Interestingly, Pang et al. found that SDHB-mutated PHEO/PGL tumor tissue and SDHBKD PHEO cell culture (mouse metastatic tumor tissue; MTT) had increased mitochondrial complex I activity, which catalyzes the first step of the electron transport chain and oxidizes NADH to NAD+ [38]. Here, SDHB is linked to metastatic neoplasm.