The results revealed that a gene signature including COX6A1, COX7B, ATP5H, COQ10A, NDUFA1, NDUFA5, NDUFA6, NDUFA8, NDUFA12, and NDUFC1 belonging to the TCA-cycle was significantly down-regulated in high-risk CSCC patients, as determined by Wilcoxon p-value comparison between high- and low-risk groups predicted by the model (P = 0.0026) (Supplementary Methods, Fig. 5b). This evidence concerns the gene NDUFA6 and skin squamous cell carcinoma.