Stage-Specific Alteration and Prognostic Relationship of Serum Fumarate Hydratase Autoantibodies in Gastric Cancer

The relationship between energy production and cancer is attracting attention. This study aimed to investigate the clinicopathological significance of fumarate hydratase (FH), a tricarboxylic acid cycle enzyme, in gastric cancer using autoantibodies as biomarkers. The study analyzed 116 patients who underwent gastric cancer surgery and 96 healthy controls. Preoperative serum FH autoantibody (s-FH-Ab) titers were analyzed using an immunosorbent assay with an amplified luminescent proximity homogeneous assay. Receiver operating characteristic analysis was used to determine the cutoff s-FH-Ab titer. Clinicopathological factors and prognosis were compared between the high and low s-FH-Ab groups. The s-FH-Ab levels were significantly higher in the gastric cancer group than in the control group (p = 0.01). Levels were elevated even in patients with stage I gastric cancer compared with healthy controls (p = 0.02). A low s-FH-Ab level was significantly associated with distant metastasis (p = 0.01), peritoneal dissemination (p < 0.05), and poor overall survival (p < 0.01). Multivariate analysis revealed that low s-FH-Ab levels were an independent risk factor for poor prognosis (p < 0.01). Therefore, s-FH-Ab levels may be a useful biomarker for early diagnosis and the prediction of prognosis in patients with gastric cancer.

Case report: Uterine leiomyoma with fumarate hydratase deficiency

Hereditary leiomyomatosis and renal cell cancer syndrome is a rare autosomal dominant disease caused by mutations in the fumarate hydratase gene. The syndrome is characterized by skin leiomyomatosis, uterine leiomyomatosis, and renal cell carcinoma. Herein, we report a case of fumarate hydratase deficient leiomyoma. The patient was a young female presenting with large uterine leiomyoma and multiple kidney angiomyolipomas. The report presents the chosen treatment and the challenges of differential diagnosis.

Malignant glomus tumor arising in association with a fumarate hydratase-deficient leiomyoma: An unusual collision tumor

Collision tumors, defined as "two independent neoplasms that occur in close proximity to one another but maintain distinct boundaries," are quite rare. We report an exceptional collision tumor composed of a genetically confirmed malignant glomus tumor and a fumarate hydratase (FH)-deficient leiomyoma, presenting as a subcutaneous thigh mass in a 38-year-old male who was known to have hereditary leiomyomatosis and renal cell carcinoma syndrome. Microscopic examination identified a biphasic subcutaneous mass comprising sheets and nodules of glomus cells, with nuclear atypia and mitotic activity, and fascicles of mitotically inactive smooth muscle with variably pleomorphic nuclei and intracytoplasmic eosinophilic inclusions, features of FH-deficient leiomyoma. Immunohistochemistry demonstrated loss of FH and robust 2-succinocysteine expression in the smooth muscle, with a normal (FH-retained) expression pattern in the glomus tumor. Next-generation sequencing, performed on the glomus tumor component, identified CARMN::NOTCH2 fusion, characteristic of malignant glomus tumors. Awareness of the distinctive morphologic, immunohistochemical, and molecular genetic features of glomus tumors and FH-deficient leiomyomas is important for correct clinical management of patients with exceptional collision tumors of this type.

Fumarate hydratase mutation associated uterine leiomyomas: A case report and literature review

The patient was found to have multiple uterine myomas at the age of 19, underwent laparoscopic myomectomy at the age of 20, and underwent laparotomic myomectomy again at the age of 23 due to the recurrence of uterine myoma. At the age of 25, the patient reappeared with symptoms and recurrence, and was diagnosed with uterine leiomyomas (ULMs) of FH mutation and high-grade squamous intraepithelial lesion (HSIL/CIN III) with gland involvement, after complete examination. Fumarate hydratase (FH) mutation screening is important when gynecologists encounter patients with early onset and multiple ULMs, it can give early diagnosis and treatment and fertility guidance. The patient had their uterus removed at the age of 26. FH mutation screening is important when gynecologists encounter patients with early onset and multiple ULMs, it can give early diagnosis and treatment and fertility guidance. It is also helpful for early diagnosis of renal cell carcinoma.

Bilateral fumarate hydratase deficient renal cell carcinoma in a patient with hereditary leiomyomatosis and renal cell cancer syndrome

Introduction

Patients with hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome have high risks of uterine and cutaneous leiomyomas and renal cell carcinoma (RCC), which are caused by germline mutation of the fumarate hydratase (FH) gene. RCC lesions are mostly high-grade tumors with a poor prognosis.

Case presentation

A 37-year-old man who had previously undergone treatment for a left RCC was referred to our hospital with a diagnosis of right RCC. Robot-assisted partial nephrectomy was performed, and the pathological diagnosis revealed fumarate hydratase (FH)-deficient RCC. The left RCC, which was originally diagnosed as mucinous tubular and spindle cell carcinoma, was reviewed and diagnosed as FH-deficient RCC. The patient's father and uncle both died of RCC, and the father's tumor was also immunohistochemically proven to be FH-deficient RCC.

Conclusion

HLRCC-related RCC should be considered in a differential diagnosis of young patients with a family history of RCC.

The clinicopathologic and molecular features, and treatment outcome of fumarate hydratase-deficient renal cell carcinoma: a retrospective comparison with type 2 papillary renal cell carcinoma

BACKGROUND

To compare clinicopathologic, molecular features, and treatment outcome between fumarate hydratase-deficient renal cell carcinoma (FH-dRCC) and type 2 papillary renal cell carcinoma (T2 pRCC).

METHODS

Data of T2 pRCC patients and FH-dRCC patients with additional next-generation sequencing information were retrospectively analyzed. The cancer-specific survival (CSS) and disease-free survival (DFS) were primary endpoint.

RESULTS

A combination of FH and 2-succino-cysteine (2-SC) increased the rate of negative predictive value of FH-dRCC. Compared with T2 pRCC cases, FH-dRCC cases displayed a greater prevalence in young patients, a higher frequency of radical nephrectomy. Seven FH-dRCC and two T2 pRCC cases received systemic therapy. The VEGF treatment was prescribed most frequently, with an objective response rate (ORR) of 22.2% and a disease control rate (DCR) of 30%. A combined therapy with VEGF and checkpoint inhibitor reported an ORR of 40% and a DCR of 100%. FH-dRCC cases showed a shortened CSS (P = 0.042) and DFS (P < 0.001). The genomic sequencing revealed 9 novel mutations.

CONCLUSIONS

Coupled with genetic detection, immunohistochemical biomarkers (FH and 2-SC) can distinguish the aggressive FH-dRCC from T2 pRCC. Future research is awaited to illuminate the association between the novel mutations and the clinical phenotypes of FH-dRCC in the disease progression.

