Detection methods for mitochondrial DNA heteroplasmy and their potential single-cell applications in cancer

Mitochondrial DNA (mtDNA) is crucial for cellular metabolism, oxidative stress responses, and genomic stability, with mutations linked to cancer progression and therapeutic resistance. Mitochondrial heteroplasmy, the coexistence of wild-type and mutant mtDNA within a cell or across populations, plays a key role in mitochondrial dysfunction, tumor heterogeneity, and disease pathogenesis. Advances in single-cell technologies like quantitative PCR (qPCR), digital droplet PCR (ddPCR), next-generation sequencing (NGS), and long-read sequencing (TGS) have enabled precise mapping of heteroplasmic variants, providing insights into their role in cancer. This review evaluates current detection methods, discussing their strengths, limitations, and relevance to cancer research. We also explore the biological implications of heteroplasmy in cellular dynamics, nuclear mitochondrial DNA segments (NUMTs), and cancer pathogenesis, highlighting emerging technologies and future directions for studying mtDNA mutations at single-cell resolution in cancer. Ultimately, this review provides a critical synthesis of how single-cell mtDNA heteroplasmy analysis is reshaping our understanding of tumorigenesis and identifies key methodological and challenges that must be addressed to realize its full potential in precision oncology.