbers were evaluated with quantitative-PCR. The ESRD patients exhibited greater cell-free mtDNA contents than the healthy controls but less intracellular mtDNA. Haplogroup D exhibited a further increase in cell-free mtDNA content and a decrease in intracellular mtDNA content among the ESRDs patients. Our findings suggest that mtNDA haplogroup D may contributes to pathogenesis of early-onset ESRD through alterations of mtDNA copy numbers.

Analysis on clinical characteristics and influencing factors of patients with locoregionally advanced nasopharyngeal carcinoma

BACKGROUND

To explore the independent prognostic factors for the recurrence/metastasis of patients with locoregionally advanced nasopharyngeal carcinoma (LANPC).

MATERIALS AND METHODS

A total of 604 patients initially diagnosed as LANPC by pathohistology in Fujian Provincial Cancer Hospital were selected to analyze the relationship between the clinical pathological patterns, therapeutic protocols and clinical stages with the recurrence/metastasis of LANPC.

RESULTS

The 1-, 3- and 5-year locoregionally recurrent rates of LANPC patients were 2.0%, 9.5% and 12.9% respectively, with average recurrent period being 78 months. Univariate analysis results indicated that clinical stages had certain influence on the recurrent period of LANPC patients. However, COX regression models showed that ages, genders and clinical stages were not the independent prognostic factors influencing the recurrence. The 1-, 3- and 5-year metastatic rates of LANPC patients were 6.6%, 17.5% and 18.8% respectively, with average metastatic period of 73 months. Univariate analysis results demonstrated that ages, N stages, clinical stages, locations of lymph node, retropharyngeal lymph node and extracapsular invasion of lymph node had certain influence on the metastatic period of LANPC patients. Additionally, further COX regression analysis results suggested that T stages, reduction protocols and extracapsular invasion of lymph node were the independent prognostic factors influencing the metastasis of patients with LANPC, in which T stages and extracapsular invasion of lymph node were the pestilent factors while reduction protocols the protective factor.

CONCLUSIONS

Induction chemotherapy is beneficial to LANPC patients with initial treatment, and the metastatic rate decreases greatly after the application of reduction chemotherapy.

Association of Genes, Pathways, and Haplogroups of the Mitochondrial Genome with the Risk of Colorectal Cancer: The Multiethnic Cohort

The mitochondrial genome encodes for the synthesis of 13 proteins that are essential for the oxidative phosphorylation (OXPHOS) system. Inherited variation in mitochondrial genes may influence cancer development through changes in mitochondrial proteins, altering the OXPHOS process, and promoting the production of reactive oxidative species. To investigate the role of the OXPHOS pathway and mitochondrial genes in colorectal cancer (CRC) risk, we tested 185 mitochondrial SNPs (mtSNPs), located in 13 genes that comprise four complexes of the OXPHOS pathway and mtSNP groupings for rRNA and tRNA, in 2,453 colorectal cancer cases and 11,930 controls from the Multiethnic Cohort Study. Using the sequence kernel association test, we examined the collective set of 185 mtSNPs, as well as subsets of mtSNPs grouped by mitochondrial pathways, complexes, and genes, adjusting for age, sex, principal components of global ancestry, and self-reported maternal race/ethnicity. We also tested for haplogroup associations using unconditional logistic regression, adjusting for the same covariates. Stratified analyses were conducted by self-reported maternal race/ethnicity. In European Americans, a global test of all genetic variants of the mitochondrial genome identified an association with CRC risk (P = 0.04). In mtSNP-subset analysis, the NADH dehydrogenase 2 (MT-ND2) gene in Complex I was associated with CRC risk at a P-value of 0.001 (q = 0.015). In addition, haplogroup T was associated with CRC risk (OR = 1.66, 95% CI: 1.19-2.33, P = 0.003). No significant mitochondrial pathway and gene associations were observed in the remaining four racial/ethnic groups--African Americans, Asian Americans, Latinos, and Native Hawaiians. In summary, our findings suggest that variations in the mitochondrial genome and particularly in the MT-ND2 gene may play a role in CRC risk among European Americans, but not in other maternal racial/ethnic groups. Further replication is warranted and future studies should evaluate the contribution of mitochondrial proteins encoded by both the nuclear and mitochondrial genomes to CRC risk.

