Key P450 genes, such as CYP2A6 and CYP2C8 [17], displayed reduced expression levels in cancer progression, consistent with our bulk RNAseq and scRNA-seq results, while ETC-related genes, such as CYC1 and COX7B2, were upregulated during cancer progression, confirming that in vivo human liver tumorigenesis sustains or boosts the ETC. The gene discussed is CYP2A6; the disease is cancer.