Germline Fumarate Hydratase Mutations Research Articles

Germline Fumarate Hydratase Mutations May be Associated with High-grade Gliomas and Mimic the Methylation Profile of IDH-mutant Gliomas (P4-5.002)

Germline Fumarate Hydratase Mutations May be Associated with High-grade Gliomas and Mimic the Methylation Profile of IDH-mutant Gliomas (P4-5.002)

SAT266 Transcriptional Changes Associated With Loss Of Function Of Fumarate Hydratase In A Cellular Model Of Pheochromocytoma

Abstract Disclosure: C.L. Hall: None. J.E. Read: None. G. Salsbury: None. E. Lim: None. S. Akker: None. P. Chapple: None. Mutations in fumarate hydratase (FH) predispose to development of pheochromocytomas and paragangliomas (PPGLs), as well as leiomyomas and renal cell carcinoma. Loss of FH function leads to accumulation of fumarate which acts as an oncometabolite to drive tumorigenesis, although the molecular mechanisms leading to the development of these rare tumours are not fully understood. We have used CRISPR/Cas9 genome editing to generate a series of FH knockouts in the PC-12 cell line, derived from MAX-mutated pheochromocytoma in rat. Our knockout cell lines were used as a model to investigate the molecular consequences of loss of FH function. Comparison of the transcriptome of FH knockout cells with isogenic controls identified 1016 differentially expressed genes (adjusted p<0.05 Log2fold±1). This list of differentially expressed genes was then analysed to identify cellular pathways that were dysregulated in the absence of FH. Canonical pathways that were significantly altered, based on transcript expression relative to controls, included axonal signalling pathway (p=7.29x10-11), wound healing signalling pathway (p=1.74x10-07), pulmonary fibrosis idiopathic signalling pathway (p=4.10x10-07) and IL-15 production (p=1.03x10-05). Our results suggest cell adhesion and immune regulation pathways may be relevant to the development of PPGLs with germline mutations in FH, but will require validation in the context of human tissue. We have also performed metabolic flux analysis to identify differences in metabolite profile associated with loss of FH. Interestingly, changes in gene expression, revealed by our transcriptomic analysis, may explain some alterations in cellular metabolism of FH knockout cells. Presentation: Saturday, June 17, 2023

FOXA2 controls the anti-oxidant response in FH-deficient cells

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a cancer syndrome caused by inactivating germline mutations in fumarate hydratase (FH) and subsequent accumulation of fumarate. Fumarate accumulation leads to profound epigenetic changes and the activation of an anti-oxidant response via nuclear translocation of the transcription factor NRF2. The extent to which chromatin remodeling shapes this anti-oxidant response is currently unknown. Here, we explored the effects of FH loss on the chromatin landscape to identify transcription factor networks involved in the remodeled chromatin landscape of FH-deficient cells. We identify FOXA2 as a key transcription factor that regulates anti-oxidant response genes and subsequent metabolic rewiring cooperating without direct interaction with the anti-oxidant regulator NRF2. The identification of FOXA2 as an anti-oxidant regulator provides additional insights into the molecular mechanisms behind cell responses to fumarate accumulation and potentially provides further avenues for therapeutic intervention for HLRCC.

820 A germline mutation of fumarate hydratase in a case with multiple cutaneous leiomyomas, leading to the diagnosis of hereditary leiomyomatosis and renal cell cancer

820 A germline mutation of fumarate hydratase in a case with multiple cutaneous leiomyomas, leading to the diagnosis of hereditary leiomyomatosis and renal cell cancer

Fumarate Hydratase and S-(2-Succinyl)-Cysteine Immunohistochemistry Shows Evidence of Fumarate Hydratase Deficiency in 2% of Uterine Leiomyosarcomas: A Cohort Study of 348 Tumors.

Approximately 1% to 1.5% of uterine leiomyomas are fumarate hydratase (FH)-deficient (FHd). A subset of these are associated with germline FH mutations. However, the prevalence and clinicopathologic characteristics of FHd uterine leiomyosarcoma (uLMS) remain unknown. Clinicopathologic data were collected for 348 uLMS. Morphologic features associated with FH deficiency (staghorn-type vessels, alveolar-pattern edema, macronucleoli with perinucleolar clearing, eosinophilic cytoplasmic inclusions, and chain-like nuclear arrangement) were documented. All 348 tumors were studied by FH immunohistochemistry. Eighty-nine were also studied by S-(2-succinyl)-cysteine (2SC) immunohistochemistry. Seven (2%) FHd uLMS were identified. Five showed uniformly negative FH and diffusely positive 2SC immunostaining; 1 showed variably negative to weak to strong FH and diffusely positive 2SC immunostaining; and 1 showed retained FH staining alongside positive 2SC confined to a morphologically distinct subclone. Three of 7 patients had extrauterine disease at presentation, and 3 of 6 had persistent disease or died from disease. Macronucleoli with perinucleolar clearing were significantly more common in FHd uLMS (7/7) than in uLMS with retained FH (182/341; P =0.017). Disease-specific survival, disease-free survival, and other morphologic features of FH deficiency did not differ significantly between FHd and FH-retained tumors. Our data emphasize that immunohistochemical FH deficiency does not preclude malignancy in uterine smooth muscle tumors. However, the biological significance and molecular basis of FH deficiency in uLMS, including any relationship to germline FH mutation, remain unknown, and a larger multi-institutional effort is necessary to gather sufficient FHd uLMS for more robustly powered clinicopathologic and for molecular characterization.

