Gene Summary

Gene:FLCN; folliculin
Aliases: BHD, FLCL
Summary:This gene is located within the Smith-Magenis syndrome region on chromosome 17. Mutations in this gene are associated with Birt-Hogg-Dube syndrome, which is characterized by fibrofolliculomas, renal tumors, lung cysts, and pneumothorax. Alternative splicing of this gene results in two transcript variants encoding different isoforms. [provided by RefSeq, Jul 2008]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Source:NCBIAccessed: 11 March, 2017

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Proto-Oncogene Proteins
  • Tumor Suppressor Gene
  • Antineoplastic Agents
  • Germ-Line Mutation
  • Signal Transduction
  • Twins, Monozygotic
  • Skin Diseases
  • DNA Sequence Analysis
  • Adenoma, Oxyphilic
  • Pedigree
  • Cysts
  • Proteins
  • Differential Diagnosis
  • Uterine Cancer
  • Phenotype
  • Base Sequence
  • Lung
  • Renal Cell Carcinoma
  • Wnt Signaling Pathway
  • Breast Cancer
  • Fibroma
  • Rats, Mutant Strains
  • Hereditary Neoplastic Syndromes
  • Genetic Predisposition
  • Ultrasonography, Prenatal
  • Skin Cancer
  • Mutation
  • Prostate Cancer
  • Chromosome 17
  • DNA Mutational Analysis
  • Hair Follicle
  • Lung Diseases
  • Cancer Gene Expression Regulation
  • Salivary Glands
  • Multiple Primary Neoplasms
  • Exons
  • Kidney Cancer
  • TOR Serine-Threonine Kinases
  • Tumor Suppressor Proteins
  • X-Ray Computed Tomography
  • Birt-Hogg-Dube Syndrome
  • Molecular Sequence Data
  • Pneumothorax
Tag cloud generated 11 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: FLCN (cancer-related)

Yukawa T, Fukazawa T, Yoshida M, et al.
A Case of Birt-Hogg-Dubé (BHD) Syndrome Harboring a Novel Folliculin (FLCN) Gene Mutation.
Am J Case Rep. 2016; 17:788-792 [PubMed] Free Access to Full Article Related Publications
BACKGROUND Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant disorder clinically characterized by pulmonary cysts, spontaneous pneumothorax, renal cell cancer, and skin fibrofolliculomas. The disorder is caused by germline mutations in the FLCN gene. CASE REPORT A 56-year-old female was admitted to our hospital with a diagnosis of bilateral spontaneous pneumothorax. A computed tomography (CT) scan of the chest revealed bilateral multiple bullae predominantly located in the subpleural and mediastinal areas in the bilateral upper and lower lobes. Although she was cured by thoracic cavity drainage, she underwent resection of bilateral lung bullae because she had a prior history of right pneumothorax at 37- and 45-years of age. She had no signs of renal tumor but had fibrofolliculoma in her face and a family history of pneumothorax, we therefore suspected BHD syndrome. DNA sequence analyses determined that there was a two base pair deletion in exon 4 of the FLCN gene, confirming the diagnosis of BHD syndrome. CONCLUSIONS Here we report a case of BHD syndrome with a previously unreported FLCN mutation.

Dardour L, Verleyen P, Lesage K, et al.
Bilateral renal tumors in an adult man with Smith-Magenis syndrome: The role of the FLCN gene.
Eur J Med Genet. 2016; 59(10):499-501 [PubMed] Related Publications
Smith-Magenis syndrome (SMS) is a contiguous-gene disorder most commonly caused by a deletion of chromosome 17p11.2. We report a 57 year-old man with SMS who presents bilateral renal tumors. This is most likely related to haploinsufficiency of FLCN gene, located in the deleted region, and a known tumor suppressor gene. Haploinsufficiency of FLCN causes Birt-Hogg-Dubé syndrome (BHDS), characterized by pulmonary cysts, renal and skin tumors. The present observation suggests that the follow-up of patients with SMS should also focus on possible manifestations of BHDS.

Gupta N, Sunwoo BY, Kotloff RM
Birt-Hogg-Dubé Syndrome.
Clin Chest Med. 2016; 37(3):475-86 [PubMed] Related Publications
Birt-Hogg-Dubé syndrome (BHD) is a rare autosomal dominant disorder caused by mutations in the Folliculin gene and is characterized by the formation of fibrofolliculomas, early onset renal cancers, pulmonary cysts, and spontaneous pneumothoraces. The exact pathogenesis of tumor and lung cyst formation in BHD remains unclear. There is great phenotypic variability in the clinical features of BHD, and patients can present with any combination of skin, pulmonary, or renal findings. More than 80% of adult patients with BHD have pulmonary cysts on high-resolution computed tomography scan of the chest.

Dong L, Gao M, Hao WJ, et al.
Case Report of Birt-Hogg-Dubé Syndrome: Germline Mutations of FLCN Detected in Patients With Renal Cancer and Thyroid Cancer.
Medicine (Baltimore). 2016; 95(22):e3695 [PubMed] Free Access to Full Article Related Publications
Birt-Hogg-Dubé (BHD) is a rare autosomal dominant inherited syndrome that is characterized by the presence of fibrofolliculomas and/or trichodiscomas, pulmonary cysts, spontaneous pneumothorax, and renal tumors. Here, the 2 patients we reported with renal cell carcinomas and dermatological features were suspected to be suffering from BHD syndrome. Blood samples of these patients were sent for whole exon sequencing performed by Sanger sequencing. Eight mutations, including 5 mutations, which were mapped in noncoding region, 1 synonymous mutation, and 2 missense mutations, were detected in the FLCN gene in both patients. The 2 missense mutations, predicted to be disease-causing mutation or affecting protein function by MutationTaster and SIFT, confirmed the diagnosis. In addition, the 2 patients were also affected with papillary thyroid cancer. Total thyroidectomy and prophylactic bilateral central lymph node dissection were performed for them and the BHD-2 also received lateral lymph node dissection. Pathology reports showed that the patients had lymph node metastasis in spite of small size of thyroid lesions.The 2 missense mutations, not reported previously, expand the mutation spectrum of FLCN gene associated with BHD syndrome. For the thyroid cancer patients with BHD syndrome, total thyroidectomy and prophylactic bilateral central lymph node dissection may be suitable and the neck ultrasound may benefit BHD patients and their family members.

