Aberrant succination of proteins in fumarate hydratase-deficient mice and HLRCC patients is a robust biomarker of mutation status

Germline mutations in the FH gene encoding the Krebs cycle enzyme fumarate hydratase predispose to hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome. FH-deficient cells and tissues accumulate high levels of fumarate, which may act as an oncometabolite and contribute to tumourigenesis. A recently proposed role for fumarate in the covalent modification of cysteine residues to S-(2-succinyl) cysteine (2SC) (termed protein succination) prompted us to assess 2SC levels in our existing models of HLRCC. Herein, using a previously characterized antibody against 2SC, we show that genetic ablation of FH causes high levels of protein succination. We next hypothesized that immunohistochemistry for 2SC would serve as a metabolic biomarker for the in situ detection of FH-deficient tissues. Robust detection of 2SC was observed in Fh1 (murine FH)-deficient renal cysts and in a retrospective series of HLRCC tumours (n = 16) with established FH mutations. Importantly, 2SC was undetectable in normal tissues (n = 200) and tumour types not associated with HLRCC (n = 1342). In a prospective evaluation of cases referred for genetic testing for HLRCC, the presence of 2SC-modified proteins (2SCP) correctly predicted genetic alterations in FH in every case. In two series of unselected type II papillary renal cancer (PRCC), prospectively analysed by 2SCP staining followed by genetic analysis, the biomarker accurately identified previously unsuspected FH mutations (2/33 and 1/36). The investigation of whether metabolites in other tumour types produce protein modification signature(s) that can be assayed using similar strategies will be of interest in future studies of cancer.     

Clinical and biochemical heterogeneity associated with fumarase deficiency

Fumarase deficiency (FD), caused by biallelic alteration of the Fumarase Hydratase gene (FH), and a rare metabolic disorder that affects the Krebs cycle, causes severe neurological impairment and fumaric aciduria. Less than 30 unrelated cases are known to date. In addition, heterozygous mutations of the FH gene are responsible for hereditary leiomyomatosis and renal cell cancer (HLRCC). We report three additional patients with dramatically different clinical presentations of FD and novel missense mutations in the FH gene. One patient had severe neonatal encephalopathy, polymicrogyria, <1% enzyme activity, and mildly increased levels of urinary fumarate. The second patient had microcephaly, mental retardation, 20% of fumarase activity, and intermediate levels of urinary fumarate. The third patient had mild mental retardation, polymicrogyria, 42–61% enzyme activity in different cell types and massive amounts of urinary fumarate. In silico analysis predicted minor yet significant structural changes in the encoded proteins. The nuclear translocation of hypoxia‐inducible factor (HIF)‐1alpha (HIF1A) in cultured fibroblasts was similar to controls. These results extend the range of clinical and biochemical variation associated with FD, supporting the notion that patients with moderate increases in fumarate excretion should be investigated for this disease. The tumoral risk in the patients and their relatives requires adequate screening protocols. Hum Mutat 32:1–7, 2011. © 2011 Wiley‐Liss, Inc.     

Inhibition of α-KG-dependent histone and DNA demethylases by fumarate and succinate that are accumulated in mutations of FH and SDH tumor suppressors

Two Krebs cycle genes, fumarate hydratase (FH) and succinate dehydrogenase (SDH), are mutated in a subset of human cancers, leading to accumulation of their substrates, fumarate and succinate, respectively. Here we demonstrate that fumarate and succinate are competitive inhibitors of multiple α-ketoglutarate (α-KG)-dependent dioxygenases, including histone demethylases, prolyl hydroxylases, collagen prolyl-4-hydroxylases, and the TET (ten-eleven translocation) family of 5-methlycytosine (5mC) hydroxylases. Knockdown of FH and SDH results in elevated intracellular levels of fumarate and succinate, respectively, which act as competitors of α-KG to broadly inhibit the activity of α-KG-dependent dioxygenases. In addition, ectopic expression of tumor-derived FH and SDH mutants inhibits histone demethylation and hydroxylation of 5mC. Our study suggests that tumor-derived FH and SDH mutations accumulate fumarate and succinate, leading to enzymatic inhibition of multiple α-KG-dependent dioxygenases and consequent alterations of genome-wide histone and DNA methylation. These epigenetic alterations associated with mutations of FH and SDH likely contribute to tumorigenesis.     