Fumarate Hydratase Enhances the Therapeutic Effect of PD-1 Antibody in Colorectal Cancer by Regulating PCSK9

Despite the notable achievements of programmed death 1 (PD-1) antibodies in treating various cancers, the overall efficacy remains limited in the majority of colorectal cancer (CRC) cases. Metabolism reprogramming of tumors inhibits the tricarboxylic acid (TCA) cycle, leading to down-regulation of fumarate hydratase (FH), which is related to poor prognosis in CRC patients. By establishing a tumor-bearing mouse model of CRC with Fh1 expression deficiency, we confirmed that the therapeutic effect of PD-1 antibodies alone was suboptimal in mice with low Fh1 expression, which was improved by combination with a protein invertase subtilisin/kexin 9 (PCSK9) inhibitor. Mechanistically, FH binds to Ras-related nucleoprotein (RAN), which inhibits the nuclear import of the PCSK9 transcription factor SREBF1/2, thus reducing the expression of PCSK9. This leads to increased clonal expansion of CD8+ T cells while the number of Tregs remains unchanged, and the expression of PD-L1 does not change significantly, thus enhancing the immunotherapy response. On the contrary, the expression of PCSK9 increased in CRC cells with low FH expression, which antagonized the effects of immunotherapy. Overall, CRC patients with low FH expression may benefit from combinatorial therapy with PD-1 antibodies and PCSK9 inhibitors to enhance the curative effect.

Segregation, immunohistochemical, molecular and functional analyses classify a novel missense variant in fumarate hydratase (FH) as pathogenic

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is an autosomal dominant cancer predisposition syndrome characterized by cutaneous leiomyomas, uterine leiomyomas, and aggressive renal cancer. Germline variants in the fumarate hydratase (FH) gene predispose to HLRCC. Identifying germline pathogenic FH variants enables lifetime renal cancer screening and genetic testing for family members. In this report, we present a FH missense variant (c.1039T>C (p.S347P)), initially classified as a variant of uncertain significance. Clinical assessment, histopathological findings, molecular genetic studies, and enzymatic activity studies support the re-classification of the FH c.1039T>C variant to "pathogenic" based on ACMG/AMP criteria. Further insights into pathological recognition of FH-deficient renal cancer are discussed and should be recognized. This study has shown how (a) detailed multi-disciplinary analyses of a single variant can reclassify rare missense variants in FH and (b) careful pathological review of renal cancers is obligatory when HLRCC is suspected.

Identification of a Difluorinated Alkoxy Sulfonyl Chloride as a Novel Antitumor Agent for Hepatocellular Carcinoma through Activating Fumarate Hydratase Activity

Fenofibrate is known as a lipid-lowering drug. Although previous studies have reported that fenofibrate exhibits potential antitumor activities, IC50 values of fenofibrate could be as high as 200 μM. Therefore, we investigated the antitumor activities of six synthesized fenofibrate derivatives. We discovered that one compound, SIOC-XJC-SF02, showed significant antiproliferative activity on human hepatocellular carcinoma (HCC) HCCLM3 cells and HepG2 cells (the IC50 values were 4.011 μM and 10.908 μM, respectively). We also found this compound could inhibit the migration of human HCC cells. Transmission electron microscope and flow cytometry assays demonstrated that this compound could induce apoptosis of human HCC cells. The potential binding sites of this compound acting on human HCC cells were identified by mass spectrometry-cellular thermal shift assay (MS-CETSA). Molecular docking, Western blot, and enzyme activity assay-validated binding sites in human HCC cells. The results showed that fumarate hydratase may be a potential binding site of this compound, exerting antitumor effects. A xenograft model in nude mice demonstrated the anti-liver cancer activity and the mechanism of action of this compound. These findings indicated that the antitumor effect of this compound may act via activating fumarate hydratase, and this compound may be a promising antitumor candidate for further investigation.

Unusual Cutaneous Lesions in a 53-Year-Old Female: A Potential Indicator of Underlying Renal Cell Carcinoma

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a rare autosomal dominant genetic disorder resulting from mutations in the fumarate hydratase (FH) gene. It is characterised by a predisposition to cutaneous and uterine leiomyomas (fibroids) and an aggressive form of renal cell carcinoma (RCC). We report the case of a 53-year-old female who presented with an unusual rash in the context of a personal and family history of uterine leiomyomas requiring hysterectomy. A skin biopsy confirmed cutaneous leiomyomas and subsequent genetic testing demonstrated a pathogenic heterozygous mutation on exon 7 of the FH gene, confirming a diagnosis of HLRCC. Due to the recognised association with renal cell carcinoma in this syndrome, abdominal imaging was performed, which excluded RCC, and the patient was commenced on lifelong surveillance with annual abdominal magnetic resonance imaging.

Novel Approaches to Possible Targeted Therapies and Prophylaxis of Uterine Fibroids

Uterine leiomyomas are the most common benign tumors in women of childbearing age. They may lead to problems of conception or complications during the gestational period. The methods of treatment include surgical (myomectomy and hysterectomy, embolization of arteries) and therapeutic treatment (ulipristal acetate, leuprolide acetate, cetrorelix, goserelin, mifepristone). Both approaches are efficient but incompatible with pregnancy planning. Therefore, there is a call for medical practice to develop therapeutical means of preventing leiomyoma onset in patients planning on becoming pregnant. Based on the analysis of GWAS data on the search for mononucleotide polymorphisms associated with the risk of leiomyoma, in meta-transcriptomic and meta-methylomic studies, target proteins have been proposed. Prospective therapeutic treatments of leiomyoma may be based on chemical compounds, humanized recombinant antibodies, vaccines based on markers of the uterine leiomyoma cells that are absent in the adult organism, or DNA and RNA preparations. Three different nosological forms of the disease associated with driver mutations in the MED12, HMGA2, and FH genes should be considered when developing or prescribing drugs. For example, synthetic inhibitors and vaccines based on matrix metalloproteinases MMP11 and MMP16 are expected to be effective only for the prevention of the occurrence of MED12-dependent nodules.

Fumarate hydratase functions as a tumor suppressor in endometrial cancer by inactivating EGFR signaling

Fumarase hydratase (FH) is an enzyme that catalyzes the reversible hydration and dehydration of fumarate to malate in the tricarboxylic acid cycle. The present study addressed the role of FH in endometrial cancer and clinically observed that the expression of FH was significantly lower in endometrial cancer tissues compared with normal endometrial tissues and, furthermore, that the decreased FH expression in endometrial cancer tissues was significantly associated with increased tumor size and lymph node metastasis. Further analysis in in vitro study showed that cell proliferation, migration and invasion abilities were increased when the expression of FH in the endometrial cancer cells was knocked down, but, by contrast, overexpression of FH in endometrial cancer cells decreased cell proliferative, migratory and invasive abilities. Mechanistic studies showed that the expression of vimentin and twist, being two well-studied mesenchymal markers in endometrial cancer cells, were upregulated in fumarate hydratase-knockdowned cells. In addition, phosphokinase array analysis demonstrated that the expression of phospho-EGFR (Y1086), which promotes carcinogenesis in cancers, was increased in endometrial cancer cells when FH was knocked down. In conclusion, the present study suggested that FH is a tumor suppressor and inhibits endometrial cancer cell proliferation and metastasis by inactivation of EGFR. Further studies are required to clarify its role as a prognostic biomarker and therapeutic target for endometrial cancer.

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.