Boo L, Ho WY, Ali NM, et al.
MiRNA Transcriptome Profiling of Spheroid-Enriched Cells with Cancer Stem Cell Properties in Human Breast MCF-7 Cell Line.
Int J Biol Sci. 2016; 12(4):427-45 [PubMed] Free Access to Full Article Related Publications
Breast cancer is the second leading cause of cancer-related mortality worldwide as most patients often suffer cancer relapse. The reason is often attributed to the presence of cancer stem cells (CSCs). Recent studies revealed that dysregulation of microRNA (miRNA) are closely linked to breast cancer recurrence and metastasis. However, no specific study has comprehensively characterised the CSC characteristic and miRNA transcriptome in spheroid-enriched breast cells. This study described the generation of spheroid MCF-7 cell in serum-free condition and the comprehensive characterisation for their CSC properties. Subsequently, miRNA expression differences between the spheroid-enriched CSC cells and their parental cells were evaluated using next generation sequencing (NGS). Our results showed that the MCF-7 spheroid cells were enriched with CSCs properties, indicated by the ability to self-renew, increased expression of CSCs markers, and increased resistance to chemotherapeutic drugs. Additionally, spheroid-enriched CSCs possessed greater cell proliferation, migration, invasion, and wound healing ability. A total of 134 significantly (p<0.05) differentially expressed miRNAs were identified between spheroids and parental cells using miRNA-NGS. MiRNA-NGS analysis revealed 25 up-regulated and 109 down-regulated miRNAs which includes some miRNAs previously reported in the regulation of breast CSCs. A number of miRNAs (miR-4492, miR-4532, miR-381, miR-4508, miR-4448, miR-1296, and miR-365a) which have not been previously reported in breast cancer were found to show potential association with breast cancer chemoresistance and self-renewal capability. The gene ontology (GO) analysis showed that the predicted genes were enriched in the regulation of metabolic processes, gene expression, DNA binding, and hormone receptor binding. The corresponding pathway analyses inferred from the GO results were closely related to the function of signalling pathway, self-renewability, chemoresistance, tumorigenesis, cytoskeletal proteins, and metastasis in breast cancer. Based on these results, we proposed that certain miRNAs identified in this study could be used as new potential biomarkers for breast cancer stem cell diagnosis and targeted therapy.

Furuya M, Tanaka R, Okudela K, et al.
Pulmonary Neoplasms in Patients with Birt-Hogg-Dubé Syndrome: Histopathological Features and Genetic and Somatic Events.
PLoS One. 2016; 11(3):e0151476 [PubMed] Free Access to Full Article Related Publications
Birt-Hogg-Dubé syndrome (BHD) is an inherited disorder caused by genetic mutations in the folliculin (FLCN) gene. Individuals with BHD have multiple pulmonary cysts and are at a high risk for developing renal cell carcinomas (RCCs). Currently, little information is available about whether pulmonary cysts are absolutely benign or if the lungs are at an increased risk for developing neoplasms. Herein, we describe 14 pulmonary neoplastic lesions in 7 patients with BHD. All patients were confirmed to have germline FLCN mutations. Neoplasm histologies included adenocarcinoma in situ (n = 2), minimally invasive adenocarcinoma (n = 1), papillary adenocarcinoma (n = 1), micropapillary adenocarcinoma (n = 1), atypical adenomatous hyperplasia (n = 8), and micronodular pneumocyte hyperplasia (MPH)-like lesion (n = 1). Five of the six adenocarcinoma/MPH-like lesions (83.3%) demonstrated a loss of heterozygosity (LOH) of FLCN. All of these lesions lacked mutant alleles and preserved wild-type alleles. Three invasive adenocarcinomas possessed additional somatic events: 2 had a somatic mutation in the epidermal growth factor receptor gene (EGFR) and another had a somatic mutation in KRAS. Immunohistochemical analysis revealed that most of the lesions were immunostained for phospho-mammalian target of rapamycin (p-mTOR) and phospho-S6. Collective data indicated that pulmonary neoplasms of peripheral adenocarcinomatous lineage in BHD patients frequently exhibit LOH of FLCN with mTOR pathway signaling. Additional driver gene mutations were detected only in invasive cases, suggesting that FLCN LOH may be an underlying abnormality that cooperates with major driver gene mutations in the progression of pulmonary adenocarcinomas in BHD patients.

