Accumulation of Krebs cycle intermediates and over-expression of HIF1α in tumours which result from germline FH and SDH mutations

Abstract

The nuclear-encoded Krebs cycle enzymes, fumarate hydratase (FH) and succinate dehydrogenase (SDHB, -C and -D), act as tumour suppressors. Germline mutations in FH predispose individuals to leiomyomas and renal cell cancer (HLRCC), whereas mutations in SDH cause paragangliomas and phaeochromocytomas (HPGL). In this study, we have shown that FH-deficient cells and tumours accumulate fumarate and, to a lesser extent, succinate. SDH-deficient tumours principally accumulate succinate. In situ analyses showed that these tumours also have over-expression of hypoxia-inducible factor 1alpha (HIF1alpha), activation of HIF1alphatargets (such as vascular endothelial growth factor) and high microvessel density. We found no evidence of increased reactive oxygen species in our cells. Our data provide in vivo evidence to support the hypothesis that increased succinate and/or fumarate causes stabilization of HIF1alpha a plausible mechanism, inhibition of HIF prolyl hydroxylases, has previously been suggested by in vitro studies. The basic mechanism of tumorigenesis in HPGL and HLRCC is likely to be pseudo-hypoxic drive, just as it is in von Hippel-Lindau syndrome.

Succinate dehydrogenase and fumarate hydratase: linking mitochondrial dysfunction and cancer

“…Subsequent support for the biochemical role of succinate and fumarate in SDH-and FH-deficient tumours came from metabolomic studies of these tumours (Pollard et al, 2005b). It was clearly demonstrated that succinate levels are high in SDH-deficient HPGL tumours and that both succinate and fumarate levels are high in HLRCC tumours.…”

“…More recently, an extensive gene expression analysis of 76 phaeochromocytomas with different genetic lesions revealed a 'HIF signature' pattern of gene expression in a cluster of phaeochromocytomas with SDHB, SDHD or VHL mutations (Dahia et al, 2005). Interestingly, in the past year, it was shown that FH-deficient tumours also display high vascularity (Pollard et al, 2005a), increased HIFa levels and activity (Pollard et al, 2005b) and increased expression of glycolytic genes (measured by gene profiling) (Vanharanta et al, 2006). These independent studies collectively suggested that pseudo-hypoxia, manifested by high HIF activity under normoxic conditions, is an important factor that links mitochondrial tumour suppressors and cancer.…”

Succinate dehydrogenase deficiency is associated with decreased 5-hydroxymethylcytosine production in gastrointestinal stromal tumors: implications for mechanisms of tumorigenesis

“…Germline mutations in FH lead to hereditary leiomyomatosis and renal cell cancer and cause loss of function of FH and an accumulation of fumarate within cells. 24 IDH enzymes normally convert isocitrate to a-ketoglutarate. In contrast, tumor-associated IDH1/2 mutants lose the ability to produce a-ketoglutarate from isocitrate and also gain the neomorphic function of converting a-ketoglutarate to 2-hydroxyglutarate, which accumulates to high levels within IDH1/2 mutant cells.…”

“…Loss of SDH activity leads to the accumulation of succinate within cells. 24,25 Because of structural similarities between succinate and a-ketoglutarate, succinate is thought to inhibit the activity of a-ketoglutarate-dependent dioxygenase enzymes. 26 In particular, recent work has demonstrated that the TET family of DNA hydroxylases may be inhibited by elevated levels of succinate.…”

A proteomic analysis reveals the loss of expression of the cell death regulatory gene GRIM-19 in human renal cell carcinomas

“…Previous studies have shown that the expression of lactate dehyrogenase (Shim et al, 1997) is directly controlled by the c-myc oncogene, whose expression in turn is regulated by STAT3. In fact, a number of studies have shown an inactivation of enzymes involved in Kreb's cycle and a consequent dysfunction of oxidative phosphorylation in human tumors (Pollard et al, 2003(Pollard et al, , 2005Morris et al, 2004). Fumarate hydratase and succinate dehyrogenase B are few examples for these metabolic tumor suppressors (Pollard et al, 2003).…”