MAEL facilitates metabolic reprogramming and breast cancer progression by promoting the degradation of citrate synthase and fumarate hydratase via chaperone-mediated autophagy

Metabolic reprogramming is a hallmark of cancer. Several studies have shown that inactivation of Krebs cycle enzymes, such as citrate synthase (CS) and fumarate hydratase (FH), facilitates aerobic glycolysis and cancer progression. MAEL has been shown to play an oncogenic role in bladder, liver, colon, and gastric cancers, but its role in breast cancer and metabolism is still unknown. Here, we demonstrated that MAEL promoted malignant behaviours and aerobic glycolysis in breast cancer cells. Mechanistically, MAEL interacted with CS/FH and HSAP8 via its MAEL domain and HMG domain, respectively, and then enhanced the binding affinity of CS/FH with HSPA8, facilitating the transport of CS/FH to the lysosome for degradation. MAEL-induced degradation of CS and FH could be suppressed by the lysosome inhibitors leupeptin and NH₄ Cl, but not by the macroautophagy inhibitor 3-MA or the proteasome inhibitor MG132. These results suggested that MAEL promoted the degradation of CS and FH via chaperone-mediated autophagy (CMA). Further studies showed that the expression of MAEL was significantly and negatively correlated with CS and FH in breast cancer. Moreover, overexpression of CS or/and FH could reverse the oncogenic effects of MAEL. Taken together, MAEL promotes a metabolic shift from oxidative phosphorylation to glycolysis by inducing CMA-dependent degradation of CS and FH, thereby promoting breast cancer progression. These findings have elucidated a novel molecular mechanism of MAEL in cancer.

Dedifferentiated leiomyosarcoma of the uterus: a clinicopathologic and immunohistochemical analysis of 23 cases

AIMS

To morphologically and immunophenotypically characterize dedifferentiated uterine leiomyosarcoma (LMS).

METHODS AND RESULTS

We identified 23 dedifferentiated uterine LMS, defined as a malignant uterine smooth muscle tumour containing discrete differentiated and dedifferentiated components (i.e. with and without morphologic and immunophenotypic evidence of smooth muscle differentiation, respectively). The differentiated component was leiomyosarcoma in most cases (17/23), though some arose from a leiomyoma (n = 4) or smooth muscle tumour of uncertain malignant potential (n = 2). The dedifferentiated tumour component showed noncohesive polygonal cells with moderate to abundant cytoplasm, pleomorphic nuclei with coarse vesicular to smudged chromatin, one or more macronucleoli, frequent multinucleation, and atypical mitoses. Three cases showed heterologous osteosarcomatous or chondrosarcomatous differentiation. Immunohistochemistry revealed alterations characteristic of uterine LMS, including Rb loss (18/19); strong diffuse p16 (17/19); strong diffuse (9/19) or complete absence of (5/19) p53; and ATRX loss (6/16). Compared to a control cohort of uterine LMS without dedifferentiation, dedifferentiated uterine LMS showed significantly shorter disease-specific (median, 54 versus 20 months; 5-year DSS, 46% versus 36%; P = 0.04) and disease-free (median, 31 versus 8 months; 5-year DFS, 42% versus 8%; P = 0.002) survival. Of 19 dedifferentiated uterine LMS with follow-up, 12 had died of disease at median 14 (range, 2-73) months; four were alive with disease at 4, 12, 44, and 50 months; and three were alive with no evidence of disease at 56, 109, and 114 months.

CONCLUSION

Routine prospective recognition of dedifferentiated uterine LMS and distinction from mimics is advocated for accurate prognostication and for further characterisation of these tumours.

The spectrum of clinical and genetic findings in hereditary leiomyomatosis and renal cell cancer (HLRCC) with relevance to patient outcomes: a retrospective study from a large academic tertiary referral center

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is an autosomal dominant condition attributed to pathogenic variants in fumarate hydratase (FH) and presents with cutaneous leiomyomas (CLMs), uterine leiomyomas (ULMs) and renal cell cancer (RCC). The objective of this study was to characterize the spectrum of clinical and genetic findings in HLRCC at a large academic tertiary care referral center with a focus on dermatologic manifestations. Fifty-seven patients, 41 female and 16 male, with 27 unique pathogenic or likely-pathogenic FH variants were identified from 38 families. Mean age of HLRCC diagnosis was 44.4 years (range 8-82). CLMs were the primary reason for referral in 49.1% (n=28). CLMs were present in 43/56 patients who underwent full skin examination. Three of these 56 patients were diagnosed with cutaneous leiomyosarcoma. Incidence of ULMs was 37/41 female patients; no uterine leiomyosarcomas were observed. RCC was observed in 6/57 patients (mean age of diagnosis: 47.3 years (range 28-79)). CLMs predated RCC in the 3 patients diagnosed with both. Dermatologists have an opportunity to recognize cutaneous manifestations of HLRCC, including cutaneous leiomyomas and rarely cutaneous leiomyosarcomas, and refer for genetic evaluation to provide definitive diagnosis. Identification of HLRCC can promote family cascade testing and screening for RCC.

A Clinicopathologic and Molecular Analysis of Fumarate Hydratase-deficient Pheochromocytoma and Paraganglioma

Up to 40% of pheochromocytomas (PCCs) and paragangliomas (PGLs) are hereditary. Germline mutations/deletions in fumarate hydratase ( FH ) cause hereditary leiomyomatosis and renal cell carcinoma syndrome which manifests predominantly with FH-deficient uterine/cutaneous leiomyomas and renal cell carcinomas (RCCs)-tumors characterized by loss of immunohistochemical (IHC) expression of FH and/or positive staining for S-(2-succino)-cysteine. Occasional patients develop PCC/PGL. We investigated the incidence, morphologic, and clinical features of FH-deficient PCC/PGL. We identified 589 patients with PCC/PGLs that underwent IHC screening for FH and/or S-(2-succino)-cysteine. Eight (1.4%) PCC/PGLs were FH deficient (1.1% in an unselected population). The median age for FH-deficient cases was 55 (range: 30 to 77 y) with 50% arising in the adrenal. All 4 with biochemical data were noradrenergic. Two (25%) metastasized, 1 dying of disease after 174 months. Germline testing was performed on 7 patients, 6 of whom had FH missense mutations. None were known to have a significant family history before presentation or developed cutaneous leiomyomas, or FH-deficient RCC at extended follow-up. The patient wild-type for FH on germline testing was demonstrated to have somatic FH mutation and loss of heterozygosity corresponding to areas of subclonal FH deficiency in her tumor. One patient did not undergo germline testing, but FH mutation was demonstrated in his tumor. We conclude that FH-deficient PCC/PGL are underrecognized but can be identified by IHC. FH-deficient PCC/PGL are strongly associated with germline missense mutations but are infrequently associated with leiomyoma or RCC, suggesting there may be a genotype-phenotype correlation. FH-deficient PCC/PGL may have a higher metastatic risk.

Fumarate hydratase inhibits non-small cell lung cancer metastasis via inactivation of AMPK and upregulation of DAB2

Lung cancer is one of the leading causes of cancer mortality worldwide. As it is often first diagnosed only when cancer metastasis has already occurred, the development of effective biomarkers for the risk prediction of cancer metastasis, followed by stringent monitoring and the early treatment of high-risk patients, is essential for improving patient survival. Cancer cells exhibit alterations in metabolic pathways that enable them to maintain rapid growth and proliferation, which are quite different from the metabolic pathways of normal cells. Fumarate hydratase (FH, fumarase) is a well-known tricarboxylic acid cycle enzyme that catalyzes the reversible hydration/dehydration of fumarate to malate. The current study sought to investigate the relationship between FH expression levels and the outcome of patients with lung cancer. FH was knocked down in lung cancer cells using shRNA or overexpressed using a vector, and the effect on migration ability was assessed. Furthermore, the role of AMP-activated protein kinase (AMPK) phosphorylation and disabled homolog 2 in the underlying mechanism was investigated using an AMPK inhibitor approach. The results showed that in lung cancer tissues, low FH expression was associated with lymph node metastasis, tumor histology and recurrence. In addition, patients with low FH expression exhibited a poor overall survival in comparison with patients having high FH expression. When FH was overexpressed in lung cancer cells, cell migration was reduced with no effect on cell proliferation. Furthermore, the level of phosphorylated (p-)AMPK, an energy sensor molecule, was upregulated when FH was knocked down in lung cancer cells, and the inhibition of p-AMPK led to an increase in the expression of disabled homolog 2, a tumor suppressor protein. These findings suggest that FH may serve as an effective biomarker for predicting the prognosis of lung cancer and as a therapeutic mediator.

