COA4 and cancer: reported COA4 as a putative cancer‐promoting protein.[18] Moreover, related proteins such as COX6B2 have been reported to drive metastasis in pancreatic ductal adenocarcinoma (PDAC) by enhancing OXPHOS.[15a] However, the biological function of COA4 in mitochondrial OXPHOS of mammalian cells has not been demonstrated.