Molecular and immune landscape of FH-mutated cancers.

3125 Background: Fumarate Hydratase (FH) encodes an essential enzyme in the TCA cycle. Inactivating germline mutations in FH lead to hereditary leiomyomatosis and renal cell cancer syndrome with risk of development of certain cancers. Sporadic FH mutations have been described in different cancers but implications of somatic mutations on cancer outcomes and survival are not well described. Here, we characterize the molecular landscape of FH-mutant cancers. Methods: Tumors analyzed using NGS (NextSeq, 592 genes; NovaSeq, WES), IHC, and WTS (NovaSeq) (Caris Life Sciences, Phoenix, AZ). PD-L1 tested by 22c3, 28-8 (Agilent) and SP-142 (Spring Biosciences) IHC (>1%). MSI tested by FA, IHC, and NGS. TMB measured by totaling somatic mutations per tumor (TMB-h > 10 mutations/MB). Real-world overall survival was extracted from insurance claims data and calculated from first treatment to last contact using K-M survival curves for molecularly defined cohorts. Statistical significance was determined using chi-square and Wilcoxon rank-sum test, adjusted for multiple comparisons (q<0.05). Results: 3239 FH mutations were seen in 45 tumor types in 3149 FH-mutated tumors. NSCLC, colorectal and endometrial cancers harbored the most mutations. There were 839 pathogenic (P) or likely pathogenic (LP) and 2400 variants of unknown significance (VUS). Some tumors had multiple mutations. The most common mutations: R233H (P; 37), K477dup (LP; 555), and A41V (VUS; 70). VUS had increased TMB-H (40.4% vs 29.8%, q=0.004) and CREBBP mutations (5.1% vs 1.6%, q=0.012) compared to P+LP. A41V-mt tumors had significantly lower TMB-H than other VUS (8.8% vs 41.5%, q=0.002) and lower MSI-H (3.13% vs 3.69% vs 29.4%, q=0.003) and DICER1, PRKDC, FBXW7 mutations (q<0.05) compared to K477dup and R233. The A41V-mt patients had worse survival compared to patients with P+LP (HR: 1.4, 95% CI: 1.0-2.0, p = 0.049) and a trend toward worse survival compared to K477dup and R233H. In patients treated with chemotherapy, A41 was associated with worse survival compared to P+LP (HR: 4.6, 95% CI: 2.0-10.3, p<0.0001) and compared to K477dup and R233 (p<0.01). There was a trend towards worse survival after IO of A41-mt compared to P+LP (HR: 1.99, 95% CI: 0.88-4.5, p = 0.093). Conclusions: FH alterations are found in multiple cancers. A41V was the most common VUS mutation and is associated with a distinct molecular profile compared to K477dup-mt and R233-mt tumors; it was associated with worse survival in all-comers and after chemotherapy compared to P+LP mutations. This highlights the significance of this mutation and the need for further investigation into how this specific and other FH mutations contribute to cancer progression and treatment outcomes.

Clinicopathological and molecular characteristics of fumarate hydratase–deficient uterine smooth muscle tumors: a single-center study of 52 cases

The fumarate hydratase (FH) gene germline mutations cause hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC), predisposing carriers to uterine and cutaneous leiomyomas and renal cell carcinoma. In this study, we aim to investigate morphology and the correlation between FH mutation in FH-deficient (FH-d) uterine smooth muscle tumors (uSMTs). We conducted immunohistochemical staining in 161 cases of uSMTs to detect FH deficiency. We identified 52 cases (52/161, 32%)of FH-d, including 34 leiomyomas with bizarre nuclei, 10 uSMTs of uncertain malignant potential (STUMPs), 4 cellular leiomyomas, 3 usual type leiomyomas, and 1 leiomyosarcoma. Patients with FH-d were aged 24-67 years (median, 40 years). The most common FH-d morphological features included staghorn-shaped blood vessels (87%), bizarre nuclei (81%), alveolar pattern edema (65%), macronucleoli surrounded by a halo (65%), cytoplasmic eosinophilic globules (56%), and chain-like distribution of smooth muscle cells (52%). A targeted next-generation sequence was performed in 11 of 52 FH-d tumors. Five cases (5/11, 45%) were found with FH germline mutations, including 4 leiomyomas with bizarre nuclei and 1 STUMP. The median age of patients with germline FH mutation was 30 years. The germline mutations included 3 pathogenic, 1 likely pathogenic, and 1 rare uncertain clinical significance variants. Our results revealed that FH-d uSMTs usually exhibit the distinct morphology features and high frequency of FH germline mutations. The combination of predictive morphology evaluation, FH immunotype, and molecular testing is helpful for the screening of HLRCC in uSMTs.