Skolnik K, Tsai WH, Dornan K, et al.
Birt-Hogg-Dubé syndrome: a large single family cohort.
Respir Res. 2016; 17:22 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant condition characterized by dermatologic lesions, pulmonary manifestations, and renal tumors. The syndrome arises from germline mutations in the folliculin (FLCN) gene. We present findings from the single largest family BHD cohort described to date. Primary objectives were to characterize cystic lung changes on computed tomography (CT) chest scanning and identify features that stratify patients at higher risk of pneumothorax. Secondary objectives entailed description of the following: type and natural history of BHD-associated pneumothorax, pulmonary function characteristics, and relationship between cystic lung changes and pulmonary function.
METHODS: The study was a retrospective chart review for a case series of a single family. Over 70 family members of a proband with documented BHD were identified, 68 of which consented to genetic testing. All those with confirmed BHD were offered a clinical assessment by the Medical Genetics and Pulmonary services which included a history, physical exam, complete pulmonary function tests, and computed tomography (CT) scan of the chest and abdomen.
RESULTS: Thirty-six individuals had a heterozygous mutation in the FLCN gene (c.59delT). Of these, 100 % (28/28) had pulmonary cysts, 41 % (13/32) had spontaneous pneumothoraces, 26 % (8/31) had kidney cysts, 3 % (1/31) had renal tumors, and 53 % (18/34) had dermatologic manifestations. Recurrent pneumothoraces were common (40 %). Cyst size (OR 3.23, 95 % CI 1.35-7.73) and extent of lower lung zone disease (OR 6.43, 95 % CI 1.41-29.2) were the only findings associated with pneumothorax. The size or extent of cystic disease did not correlate with lung function results.
CONCLUSIONS: This is the largest single family cohort of patients with BHD syndrome documented to date. We found that all individuals had pulmonary cysts, pneumothoraces were common, and cyst size and lower lobe predominant disease were associated with pneumothorax. Lung function was generally preserved and not affected by a high cyst burden.

Kennedy JC, Khabibullin D, Henske EP
Mechanisms of pulmonary cyst pathogenesis in Birt-Hogg-Dube syndrome: The stretch hypothesis.
Semin Cell Dev Biol. 2016; 52:47-52 [PubMed] Related Publications
Loss-of-function mutations in the folliculin gene (FLCN) on chromosome 17p cause Birt-Hogg-Dube syndrome (BHD), which is associated with cystic lung disease. The risk of lung collapse (pneumothorax) in BHD patients is 50-fold higher than in the general population. The cystic lung disease in BHD is distinctive because the cysts tend to be basilar, subpleural and lentiform, differentiating BHD from most other cystic lung diseases. Recently, major advances in elucidating the primary functions of the folliculin protein have been made, including roles in mTOR and AMPK signaling via the interaction of FLCN with FNIP1/2, and cell-cell adhesion via the physical interaction of FLCN with plakophilin 4 (PKP4), an armadillo-repeat containing protein that interacts with E-cadherin and is a component of the adherens junctions. In addition, in just the last three years, the pulmonary impact of FLCN deficiency has been examined for the first time. In mouse models, evidence has emerged that AMPK signaling and cell-cell adhesion are involved in alveolar enlargement. In addition, the pathologic features of human BHD cysts have been recently comprehensively characterized. The "stretch hypothesis" proposes that cysts in BHD arise because of fundamental defects in cell-cell adhesion, leading to repeated respiration-induced physical stretch-induced stress and, over time, expansion of alveolar spaces particularly in regions of the lung with larger changes in alveolar volume and at weaker "anchor points" to the pleura. This hypothesis ties together many of the new data from cellular and mouse models of BHD and from the human pathologic studies. Critical questions remain. These include whether the consequences of stretch-induced cyst formation arise through a destructive/inflammatory program or a proliferative program (or both), whether cyst initiation involves a "second hit" genetic event inactivating the remaining wild-type copy of FLCN (as is known to occur in BHD-associated renal cell carcinomas), and whether cyst initiation involves exclusively the epithelial compartment versus an interaction between the epithelium and mesenchyme. Ultimately, understanding the mechanisms of cystic lung disease in BHD may help to elucidate the pathogenesis of primary spontaneous pneumothorax, with more than 20,000 cases reported annually in the United States alone.

Iribe Y, Yao M, Tanaka R, et al.
Genome-Wide Uniparental Disomy and Copy Number Variations in Renal Cell Carcinomas Associated with Birt-Hogg-Dubé Syndrome.
Am J Pathol. 2016; 186(2):337-46 [PubMed] Related Publications
Birt-Hogg-Dubé syndrome is an inherited disorder caused by germline mutations of the folliculin gene (FLCN). The affected patients are prone to developing renal cell carcinomas (RCCs). Most mutant FLCN-associated RCCs (mFLCN-RCCs) are histologically chromophobe RCCs and hybrid oncocytic/chromophobe tumors. It is incompletely understood whether mFLCN-RCCs have different chromosomal abnormalities compared with their sporadic histological counterparts. Herein, we describe somatic mutations of FLCN and DNA-copy number abnormalities using a high-density, whole-genome, single-nucleotide polymorphism array. The histological types included chromophobe RCC (n = 12), hybrid oncocytic/chromophobe tumor (n = 5), and clear-cell RCC (n = 2). Of 19 tumors, 8 had pathological somatic mutations of FLCN. Among 11 mFLCN-RCCs investigated by single-nucleotide polymorphism array, 8 showed balanced genomic profiles, 2 had gains in chromosome 3q, and 1 had gains in chromosomes 1q and 7. All had copious numbers of loss of heterozygosity in a wide range of chromosomes. The common loss-of-heterozygosity regions were chromosomes 3p24, 8q11, 16q11, Xp22-21, Xp11, Xq11, Xq13, and Xq23. Most of the loss of heterozygosity was because of uniparental disomy. Common uniparental disomy patterns in chromophobe RCCs and hybrid oncocytic/chromophobe tumors indicated that these types were relatively similar in cytogenetic events. Two clear-cell RCCs also shared several uniparental disomy regions with chromophobe RCCs and hybrid oncocytic/chromophobe tumors. mFLCN-RCCs may have common therapeutic targets among different histological types.