Mutation screening of fumarate hydratase by multiplex ligation-dependent probe amplification: detection of exonic deletion in a patient with leiomyomatosis and renal cell cancer

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a syndrome predisposing to cutaneous and uterine leiomyomatosis as well as renal cell cancer and uterine leiomyosarcoma. Heterozygous germline mutations in the fumarate hydratase (FH, fumarase) gene are known to cause HLRCC. On occasion, no FH mutation is detected by direct sequencing, despite the evident HLRCC phenotype in a family. In the present study, to investigate whole gene or exonic deletions and amplifications in FH mutation-negative patients, we used multiplex ligation-dependent probe amplification technology. The study material comprised 7 FH mutation-negative HLRCC patients and 12 patients affected with HLRCC-associated phenotypes, including papillary RCC, early-onset RCC, uterine leiomyomas, or uterine leiomyosarcoma. A novel FH mutation, a deletion of FH exon 1 that encodes the mitochondrial signal peptide, was detected in one of the HLRCC patients (1/7). The patient with the FH mutation displayed numerous painful cutaneous leiomyomas and papillary type renal cell cancer. Our finding, together with the two patients with whole FH gene deletion who had been detected previously, suggests that exonic or whole-gene FH deletions are not a frequent cause of HLRCC syndrome.     

Fumarate hydratase enzyme activity in lymphoblastoid cells and fibroblasts of individuals in families with hereditary leiomyomatosis and renal cell cancer

Background

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is the autosomal dominant heritable syndrome with predisposition to development of renal cell carcinoma and smooth muscle tumours of the skin and uterus.

Objective

To measure the fumarate hydratase (FH) enzyme activity in lymphoblastoid cell lines and fibroblast cell lines of individuals with HLRCC and other familial renal cancer syndromes.

Methods

FH enzyme activity was determined in the whole cell, cytosolic, and mitochondrial fractions in 50 lymphoblastoid and 16 fibroblast cell lines including cell lines from individuals with HLRCC with 16 different mutations.

Results

Lymphoblastoid cell lines (n = 20) and fibroblast cell lines (n = 11) from individuals with HLRCC had lower FH enzyme activity than cells from normal controls (p<0.05). The enzyme activity in lymphoblastoid cell lines from three individuals with mutations in R190 was not significantly different from individuals with other missense mutations. The cytosolic and mitochondrial FH activity of cell lines from individuals with HLRCC was reduced compared with those from control cell lines (p<0.05). There was no significant difference in enzyme activity between control cell lines (n = 4) and cell lines from affected individuals with other hereditary renal cancer syndromes (n = 22).

Conclusions

FH enzyme activity testing provides a useful diagnostic method for confirmation of clinical diagnosis and screening of at‐risk family members.     

Germline fumarate hydratase mutations in patients with ovarian mucinous cystadenoma

Germline mutations in the fumarate hydratase (FH) gene were recently shown to predispose to the dominantly inherited syndrome, hereditary leiomyomatosis and renal cell cancer (HLRCC). HLRCC is characterized by benign leiomyomas of the skin and the uterus, renal cell carcinoma, and uterine leiomyosarcoma. The aim of this study was to identify new families with FH mutations, and to further examine the tumor spectrum associated with FH mutations. FH germline mutations were screened from 89 patients with RCC, skin leiomyomas or ovarian tumors. Subsequently, 13 ovarian and 48 bladder carcinomas were analyzed for somatic FH mutations. Two patients diagnosed with ovarian mucinous cystadenoma (two out of 33, 6%) were found to be FH germline mutation carriers. One of the changes was a novel mutation (Ala231Thr) and the other one (435insAAA) was previously described in FH deficiency families. These results suggest that benign ovarian tumors may be associated with HLRCC.     