Molecular and immune landscape of FH-mutated kidney cancer.

382 Background: Hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome is caused by inactivating germline mutations in fumarate hydratase ( FH), predisposing individuals to development of certain cancers. Sporadic FH mutations have been described in different types of cancers, including kidney cancers, but the implications of somatic mutations are not well described. Here, we characterize the molecular landscape of kidney tumors with FH mutations. Methods: Tumors were analyzed using next generation sequencing of DNA (NextSeq, 592 genes and NovaSeq, WES) and RNA (NovaSeq). Immune cell fraction was estimated by immune deconvolution (Quantiseq). Significance was determined by chi-square and Wilcoxon rank sum test and adjusted for multiple comparisons (q-value <0.05). Results: Of 1956 kidney tumors, 31 had somatic pathogenic or likely pathogenic (P+LP; 1.58%) and 21 had variant of unknown significance (VUS; 1.07%) mutations in FH. Among the most commonly co-mutated genes, VHL (29.03% vs 38.1% vs 55.2%) and PBRM1 (9.68% vs 20% vs 29.8%) were less frequently mutated in P+LP compared to VUS and WT tumors; while NF2 (22.6% vs 5% vs 5.65%) was more frequently mutated in P+LP tumors compared to the others. In P+LP tumors, the HIPPO pathway (22.6% vs 4.76% vs 5.62%) was more frequently altered while the chromatin remodeling pathway (25.8% vs 28.6% vs 51.1%) was less frequently altered compared to VUS or WT tumors. P+LP tumors showed decreased NK cell infiltration (q=0.01) compared to VUS and WT tumors. Additionally, there was a trend towards increased CD8+ T cells and CTLA4 and PDCD1 expression in P+LP tumors compared to VUS but not WT tumors. Of the 1,956 kidney tumors, 315 were of clear cell renal cell carcinoma (ccRCC) histology. P+LP (n=4) ccRCC tumors showed a trend towards higher expression of immune checkpoint genes CTLA4 and IDO1 compared to VUS tumors (n=5). VHL expression was higher in P+LP ccRCC compared to VUS ccRCC tumors. P+LP ccRCC tumors showed a trend toward increased CD4+ (2.59% vs 0%) and CD8+ (2.14% vs 0%) T cells as well as T cell inflammation (25% vs 0%) and median Interferon score compared to VUS ccRCC tumors. Conclusions: P+LP FH mutated kidney tumors may have a different mutational and immune landscape than VUS FH mutated and WT tumors. Despite the small sample size, our study highlights potential therapeutic implications that will require further study.[Table: see text]

Abstract P055: Targeting Krebs-cycle-deficient renal cell carcinoma with PARP inhibitor and low-dose alkylating chemotherapy

