MT-ND6 and cancer: In general, we observed that the mtOXPHOS mRNA levels were upregulated across the Pheo-Type-based gene-expression signatures, with downregulation of MT-ND2/ND6 genes, encoding two subunits of complex I. The differences in complex I gene expression have been observed previously in many cancers (e.g., lung, colon, and bladder) [41,42].