Whitworth J, Skytte AB, Sunde L, et al.
Multilocus Inherited Neoplasia Alleles Syndrome: A Case Series and Review.
JAMA Oncol. 2016; 2(3):373-9 [PubMed] Related Publications
Mendelian causes of inherited cancer susceptibility are mostly rare and characterized by variable expression and incomplete penetrance. Phenotypic variability may result from a range of causes including locus heterogeneity, allelic heterogeneity, genetic and environmental modifier effects, or chance. Another potential cause is the presence of 2 or more inherited cancer predisposition alleles in the same individual. Although the frequency of such occurrences might be predicted to be low, such cases have probably been underascertained because standard clinical practice has been to test candidate inherited cancer genes sequentially until a pathogenic mutation is detected. However, recent advances in next-generation sequencing technologies now provide the opportunity to perform simultaneous parallel testing of large numbers of inherited cancer genes. Herein we provide examples of patients who harbor pathogenic mutations in multiple inherited cancer genes and review previously published examples to illustrate the complex genotype-phenotype relationships in these cases. We suggest that clinicians should proactively consider the likelihood of this phenomenon (referred to herein as multilocus inherited neoplasia alleles syndrome [MINAS]) in patients with unusual inherited cancer syndrome phenotypes. To facilitate the clinical management of novel cases of MINAS, we have established a database to collect information on what is likely to be an increasingly recognized cohort of such individuals.

Hasumi H, Baba M, Hasumi Y, et al.
Birt-Hogg-Dubé syndrome: Clinical and molecular aspects of recently identified kidney cancer syndrome.
Int J Urol. 2016; 23(3):204-10 [PubMed] Related Publications
Birt-Hogg-Dubé syndrome is an autosomal dominantly inherited disease that predisposes patients to develop fibrofolliculoma, lung cysts and bilateral multifocal renal tumors, histologically hybrid oncocytic/chromophobe tumors, chromophobe renal cell carcinoma, oncocytoma, papillary renal cell carcinoma and clear cell renal cell carcinoma. The predominant forms of Birt-Hogg-Dubé syndrome-associated renal tumors, hybrid oncocytic/chromophobe tumors and chromophobe renal cell carcinoma are typically less aggressive, and a therapeutic principle for these tumors is a surgical removal with nephron-sparing. The timing of surgery is the most critical element for postoperative renal function, which is one of the important prognostic factors for Birt-Hogg-Dubé syndrome patients. The folliculin gene (FLCN) that is responsible for Birt-Hogg-Dubé syndrome was isolated as a novel tumor suppressor for kidney cancer. Recent studies using murine models for FLCN, a protein encoded by the FLCN gene, and its two binding partners, folliculin-interacting protein 1 (FNIP1) and folliculin-interacting protein 2 (FNIP2), have uncovered important roles for FLCN, FNIP1 and FNIP2 in cell metabolism, which include AMP-activated protein kinase-mediated energy sensing, Ppargc1a-driven mitochondrial oxidative phosphorylation and mTORC1-dependent cell proliferation. Birt-Hogg-Dubé syndrome is a hereditary hamartoma syndrome, which is triggered by metabolic alterations under a functional loss of FLCN/FNIP1/FNIP2 complex, a critical regulator of kidney cell proliferation rate; a mechanistic insight into the FLCN/FNIP1/FNIP2 pathway could provide us a basis for developing new therapeutics for kidney cancer.

Wu M, Si S, Li Y, et al.
Flcn-deficient renal cells are tumorigenic and sensitive to mTOR suppression.
Oncotarget. 2015; 6(32):32761-73 [PubMed] Free Access to Full Article Related Publications
Deficiency of tumor suppressor FLCN leads to the activation of the mTOR signaling pathway in human BHD-associated renal cell carcinomas (RCC). We have previously developed a renal distal tubule-collecting duct-Henle's loop-specific Flcn knockout (KO) mouse model (Flcnflox/flox/Ksp-Cre). This mouse model can only survive for three weeks after birth due to the development of polycystic kidney and uremia. Whether these cystic solid hyperplasia changes seen in those KO mice are tumorigenic or malignant is unknown. In this study, we demonstrated that genetic disruption of Flcn in mouse kidney distal tubule cells could lead to tumorigenic transformation of these cells to develop allograft tumors with an aggressive histologic phenotype. Consistent with previous reports, we showed that the mTOR pathway plays an important role in the growth of these Flcn-deficient allograft and human UOK 257-1 xenograft tumors. We further demonstrated that the mTOR inhibitor, sirolimus, suppresses the tumor's growth, suggesting that mTOR inhibitors might be effective in control of FLCN-deficient RCC, especially in BHD renal tumorigenesis.

Näf E, Laubscher D, Hopfer H, et al.
Birt-Hogg-Dubé syndrome: novel FLCN frameshift deletion in daughter and father with renal cell carcinomas.
Fam Cancer. 2016; 15(1):127-32 [PubMed] Free Access to Full Article Related Publications
Germline mutation of the FLCN gene causes Birt-Hogg-Dubé syndrome (BHD), a rare autosomal dominant condition characterized by skin fibrofolliculomas, lung cysts, spontaneous pneumothorax and renal tumours. We identified a hitherto unreported pathogenic FLCN frameshift deletion c.563delT (p.Phe188Serfs*35) in a family of a 46-year-old woman presented with macrohematuria due to bilateral chromophobe renal carcinomas. A heritable renal cancer was suspected due to the bilaterality of the tumour and as the father of this woman had suffered from renal cancer. Initially, however, BHD was overlooked by the medical team despite the highly suggestive clinical presentation. We assume that BHD is underdiagnosed, at least partially, due to low awareness of this variable condition and to insufficient use of appropriate genetic testing. Our study indicates that BHD and FLCN testing should be routinely considered in patients with positive family or personal history of renal tumours. In addition, we demonstrate how patients and their families can play a driving role in initiating genetic diagnosis, presymptomatic testing of at-risk relatives, targeted disease management, and genetic counselling of rare diseases such as BHD.