Depletion of Fumarate Hydratase, an Essential TCA Cycle Enzyme, Drives Proliferation in a Two-Step Model

Fumarate hydratase (FH) is an evolutionary conserved TCA cycle enzyme that reversibly catalyzes the hydration of fumarate to L-malate and has a moonlight function in the DNA damage response (DDR). Interestingly, FH has a contradictory cellular function, as it is pro-survival through its role in the TCA cycle, yet its loss can drive tumorigenesis. Here, we found that in both non-cancerous (HEK-293T) and cancerous cell lines (HepG2), the cell response to FH loss is separated into two distinct time frames based on cell proliferation and DNA damage repair. During the early stages of FH loss, cell proliferation rate and DNA damage repair are inhibited. However, over time the cells overcome the FH loss and form knockout clones, indistinguishable from WT cells with respect to their proliferation rate. Due to the FH loss effect on DNA damage repair, we assumed that the recovered cells bear adaptive mutations. Therefore, we applied whole-exome sequencing to identify such mutated genes systematically. Indeed, we identified recurring mutations in genes belonging to central oncogenic signaling pathways, such as JAK/STAT3, which we validated in impaired FH-KO clones. Intriguingly, we demonstrate that these adaptive mutations are responsible for FH-KO cell proliferation under TCA cycle malfunction.

Fumarate Hydratase is a Novel Gene for Familial Non-Medullary Thyroid Cancer

CONTEXT

The majority of cases of epithelial cell-derived thyroid cancer are sporadic. Familial non-medullary thyroid cancer (FNMTC) occurs in about 5% to 9% of cases, either as a part of known syndromes such as Cowden syndrome or in the form of familial clustering of 2 or more affected family members. Hereditary leiomyoma and renal cell cancer (HLRCC) syndrome is a rare familial cancer syndrome. The underlying etiology is heterozygous germline mutations of the fumarate hydratase (FH) gene. In addition to extensive uterine and skin leiomyomas and RCC, other tumors may arise in this syndrome. However, thyroid cancer has never been described as part of HLRCC. Here, we describe a woman who presented with an aggressive poorly differentiated thyroid cancer (PDTC) and was found to have HLRCC syndrome because of a novel heterozygous germline FH mutation.

RESULTS

A 43-year-old woman presented with a large lower neck mass that was found to be PDTC. During her evaluation, she was found to have extensive uterine leiomyomatosis and bilateral adrenal nodules. Whole exome and subsequent Sanger sequencing of leucocyte DNA revealed a novel monoallelic nonsense FH mutation (c.760C>T, p.Q254*). Sequencing of the thyroid tumor tissue showed a biallelic loss at the same mutation site (loss of heterozygosity) and immunohistochemistry of the PDTC showed loss of FH staining in the tumor tissue, indicating the pathogenic role of this mutation in the development of PDTC in this patient.

CONCLUSION

Thyroid cancer is a novel feature of the FH-related HLRCC syndrome. This syndrome can be added to the rare genetic causes of syndromic FNMTC.

Uterine leiomyoma with fumarate hydratase deficiency: A case report

RATIONALE

Hereditary leiomyomatosis and renal cell carcinoma is an uncommon autosomal dominant disease caused by mutations in the fumarate hydratase (FH) gene. They usually demonstrated multiple uterine myomas and preformed surgical procedures for myomectomy and/or hysterectomy 10 years earlier than sporadic myomas due to early development. This case report describes a woman with multiple uterine leiomyomas diagnosed with FH deficiency.

PATIENT CONCERNS

A 37-year-old woman visited a gynecological clinic for the discovery of uterine leiomyoma for more than 1 year. The size of the largest grew from 42 × 27 × 46 to 98 × 85 × 113 mm in 1 year. She had a history of surgery for breast cancer and thyroid cancer but denied a history of uterine leiomyoma in her family.

DIAGNOSIS AND INTERVENTIONS

The patient underwent successful transabdominal hysterectomy. The pathological results showed multiple uterine leiomyomas (partly cellular leiomyomas) with scattered large bizarre giant cells. Immunohistochemistry results demonstrated FH deficiency.

OUTCOMES

On follow-up, the patient did not have any complications. She was finally referred to the oncologists and urologists for follow-up.

LESSONS

Gynecologists should be aware that early onset uterine leiomyoma presenting as large, multiple, and symptomatic lesion, may be associated with FH deficiency.

Reduced expression of mitochondrial fumarate hydratase in progressive multiple sclerosis contributes to impaired in vitro mesenchymal stromal cell-mediated neuroprotection

Background:

Cell-based therapies for multiple sclerosis (MS), including those employing autologous bone marrow-derived mesenchymal stromal cells (MSC) are being examined in clinical trials. However, recent studies have identified abnormalities in the MS bone marrow microenvironment.

Objective:

We aimed to compare the secretome of MSC isolated from control subjects (C-MSC) and people with MS (MS-MSC) and explore the functional relevance of findings.

Methods:

We employed high throughput proteomic analysis, enzyme-linked immunosorbent assays and immunoblotting, as well as in vitro assays of enzyme activity and neuroprotection.

Results:

We demonstrated that, in progressive MS, the MSC secretome has lower levels of mitochondrial fumarate hydratase (mFH). Exogenous mFH restores the in vitro neuroprotective potential of MS-MSC. Furthermore, MS-MSC expresses reduced levels of fumarate hydratase (FH) with downstream reduction in expression of master regulators of oxidative stress.

Conclusions:

Our findings are further evidence of dysregulation of the bone marrow microenvironment in progressive MS with respect to anti-oxidative capacity and immunoregulatory potential. Given the clinical utility of the fumaric acid ester dimethyl fumarate in relapsing–remitting MS, our findings have potential implication for understanding MS pathophysiology and personalised therapeutic intervention.

Fumarate hydratase variant prevalence and manifestations among individuals receiving germline testing

BACKGROUND

Germline variants in fumarate hydratase (FH) are associated with autosomal dominant (AD) hereditary leiomyomatosis and renal cell cancer (HLRCC) and autosomal recessive (AR) fumarase deficiency (FMRD). The prevalence and cancer penetrance across different FH variants remain unclear.

METHODS

A database containing 120,061 records from individuals undergoing cancer germline testing was obtained. FH variants were classified into 3 categories: AD HLRCC variants, AR FMRD variants, and variants of unknown significance (VUSs). Individuals with variants from these categories were compared with those with negative genetic testing.

RESULTS

FH variants were detected in 1.3% of individuals (AD HLRCC, 0.3%; AR FMRD, 0.4%; VUS, 0.6%). The rate of AD HLRCC variants discovered among reportedly asymptomatic individuals without a clear indication for HLRCC testing was 1 in 2668 (0.04%). In comparison with those with negative genetic testing, the renal cell carcinoma (RCC) prevalence was elevated with AD HLRCC variants (17.0% vs 4.5%; P < .01) and VUSs (6.4% vs 4.5%; P = .02) but not with AR FMRD variants.