Blood cadmium burden and the risk of nasopharyngeal carcinoma: a case-control study in Chinese Chaoshan population

Cadmium is a ubiquitous carcinogenic pollutant with multiple biological effects. Both observational and experimental studies have suggested associations between cadmium and the rates of many types of cancers. The aim of the present study was to evaluate whether cadmium exposure is associated with nasopharyngeal carcinoma (NPC) in a population with a relatively high prevalence in southeast China. Hospital-based 134 NPC cases and 132 cancer-free controls were recruited from a cancer hospital in Chaoshan area, southeast of China. Basic clinical data and information of lifetime styles, smoking, and drinking as well as other demographic characteristics were also collected from medical records. Blood cadmium levels (BCLs) were detected by graphite-furnace atomizer absorption spectrophotometer (GFAAS). BCLs and over-limit ratios between cases and controls were compared. The relationships between BCLs and NPC were explored by comparing BCLs differences between/among different characteristics of related factors and logistic regression analysis. In addition, BCLs within cases were also compared in relation to the disease clinical stages, pathological types, and metastasis. The median concentration of blood cadmium in cases (3.84, interquartile range 2.21-6.10) was significantly higher than that of controls (2.28, interquartile range 1.79-3.45). The over-limit ratio (≥5 μg/L) in cases was also higher than that in controls (35.1 vs. 13.6%, χ(2) = 16.55, p < 0.001). Smokers tended to have high levels of cadmium burden, and smokers with longer smoking pack-years in cases had relatively higher BCLs (p = 0.001). NPC patients with diseases history presented lower cadmium burden (p = 0.020). In the NPC cases, BCLs were positively associated with clinical stages and N classification (r = 0.193, 0.187, respectively, p < 0.05). Cadmium seems to be a risk factor of NPC, and high cadmium exposure may promote the occurrence and development of NPC.

Population data of mitochondrial DNA HVS-I and HVS-II sequences for 208 Henan Han Chinese

The two hypervariable segments (HVS-I and HVS-II) of mitochondrial DNA (mtDNA) control region were sequenced for a population of 208 unrelated healthy individuals sampled from Suiping County, Henan Province, China. A total of 192 different haplotypes were identified, of which 179 haplotypes were unique (93.23%). The variation of the mtDNA HVS-I and HVS-II was confined to 166 nucleotide positions, of which 115 were observed in the HVS-I and 51 in the HVS-II. The haplotype diversity and random match probability were 0.9991 and 0.0061, respectively. Following the principle of the updated East Asian mtDNA phylogeny tree, individual samples were assigned to the specific haplogroups based on the information both from control region and coding-region obtained. Haplogroup D was the most common haplogroup (25.96%). The northern China-prevalent haplogroups (A, C, D, G, M8, Y, and Z) and the southern China-prevalent haplogroups (B, F, M7, N9, and R9) accounted for 48.56% and 46.63%, respectively, of the Henan Han mtDNA gene pool. The mtDNA hypervariable region was highly polymorphic in Henan Han population. These sequences could serve as mtDNA reference data for forensic casework in Henan population as well as for population genetic study.

Mitochondrial DNA Haplogroup A may confer a genetic susceptibility to AIDS group from Southwest China

The acquired immunodeficiency syndrome (AIDS) in humans was one of the chronic infections caused by human immunodeficiency virus (HIV), and the interactions between viral infection and mitochondrial energetic implicated that mitochondrial DNA (mtDNA) variation(s) may effect genetic susceptibility to AIDS. Thus, to illustrate the maternal genetic structure and further identify whether mtDNA variation(s) can effect HIV infection among southwest Chinese AIDS group, the whole mtDNA control region sequences of 70 AIDS patients and 480 health individuals from southwest China were analyzed here. Our results indicated the plausible recent genetic admixture results of AIDS group; comparison of matrilineal components between AIDS and matched Han groups showed that mtDNA haplogroup A (p = 0.048, OR = 3.006, 95% CI = 1.109-8.145) has a significant higher difference between the two groups; further comparison illustrated that mtDNA mutations 16,209 (p = 0.046, OR = 2.607, 95% CI = 0.988-6.876) and 16,319 (p = 0.009, OR = 2.965, 95% CI = 1.278-6.876) have significant differences between AIDS and matched control groups, and both of which were the defining variations of mtDNA haplogroup A, they further confirmed that mtDNA haplogroup A may confer genetic susceptibility to AIDS. Our results suggested that haplogroup A may confer a genetic susceptibility to AIDS group from Southwest China.