Schmidt LS, Linehan WM
Molecular genetics and clinical features of Birt-Hogg-Dubé syndrome.
Nat Rev Urol. 2015; 12(10):558-69 [PubMed] Free Access to Full Article Related Publications
Birt-Hogg-Dubé (BHD) syndrome is an inherited renal cancer syndrome in which affected individuals are at risk of developing benign cutaneous fibrofolliculomas, bilateral pulmonary cysts and spontaneous pneumothoraces, and kidney tumours. Bilateral multifocal renal tumours that develop in BHD syndrome are most frequently hybrid oncocytic tumours and chromophobe renal carcinoma, but can present with other histologies. Germline mutations in the FLCN gene on chromosome 17 are responsible for BHD syndrome--BHD-associated renal tumours display inactivation of the wild-type FLCN allele by somatic mutation or chromosomal loss, confirming that FLCN is a tumour suppressor gene that fits the classic two-hit model. FLCN interacts with two novel proteins, FNIP1 and FNIP2, and with AMPK, a negative regulator of mTOR. Studies with FLCN-deficient cell and animal models support a role for FLCN in modulating the AKT-mTOR pathway. Emerging evidence links FLCN with a number of other molecular pathways and cellular processes important for cell homeostasis that are frequently deregulated in cancer, including regulation of TFE3 and/or TFEB transcriptional activity, amino-acid-dependent mTOR activation through Rag GTPases, TGFβ signalling, PGC1α-driven mitochondrial biogenesis, and autophagy. Currently, surgical intervention is the only therapy available for BHD-associated renal tumours, but improved understanding of the FLCN pathway will hopefully lead to the development of effective forms of targeted systemic therapy for this disease.

Jafri M, Wake NC, Ascher DB, et al.
Germline Mutations in the CDKN2B Tumor Suppressor Gene Predispose to Renal Cell Carcinoma.
Cancer Discov. 2015; 5(7):723-9 [PubMed] Related Publications
UNLABELLED: Familial renal cell carcinoma (RCC) is genetically heterogeneous and may be caused by mutations in multiple genes, including VHL, MET, SDHB, FH, FLCN, PTEN, and BAP1. However, most individuals with inherited RCC do not have a detectable germline mutation. To identify novel inherited RCC genes, we undertook exome resequencing studies in a familial RCC kindred and identified a CDKN2B nonsense mutation that segregated with familial RCC status. Targeted resequencing of CDKN2B in individuals (n = 82) with features of inherited RCC then revealed three candidate CDKN2B missense mutations (p.Pro40Thr, p.Ala23Glu, and p.Asp86Asn). In silico analysis of the three-dimensional structures indicated that each missense substitution was likely pathogenic through reduced stability of the mutant or reduced affinity for cyclin-dependent kinases 4 and 6, and in vitro studies demonstrated that each of the mutations impaired CDKN2B-induced suppression of proliferation in an RCC cell line. These findings identify germline CDKN2B mutations as a novel cause of familial RCC.
SIGNIFICANCE: Germline loss-of-function CDKN2B mutations were identified in a subset of patients with features of inherited RCC. Detection of germline CDKN2B mutations will have an impact on familial cancer screening and might prove to influence the management of disseminated disease.

Ray A, Paul S, Chattopadhyay E, et al.
Genetic analysis of familial spontaneous pneumothorax in an Indian family.
Lung. 2015; 193(3):433-8 [PubMed] Related Publications
Familial spontaneous pneumothorax is one of the phenotypes of Birt-Hogg-Dubé syndrome (BHDS), an autosomal dominant condition associated with folliculin (FLCN). We investigated clinical and genetic data of an Indian family having two patients suffering from spontaneous pneumothorax in the absence of skin lesions or renal tumors. HRCT scan of patient's lung revealed paracardiac cysts, and DNA sequencing of all 14 exons of FLCN from patients showed the presence of heterozygous "C allele" deletion in the poly-cytosine (poly-C) tract of exon 11 leading to truncated folliculin. This mutation was also observed in four asymptomatic members of the family. Our results confirmed the presence of deletion mutation in poly-C tract of FLCN in members of BHDS family. This is the first report of genetic insight in a BHDS family from India but in-depth studies with a larger sample set are necessary to understand mechanism of familial pneumothorax.

Moch H, Montironi R, Lopez-Beltran A, et al.
Oncotargets in different renal cancer subtypes.
Curr Drug Targets. 2015; 16(2):125-35 [PubMed] Related Publications
Renal cell cancer is a heterogeneous group of cancers with different histologic subtypes. The majority of renal tumors in adults are clear cell renal cell carcinomas, which are characterized by von Hippel- Lindau (VHL) gene alterations. Recent advances in defining the genetic landscape of renal cancer has shown the genetic heterogeneity of clear cell renal cell carcinomas (ccRCC) and the presence of at least 3 additional ccRCC tumor suppressor genes on chromosome 3p. Due to inactivation of VHL, renal cancer cells produce the HIF-responsive growth factor VEGF. The PI3K--mTORC1 signaling axis also represents a target for therapy. The new systemic therapies, including tyrosine kinase inhibitors, monoclonal antibodies, and mTOR inhibitors, aim to suppress angiogenesis with vascular endothelial growth factor as a target. Various VEGF-inhibitors are approved for the treatment of ccRCC and we discuss recent advancements in the treatment of metastatic ccRCC. Other gene alterations have been identified in hereditary cancer syndromes, e.g. FLCN, TSC1, TSC2, TFE3, TFEB, MITF, FH, SDHB, SDHD, MET, and PTEN and we review their role in renal tumor carcinogenesis, prognosis, and targeted therapy. By reviewing the associations between morphologic features and molecular genetics of renal cancer we provide insight into the basis for targeted renal cancer therapy.