CONCLUSIONS

The prevalence of HLRCC discovered incidentally on germline testing is similar to recent population carrier estimates, and this suggests that this is a relatively common cancer syndrome. Compared with those with negative genetic testing, those with VUSs had an elevated risk of RCC, whereas those with AR FMRD variants did not.

HEREDITARY LEIOMYOMATOSIS AND ACUTE LYMPHOBLASTIC LEUKEMIA: a LINK THROUGH FUMARATE DYSHYDRATASE MUTATION?

BACKGROUND

: Hereditary leiomyomatosis (HL) is an autosomal dominant condition due to a variety of fumarate hydratase (FH) mutations in which individuals tend to develop cutaneous leiomyomas, multiple uterine leiomyomas and are at risk for developing aggressive papillary renal cell carcinoma.

CASE PRESENTATION

: A 26-year-old man with a past history of acute lymphoblastic leukemia (T-ALL) presented with numerous painful light brown papules and nodules spread all over his body except for the head, appearing since infancy. Similar lesions were present in his mother's family. A cutaneous biopsy revealed a cutaneous leiomyoma. His mother died from metastatic uterine neoplasia and his sister suffered from leiomyoma of the uterus. No renal cancer was reported in his family. A heterozygous pathogenic variant was detected in the FH gene.

CONCLUSION

: To our knowledge, this is the first case possibly linking HL and T-ALL through FH deficiency.

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

INTRODUCTION

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.

MATERIAL AND METHODS

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.

RESULTS

The women with HLRCC were diagnosed with uterine leiomyomas at a young age compared with the sporadic leiomyoma group (mean 33.8 years vs. 45.4 years, 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 37.3 years vs. 48.3 years, P < 0.0001). HLRCC leiomyomas had denser microvasculature highlighted by CD34 immunostaining when compared with the sporadic leiomyoma group (112.6 mean 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.

CONCLUSIONS

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.

Germline Whole-Gene Deletion of FH Diagnosed from Tumor Profiling

Hereditary leiomyomatosis and renal cell carcinoma (HL (RCC)) entails cutaneous and uterine leiomyomatosis with aggressive type 2 papillary RCC-like histology. HLRCC is caused by pathogenic variants in the FH gene, which encodes fumarate hydratase (FH). Here, we describe an episode of young-onset RCC caused by a genomic FH deletion that was diagnosed via clinical sequencing. A 35-year-old woman was diagnosed with RCC and multiple metastases: histopathological analyses supported a diagnosis of FH-deficient RCC. Although the patient had neither skin tumors nor a family history of HLRCC, an aggressive clinical course at her age and pathological diagnosis of FH-deficient RCC suggested a germline FH variant. After counseling, the patient provided written informed consent for germline genetic testing. She was simultaneously subjected to paired tumor profiling tests targeting the exome to identify a therapeutic target. Although conventional germline sequencing did not detect FH variants, exome sequencing revealed a heterozygous germline FH deletion. As such, paired tumor profiling, not conventional sequencing, was required to identify this genetic deletion. RCC caused by a germline FH deletion has hitherto not been described in Japan, and the FH deletion detected in this patient was presumed to be of maternal European origin. Although the genotype-phenotype correlation in HLRCC-related tumors is unclear, the patient’s family was advised to undergo genetic counseling to consider additional RCC screening.

Single nucleotide variants of succinate dehydrogenase A gene in renal cell carcinoma

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is mainly associated with a mutation in the SDHB gene and sometimes with mutations in the SDHC or SDHD genes. However, only three cases of succinate dehydrogenase A (SDHA)-deficient RCC have been reported, and the relation between SDHA mutations and RCC has not been clarified. This study assessed the role of SDHA gene mutations in human RCC. We investigated SDHA/B/C/D gene mutations in 129 human RCCs. Targeted next-generation sequencing and direct Sanger sequencing revealed single nucleotide variants (SNVs) of the SDHA gene with amino acid sequence variations in 11/129 tumors, while no SDHB/C/D gene mutations were found. Tumor cells with SNVs of the SDHA gene were characterized by eosinophilic cytoplasm and various patterns of proliferation. Immunohistochemistry examination found that the 11 tumors with SNVs of the SDHA gene showed significant reduction of SDHA protein and SDHB protein expression compared to the 19 tumors without SDHA or SDHB mutations (both P < .0001). Western blotting showed a greater decrease in the expression of SDHA and SDHB proteins in the 11 tumors with SNVs of the SDHA gene than in the 19 tumors without (both P < .0001). There was a positive correlation between SDHA and SDHB protein levels (P < .0001). On immunohistochemistry and Western blotting, the 11 tumors with SNVs of the SDHA gene had higher protein expression for nuclear factor E2-related factor 2 (Nrf2) compared to the 19 tumors without the mutation (P < .01). These observations suggest that SDHA gene mutations might be associated with a subset of RCC.

Hereditary Leiomyomatosis and Renal Cell Cancer: Recent Insights Into Mechanisms and Systemic Treatment

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is a rare autosomal dominant hereditary cancer syndrome characterized by a predisposition to cutaneous leiomyomas, uterine leiomyomas, and renal cell carcinoma (RCC). It is known to be caused by germline mutations of the fumarate hydratase (FH) gene, which encodes an enzyme component of the citric acid cycle and catalyzes the conversion of fumarate to L-malate. Currently, there is no standardized treatment for HLRCC, which may be due in part to a lack of understanding of the underlying mechanisms. Here, the underlying molecular mechanisms by which the inactivation of FH causes HLRCC are discussed. Additionally, potential therapeutic pharmacological strategies are also summarized to provide new perspectives for the prevention and treatment of HLRCC.

Perinatal undernourishment provokes long-lasting alterations of clusterin and fumarate hydratase expression in the rat nucleus accumbens

BACKGROUND

Background: Perinatal malnutrition seems to provoke important neurochemical alterations in the brain that lead to higher vulnerability to develop neuropsychiatric disorders in the adulthood.

OBJECTIVES

We have examined the persistence and reversibility of the changes induced by perinatal undernourishment on the expression of fumarate hydratase in the rat nucleus accumbens, bearing in mind that this expression has been previously linked with addictive disorders. Clusterin, a multifunctional protein known to be neuroprotective and possibly related to addiction in humans, was studied in parallel.

METHODS

Female Wistar rats underwent a severe restriction of food during gestation and lactation. Upon weaning, a subgroup of undernourished animals was switched to normal chow and another one continued under food restriction. Control rats and their mothers were fed on chow along the experiment. Fumarate hydratase and clusterin were quantified by western blot after five months of postnatal life in the three experimental groups.

RESULTS

Food restriction along the whole experimental period provoked a marked upregulation of both clusterin and fumarate hydratase in the mitochondrial fraction of the nucleus accumbens. In the case of clusterin, this upregulation was also observed in the cytosolic fraction of the nucleus accumbens. When undernourishment was limited to gestation and lactation the two proteins appeared downregulated with respect to controls.

CONCLUSION

The results are consistent with the idea that perinatal malnutrition provokes marked changes in brain neurochemistry that are not fully corrected by the rehabilitation of normal feeding and could be linked to behavioural disturbances in the adulthood, that is, increased vulnerability to addiction.

