Mitochondrial Deficiencies in the Predisposition to Paraganglioma

Paragangliomas and pheochromocytomas are rare neuroendocrine tumours with a very strong genetic component. It is estimated that around 40% of all cases are caused by a germline mutation in one of the 13 predisposing genes identified so far. Half of these inherited cases are intriguingly caused by mutations in genes encoding tricarboxylic acid enzymes, namely SDHA, SDHB, SDHC, SDHD, and SDHAF2 genes, encoding succinate dehydrogenase and its assembly protein, FH encoding fumarate hydratase, and MDH2 encoding malate dehydrogenase. These mutations may also predispose to other type of cancers, such as renal cancer, leiomyomas, or gastro-intestinal stromal tumours. SDH, which is also the complex II of the oxidative respiratory chain, was the first mitochondrial enzyme to be identified having tumour suppressor functions, demonstrating that 80 years after his initial proposal, Otto Warburg may have actually been right when he hypothesized that low mitochondrial respiration was the origin of cancer. This review reports the current view on how such metabolic deficiencies may lead to cancer predisposition and shows that the recent data may lead to the development of innovative therapeutic strategies and establish precision medicine approaches for the management of patients affected by these rare diseases.