Furuya M, Hong SB, Tanaka R, et al.
Distinctive expression patterns of glycoprotein non-metastatic B and folliculin in renal tumors in patients with Birt-Hogg-Dubé syndrome.
Cancer Sci. 2015; 106(3):315-23 [PubMed] Free Access to Full Article Related Publications
Birt-Hogg-Dubé syndrome (BHD) is an inherited disorder associated with a germline mutation of the folliculin gene (FLCN). The affected families have a high risk for developing multiple renal cell carcinomas (RCC). Diagnostic markers that distinguish between FLCN-related RCC and sporadic RCC have not been investigated, and many patients with undiagnosed BHD fail to receive proper medical care. We investigated the histopathology of 27 RCCs obtained from 18 BHD patients who were diagnosed by genetic testing. Possible somatic mutations of RCC lesions were investigated by DNA sequencing. Western blotting and immunohistochemical staining were used to compare the expression levels of FLCN and glycoprotein non-metastatic B (GPNMB) between FLCN-related RCCs and sporadic renal tumors (n = 62). The expression of GPNMB was also evaluated by quantitative RT-PCR. Histopathological analysis revealed that the most frequent histological type was chromophobe RCC (n = 12), followed by hybrid oncocytic/chromophobe tumor (n = 6). Somatic mutation analysis revealed small intragenic mutations in six cases and loss of heterozygosity in two cases. Western blot and immunostaining analyses revealed that FLCN-related RCCs showed overexpression of GPNMB and underexpression of FLCN, whereas sporadic tumors showed inverted patterns. GPNMB mRNA in FLCN-related RCCs was 23-fold more abundant than in sporadic tumors. The distinctive expression patterns of GPNMB and FLCN might identify patients with RCCs who need further work-up for BHD.

Guda K, Veigl ML, Varadan V, et al.
Novel recurrently mutated genes in African American colon cancers.
Proc Natl Acad Sci U S A. 2015; 112(4):1149-54 [PubMed] Free Access to Full Article Related Publications
We used whole-exome and targeted sequencing to characterize somatic mutations in 103 colorectal cancers (CRC) from African Americans, identifying 20 new genes as significantly mutated in CRC. Resequencing 129 Caucasian derived CRCs confirmed a 15-gene set as a preferential target for mutations in African American CRCs. Two predominant genes, ephrin type A receptor 6 (EPHA6) and folliculin (FLCN), with mutations exclusive to African American CRCs, are by genetic and biological criteria highly likely African American CRC driver genes. These previously unsuspected differences in the mutational landscapes of CRCs arising among individuals of different ethnicities have potential to impact on broader disparities in cancer behaviors.

Omar H, Lim CR, Chao S, et al.
Blood gene signature for early hepatocellular carcinoma detection in patients with chronic hepatitis B.
J Clin Gastroenterol. 2015; 49(2):150-7 [PubMed] Related Publications
PURPOSE: Up to 25% of chronic hepatitis B (CHB) patients eventually develop hepatocellular carcinoma (HCC), a disease with poor prognosis unless detected early. This study identifies a blood-based RNA biomarker panel for early HCC detection in CHB.
MATERIALS AND METHODS: A genome-wide RNA expression study was performed using RNA extracted from blood samples from Malaysian patients (matched HCC, CHB, controls). Genes differentiating HCC from controls were selected for further testing using quantitative real-time polymerase chain reaction. Finally, a 6-gene biomarker panel was identified and characterized using a training set (cohort I = 126), and tested against 2 test sets (cohort II = 222; cohort III = 174). The total number of samples used for each group is: HCC + CHB = 143, CHB = 211, control = 168.
RESULTS: Our gene panel displays a consistent trend distinguishing HCC from controls in our test sets, with an area under receiver-operating characteristic curve of 0.9 in cohort III. Our independent test set (cohort III) showed that the gene panel had a sensitivity of 70% with a specificity of 92%. The biomarker profile for HCC was consistently detected in a small subgroup of CHB patients, thus potentially predicting early, preclinical cases of cancer that should be screened more intensively.
CONCLUSION: The biomarkers identified in this study can be used as the basis of a blood-based test for the detection of early HCC in CHB.

Dal Sasso AA, Belém LC, Zanetti G, et al.
Birt-Hogg-Dubé syndrome. State-of-the-art review with emphasis on pulmonary involvement.
Respir Med. 2015; 109(3):289-96 [PubMed] Related Publications
BACKGROUND: Birt-Hogg-Dubé syndrome (BHDS) is a rare, inherited autosomal-dominant disorder characterized by the development of cutaneous lesions, renal tumors, pulmonary cysts, and spontaneous pneumothorax. The gene responsible for BHDS is located on the short arm of chromosome 17 (17p11.2) and codes for the protein folliculin, which is believed to be an oncogene suppressor protein.
METHODS: We reviewed currently published literature on the main characteristics of BHDS.
RESULTS: Pulmonary cysts and spontaneous pneumothorax are often the presenting manifestations that lead to a final diagnosis in family members affected by the syndrome.
CONCLUSIONS: Certain imaging characteristics of pulmonary cysts, including size and location, can suggest the diagnosis of BHDS based on chest computed tomography alone. The main concern in patients with BHDS is the increased risk of renal carcinoma. The aim of this review is to describe the main pathological, clinical, and imaging aspects of BHDS, ranging from its genetic basis to treatment, with emphasis on pulmonary involvement.

Lin Z, Gong K, Pang B, et al.
Birt-Hogg-Dubé syndrome with clear cell renal cell carcinoma in a Chinese family.
Intern Med. 2014; 53(24):2825-8 [PubMed] Related Publications
Birt-Hogg-Dubé syndrome (BHDS) is a rare autosomal dominant genodermatosis that presents as a clinical triad including follicular hamartomas, renal neoplasms and lung cysts associated with an increased risk of pneumothorax. FLCN gene defects have been identified as being responsible for BHDS. We herein report the case of a 67-year-old woman with the full-blown BHDS phenotype, characterized by skin lesions, multiple lung bullae and renal neoplasms. In her family history, one of the patient's sons exhibited a similar phenotype, without renal neoplasms. Due to the relatively late age of onset of renal neoplasms among variable BHDS phenotypes, follow-up imaging is recommended for the son who has not yet developed renal neoplasms.