Integrated histologic and molecular analysis of uterine leiomyosarcoma and 2 benign variants with nuclear atypia

Uterine leiomyosarcoma (LMS) is a rare but deadly disease. Due to poor understanding of the molecular and genetic causes of the disease, the diagnosis of LMS has been based primarily on histology. Nuclear atypia is one of hallmarks in LMS, however, it also occurs in 2 clinically benign variants, including smooth muscle tumors with fumarate hydratase alteration (SMT‐FH) and leiomyoma with bizarre nuclei (LM‐BN). In addition to nuclear atypia, many well recognized biomarkers used for LMS are also frequently overexpressed in LM‐BN, and the histogenesis and molecular natures for LM‐BN and LMS remain largely unknown. To characterize the molecular profiling of LMS, SMT‐FH, and LM‐BN, we performed integrated comprehensive genomic profiling including whole‐genome sequencing (WGS) and RNA sequencing and genomic microarray analyses to assess genome‐wide copy number alterations (CNAs) and immunohistochemistry (IHC) in all 3 tumor types. We found that both LM‐BN and LMS showed genomic instability and harbored extensive CNAs throughout the whole genome. By contrast, the SMT‐FH presented its characteristic 1q43‐44 deletions in all cases tested, with minimal CNAs in the rest of genomic regions. Further analyses revealed that LMS and LM‐BN groups showed similar patterns of CNAs that are tended to cluster together and separated from the SMT‐FH group. The integrated molecular profiling enabled the detection of novel and traditional biomarkers and showed excellent discrimination between LM‐BN and LMS. Our study suggests that LM‐BN, despite having similar nuclear atypia to SMT‐FH, showed similar genomic instability but distinct genomic alterations with its malignant counterpart of LMS. The integrated molecular profiling is of clinical importance in characterizing these rare uterine smooth muscle tumors.

A Non-Hereditary Case of Hereditary Leiomyomatosis and Renal Cell Carcinoma Syndrome

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome is believed to result from an autosomal dominant mutation in the fumarate hydratase (FH) gene on chromosome 1. It is characterized by leiomyomas, mainly uterine or cutaneous, and renal cell carcinoma (RCC). The most common type of RCC associated with HLRCC is type II papillary RCC although other types are seen. Of note, chromophobe RCC has not been described in previously documented cases of HLRCC. HLRCC is typically associated with germline mutations with occasional somatic mutations reported, however, to the best of our knowledge, none have yielded the full phenotype until now. Herein, we report a case of a 45-year-old woman who underwent a hysterectomy following a year of heavy vaginal bleeding, yielding a diagnosis of uterine leiomyomas. Eight months later, the patient presented with hematuria and was subsequently found to have a left renal mass. Following a left radical nephrectomy, histologic exam revealed a chromophobe RCC with FH deficiency.

Hereditary leiomyomatosis and renal cell carcinoma syndrome-associated renal cell carcinoma: Morphological appraisal with a comprehensive review of differential diagnoses

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an autosomal dominant syndrome wherein affected individuals are at risk for the development of cutaneous leiomyomas, early-onset multiple uterine leiomyomas, and an aggressive subtype of renal cell cancer. HLRCC is caused by germline mutations in the fumarate hydratase (FH) gene, which inactivates the enzyme and alters the function of the tricarboxylic acid/Krebs cycle. This article reviews the hitherto described morphologic features of HLRCC-associated renal cell carcinoma (RCC) and outlines the differential diagnosis and ancillary use of immunohistochemistry and molecular diagnostics for these tumors. The morphologic spectrum of HLRCC-associated RCC is wide and histologic features, including tumor cells with prominent nucleoli, perinucleolar halos, and multiple architectural patterns within the same tumor, which are suggestive of this diagnosis. FH immunohistochemistry in conjunction with genetic counseling and germline FH testing are the important parameters for detection of this entity. These kidney tumors warrant prompt treatment as even smaller sized lesions can demonstrate aggressive behavior and systemic oncologic treatment in metastatic disease should, if possible, be part of a clinical trial. Screening procedures in HLRCC families should preferably be evaluated in large cohorts.

Cardiac Myxoma Caused by Fumarate Hydratase Gene Deletion in Patient With Cortisol-Secreting Adrenocortical Adenoma

CONTEXT

Germline mutations in fumarate hydratase (FH) gene are known to cause hereditary leiomyomatosis and renal cell carcinoma (HLRCC) and are occasionally accompanied with cutaneous and uterine leiomyoma or cortisol-producing adrenocortical hyperplasia. However, the association between FH mutations and cardiac or adrenocortical tumors has remained unknown. Here, we identified a novel deletion in FH, exhibiting cardiac myxoma and subclinical Cushing syndrome due to adrenocortical tumor.

CASE DESCRIPTION

A 44-year-old man was referred to our hospital for cardiac and adrenal tumor evaluation. He had a history of multiple painful, dermal papules and nodules diagnosed as cutaneous leiomyoma. The surgically resected cardiac tumor was diagnosed as myxoma. The adrenal tumor was clinically diagnosed as subclinical Cushing syndrome. Laparoscopically resected adrenal tumor was pathologically diagnosed as adrenocortical adenoma harboring unique histological findings similar to primary pigmented nodular adrenocortical disease (PPNAD). DNA analysis revealed a germline deletion in FH c0.737delT (p. Phe225Leufs*31) and loss of heterozygosity (LOH) in cardiac myxoma. As a functional analysis of FH in cardiac myxoma, low FH protein expression with elevated 2-succinocysteine (2SC), a marker of FH dysfunction, was immunohistochemically detected. However, in adrenocortical tumor, LOH of FH was not detected, and FH or 2SC expression was not altered.

CONCLUSIONS

This is the first case of HLRCC complicated by cardiac myxoma. LOH of FH deletion and its dysfunction were identified in cardiac myxoma. The association between FH deletion and adrenocortical lesion, however, needs to be further clarified.

Fumarate hydratase c.914T > C (p.Phe305Ser) is a pathogenic variant associated with hereditary leiomyomatosis and renal cell cancer syndrome

Background

Hereditary leiomyomatosis and renal cell cancer syndrome (HLRCC), caused by heterozygous germline pathogenic variants in the FH, confers an increased risk for cutaneous and uterine leiomyomas and renal cancer.

Methods

About 13,722 advanced cancer patients, including 560 with renal cell carcinoma, had germline analysis performed in the context of tumor‐normal sequencing under an IRB approved protocol.

Results

We report two unrelated individuals with early onset kidney cancer who both carried the c.914C > T (p.Phe305Ser) germline variant in the FH. Both tumors exhibited loss of FH staining by immunohistochemistry and/or positive 2SC staining. Subsequent familial testing discovered that a daughter of a proband who carried the variant had both cutaneous and uterine leiomyomas.

Conclusion

This combination of evidence suggests that the FH c.914C > T (p.Phe305Ser) is pathogenic for HLRCC.