Conventional renal cancer in a patient with fumarate hydratase mutation

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a tumor predisposition syndrome caused by mutations in the fumarate hydratase (FH) gene. HLRCC is characterized by uterine and cutaneous leiomyomas, renal cell cancer, and uterine leiomyosarcoma. Typically, renal cell cancers in HLRCC are unilateral and display a papillary type 2 or ductal histology. We describe here a 23-year-old patient carrying a novel FH mutation (N330S) with a bilateral renal cell center. Carcinoma of the right kidney showed papillary structure, but the left tumor was diagnosed as a conventional (clear cell) renal carcinoma, a type not previously described in HLRCC. The clear cell renal carcinoma also displayed loss of the normal FH allele and the FH immunostaining. Our finding extends the number of cases in which HLRCC can be suspected, and the FH immunohistochemistry may serve as a useful tool to screen for HLRCC in young individuals with clear cell renal carcinoma.     

Molecular and biochemical investigations in fumarase deficiency

Fumarase (FH) deficiency is a rare autosomal recessive disease of the Krebs cycle causing severe neurological impairment in early childhood, characterized by encephalopathy with seizures and muscular hypotonia. Only a handful of patients with various recessive mutations in the FH gene have been described so far. Interestingly, autosomal dominant mutations in the same gene are associated with hereditary leiomyomatosis and renal cell cancer (HLRCC). We investigated a boy with developmental and growth delay, microcephaly, and muscular hypotonia recognized at the age of 3 months. No leiomyomatosis or renal cancer is known in the parents. Investigation of the patient's urine revealed massive fumarate excretion. FH activity was severely reduced in muscle and fibroblasts. Respirometric investigation of fibroblasts showed only modest changes indicating that fumarate mediated inhibition of enzymatic pathways other than oxidative phosphorylation might be more relevant in pathophysiology of FH deficiency. Molecular analysis revealed a known 435insK mutation on the paternal allele and a novel H275L mutation due to an A to T transversion of nucleotide 824 on the maternal allele. This mutation affects the same codon as a C to T transition of nucleotide 823, resulting in a H275Y mutation that was found in two families with HLRCC.     

Mitochondrial succinate is instrumental for HIF1alpha nuclear translocation in SDHA-mutant fibroblasts under normoxic conditions

The genes encoding succinate dehydrogenase (SDH) subunits B, C and D, act as tumour suppressors in neuro-endocrine tissues. Tumour formation has been associated with succinate accumulation. In paraganglioma cells, two forms of SDHA (type I, II) were found which might preclude significant succinate accumulation in the case of a mutation in either form. In fibroblasts only SDHA type I is found. In these cells, SDHA type I mutation leads to SDH deficiency, succinate accumulation and hypoxia-inducible factor 1alpha(HIF1alpha) nuclear translocation. HIF1alpha nuclear translocation was not observed in ATPase-deficient fibroblasts with increased superoxide production and was found to be independent of cellular iron availability in SDHA-mutant cells. This suggests that neither superoxides nor iron were causative of HIF1alpha nuclear translocation. Conversely, alpha-ketoglutarate (alpha-KG) inhibits this nuclear translocation. Therefore, the pseudo-hypoxia pathway in SDH-deficient cells depends on the HIF1alphaprolyl hydroxylase product/substrate (succinate/alpha-KG) equilibrium. In SDH deficiency, organic acids thus appear instrumental in the HIF1alpha-dependent cascade suggesting a direct link between SDH and tumourigenesis.     