Johannesma PC, Houweling AC, van Waesberghe JH, et al.
The pathogenesis of pneumothorax in Birt-Hogg-Dubé syndrome: a hypothesis.
Respirology. 2014; 19(8):1248-50 [PubMed] Related Publications
The development and natural course of lung cysts in patients with Birt-Hogg-Dubé syndrome (BHD) is still unclear, and the relationship between lung cysts and pneumothorax is not fully clarified. Based on the follow-up results of thoracic imaging in six patients with BHD, we hypothesize that decreased potential for stretching of the cysts' wall and extensive contact with the visceral pleura are probably responsible for rupture of the cyst wall resulting in increased risk for pneumothorax.

Sirintrapun SJ, Geisinger KR, Cimic A, et al.
Oncocytoma-like renal tumor with transformation toward high-grade oncocytic carcinoma: a unique case with morphologic, immunohistochemical, and genomic characterization.
Medicine (Baltimore). 2014; 93(15):e81 [PubMed] Free Access to Full Article Related Publications
Renal oncocytoma is a benign tumor with characteristic histologic findings. We describe an oncocytoma-like renal tumor with progression to high-grade oncocytic carcinoma and metastasis. A 74-year-old man with no family history of cancer presented with hematuria. Computed tomography showed an 11 cm heterogeneous multilobulated mass in the right kidney lower pole, enlarged aortocaval lymph nodes, and multiple lung nodules. In the nephrectomy specimen, approximately one third of the renal tumor histologically showed regions classic for benign oncocytoma transitioning to regions of high-grade carcinoma without sharp demarcation. With extensive genomic investigation using single nucleotide polymorphism-based array virtual karyotyping, multiregion sequencing, and expression array analysis, we were able to show a common lineage between the benign oncocytoma and high-grade oncocytic carcinoma regions in the tumor. We were also able to show karyotypic differences underlying this progression. The benign oncocytoma showed no chromosomal aberrations, whereas the high-grade oncocytic carcinoma showed loss of the 17p region housing FLCN (folliculin [Birt-Hogg-Dubé protein]), loss of 8p, and gain of 8q. Gene expression patterns supported dysregulation and activation of phosphoinositide 3-kinase (PI3K)/v-akt murine thymoma viral oncogene homolog (Akt), mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated kinase (ERK), and mechanistic target of rapamycin (serine/threonine kinase) (mTOR) pathways in the high-grade oncocytic carcinoma regions. This was partly attributable to FLCN underexpression but further accentuated by overexpression of numerous genes on 8q. In the high-grade oncocytic carcinoma region, vascular endothelial growth factor A along with metalloproteinases matrix metallopeptidase 9 and matrix metallopeptidase 12 were overexpressed, facilitating angiogenesis and invasiveness. Genetic molecular testing provided evidence for the development of an aggressive oncocytic carcinoma from an oncocytoma, leading to aggressive targeted treatment but eventual death 39 months after the diagnosis.

Bradley M, Nordfors C, Vlastos A, et al.
No association between Birt-Hogg-Dubé syndrome skin fibrofolliculomas and the first 10 described human polyomaviruses or human papillomaviruses.
Virology. 2014; 468-470:244-7 [PubMed] Related Publications
The rare autosomal dominant condition Birt-Hogg-Dubé syndrome (BHD) is attributed to mutations on chromosome 17 in the folliculin (FLCN) gene, but not always diagnosed due to lack of, or a variety of symptoms such as fibrofolliculomas, lung cystic lesions, spontaneous pneumothorax and renal cancer. We hypothesized that the lack of or variability in symptoms could be due to BHD patients potentially being abnormally susceptible to infections with human papillomavirus (HPV) or human polyomavirus (HPyV), which can be associated with skin lesions or latency in the kidneys. Seven fibrofolliculoma skin lesions, one renal cancer and one lung cyst from nine patients with BHD treated at the Karolinska University Hospital were therefore analyzed for cutaneous and mucosal HPV types and 10 HPyVs by bead based multiplex assays or by PCR. All samples were negative for viral DNA. In conclusion, the data suggest that HPV and HPyVs do not contribute to BHD pathology.

Dunlop EA, Seifan S, Claessens T, et al.
FLCN, a novel autophagy component, interacts with GABARAP and is regulated by ULK1 phosphorylation.
Autophagy. 2014; 10(10):1749-60 [PubMed] Free Access to Full Article Related Publications
Birt-Hogg-Dubé (BHD) syndrome is a rare autosomal dominant condition caused by mutations in the FLCN gene and characterized by benign hair follicle tumors, pneumothorax, and renal cancer. Folliculin (FLCN), the protein product of the FLCN gene, is a poorly characterized tumor suppressor protein, currently linked to multiple cellular pathways. Autophagy maintains cellular homeostasis by removing damaged organelles and macromolecules. Although the autophagy kinase ULK1 drives autophagy, the underlying mechanisms are still being unraveled and few ULK1 substrates have been identified to date. Here, we identify that loss of FLCN moderately impairs basal autophagic flux, while re-expression of FLCN rescues autophagy. We reveal that the FLCN complex is regulated by ULK1 and elucidate 3 novel phosphorylation sites (Ser406, Ser537, and Ser542) within FLCN, which are induced by ULK1 overexpression. In addition, our findings demonstrate that FLCN interacts with a second integral component of the autophagy machinery, GABA(A) receptor-associated protein (GABARAP). The FLCN-GABARAP association is modulated by the presence of either folliculin-interacting protein (FNIP)-1 or FNIP2 and further regulated by ULK1. As observed by elevation of GABARAP, sequestome 1 (SQSTM1) and microtubule-associated protein 1 light chain 3 (MAP1LC3B) in chromophobe and clear cell tumors from a BHD patient, we found that autophagy is impaired in BHD-associated renal tumors. Consequently, this work reveals a novel facet of autophagy regulation by ULK1 and substantially contributes to our understanding of FLCN function by linking it directly to autophagy through GABARAP and ULK1.