Abstract Loss-of-function mutations in genes encoding the Krebs cycle enzymes fumarate hydratase (FH) and succinate dehydrogenase (SDH) lead to excess accumulation of fumarate and succinate, respectively. Germline mutations in FH lead to a genetic predisposition to hereditary leiomyomatosis and renal cell cancer (HLRCC)-associated RCC. Similarly, loss-of-function alterations of SDH, most commonly SDHB, are associated with SDH-deficient neoplasms, including RCC. FH and SDHB deficient RCC tends to be aggressive and metastasize early with very limited treatment options. The oncometablites produced by these mutations, fumarate and succinate, competitively inhibit αKG-dependent dioxygenases, resulting in dysregulated DNA methylation and histone modification. We have previously demonstrated that elevated levels of fumarate and succinate both suppress the homologous recombination (HR) DNA-repair pathway through inhibition of the lysine demethylase KDM4B, resulting in aberrant hypermethylation of histone 3 lysine 9 (H3K9) at loci surrounding DNA breaks and masking a local H3K9 trimethylation signal that is essential for the proper execution of HR. In this study, we sought to identify novel treatment approaches that exploit genomic instability in FH- and SDHB-deficient RCC. Temozolomide (TMZ), an alkylating agent, mediates its cytotoxic effect by attaching methyl groups to DNA (O6-guanine, N7-guanine and N3-adenine). 16 N3-MetA and N7-MetG repair are mediated by the base excision repair (BER) in a process involving PARP. While the combination of PARP inhibitors with TMZ has been shown to increase TMZ-induced cytotoxicity, clinical trials investigating combination therapy have been hampered by significant toxicity. Using CRISPR/Cas9, we developed new syngeneic FH- and SDHB-deficient murine models of RCC. We demonstrate that FH- and SDHB-deficient cells have accumulation of fumarate and succinate leading to an increase in unresolved DNA double-strand breaks (DSBs). Treatment with PARP inhibition and temozolomide results in marked in vitro cytotoxicity in FH- and SDHB-deficient cells, even at low concentrations of TMZ (50 µM). In vivo, the combination of standard dose BGB-290 and low-dose TMZ (3mg/kg/dose) results in significantly delayed tumor progression in an SDHB deficient RENCA model without any significant increase in toxicity. Notably, the TMZ dose of 3mg/kg/dose is significantly lower than the 50mg/kg/dose that is commonly used for in vivo studies. Taken together, these findings provide the basis for a novel therapeutic strategy exploiting HR deficiency in FH and SDHB-deficient RCC with combined PARP inhibition and low-dose alkylating chemotherapy. Furthermore, the development of a new syngeneic mouse model provides a tool for the future study of immunotherapy in Krebs-cycle-deficient RCC. Citation Format: Daiki Ueno, Amrita Sule, Jiayu Liang, Jinny van Doorn, Ranjini Sundaram, Randy Caliliw, Huihui Ye, Rong Rong Huang, Jing Li, Karla Boyd, Ranjit S. Bindra, Juan C. Vasquez, Brian M. Shuch. Targeting Krebs-cycle-deficient renal cell carcinoma with PARP inhibitor and low-dose alkylating chemotherapy [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P055.

Uterine leiomyomas in hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome can be identified through distinct clinical characteristics and typical morphology.

Hereditary leiomyomatosis and renal cell cancer (HLRCC) constitute a tumor susceptibility syndrome caused by germline mutations in the fumarate hydratase (FH) gene. The most common features are leiomyomas of the uterus and the skin. The syndrome includes a predisposition to early-onset, aggressive renal cell cancer. It is important to identify women with HLRCC among other uterine leiomyoma patients in order to direct them to genetic counseling and to identify other affected family members. We conducted a nationwide historical study to identify typical clinical characteristics, uterine leiomyoma morphology, and immunohistochemistry for diagnosing HLRCC. The study included 20 women with a known FH germline mutation and 77 women with sporadic uterine leiomyomas. The patient records of all women were reviewed to obtain clinical details regarding their leiomyomas. Uterine leiomyoma tissue specimens from 43 HLRCC-related leiomyomas and 42 sporadic leiomyomas were collected and prepared for histology analysis. A morphologic description was performed on hematoxylin & eosin-stained tissue slides, and immunohistochemical analysis was carried out for CD34, Bcl-2, and p53 stainings. The women with HLRCC were diagnosed with uterine leiomyomas at a young age compared with the sporadic leiomyoma group (mean 33.8years vs. 45.4years, P<0.0001), and their leiomyomas occurred as multiples compared with the sporadic leiomyoma group (more than four tumors 88.9% vs. 30.8%, P<0.0001). Congruently, these women underwent surgical treatment at younger age compared with the sporadic leiomyoma group (mean 37.3years vs. 48.3years, P<0.0001). HLRCC leiomyomas had denser microvasculature highlighted by CD34 immunostaining when compared with the sporadic leiomyoma group (112.6mean count/high-power field, SD 20.8 vs. 37.4 mean count/high-power field, SD 21.0 P<0.0001) and stronger anti-apoptotic protein Bcl-2 immunostaining when compared with the sporadic leiomyoma group (weak 4.7%, moderate 44.2%, strong 51.2% vs. 26.2%, 52.4%, 21.4%, respectively, P=0.003). No differences were observed in p53 staining. Women with HLRCC may be identified through the distinct clinical characteristics: symptomatic and numerous leioymyomas at young age, and morphologic features of FH-mutant leiomyomas, aided by Bcl-2 and CD34 immunohistochemistry. Further, distinguishing individuals with a germline FH mutation enables proper genetic counseling and regular renal monitoring.

