Characterization of Mitochondrial Double-Stranded RNA Levels in Non-Small Cell Lung Carcinoma.

Mitochondrial double-stranded RNA (mtdsRNA) is exported to the cytoplasm when mitochondrial RNA degradation is impaired, serving as a novel damage-associated molecular pattern for mitochondrial stress. Although mtdsRNA has been detected in certain cancers, its prevalence and functional role remain largely underexplored. Moreover, mtdsRNA is not readily detectable in large-scale computational datasets, reflecting technical limitations in the detection of structured mitochondrial transcripts. In this study, we used comprehensive computational characterization of non-small cell lung cancer (NSCLC) cell lines and identified elevated light-strand transcripts in a subset of cell lines, suggesting a potential for mtdsRNA formation. We stratify NSCLC lines into groups with high and low mtdsRNA abundance. Despite high cytoplasmic mtdsRNA levels in select NSCLC cell lines, we did not identify significant correlation with mtdsRNA abundance and type-I interferon (IFN-l) response. RT-qPCR analysis revealed that only USP18 transcripts amongst the IFN-l transcripts probed were significantly regulated in select NSCLC lines, indicating a partial or suppressed IFN-I response. Strand-specific RT-qPCR also revealed no bias in mitochondrial gene expression. These findings indicate that basal mtdsRNA accumulation alone is insufficient to trigger IFN-I signaling and may be tolerated in NSCLC, indicating adaptive mechanisms. Our findings suggest that mtdsRNAs could serve alternative nonimmunogenic roles in tumor biology. Importantly, our work reports that mtdsRNA is upregulated in a subset of NSCLC cell lines and in other cancer cell types, suggesting that mtdsRNA may serve as a new marker of mitochondrial dysfunction in cancer. SIGNIFICANCE: Our study identified and characterized NSCLC cell lines with elevated mtdsRNAs, suggesting that mtdsRNA may be a new signaling molecule in lung cancer for mitochondrial stress. We identified that accumulation of mtdsRNAs did not necessarily activate IFN-l response, indicating that NSCLC cell lines may have adaptive mechanisms to reduce IFN-l response.