Presence of Stromal Cells Enhances Epithelial-to-Mesenchymal Transition (EMT) Induction in Lung Bronchial Epithelium after Protracted Exposure to Oxidative Stress of Gamma Radiation.

The aim of the study was to investigate the role of a microenvironment in the induction of epithelial-to-mesenchymal transition (EMT) as a sign of early stages of carcinogenesis in human lung epithelial cell lines after protracted low-dose rate γ-radiation exposures. BEAS-2B and HBEC-3KT lung cell lines were irradiated with low-dose rate γ-rays (137Cs, 1.4 or 14 mGy/h) to 0.1 or 1 Gy with or without adding TGF-ß. TGF-ß-treated samples were applied as positive EMT controls and tested in parallel to find out if the radiation has a potentiating effect on the EMT induction. To evaluate the effect of the stromal component, the epithelial cells were irradiated in cocultures with stromal MRC-9 lung fibroblasts. On day 3 post treatment, the EMT markers: α-SMA, vimentin, fibronectin, and E-cadherin, were analyzed. The oxidative stress levels were evaluated by 8-oxo-dG analysis in both epithelial and fibroblast cells. The protracted exposure to low Linear Energy Transfer (LET) radiation at the total absorbed dose of 1 Gy was able to induce changes suggestive of EMT. The results show that the presence of the stromal component and its signaling (TGF-ß) in the cocultures enhances the EMT. Radiation had a minor cumulative effect on the TGF-ß-induced EMT with both doses. The oxidative stress levels were higher than the background in both epithelial and stromal cells post chronic irradiation (0.1 and 1 Gy); as for the BEAS-2B cell line, the increase was statistically significant. We suggest that the induction of EMT in bronchial epithelial cells by radiation requires more than single acute exposure and the presence of stromal component might enhance the effect through free radical production and accumulation.

A laboratory inter-comparison of the importance of serum serotonin levels in the measurement of a range of radiation-induced bystander effects: overview of study and results presentation.

PURPOSE: Recent research has suggested that serotonin may play an important role in the expression of radiation-induced bystander effects. Serotonin levels in serum were reported to range from 6-22 µM and to correlate inversely with the magnitude of cellular colony-forming ability in medium transfer bystander assays. That is, high serotonin concentration correlated with a low cloning efficiency in cultures receiving medium derived from irradiated cells. METHODS: Because of the potential importance of this observation, the European Union's Non-targeted Effects Integrated Project (NOTE) performed an inter-comparison exercise where serum samples with high and low serotonin levels were distributed to seven laboratories which then performed their own assay to determine the magnitude of the bystander effect. RESULTS: The results provided some support for a role for serotonin in four of the laboratories. Two saw no difference between the samples and one gave inconclusive results. In this summary paper, full data sets are presented from laboratories whose data was inconclusive or insufficient for a full paper. Other data are published in full in the special issue. CONCLUSION: The data suggest that there may be multiple bystander effects and that the underlying mechanisms may be modulated by both the culture conditions and the intrinsic properties of the cells used in the assay.

Analysis of a Finnish family confirms RHBDF2 mutations as the underlying factor in tylosis with esophageal cancer.

Tylosis with esophageal cancer (TOC) is a rare familial cancer syndrome inherited in an autosomal-dominant manner and characterized by esophageal cancer susceptibility and hyperkeratotic skin lesions. Two heterozygous missense mutations in the RHBDF2 gene were recently reported to be associated with TOC in three families: a p.Ile186Thr mutation was found in families from the UK and the US and a p.Pro189Leu mutation was detected in a German TOC family. We aimed to validate these novel results in an independent material by screening RHBDF2 in a previously unreported Finnish TOC family. We identified a new missense mutation, p.Asp188Asn, segregating with TOC in the Finnish family, and interestingly the detected mutation alters a codon located between the two previously reported mutation sites. Thus, we confirmed RHBDF2 mutations as the underlying cause of the TOC syndrome and our results suggest that the TOC associated mutations might be specific for this particular site in the RHBDF2 gene. These results enable the genetic counseling and diagnostic mutation screening of the members of TOC families.

MED12, the mediator complex subunit 12 gene, is mutated at high frequency in uterine leiomyomas.

Uterine leiomyomas, or fibroids, are benign tumors that affect millions of women worldwide and that can cause considerable morbidity. To study the genetic basis of this tumor type, we examined 18 uterine leiomyomas derived from 17 different patients by exome sequencing and identified tumor-specific mutations in the mediator complex subunit 12 (MED12) gene in 10. Through analysis of 207 additional tumors, we determined that MED12 is altered in 70% (159 of 225) of tumors from a total of 80 patients. The Mediator complex is a 26-subunit transcriptional regulator that bridges DNA regulatory sequences to the RNA polymerase II initiation complex. All mutations resided in exon 2, suggesting that aberrant function of this region of MED12 contributes to tumorigenesis.

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

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

Exome sequencing reveals germline NPAT mutation as a candidate risk factor for Hodgkin lymphoma.

A strong clustering of Hodgkin lymphoma in certain families has been long acknowledged. However, the genetic factors in the background of familial Hodgkin lymphoma are largely unknown. We have studied a family of 4 cousins with a rare subtype of the disease, nodular lymphocyte predominant Hodgkin lymphoma. We applied exome sequencing together with genome-wide linkage analysis to this family and identified a truncating germline mutation in nuclear protein, ataxia-telangiectasia locus (NPAT) gene, which segregated in the family. We also studied a large number of samples from other patients with Hodgkin lymphoma, and a germline variation leading to the deletion of serine 724 was found in several cases suggesting an elevated risk for the disease (odds ratio = 4.11; P = .018). NPAT is thus far the first gene implicated in nodular lymphocyte predominant Hodgkin lymphoma predisposition.