Hereditary leiomyomatosis and renal cell cancer (HLRCC): Case series and review of the literature

BackgroundHereditary leiomyomatosis and renal cell cancer (HLRCC) is an autosomal dominant syndrome caused by heterozygous pathogenic germline variants in the fumarate hydratase (FH) gene. It is characterized by cutaneous and uterine leiomyomas and an increased risk of developing renal cell carcinoma (RCC). HLRCC-related RCC tends to be aggressive. To date, only a few publications have described HLRCC-related RCC, and the clinical, morphological and molecular aspects of HLRCC-related RCC need to be further studied. MethodsWe retrospectively analyzed the clinical and pathological data of 3 patients with HLRCC recently diagnosed. Immunohistochemistry and Whole-exome sequencing was performed on 3 patients. The function of the DNA variant was predicted in silico. ResultsWe reported 3 patients from unrelated Chinese families, with HLRCC-related RCC and identified 3 different germline FH mutations (2 missense and 1 nonsense). A novel missense mutation of FH gene (c.454A>G, p.N152D) was predicted to be probably pathogenic and deleterious by multiple protein function predicting software. This study indicated that the novel mutation may be responsible for the occurrence of HLRCC-related RCC. 100% (2/2) female RCC patients had uterine fibroids. No cutaneous manifestations were identified. ConclusionWe indicate that germline screening should be encouraged in early-onset patients. Clinicopathological data, such as family history and immunohistochemical results can provide valuable clinical information for the differential diagnosis of HLRCC-associated RCC in advance.

A Case of Renal Cell Carcinoma and Pheochromocytoma Due to Germline Inactivating Mutation in Fumarate Hydratase (FH)

A 60-year-old female with a history of well-controlled hypertension, prediabetes, status post hysterectomy for fibroids, presented for evaluation of hematuria and unintentional weight loss. She denied palpitations, headaches, tremors, and diaphoresis. Initial CT demonstrated a right renal mass suspicious for renal cell carcinoma and an adrenal mass. Magnetic resonance imaging (MRI) confirmed a hypervascular, right adrenal mass (6.7 x 6 x 5 cm) without loss of signal.Laboratory Testing: elevated 24-hour urine vanillylmandelic acid (VMA) 17.5 mg/24 h (<6), and urine normetanephrines 2276 ug/24 h (122-676) with normal urine metanephrines 158 ug/24 h (90-315). 24-hour urine free cortisol was normal. The patient underwent a right adrenalectomy and partial nephrectomy. Pathology confirmed a low-grade renal cell carcinoma (RCC) and a 6.8 cm pheochromocytoma (PCC). Genetic analysis revealed an inherited mutation in the fumarate hydratase (FH) gene, which is diagnostic of hereditary leiomyomatosis and renal cell cancer (HLRCC). Wildtype FH codes for an enzyme that converts fumarate to malate in the mitochondrial Krebs cycle. Inactivating mutations in FH trigger the hypoxia pathway by activating hypoxia-inducible factor (HIF) thereby promoting tumor growth and angiogenesis.In PCC, 30-40% are hereditary and another 40-50% are found to have somatic mutations in 1 of 20 PCC susceptibility genes. Several autosomal dominant heritable syndromes, including Neurofibromatosis type 1 (NF-1), von Hippel-Lindau (VHL), Multiple Endocrine Neoplasia Type 2 (MEN 2), and Paraganglioma Syndromes Types 1–5, have an increased incidence of PCC, most of which modulate hypoxia pathways. FH mutations are similarly inherited in an autosomal dominant fashion and cause HLRCC.HLRCC is associated with 75-80% risk for cutaneous and uterine leiomyomas, and a 10-16% risk for type II papillary renal cell carcinoma. The risk of RCC in patients with FH mutations is much greater than in the general population, where the prevalence is ~2% in those who lack the mutation. In one study, FH deficiencies attribute between 19-41% of all RCC cases. Rare families with PGL/PCC have also been found to carry this germline FH mutation. This FH mutation is associated with increased risk of metastasis in patients with PGL/PCC by a similar mechanism of carcinogenesis via the hypoxia pathway. Currently, there are no strict guidelines for surveillance in individuals with HLRCC, however, patients should have a yearly abdominal MRI, skin examination every 2 years, and an annual gynecological evaluation for leiomyosarcoma. Each first-degree relative should be offered genetic testing of the FH mutation, as 50% of relatives may carry the gene. This case underscores the importance of genetic workups in patients with PCC, especially if associated with other tumors.

Treatment strategy for papillary renal cell carcinoma type 2: a case series of seven patients treated based on next generation sequencing data.

