Recurrent Germline DLST Mutations in Individuals with Multiple Pheochromocytomas and Paragangliomas

Abstract

Pheochromocytomas and paragangliomas (PPGLs) provide some of the clearest genetic evidence for the critical role of metabolism in the tumorigenesis process. Approximately 40% of PPGLs are caused by driver germline mutations in 16 known susceptibility genes, and approximately half of these genes encode members of the tricarboxylic acid (TCA) cycle. Taking as a starting point the involvement of the TCA cycle in PPGL development, we aimed to identify unreported mutations that occurred in genes involved in this key metabolic pathway and that could explain the phenotypes of additional individuals who lack mutations in known susceptibility genes. To accomplish this, we applied a targeted sequencing of 37 TCA-cycle-related genes to DNA from 104 PPGL-affected individuals with no mutations in the major known predisposing genes. We also performed omics-based analyses, TCA-related metabolite determination, and 13 C 5 -glutamate labeling assays. We identified five germline variants affecting DLST in eight unrelated individuals ($7%); all except one were diagnosed with multiple PPGLs. A recurrent variant, c.1121G>A (p.Gly374Glu), found in four of the eight individuals triggered accumulation of 2-hydroxyglutarate, both in tumors and in a heterologous cell-based assay designed to functionally evaluate DLST variants. p.Gly374Glu-DLST tumors exhibited loss of heterozygosity, and their methylation and expression profiles are similar to those of EPAS1-mutated PPGLs; this similarity suggests a link between DLST disruption and pseudohypoxia. Moreover, we found positive DLST immunostaining exclusively in tumors carrying TCA-cycle or EPAS1 mutations. In summary, this study reveals DLST as a PPGL-susceptibility gene and further strengthens the relevance of the TCA cycle in PPGL development.

ABHD11 maintains 2-oxoglutarate metabolism by preserving functional lipoylation of the 2-oxoglutarate dehydrogenase complex

“…The importance of DLST and its lipoylation is highlighted by the recent identification of genetic mutations leading to human disease. Patients with germline mutations in lipoic acid synthesis genes develop a severe variant of the neurological condition, Leigh syndrome 13 , and loss of heterozygosity mutations in the OGDHc lead to angiogenic tumours (pheochromocytomas and paragangliomas), similar to other hereditary cancer syndromes activating the HIF pathway 14 . However, how OGDHc function and 2-OG abundance is regulated is unclear.…”

MYO5B mutations in pheochromocytoma/paraganglioma promote cancer progression

“… The 40 genes for calling of mutations in exomes were selected based on the following criteria; previously established or reported with germline and/or recurrent somatic mutations in PPGL (Buffet 2018 [ 9 ], Cascon 2015 [ 10 ], Dahia 2014 [ 7 ], Dwight 2017 [ 71 ], Fishbein 2017 [ 4 ], Papathomas 2014 [ 11 ], Remacha 2018 [ 12 ], Remacha 2019 [ 13 ], Yang 2015 [ 15 ], Yeh [ 77 ]), or recurrently occurring genes between lists of several PPGL studies (Castro-Vega 2015 [ 70 ], Flynn 2015 [ 72 ], Juhlin 2015 [ 73 ], Fishbein 2015 [ 18 ]), or recurrently mutated within our previous study (Wilzén 2016 [ 14 ]). Also, MYO5B -paralogs MYO5A and MYO5C were included.…”

Pheochromocytomas and Paragangliomas: Bypassing Cellular Respiration

“…Recently, a recurrent germline variant affecting DLST was found in PPGL patients with multiple tumors [80]. DLST (dihydrolipoamide S -succinyltransferase) is one of the three components (the E2 component) of the 2-oxoglutarate dehydrogenase (OGDH) complex that catalyzes the overall conversion of αKG to succinyl-CoA and CO 2 .…”

“…To note, one of these methylation-based studies also uncovered mutations in FH as a cause of hereditary PPGL [13], expanding the CIMP to another TCA cycle-related gene beyond the SDHx genes. In addition, a sporadic PPGL has been also described showing CIMP associated with the presence of a IDH1 mutation [49] but, as previously mentioned, tumors carrying DLST mutations do not exhibit the characteristic CIMP profile despite their accumulation of TCA metabolites [80]. To date, the presence of mutations in other genes involved in the epigenetic machinery in PPGLs exhibiting hypermethylation [121,122], and the finding of tumors with a CIMP profile not associated with mutations in any TCA cycle-related gene [49], further suggest that other genes and pathways may be involved in this particular phenotype.…”