Strong family history of uterine leiomyomatosis warrants fumarate hydratase mutation screening

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a tumor predisposition syndrome characterized by cutaneous and uterine leiomyomas and renal cell cancer. HLRCC is caused by heterozygous germline mutations in the fumarate hydratase (FH) gene. A Finnish family with nine closely related women with uterine leiomyomas was detected by an alert gynecologist. No cutaneous or renal cell tumors were reported in the family when it was referred to genetic analyses. Samples were available from seven patients, and a novel germline FH mutation was detected in five of them. Mutation carriers were symptomatic, had multiple tumors and were diagnosed at an early age. This study emphasizes the importance of considering FH mutation screening when gynecologists encounter families with multiple severe uterine leiomyoma cases. Due to possibility of phenocopies more than one patient should be tested. Early mutation detection allows regular screening of the mutation carriers and enables early detection of possible highly aggressive renal tumors. It may also affect family planning as multiple myomas at early age may significantly reduce fertility.     

Biallelic inactivation of fumarate hydratase (FH) occurs in nonsyndromic uterine leiomyomas but is rare in other tumors

Germline mutations in the fumarate hydratase (FH) gene at 1q43 predispose to dominantly inherited cutaneous and uterine leiomyomas, uterine leiomyosarcoma, and papillary renal cell cancer (HLRCC syndrome). To evaluate the role of FH inactivation in sporadic tumorigenesis, we analyzed a series of 299 malignant tumors representing 10 different malignant tumor types for FH mutations. Additionally, 153 uterine leiomyomas from 46 unselected individuals were subjected to and informative in loss of heterozygosity analysis at the FH locus, and the five (3.3%) tumors displaying loss of heterozygosity were subjected to FH mutation analysis. Although mutation search in the 299 malignant tumors was negative, somatic FH mutations were found in two nonsyndromic leiomyomas; a splice site change IVS4 + 3A>G, leading to deletion of exon four, and a missense mutation Ala196Thr. The occurrence of somatic mutations strongly suggests that FH is a true target of the 1q43 deletions. Although uterine leiomyomas are the most common tumors of women, specific inactivating somatic mutations contributing to the formation of nonsyndromic leiomyomas have not been reported previously. Taking into account the apparent risk of uterine leiomyosarcoma associated with FH germline mutations, the finding raises the possibility that also some nonsyndromic leiomyomas may have a genetic profile that is more prone to malignant degeneration. Our data also indicate that somatic FH mutations appear to be limited to tumor types observed in hereditary leiomyomatosis and renal cell cancer.     

Genetic and functional analyses of FH mutations in multiple cutaneous and uterine leiomyomatosis,hereditary leiomyomatosis and renal cancer,and fumarate hydratase deficiency

Germline mutations of the fumarate hydratase (FH, fumarase) gene are found in the recessive FH deficiency syndrome and in dominantly inherited susceptibility to multiple cutaneous and uterine leiomyomatosis (MCUL). We have previously reported a number of germline FH mutations from MCUL patients. In this study, we report additional FH mutations in MCUL and FH deficiency patients. Mutations can readily be found in about 75% of MCUL cases and most cases of FH deficiency. Some of the more common FH mutations are probably derived from founding individuals. Protein-truncating FH mutations are functionally null alleles. Disease-associated missense FH changes map to highly conserved residues, mostly in or around the enzyme's active site or activation site; we predict that these mutations severely compromise enzyme function. The mutation spectra in FH deficiency and MCUL are similar, although in the latter mutations tend to occur earlier in the gene and, perhaps, are more likely to result in a truncated or absent protein. We have found that not all mutation-carrier parents of FH deficiency children have a strong predisposition to leiomyomata. We have confirmed that renal carcinoma is sometimes part of MCUL, as part of the variant hereditary leiomyomatosis and renal cancer (HLRCC) syndrome, and have shown that these cancers may have either type II papillary or collecting duct morphology. We have found no association between the type or site of FH mutation and any aspect of the MCUL phenotype. Biochemical assay for reduced FH functional activity in the germline of MCUL patients can indicate carriers of FH mutations with high sensitivity and specificity, and can detect reduced FH activity in some patients without detectable FH mutations. We conclude that MCUL is probably a genetically homogeneous tumour predisposition syndrome, primarily resulting from absent or severely reduced fumarase activity, with currently unknown functional consequences for the smooth muscle or kidney cell.     