BackgroundPapillary renal cell carcinoma type 2 (PRCC2) is refractory to systemic treatment and has a dismal prognosis. Previous studies showed that genetic alterations in PRCC2 were heterogeneous regardless of germline or somatic mutations. In this study, we aimed to perform precision treatment of PRCC2 based on genetic information.MethodsWe performed exome and genome sequencing of tumor tissues and matched normal samples. Based on sequencing data, we treated patients with metastatic PRCC2 using precision oncology.ResultsFour patients underwent curative surgery of PRCC2 and three patients had metastatic PRCC2. All PRCC2 heterogeneously harbored own driver mutations. Two out of the three patients with metastatic disease had fumarate hydratase (FH) germline mutations. One patient with a germline FH mutation was diagnosed with hereditary leiomyomatosis RCC. He was treated with bevacizumab and erlotinib combination and showed a durable response. The other metastatic PRCC2 patient harboring a germline FH mutation had an additional somatic FH mutation and was durably controlled with pazopanib. Other metastatic PRCC2 patient with somatic PBRM1 and SETD2 mutations had over 5 years of overall survival with axitinib treatment.ConclusionsWe performed precision systemic treatment based on genetic information. Genome sequencing could help identify candidates for targeted therapy in PRCC2, a genetically heterogeneous disease.

Estimation of the carrier frequency of fumarate hydratase alterations and implications for kidney cancer risk in hereditary leiomyomatosis and renal cancer.

Hereditary leiomyomatosis and renal cancer (HLRCC) is a cancer syndrome associated with a germline mutation in fumarate hydratase (FH). The syndrome is associated with cutaneous and uterine leiomyomas, and some patients develop a lethal form of kidney cancer. This study provides estimates for the FH carrier frequency and kidney cancer penetrance. Data sets containing sequencing data for the FH gene were used: the 1000 Genomes Project (1000GP) and the Exome Aggregation Consortium (ExAC). Alterations in the FH gene were characterized on the basis of different variant risk tiers: 1) ClinVar annotated variants, 2) loss-of-function alterations, and 3) highly impactful missense alterations. The cumulative incidence of FH alterations overall and by different world populations was evaluated in 1000GP and ExAC. A lifetime penetrance of HLRCC kidney cancer risk was generated with 3 estimates of the annual incidence. The overall allele frequencies of tier 1 to 3 FH alterations in the ExAC and 1000GP data sets were 2.54 × 10-3 (1 in 393) and 1.20 × 10-3 (1 in 835), respectively. There were differences in the allele frequencies of FH alterations between world populations. Based on various estimates of the percentage of kidney cancers with FH alterations, the lifetime kidney cancer penetrance for carrier estimate 3 in ExAC was 1.7% to 5.8%. FH alterations are common and are carried by approximately 1 in 1000 individuals according to the more conservative estimates. The lifetime kidney cancer penetrance appears lower than previously estimated. Although databases are not population cohorts, they provide a useful quantitative estimate of rare variants with low penetrance.

Clinicopathological and molecular features of hereditary leiomyomatosis and renal cell cancer-associated renal cell carcinomas

AimsHereditary leiomyomatosis and renal cell cancer (HLRCC) is an autosomal dominant disorder caused by germline mutations in fumarate hydratase (FH). Affected families have an increased risk of renal cell carcinoma...

Response to systemic therapy in patients with metastatic fumarate hydratase (FH) deficient renal cell carcinoma (RCC).

686 Background: FH-deficient RCC (FHRCC) is characterized by unique pathologic features and lack of FH staining on immunohistochemistry (IHC). Most cases are associated with germline FH mutations and poor prognosis, but there is limited data on the efficacy of systemic therapy. Methods: Patients with metastatic FHRCC, defined by presence of FH germline or somatic mutation with loss of FH by IHC [FH and 2-succino-cysteine (2SC)], were identified from an institutional database. Clinical and treatment data was obtained from electronic records. The primary outcome was best objective response rate to first, second or third-line systemic therapy by blinded investigator RECIST v1.1 assessment. Results: 32 patients (median age 46; range 20-74; M:F, 20:12) were identified. All patients had evidence of FH-deficiency by IHC, 23 (72%) had germline FH mutations, 9 (28%) had somatic only FH mutations. 20 patients (62.5%) presented with de novo metastatic disease. Most common sites of metastasis were retroperitoneal lymph nodes (82%), lung (78%) and peritoneal spread (70%); no patients developed brain metastases. Median overall survival (OS) from diagnosis of metastatic disease is 28.1 months (95% CI: 14.9, 33.8). Median follow-up is 14.8 months. 25 patients were evaluable for response to first-line therapy, 5 to second-line and 4 to third-line therapy (Table). Most common first-line therapies were combination mTOR/VEGFR (50%) and VEGFR monotherapy (20%). ORR to first, second and third-line therapy was 40%, 20% and 25%, with no complete responses. 8 patients who received IO monotherapy were evaluable; 3 had stable disease, no responses were seen. Conclusions: Patients with FHRCC show distinct patterns of disease progression with primary peritoneal spread. Although there was high ORR to VEGFR/mTOR inhibitor combinations, there were limited responses to IO monotherapy.[Table: see text]

Prevalence of somatic and germline mutations of Fumarate hydratase in uterine leiomyomas from young patients.

Hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome is caused by germline mutations in the Fumarate hydratase (FH) gene. In young women, the syndrome often presents with symptomatic uterine leiomyomas, leading to myomectomy or hysterectomy. In this study, we aimed to investigate the incidence and mutational profiles of FH-negative leiomyomas from young patients, thus allowing for early identification and triage of syndromic patients for surveillance. We evaluated 153 cases of uterine leiomyomas from women aged up to 30years for loss of FH expression by tissue microarray (TMA)-based immunohistochemical staining. Mutational analysis of tumours with loss of FH was carried out by polymerase chain reaction (PCR) amplification of 10 exons within the FH gene and subsequent Sanger sequencing. The status of promoter methylation was assessed by bisulphite sequencing. Loss of FH protein expression was detected in seven (4.6%) of 153 tested uterine leiomyomas from young patients. All FH-negative leiomyomas displayed staghorn vasculature and fibrillary/neurophil-like cytoplasm. We found that six (86%) of seven FH-negative tumours detected by immunohistochemistry harboured FH mutations, 50% of which contained germline mutations. In particular, the germline mutational rate in FH gene was 2.0% (three of 153 cases). Bisulphite sequencing analysis failed to detect promoter methylation in any of the seven tumours. Our study showed a relatively high rate of FH germline mutation in FH-negative uterine leiomyomas from patients aged up to 30years. While genetic mutations confer protein expression loss, epigenetic regulation of the FH gene appears to be unrelated to this phenotype.

Detailed Morphologic and Immunohistochemical Characterization of Myomectomy and Hysterectomy Specimens From Women With Hereditary Leiomyomatosis and Renal Cell Carcinoma Syndrome (HLRCC).

Hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC), caused by a germline mutation in the fumarate hydratase (FH) gene, predisposes patients to uterine and cutaneous smooth muscle tumors and an aggressive type of renal cell carcinoma. Almost all women with HLRCC develop symptomatic uterine leiomyomas resulting in surgery at young ages, presenting an ideal opportunity for early detection of these patients and the implementation of surveillance measures for renal cell carcinoma. FH-deficient uterine leiomyomas can show characteristic morphologic features (FH-d morphology) that have been previously described. Immunohistochemistry (IHC) for FH can also be helpful in detecting FH deficiency in leiomyomas, which manifests as complete loss of staining for FH. However, the distribution and topography of FH-d morphology and FH loss by IHC in the context of multiple leiomyomas in patients with HLRCC has not been evaluated. The aim of this study is to describe in detail the clinical and pathologic characteristics of uterine leiomyomas from women with HLRCC. Six patients with proven FH germline mutations were included. All available slides were reviewed and FH IHC staining was performed on multiple blocks when possible. Clinical data were extracted from online medical records. All 6 patients presented with symptomatic uterine fibroids and underwent myomectomy (age 24 to 36 y), followed by hysterectomy in 2 patients (age 31 and 40 y). Specimens showed conventional leiomyomas, cellular leiomyomas and leiomyomas with bizarre nuclei. FH-d morphology was present in leiomyomas from all patients and was typically observed as a diffuse finding in the majority of slides across different leiomyoma types. FH-d morphology was absent in some leiomyoma sections from one patient and the morphologic features were focal and subtle in leiomyomas from 2 patients. Both hysterectomy specimens were also notable for showing scattered irregular tongues and nodules of smooth muscle proliferation (leiomyomatosis-like) in the background myometrium. Immunohistochemical staining of multiple slides per patient for FH showed either retained staining in all sections (2/6 cases), loss of staining in all sections (1 case) or variable staining across different leiomyomas (3 cases). In conclusion, patients with HLRCC undergo surgery at young ages for highly symptomatic uterine leiomyomas. FH-d morphology is usually a diffuse and well developed finding across different leiomyomas but may be absent or focal and subtle. FH IHC can show variable results and presence of retained FH staining should not be used to exclude the possibility of HLRCC. Referral for genetic counselling and testing should be considered in a young patient with uterine leiomyomas showing FH-d morphology even if immunohistochemical staining for FH is retained.

