The use of next generation sequencing technology to study the effect of radiation therapy on mitochondrial DNA mutation

Abstract

The human mitochondrial genome has an exclusively maternal mode of inheritance. Mitochondrial DNA (mtDNA) is particularly vulnerable to environmental insults due in part to an underdeveloped DNA repair system, limited to base excision and homologous recombination repair. Radiation exposure to the ovaries may cause mtDNA mutations in oocytes, which may in turn be transmitted to offspring. We hypothesized that the children of female cancer survivors who received radiation therapy may have an increased rate of mtDNA heteroplasmy mutations, which conceivably could increase their risk of developing cancer and other diseases. We evaluated 44 DNA blood samples from 17 Danish and 1 Finnish families (18 mothers and 26 children). All mothers had been treated for cancer as children and radiation doses to their ovaries were determined based on medical records and computational models. DNA samples were sequenced for the entire mitochondrial genome using the Illumina GAII system. Mother’s age at sample collection was positively correlated with mtDNA heteroplasmy mutations. There was evidence of heteroplasmy inheritance in that 9 of the 18 families had at least one child who inherited at least one heteroplasmy site from his or her mother. No significant difference in single nucleotide polymorphisms between mother and offspring, however, was observed. Radiation therapy dose to ovaries also was not significantly associated with the heteroplasmy mutation rate among mothers and children. No evidence was found that radiotherapy for pediatric cancer is associated with the mitochondrial genome mutation rate in female cancer survivors and their children.

Comprehensive next-generation sequence analyses of the entire mitochondrial genome reveal new insights into the molecular diagnosis of mitochondrial DNA disorders

“…36 In addition to forensic applications, heteroplasmic mtDNA variants have been considered useful genetic markers for genetic disease diagnosis, cancer prognosis, and other research studies. 17,18,37,38 Knowing the limitation of the MPS technologies and the interference of NUMTs and SNPs, evaluation and interpretation of mtDNA sequence results should be carried out with caution. When paraffin-fixed tumor tissues are used and target enrichment is limited to the use of multiple pairs of primers for PCR enrichment, 18 interference of NUMTs and SNPs is significant, and cautious interpretation of results derived from these approaches is indicated.…”

How do changes in the mtDNA and mitochondrial dysfunction influence cancer and cancer therapy? Challenges, opportunities and models

“…Additionally, a decrease in mtDNA content has been reported as a result of radiotherapy in cancer patients [191]. However, another study found no evidence that radiotherapy for pediatric cancer, which resulted in scatter radiation to the ovaries, is associated with the mitochondrial genome mutation frequency in female cancer survivors and their children [192]. In conclusion, mtDNA mutations (induced by radiotherapy or germline) can also affect the response and therefore the outcome of radiotherapy although the precise role and mechanisms are not yet fully understood.…”

Very Low-Level Heteroplasmy mtDNA Variations Are Inherited in Humans

“…In recent years, high-throughput sequencing technologies have matured in step with reduced costs. The high-coverage generated by the new high-throughput sequencing methods provides a powerful tool for the study of mtDNA heteroplasmy (Guo et al, 2012a; Tang and Huang, 2010). …”