Mitochondrial DNA Levels in Blood and Tissue Samples from Breast Cancer Patients of Different Stages

Aims: Alterations in mitochondrial DNA (mtDNA) have been implicated in carcinogenesis and tumorprogression. We here evaluated the diagnostic and prognostic potential of mtDNA as a biomarker for breastcancer.
Methods: Using multiplex real-time polymerase chain reaction, nuclear DNA (nDNA) and mtDNA levels inserum, buffy coat, tumor, and tumor-adjacent tissue samples from 50 breast cancer patients were determined andassessed for associations with clinicopathological features. To evaluate mtDNA as a biomarker for distinguishingbetween the four sample types, we created receiver operating characteristic (ROC) curves.
Results: The mtDNAlevels in buffy coat were significantly lower than in other sample types. Relative to tumor-adjacent tissue,reduced levels of mtDNA were identified in buffy coat and tumor tissue but not in serum. According to ROCcurve analysis, mtDNA levels could be used to distinguish between buffy coat and tumor-adjacent tissue sampleswith good sensitivity (77%) and specificity (83%). Moreover, mtDNA levels in serum and tumor tissue werepositively associated with cancer TMN stage.
Conclusions: The mtDNA levels in blood samples may representa promising, non-invasive biomarker in breast cancer patients. Additional, large-scale validation studies arerequired to establish the potential use of mtDNA levels in the early diagnosis and monitoring of breast cancer.