Anti-senescence role of heterozygous fumarate hydratase gene knockout in rat lung fibroblasts in vitro

Abnormalities in tricarboxylic acid (TCA) cycle function were related to a variety of pathological processes. Fumarate hydratase (FH) is a required enzyme in the TCA cycle. To explore the general influence of FH knockout, we isolated FH^+/- rat and normal rat lung fibroblasts and cultured these cells in vitro. The isolated fibroblasts with the current method were rather homogeneous and were confirmed spindle in morphology, positive for vimentin and negative for α-SMA (α-smooth muscle actin). Sequencing of the PCR (polymerase chain reaction) products flanking the FH gene mutation verified the FH^+/- status, and the FH gene and protein expression were confirmed to be reduced in the FH^+/- cells. No sign of ageing for the FH^+/- cells after 61 passages was observed, but the controls died out at this stage. Flow cytometry revealed increased S-phase and decreased G1/G0 proportions with significantly less early apoptosis in FH^+/- cells compared to that in control cells. At the same time, increased glucose consumption, intracellular fumarate production and extracellular lactate secretion were verified in the FH^+/- cells. Correspondingly, FH^+/- cells showed a lower basal oxygen consumption rate (OCR) but a higher level of reactive oxygen species (ROS) production. Single cell cloning and cell line establishment were successfully performed with the FH^+/- cells at the 84^th passage. All the above results indicate an important role for FH^+/- in the longevity or immortality of the FH^+/- cells, in which increased p53 and TERT (telomerase reverse transcriptase) protein expression, decreased p21 and p16 protein expression and negative SA-β-Gal (senescence-associated beta-galactosidase) were verified along with metabolic reprogramming.

Functional Genomics Reveals Synthetic Lethality between Phosphogluconate Dehydrogenase and Oxidative Phosphorylation

The plasticity of a preexisting regulatory circuit compromises the effectiveness of targeted therapies, and leveraging genetic vulnerabilities in cancer cells may overcome such adaptations. Hereditary leiomyomatosis renal cell carcinoma (HLRCC) is characterized by oxidative phosphorylation (OXPHOS) deficiency caused by fumarate hydratase (FH) nullizyogosity. To identify metabolic genes that are synthetically lethal with OXPHOS deficiency, we conducted a genetic loss-of-function screen and found that phosphogluconate dehydrogenase (PGD) inhibition robustly blocks the proliferation of FH mutant cancer cells both in vitro and in vivo. Mechanistically, PGD inhibition blocks glycolysis, suppresses reductive carboxylation of glutamine, and increases the NADP⁺/NADPH ratio to disrupt redox homeostasis. Furthermore, in the OXPHOS-proficient context, blocking OXPHOS using the small-molecule inhibitor IACS-010759 enhances sensitivity to PGD inhibition in vitro and in vivo. Together, our study reveals a dependency on PGD in OXPHOS-deficient tumors that might inform therapeutic intervention in specific patient populations.

Synthetically Lethal Interactions of Heme Oxygenase-1 and Fumarate Hydratase Genes

Elevated expression of heme oxygenase-1 (HO-1, encoded by HMOX1) is observed in various types of tumors. Hence, it is suggested that HO-1 may serve as a potential target in anticancer therapies. A novel approach to inhibit HO-1 is related to the synthetic lethality of this enzyme and fumarate hydratase (FH). In the current study, we aimed to validate the effect of genetic and pharmacological inhibition of HO-1 in cells isolated from patients suffering from hereditary leiomyomatosis and renal cell carcinoma (HLRCC)-an inherited cancer syndrome, caused by FH deficiency. Initially, we confirmed that UOK 262, UOK 268, and NCCFH1 cell lines are characterized by non-active FH enzyme, high expression of Nrf2 transcription factor-regulated genes, including HMOX1 and attenuated oxidative phosphorylation. Later, we demonstrated that shRNA-mediated genetic inhibition of HMOX1 resulted in diminished viability and proliferation of cancer cells. Chemical inhibition of HO activity using commercially available inhibitors, zinc and tin metalloporphyrins as well as recently described new imidazole-based compounds, especially SLV-11199, led to decreased cancer cell viability and clonogenic potential. In conclusion, the current study points out the possible relevance of HO-1 inhibition as a potential anti-cancer treatment in HLRCC. However, further studies revealing the molecular mechanisms are still needed.

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

AIMS

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.

METHODS AND RESULTS

We evaluated 153 cases of uterine leiomyomas from women aged up to 30 years 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.

CONCLUSION

Our study showed a relatively high rate of FH germline mutation in FH-negative uterine leiomyomas from patients aged up to 30 years. While genetic mutations confer protein expression loss, epigenetic regulation of the FH gene appears to be unrelated to this phenotype.

Targeting of Fumarate Hydratase from Mycobacterium tuberculosis Using Allosteric Inhibitors with a Dimeric-Binding Mode

With the growing worldwide prevalence of antibiotic-resistant strains of tuberculosis (TB), new targets are urgently required for the development of treatments with novel modes of action. Fumarate hydratase (fumarase), a vulnerable component of the citric acid cycle in Mycobacterium tuberculosis (Mtb), is a metabolic target that could satisfy this unmet demand. A key challenge in the targeting of Mtb fumarase is its similarity to the human homolog, which shares an identical active site. A potential solution to this selectivity problem was previously found in a high-throughput screening hit that binds in a nonconserved allosteric site. In this work, a structure-activity relationship study was carried out with the determination of further structural biology on the lead series, affording derivatives with sub-micromolar inhibition. Further, the screening of this series against Mtb in vitro identified compounds with potent minimum inhibitory concentrations.

Novel FH mutation associated with multiple uterine leiomyomas in Chinese siblings

Background

Fumarate hydratase (FH) plays an important role in cell metabolism. Germline mutation of FH may cause hereditary leiomyomatosis and renal cell cancer syndrome. The correlation between various mutations of FH gene and the phenotype is controversial and needs further study. Therefore, this article described a novel mutation in siblings with multiple uterine leiomyomas.

Methods

Whole‐exome sequencing was performed on the two patients and their family members using their peripheral blood. The function of the DNA variant was predicted in silico.

Results

Pathology results showed characteristics of leiomyoma. A novel missense mutation of FH gene (c.1214A＞G, p.Leu405Ser) was identified in both patients and their father. This mutation was predicted to be probably pathogenic and deleterious.

Conclusion

This study indicated that the novel mutation may be responsible for the occurrence of multiple uterine leiomyomas. However, the risk of renal disease should not be ignored and regular screening was recommended.

SCINA: A Semi-Supervised Subtyping Algorithm of Single Cells and Bulk Samples

Advances in single-cell RNA sequencing (scRNA-Seq) have allowed for comprehensive analyses of single cell data. However, current analyses of scRNA-Seq data usually start from unsupervised clustering or visualization. These methods ignore prior knowledge of transcriptomes and the probable structures of the data. Moreover, cell identification heavily relies on subjective and possibly inaccurate human inspection afterwards. To address these analytical challenges, we developed SCINA (Semi-supervised Category Identification and Assignment), a semi-supervised model that exploits previously established gene signatures using an expectation-maximization (EM) algorithm. SCINA is applicable to scRNA-Seq and flow cytometry/CyTOF data, as well as other data of similar format. We applied SCINA to a wide range of datasets, and showed its accuracy, stability and efficiency, which exceeded most popular unsupervised approaches. SCINA discovered an intermediate stage of oligodendrocytes from mouse brain scRNA-Seq data. SCINA also detected immune cell population changes in cytometry data in a genetically-engineered mouse model. Furthermore, SCINA performed well with bulk gene expression data. Specifically, we identified a new kidney tumor clade with similarity to FH-deficient tumors (FHD), which we refer to as FHD-like tumors (FHDL). Overall, SCINA provides both methodological advances and biological insights from perspectives different from traditional analytical methods.

