Mitochondrial genome variability and metabolic alterations reveal new biomarkers of resistance in testicular germ cell tumors

Aim: Mutations in the mitochondrial (mt) genome contribute to metabolic dysfunction and their accumulation relates to disease progression and resistance development in cancer cells. This study explores the mutational status of the mt genome of cisplatin-resistant vs. -sensitive testicular germ cell tumor (TGCT) cells and explores its association with their respiration parameters, expression of respiratory genes, and preferences for metabolic pathways to reveal new markers of therapy resistance in TGCTs. Methods: Using Illumina sequencing with Twist Enrichment Panel, the mutations of mt genomes of sensitive 2102EP, H12.1, NTERA-2, T-cam and resistant 2102EP Cis, H12.1 ODM, 1411HP, 1777NRpmet, NTERA-2 Cis and T-cam Cis cell lines were identified. The mt respiration of the cells was assessed using high-resolution respirometry method (O2k-respirometer Oroboros) and the differential expression profiles of mt respiratory genes were determined using RT-qPCR. Associated preferences for metabolic pathways were compared using Glycolysis/OXPHOS assay. Results: In resistant TGCT cells, new mutations in mt genes MT-ND1-6, MT-RNR, MT-CO1-3, MT-ATP6, and MT-CYB were recognized. The respiratory rates of the 1777NRpmet cell line were the highest, while those of the 1411HP line the lowest; rates of the control and all other TGCT cell lines fell between these two lines. The statistically significant differences in gene expression of the respiratory genes were recorded only in NTERA-2 Cis and T-cam Cis cell lines. Sensitive cell lines NTERA-2 and 2102EP preferred oxidative phosphorylation (OXPHOS), while glycolysis was typical for resistant NTERA-2 Cis, 2102EP Cis and 1411HP cell lines. Metastatic 1777NRpmet cells seem to utilize both. An isogenic pair of cell lines H12.1 and H12.1ODM showed the opposite dependence, sensitive H12.1 preferring glycolysis, while resistant H12.1ODM OXPHOS. Conclusion: In summary, our study identified new mutations in mt genes of resistant TGCT cell lines that are associated with different mt respiration parameters, gene expression patterns and preferences for metabolic pathways, providing potential novel molecular biomarkers that distinguish the resistant TGCT phenotype or specify its histological classification.