Mitochondrial DNA haplogroup M is associated with late onset of hepatocellular carcinoma

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.

Mitochondrial DNA haplogroup N is associated good outcome of gastric cancer

Accumulation of mutations and single nucleotide polymorphisms (SNPs) in the displacement loop (D-loop) of mitochondrial DNA (mtDNA) has been identified for their association with cancer risk and disease outcome in a variety of cancers. We have identified cancer risk-associated D-loop SNPs in gastric cancer patients. In this study, we evaluated the predictive value of these SNPs for cancer outcome. Two SNP sites of nucleotides 489C/T and 523-524AC/del were identified for statistically significant prediction of postoperative survival in gastric cancer by univariate analysis with log-rank test. In addition, the mitochondrial DNA haplogroup N (489T) contributed to the good survival of gastric cancer patients compared with the mitochondrial DNA haplogroup M (489C) genotype (relative risk, 1.753; 95 %CI, 1.005-3.060; p = 0.048) by multivariate analysis with COX hazards model. In conclusion, analysis of genetic polymorphisms in the mitochondrial D-loop can help identify subgroups of patients who are at a high risk of a poor disease outcome.

Identification of sequence polymorphisms in the mitochondrial displacement loop as risk factors for sporadic and familial breast cancer

The accumulation of single nucleotide polymorphisms (SNPs) in the displacement loop (D-loop) of mitochondrial DNA (mtDNA) has been described for different types of cancers, and the association of these SNPs with cancer risk and disease outcome has been exhaustively studied. We sequenced a region of approximately 1 kb flanking the majority of the D-Loop in the DNA from the blood of breast cancer patients and the controls to identify cancer risk-associated D-loop SNPs. The D-loop region of mtDNA was sequenced from 92 sporadic breast cancer patients, 60 familial breast cancer patients and 41 relatives, and 93 healthy controls. Paired and unpaired Student's t tests were used as appropriate to determine the differences in SNP distribution within the D-loop region and in the number of SNPs per patient among the groups. The χ (2) test was used to analyze dichotomous values, such as the presence or absence of an individual SNP among each group, and the clinical characteristics between every two groups. The distribution frequencies of 315C/Cinsert, 524C/del, 16247A/del, 16248C/del, 16249T/C, 16257C/A, 16258A/del, 16259C/del, 16262C/del, 16268C/del, 16279C/del, 16280A/del, 16297T/C, and 16300A/del were significantly different between sporadic breast cancer patients and the normal controls. The SNP sites at nucleotides 310, 315, and 16362 were identified as cancer risk-associated SNPs specific for familial breast cancer. The N haplogroup, defined as 489T, was identified as a specific risk-associated SNP for families of breast cancer patients by comparing familial breast cancer patients with their relatives. The analysis of genetic polymorphisms in the D-loop may help to predict cancer risk for familial breast cancer and thereby help to detect and refine therapeutic decisions earlier.

Single nucleotide polymorphisms in the mitochondrial displacement loop and age at onset of non-Hodgkin lymphoma

OBJECTIVE

Single nucleotide polymorphisms (SNPs) accumulated frequently in the mitochondrial displacement loop (D-loop) in many cancers. We had identified cancer risk-associated SNPs in the D-loop of non-Hodgkin lymphoma (NHL) patients previously, in this study, we investigated the association of age at onset and D-loop SNPs in NHL patients.

MATERIALS AND METHODS

The D-loop region of mtDNA was sequenced for 133 NHL patients recorded at the Fourth Hospital of Hebei Medical University. The Kaplan-Meier method was used to identify age at onset-associated SNPs in the D-loop of NHL patients. The Cox proportional hazards model was used to identify independent risk factors for age at onset.

RESULTS

The SNP sites of nucleotides 146C/T, 151T/C, 194T/C, 315C/C insert, 523Del/A, and 525Del/C were identified for their association with age at onset, by the logrank test. In an overall multivariate analysis, allele 146 (relative risk, 0.403; 95% confidence interval [CI]: 0.182-0.895) (P = 0.026), allele 151 (relative risk, 0.378; 95% CI: 0.165-0.868) (P = 0.022), and allele 315 (relative risk, 3.554; 95% CI: 1.344-9.400) (P = 0.011) were identified as independent predictors for age at onset in NHL patients.

CONCLUSION

SNPs in the D-loop can predict age at onset in NHL patients. Analysis of the D-loop SNPs can help identify NHL patient subgroups at high risk of early onset.

Identification of sequence polymorphisms in the displacement loop region of mitochondrial DNA as a risk factor for renal cell carcinoma

The accumulation of single-nucleotide polymorphisms (SNPs) in the displacement loop (D-loop) of mitochondrial DNA (mtDNA) may be associated with an increased cancer risk. In this case-control study, the SNPs in the mitochondrial D-loop of renal cell carcinoma (RCC) patients were identified and their association with cancer risk was evaluated. The minor alleles of nucleotides 16293A/G, 262A/G and 488T/C were associated with an increased risk, whereas the minor alleles of nucleotides 16298T/C and 16319G/A were associated with a decreased risk for RCC. Moreover, the nucleotides 16293, 262, 16298 and 16319 were identified as specifically associated with the risk of clear cell RCC (ccRCC), whereas 262 and 488 were specifically associated with papillary RCC and renal oncocytoma. In conclusion, SNPs in mtDNA are potential modifiers of RCC. The analysis of genetic polymorphisms in the mitochondrial D-loop may help identify the patient subgroups at a high risk of developing RCC.