Fumarate hydratase deficient renal cell carcinoma and fumarate hydratase deficient-like renal cell carcinoma: Morphologic comparative study of 23 genetically tested cases

Hereditary leiomyomatosis and renal cell carcinoma-associated renal cell carcinoma (HLRCC)/ fumarate hydratase deficient renal cell carcinoma (FHRCC) is an aggressive tumor defined by molecular genetic changes - alteration in fumarate hydratase (FH) gene. The morphologic spectrum of HLRCC/FHDRCC is remarkably variable. The presence of large nuclei and prominent dark red inclusion-like nucleoli and perinucleolar clearing are considered as helpful morphologic clue. We selected 23 renal neoplasms primarily based on their morphologic features suspicious for HLRCC/FHDRCC. Morphological, basic immunohistochemical, and genetic analysis was performed. The tumors were divided in two groups according to the molecular genetic findings. The first group included 13 tumors with detected FH mutation/LOH (compatible with diagnosis FHRCC), and the second group included 10 tumors without FH mutation/LOH (FH-like RCCs). In the FHRCC group, the vast majority of cases (9/13) had mixed morphology with different architectural growth patterns. All cases showed prominent macronucleoli, and perinucleolar clearing was found in 10/13 cases. Immunohistochemically, 6/7 FHRCC cases were negative for FH antibody, while one case showed strong diffuse FH reactivity. The FH-like RCC group showed more uniform architectural growth pattern. All 10 tumors had prominent macronucleoli, and perinucleolar clearing was present in 8/10 cases. Eight FH-like RCC cases showed diffuse strong positivity for FH, although 2 cases were completely negative for FH. It is evident that neither morphologic feature nor immunohistochemical analysis can be reliably used in routine practice for the diagnosis of HLRCC/FHRCC. In suspected cases, the diagnosis of HLRCC/FHRCC can be confirmed by molecular-genetic testing for FH mutation. It should be noted that the traditionally described morphologic features of HLRCC/FHRCC (prominent eosinophilic macronuclei with perinucleolar halos) can frequently be seen in other renal neoplasms.

mTORC1-driven accumulation of the oncometabolite fumarate as a potential critical step in renal cancer progression

Modeling renal cancer in the mouse has been challenging. We recently showed that upregulation of mechanistic target of rapamycin complex 1 (mTORC1) in a restricted segment of the renal tubule leads to downregulation of the tricarboxylic acid (TCA) cycle enzyme fumarate hydratase, to accumulation of the oncometabolite fumarate, and gradual transformation from benign cysts into cystadenomas and papillary carcinomas.

MED12 mutations and fumarate hydratase inactivation in uterine adenomyomas

STUDY QUESTION

Do the uterine leiomyoma driver events – mediator complex subunit 12 (MED12) mutations, high mobility group AT-hook (HMGA2) overexpression, and fumarate hydratase (FH) inactivation – also contribute to the development of uterine adenomyomas?

SUMMARY ANSWER

MED12 mutations and FH deficiency occur in a subset of uterine adenomyomas, but at lower frequencies than in leiomyomas.

WHAT IS KNOWN ALREADY

Uterine adenomyomas are benign tumours with clinical features very similar to uterine leiomyomas. Mutations affecting MED12, HMGA2 and FH account for up to 80–90% of leiomyomas, but their contribution to adenomyomas is not known.

STUDY DESIGN, SIZE, DURATION

Formalin-fixed paraffin-embedded adenomyoma samples from 21 patients operated on during 2012–2014 were collected at the pathology department’s archives and analysed for uterine leiomyoma driver events.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Adenomyoma diagnoses were verified by a specialized pathologist and representative areas were marked on haematoxylin-eosin slides. DNA was extracted from the tissue samples and sequenced to detect mutations in MED12. Expression levels of HMGA2 and 2SC, a robust indirect method to detect FH inactivation, were analysed by immunohistochemistry (IHC). The coding region of FH was sequenced in one adenomyoma sample showing strong 2SC staining as well as in the same patient’s normal tissue sample. All patients’ medical histories were collected and reviewed.

MAIN RESULTS AND THE ROLE OF CHANCE

MED12 mutation c.131G > A, p.G44D, the most common mutation in uterine leiomyomas, was identified in two samples (2/21; 9.5%). One adenomyoma displayed strong 2SC positivity and subsequent sequencing revealed a frameshift FH mutation c.911delC, p.P304fs in the tumour. The mutation was also present in the patient’s normal tissue sample, indicating that she has a hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome. HMGA2 protein expression was normal in all adenomyomas.

LIMITATIONS, REASONS FOR CAUTION

Restricted sample size limits the determination of exact mutation frequencies of the studied aberrations in adenomyomas.

WIDER IMPLICATIONS OF THE FINDINGS

Uterine leiomyoma driver mutations do contribute to the development of some adenomyomas. We also report an adenomyoma in the context of hereditary HLRCC syndrome. Despite clinical similarities, the pathogenic mechanisms of adenomyomas and leiomyomas are likely different. Large-scale genomic analyses are warranted to elucidate the complete molecular background of adenomyomas.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by The Academy of Finland, the Sigrid Jusélius Foundation, and the Cancer Society of Finland. The authors declare no conflict of interest.

Fumarate hydratase inactivation in hereditary leiomyomatosis and renal cell cancer is synthetic lethal with ferroptosis induction

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a hereditary cancer syndrome characterized by inactivation of the Krebs cycle enzyme fumarate hydratase (FH). HLRCC patients are at high risk of developing kidney cancer of type 2 papillary morphology that is refractory to current radiotherapy, immunotherapy and chemotherapy. Hence, an effective therapy for this deadly form of cancer is urgently needed. Here, we show that FH inactivation (FH-/- ) proves synthetic lethal with inducers of ferroptosis, an iron-dependent and nonapoptotic form of cell death. Specifically, we identified gene signatures for compound sensitivities based on drug responses for 9 different drug classes against the NCI-60 cell lines. These signatures predicted that ferroptosis inducers would be selectively toxic to FH-/- cell line UOK262. Preferential cell death against UOK262-FH-/- was confirmed with 4 different ferroptosis inducers. Mechanistically, the FH-/- sensitivity to ferroptosis is attributed to dysfunctional GPX4, the primary cellular defender against ferroptosis. We identified that C93 of GPX4 is readily post-translationally modified by fumarates that accumulate in conditions of FH-/- , and that C93 modification represses GPX4 activity. Induction of ferroptosis in FH-inactivated tumors represents an opportunity for synthetic lethality in cancer.

mTORC1 Upregulation Leads to Accumulation of the Oncometabolite Fumarate in a Mouse Model of Renal Cell Carcinoma

Renal cell carcinomas (RCCs) are common cancers diagnosed in more than 350,000 people each year worldwide. Several pathways are de-regulated in RCCs, including mTORC1. However, how mTOR drives tumorigenesis in this context is unknown. The lack of faithful animal models has limited progress in understanding and targeting RCCs. Here, we generated a mouse model harboring the kidney-specific inactivation of Tsc1. These animals develop cysts that evolve into papillae, cystadenomas, and papillary carcinomas. Global profiling confirmed several metabolic derangements previously attributed to mTORC1. Notably, Tsc1 inactivation results in the accumulation of fumarate and in mTOR-dependent downregulation of the TCA cycle enzyme fumarate hydratase (FH). The re-expression of FH in cellular systems lacking Tsc1 partially rescued renal epithelial transformation. Importantly, the mTORC1-FH axis is likely conserved in human RCC specimens. We reveal a role of mTORC1 in renal tumorigenesis, which depends on the oncometabolite fumarate.