unstable mitochondrial DNA mutations in HCC at single-cell resolution

Unstable mitochondrial DNA (mtDNA) mutations in hepatocellular carcinoma (HCC) were studied using a novel sequencing platform called single-cell capture-based mtDNA sequencing (sc-CAMS). This method allowed researchers to analyze mtDNA mutations at single-cell resolution, providing detailed insights into tumor heterogeneity. In the study, 1,641 single cells from 11 HCC patients and 528 cells from two xenograft mouse models were analyzed, revealing two types of mtDNA mutations: stable mutations (consistent heteroplasmy across cells) and unstable mutations (high variability in heteroplasmy among cells).

Unstable mtDNA mutations were strongly linked to intratumor heterogeneity (ITH), a hallmark of aggressive tumors. Tumors with high levels of unstable mutations exhibited proliferative and aggressive clinical features. These mutations evolved bidirectionally during tumor progression, undergoing both positive selection (expansion) and negative selection (elimination), showcasing the dynamic nature of tumor evolution. Through evolutionary reconstruction, researchers demonstrated that HCC follows both linear and branched progression models, indicating multiple evolutionary paths within the same tumor.

The study also visualized the spatiotemporal evolution of mtDNA mutations in patient-derived xenografts and multifocal tumor regions, showing how these mutations influence metabolic homeostasis, tumor evolution, and therapeutic resistance. Unstable mtDNA mutations could serve as biomarkers for tumor prognosis, stratification, and targeted therapies in HCC.