Immunoexpression of SDHB,FH, and CK20 among eosinophilic renal tumors: A tissue microarray study

BackgroundDifferential diagnosis can be a challenge for eosinophilic subtypes of renal cell tumors due to their overlapping histomorphological and immunohistochemical features. We aimed to investigate the frequency of rare variants of renal cell carcinomas (RCCs) such as succinate dehydrogenase-deficient RCC (SDDRCC), hereditary leiomyomatosis and RCC (HLRCC)-associated RCC, and eosinophilic, solid, and cystic RCC (ESCRCC) in our population.Materials and methodsRenal tumors which could be considered in the eosinophilic tumor category were included: 91 conventional clear cell RCCs with eosinophilic cytoplasm, 72 papillary RCCs, 74 chromophobe RCCs, 88 oncocytomas, and 37 other rare subtypes. Using the tissue microarray method, succinate dehydrogenase B (SDHB), fumarate hydratase (FH), and cytokeratin 20 (CK20) antibodies were performed by immunohistochemistry. Immunohistochemistry was repeated on whole block sections for selected cases. The utility of these antibodies in the differential diagnosis was also investigated.ResultsLoss of SDHB expression was detected in three tumors, two of which showed typical morphology for SDDRCC. In additional two tumors, SDHB showed weak cytoplasmic expression without a mitochondrial pattern (possible-SDHB deficient). None of the tumors showed loss of FH expression. Heterogeneous reactions were observed with SDHB and FH antibodies. Only one ESCRCC was detected with diffuse CK20 positivity.ConclusionSDDRCCs, HLRCC-associated RCCs, and ESCRCCs are very rare tumors depending on the population. Possible weak staining and focal loss of SDHB and FH expression should be kept in mind and genetic testing must be included for equivocal results.     

No germline FH mutations in familial breast cancer patients

Fumarate hydratase: (FH) was recently identified as the predisposing gene for a tumor predisposition syndrome, hereditary leiomyomatosis and renal cell cancer (HLRCC) (MIM 605839). In HLRCC, individuals with a germline heterozygous mutation in the FH gene typically develop benign leiomyomas of the skin and the uterus (fibroids, myomas). In a subset of the families, predisposition to renal cell carcinoma and uterine leiomyosarcoma occurs. Other malignancies including breast cancer have also been detected in patients with a germline FH mutation. To examine whether FH could be involved in predisposition to breast cancer, we analyzed germline FH mutations from 85 Finnish breast cancer patients. Most of the cases were selected based on positive family or personal history for malignancies associated with HLRCC. No mutations were found. These results show that FH is not a major predisposing gene for familial breast cancer.     

Novel morphological and genetic features of fumarate hydratase deficient renal cell carcinoma in HLRCC syndrome patients with a tailored therapeutic approach

The hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC) is defined by germline mutations in the fumarate hydratase (FH) gene and associated with leiomyomas and aggressive renal cell carcinomas with FH deficiency. Here, we comprehensively characterize two new patients with HLRCC syndrome on a morphological, immunohistochemical and genetic level. The patients developed aggressive HLRCC syndrome‐associated RCCs, uterine leiomyomas and dermal leiomyomas. One HLRCC syndrome‐associated RCC exhibited an unusual morphology with accumulation of “colloid‐like” cytoplasmic inclusions, which might serve as a novel sentinel feature to trigger further testing. This case showed partially retained FH expression, initially hampering correct diagnosis. Comprehensive next‐generation sequencing analyses of HLRCC syndrome‐associated RCC and leiomyomas in our patients revealed divergent genetic changes in the FH gene in different tumors from the same patient. While all leiomyomas (uterine and cutaneous) showed a FH loss of heterozygosity (LOH) as a wildtype allele inactivating event, one HLRCC‐RCC showed a second, undescribed NM_000143.3; c.947C>T; p.Ala316Val FH mutation accompanying the preexisting splice site mutation c.378+2T>C. In the other HLRCC syndrome‐associated RCC, the FH mutation (NM_000143.3; c.462T>G; p.Asn154Lys with a somatic LOH) represents another variant of unknown significance that we link to HLRCC ‐ and thus classify as likely pathogenic. Due to the specific diagnosis of metastatic HLRCC syndrome‐associated RCC, both cases were treated in first line with bevacizumab/erlotinib and showed remarkable and long lasting responses. These findings allow new morphological and molecular insights into the biology of the HLRCC syndrome, corroborate the “second hit” hypothesis of tumor formation in HLRCC patients and may promote a distinct therapeutic approach.     

Novel mutations in FH and expansion of the spectrum of phenotypes expressed in families with hereditary leiomyomatosis and renal cell cancer

Background

Hereditary leiomyomatosis and renal cell cancer (HLRCC; OMIM 605839) is the predisposition to develop smooth muscle tumours of the skin and uterus and/or renal cancer and is associated with mutations in the fumarate hydratase gene (FH). Here we characterise the clinical and genetic features of 21 new families and present the first report of two African‐American families with HLRCC.

Methods

Using direct sequencing analysis we identified FH germline mutations in 100% (21/21) of new families with HLRCC.

Results

We identified 14 germline FH mutations (10 missense, one insertion, two nonsense, and one splice site) located along the entire length of the coding region. Nine of these were novel, with six missense (L89S, R117G, R190C, A342D, S376P, Q396P), one nonsense (S102X), one insertion (111insA), and one splice site (138+1G>C) mutation. Four unrelated families had the R58X mutation and five unrelated families the R190H mutation. Of families with HLRCC, 62% (13/21) had renal cancer and 76% (16/21) cutaneous leiomyomas. Of women FH mutation carriers from 16 families, 100% (22/22) had uterine fibroids. Our study shows that expression of cutaneous manifestations in HLRCC ranges from absent to mild to severe cutaneous leiomyomas. FH mutations were associated with a spectrum of renal tumours. No genotype‐phenotype correlations were identified.

Conclusions

In combination with our previous report, we identify 31 different germline FH mutations in 56 families with HLRCC (20 missense, eight frameshifts, two nonsense, and one splice site). Our FH mutation detection rate is 93% (52/56) in families suspected of HLRCC.     

Fumarate hydratase deficient renal cell carcinoma: Chromosomal numerical aberration analysis of 12 cases

Hereditary leiomyomatosis and renal cell carcinoma-associated renal cell carcinoma (HLRCC)/fumarate hydratase deficient renal cell carcinoma (FHRCC) is defined by molecular genetic changes (mutation/LOH in fumarate hydratase (FH) gene). We investigated chromosomal numerical aberration pattern (CNV) in FHRCC/HLRCC using array comparative genomic hybridization analysis and low pass whole genome sequencing. Genetic analysis was successfully completed in 12 tumors. Most common chromosomal aberrations detected were a complete or partial loss of chromosome 4 (5/12 cases), chromosome 15 (4/12 cases), and chromosomes 9, 13, and 14 (each in 3/12 cases), as well as a complete or partial gain of chromosome 17 (in 4/12 cases). No chromosomal losses or gains were detected in 4 cases. Copy number variation pattern in FHRCC/HLRCC appears to be highly variable and does not provide a useful diagnostic tool in identifying these cases. Immunohistochemical staining and especially molecular genetic evaluation of FH gene mutations/LOH remain the gold standard in identifying FHRCC/HLRCC.