# Exploring the oncogenic impact of heteroplasmic de novo MT-ND5 truncating mutations

## TL;DR

This study shows that mutations in the MT-ND5 mitochondrial gene can lead to cancer by increasing harmful oxygen molecules and disrupting cell stability.

## Contribution

The novel use of DddA-derived cytosine base editors to induce and study heteroplasmic MT-ND5 mutations in cancer.

## Key findings

- Low heteroplasmic MT-ND5 mutations impair mitochondrial function and increase ROS.
- Mutations promote oncogenesis through genome instability and altered redox balance.
- Transcriptomic analysis shows upregulated cancer pathways and downregulated ROS scavenging.

## Abstract

Numerous mitochondrial DNA (mtDNA) variants are associated with cancers, yet the causal link remains inconclusive. Using DddA-derived cytosine base editors, we induced de novo truncating mutations in MT-ND5 in HEK293 cells, establishing heteroplasmy, the coexistence of mutant and wild-type mtDNA. This study aimed to investigate the full molecular etiology following these deleterious mtDNA mutations, particularly in oncogenesis. We found that low to moderate heteroplasmic levels of the mutants were sufficient to impair mitochondrial functions and alter cellular redox status. Cellular adaptation to elevated ROS (Reactive Oxygen Species), energy crisis, and altered redox status was observed across varying heteroplasmy levels. Increased oncogenic potential was confirmed through in vitro oncogenesis and in vivo xenograft assays. Transcriptomic analysis revealed upregulated migration, invasion, and genome instability pathways, and downregulated ROS scavenging pathways. Our results demonstrate that MT-ND5 mutations drive cancer progression by increasing cellular ROS and genome instability, and by altering the redox balance and epigenetic landscapes.