Kuroda N, Furuya M, Nagashima Y, et al.
Review of renal tumors associated with Birt-Hogg-Dubé syndrome with focus on clinical and pathobiological aspects.
Pol J Pathol. 2014; 65(2):93-9 [PubMed] Related Publications
Birt-Hogg-Dubé syndrome (BHDS) is an autosomal dominant inherited disorder characterized by clinical features of skin lesions, pulmonary lesions and renal tumor. The gene responsible for this syndrome is located on chromosome 17p11.2 and designated as FLCN. In this article, we review renal tumors associated with BHDS with a focus on clinical and pathobiological aspects. Renal tumors often occur multifocally or bilaterally in the imaging analyses or gross examination. Histological examination of renal tumors includes a variety of subtypes such as hybrid oncocytic tumor, chromophobe renal cell carcinoma (RCC), oncocytoma, clear cell RCC and papillary RCC. The histologic discordance in multiple tumors seems to be characteristic of this syndrome. Oncocytosis is observed histologically in about half of the cases. Several investigations have elucidated that folliculin may be involved in the mammalian target of rapamycin (mTOR) pathway recently. Renal tumors composed of clear cells may behave in an aggressive fashion. However, renal tumors including hybrid oncocytic tumor, chromophobe RCC and oncocytoma behave mostly in an indolent fashion.

Ramzi NH, Chahil JK, Lye SH, et al.
Role of genetic & environment risk factors in the aetiology of colorectal cancer in Malaysia.
Indian J Med Res. 2014; 139(6):873-82 [PubMed] Free Access to Full Article Related Publications
BACKGROUND & OBJECTIVES: Colorectal cancer (CRC) is second only to breast cancer as the leading cause of cancer-related deaths in Malaysia. In the Asia-Pacific area, it is the highest emerging gastrointestinal cancer. The aim of this study was to identify single nucleotide polymorphisms (SNPs) and environmental factors associated with CRC risk in Malaysia from a panel of cancer associated SNPs.
METHODS: In this case-control study, 160 Malaysian subjects were recruited, including both with CRC and controls. A total of 768 SNPs were genotyped and analyzed to distinguish risk and protective alleles. Genotyping was carried out using Illumina's BeadArray platform. Information on blood group, occupation, medical history, family history of cancer, intake of red meat and vegetables, exposure to radiation, smoking and drinking habits, etc was collected. Odds ratio (OR), 95% confidence interval (CI) were calculated.
RESULTS: A panel of 23 SNPs significantly associated with colorectal cancer risk was identified (P<0.01). Of these, 12 SNPs increased the risk of CRC and 11 reduced the risk. Among the environmental risk factors investigated, high intake of red meat (more than 50% daily proportion) was found to be significantly associated with increased risk of CRC (OR=6.52, 95% CI :1.93-2.04, P=0.003). Two SNPs including rs2069521 and rs10046 in genes of cytochrome P450 (CYP) superfamily were found significantly associated with CRC risk. For gene-environment analysis, the A allele of rs2069521 showed a significant association with CRC risk when stratified by red meat intake.
INTERPRETATION & CONCLUSIONS: In this preliminary study, a panel of SNPs found to be significantly associated with CRC in Malaysian population, was identified. Also, red meat consumption and lack of physical exercise were risk factors for CRC, while consumption of fruits and vegetables served as protective factor.

De Keyzer L, De Leenheer EM, Claes K, Janssens S
A vestibular schwannoma in a patient with Birt-Hogg-Dube syndrome.
Genet Couns. 2014; 25(2):203-8 [PubMed] Related Publications
Birt-Hogg Dubé syndrome is an autosomal dominant disease with variable clinical expression. It is characterized by cutaneous manifestations, renal tumors and lung cysts. Other tumors, such as adrenal tumors and tumors originating from the neural crest cells such as meningioma and neurothekeoma have also been described. This syndrome is caused by germline mutations in the folliculin (FLCN) gene located on chromosome 17p. We report, for the first time, a patient with BHDS and a history of a vestibular schwannoma in adolescence. The diagnosis of BHDS was confirmed, by identifying a nonsense mutation in exon 10 of the FLCN gene. A vestibular schwannoma also originates from neural crest cells, just as other neural tumors, previously encountered in patients with BHDS. The reported mutations cause a truncation of the protein, folliculin. The exact role of folliculin is still undetermined. Two different theories suggest the effect of tumorigenesis. One is that folliculin plays an important role in the AMPK-mTOR pathway which leads to proliferation of cells when activated. The other is that the folliculin acts as a possible tumor suppressor gene, since there is a high frequency of second hits in the FLCN-gene. In order to confirm a possible relation of BHDS and neural crest tumors, further research is necessary in the tumorigenesis of the folliculin gene.

Pritchard SE, Mahmoudizad R, Parekh PK
Successful treatment of facial papules with electrodessication in a patient with Birt-Hogg-Dubé syndrome.
Dermatol Online J. 2014; 20(7) [PubMed] Related Publications
We report a case of a 51-year-old Hispanic female who presented with a several year history of multiple flesh colored papules of cosmetic concern on the nose and medial cheeks. Biopsies revealed fibrofolliculoma and trichodiscoma. The patient was referred for genetic testing and was found to be positive for the FLCN gene defect, confirming a diagnosis of Birt-Hogg-Dubé syndrome. Further work-up with screening renal ultrasound and CT scan of the thorax and abdomen was unrevealing. For treatment of these skin lesions, dermasanding was attempted initially with only minimal benefit. She subsequently had multiple lesions treated with electrodessication at a low setting and was very pleased with the results. Curettage was not performed and importantly, there has yet to be a recurrence of lesions treated with only hyfrecation.

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