Abstract SY21-02: Oncometabolites suppress homologous recombination DNA repair by inhibition of chromatin remodeling at the DNA double-strand break

Abstract Elevated levels of the metabolites, 2-hydroxyglutarate (2HG), fumarate, and succinate, can occur in human malignancies due to somatic mutations in the isocitrate dehydrogenase 1/2 (IDH1/2) genes or germline mutations in fumarate hydratase (FH) and succinate dehydrogenase (SDH) genes, respectively. Mutations in IDH1 and IDH2 are found in a large number of human malignancies, most notably gliomas and acute myelogenous leukemias, along with cholangiocarcinomas, chondrosarcomas, and melanomas. Inherited mutations in FH and SDH, are linked to the familial cancer predisposition syndromes, Hereditary Leiomyomatosis and Renal Cell Cancer (HLRCC) and Hereditary Paraganglioma and Pheochromocytoma (SDH PGL/PCC), respectively. These structurally related metabolites inhibit α-ketoglutarate-dependent enzymes, including dioxygenases that modify chromatin. We have shown that they consequently suppress the pathway of homology-dependent DNA repair (HDR), conferring an exquisite sensitivity to PARP inhibitors that is currently being tested in clinical trials. In this presentation, we will discuss our recent work elucidating the mechanistic basis for this suppression of DNA repair. Rather than acting indirectly through epigenetic regulation of gene expression, we find that these metabolites act directly by inhibiting HDR factor recruitment to DNA double-strand breaks (DSBs). The metabolites inhibit the lysine demethylases, KDM4A/B, causing aberrant hypermethylation of H3K9 and disrupting signaling at the break, thereby delaying the stepwise recruitment of key HDR factors. These results define a novel mechanism of decreased DNA repair in oncometabolite producing human tumors and may provide the basis for the rational design of novel therapeutic strategies for these malignancies. Citation Format: Parker S. Sulkowski, Sebstian Oeck, Jing Li, Brian Shuch, Megan C. King, Ranjit S. Bindra, Peter M. Glazer. Oncometabolites suppress homologous recombination DNA repair by inhibition of chromatin remodeling at the DNA double-strand break [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr SY21-02.

Abstract 3992: Comparison of AKR1B10, 2SC, and FH as biomarkers for HLRCC detection

Abstract HLRCC is an autosomal dominant tumor predisposition syndrome characterized by cutaneous and uterine leiomyomas (ULs), and increased risk for aggressive type 2 papillary renal cell carcinoma (RCC). The syndrome is caused by germline mutations in fumarate hydratase (FH). Loss of FH causes dysfunction of the Crebs cycle and an increase of succinated proteins, which can be detected using anti-2-succinocysteine (2SC) antibody. Recently, we have observed that aldo-keto reductase family 1, member B10 (AKR1B10) is overexpressed in RNA-level in ULs with biallelic loss of FH. Here, we compared anti-AKR1B10, anti-2SC, and anti-FH antibodies in detection of FH loss in protein-level in HLRCC-associated ULs. The study material consisted of 142 formalin-fixed paraffin-embedded (FFPE) UL samples collected at the University hospitals in Finland. The sample series include 77 FH-deficient UL samples from 25 HLRCC patients and 65 sporadic conventional ULs. HLRCC background was verified by detected germline mutation of FH. Four 0.8 mm cores of representative FFPE tumor tissue were used to construct tissue microarrays. Immunohistochemistry (IHC) was executed using an anti-AKR1B10 (1:300, H00057016-M01, Abnova), anti-2SC (1:2000, provided by Dr. Norma Frizzell), and anti-FH (1:1000, sc-100743, Santa Cruz Biotechnology, Inc) antibodies. Expression was detected by BrightVision (Immunologic) and DAB Quanto (Thermo Fisher Scientific) systems. Pathologist specialized in gynecological pathology evaluated the IHC staining from the smooth muscle tumor cells. AKR1B10 and 2SC detected all 77 HLRCC samples. AKR1B10 displayed either mild (12/77, 16%) or strong (65/77, 84%) expression and succination level was strong in all cases. Loss of FH expression was displayed in 68/77 (88%) of the FH-deficient ULs. All conventional ULs displayed negative AKR1B10 and 2SC staining and expressed FH. FH was expressed either mildly (15/65, 23%) or strongly (50/65, 77%) in the samples. Reliable methods for FH-deficient UL detection in the clinics are currently lacking. Here, comparison of AKR1B10, 2SC, and FH showed that all three biomarkers identified HLRCC-ULs with 100% specificity. The sensitivity was 100% with AKR1B10 and 2SC, and 88% with FH. It seems that even with known mutation in FH, in some cases the likely inactive protein is retained in tumor cells and is thus detectable by anti-FH. To conclude, we show that anti-AKR1B10 and anti-2SC detect FH-deficient ULs with 100% specificity and sensitivity. Anti-FH is lacking sensitivity in 12% of HLRCC cases. Reliable detection of FH-deficient ULs enables the patients and their families to be directed to genetic counseling, family planning, and regular renal monitoring. Citation Format: Terhi Ahvenainen, Outi Uimari, Anne Ahtikoski, Kati Kämpjärvi, Ralf Bützow, Pia Vahteristo. Comparison of AKR1B10, 2SC, and FH as biomarkers for HLRCC detection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3992.