Expression profiling in progressive stages of fumarate-hydratase deficiency: the contribution of metabolic changes to tumorigenesis.

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is caused by mutations in the Krebs cycle enzyme fumarate hydratase (FH). It has been proposed that "pseudohypoxic" stabilization of hypoxia-inducible factor-α (HIF-α) by fumarate accumulation contributes to tumorigenesis in HLRCC. We hypothesized that an additional direct consequence of FH deficiency is the establishment of a biosynthetic milieu. To investigate this hypothesis, we isolated primary mouse embryonic fibroblast (MEF) lines from Fh1-deficient mice. As predicted, these MEFs upregulated Hif-1α and HIF target genes directly as a result of FH deficiency. In addition, detailed metabolic assessment of these MEFs confirmed their dependence on glycolysis, and an elevated rate of lactate efflux, associated with the upregulation of glycolytic enzymes known to be associated with tumorigenesis. Correspondingly, Fh1-deficient benign murine renal cysts and an advanced human HLRCC-related renal cell carcinoma manifested a prominent and progressive increase in the expression of HIF-α target genes and in genes known to be relevant to tumorigenesis and metastasis. In accord with our hypothesis, in a variety of different FH-deficient tissues, including a novel murine model of Fh1-deficient smooth muscle, we show a striking and progressive upregulation of a tumorigenic metabolic profile, as manifested by increased PKM2 and LDHA protein. Based on the models assessed herein, we infer that that FH deficiency compels cells to adopt an early, reversible, and progressive protumorigenic metabolic milieu that is reminiscent of that driving the Warburg effect. Targets identified in these novel and diverse FH-deficient models represent excellent potential candidates for further mechanistic investigation and therapeutic metabolic manipulation in tumors.

Mutations in the circadian gene CLOCK in colorectal cancer.

The circadian clock regulates daily variations in physiologic processes. CLOCK acts as a regulator in the circadian apparatus controlling the expression of other clock genes, including PER1. Clock genes have been implicated in cancer-related functions; in this work, we investigated CLOCK as a possible target of somatic mutations in microsatellite unstable colorectal cancers. Combining microarray gene expression data and public gene sequence information, we identified CLOCK as 1 of 790 putative novel microsatellite instability (MSI) target genes. A total of 101 MSI colorectal carcinomas (CRC) were sequenced for a coding microsatellite in CLOCK. The effect of restoring CLOCK expression was studied in LS180 cells lacking wild-type CLOCK by stably expressing GST-CLOCK or glutathione S-transferase empty vector and testing the effects of UV-induced apoptosis and radiation by DNA content analysis using flow cytometry. Putative novel CLOCK target genes were searched by using ChIP-seq. CLOCK mutations occurred in 53% of MSI CRCs. Restoring CLOCK expression in cells with biallelic CLOCK inactivation resulted in protection against UV-induced apoptosis and decreased G(2)-M arrest in response to ionizing radiation. Using ChIP-Seq, novel CLOCK-binding elements were identified near DNA damage genes p21, NBR1, BRCA1, and RAD50. CLOCK is shown to be mutated in cancer, and altered response to DNA damage provides one plausible mechanism of tumorigenesis.

No evidence for a genetic modifier for renal cell cancer risk in HLRCC syndrome.

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a tumor predisposition syndrome caused by heterozygous germline mutations in the fumarate hydratase (FH) gene. Cutaneous and uterine leiomyomas are the most common clinical manifestations of HLRCC, whereas only approximately 20% of the families display renal cell cancer (RCC). The number of RCC cases in these families varies from one to five. Interestingly, families with multiple RCC cases are mainly found in Finland and the USA. Such aggregation of RCC in only some families and populations has led to the hypothesis that besides FH mutations also other inherited genetic and/or environmental factors may contribute to the malignant kidney tumor formation. To search for such a genetic modifier we have performed a genome-wide linkage analysis in two and an identical by descent analysis in four Finnish HLRCC families with several RCC patients. Additional Finnish and French families were used in fine-mapping and haplotype analyses. The only region compatible with linkage was the locus surrounding the FH gene itself in chromosome 1q43. The genes in the putative candidate region were screened, but no potentially pathogenic alterations were observed. Although these data do not rule out the existence of a genetic modifier, they emphasize the contribution of the FH genotype in HLRCC related RCC. Therefore, as all FH mutation carriers may have an increased risk for developing renal cancer, counseling and genetic testing should be offered for all HLRCC family members and clinical follow-up should be organized for the mutation carriers.

The expression of AIP-related molecules in elucidation of cellular pathways in pituitary adenomas.

Germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene predispose to the development of pituitary adenomas. Here, we characterized AIP mutation positive (AIPmut+) and AIP mutation negative (AIPmut-) pituitary adenomas by immunohistochemistry. The expressions of the AIP-related proteins aryl hydrocarbon receptor (AHR), AHR nuclear translocator (ARNT), cyclin-dependent kinase inhibitor 1B encoding p27(Kip1), and hypoxia-inducible factor 1-alpha were examined in 14 AIPmut+ and 53 AIPmut- pituitary adenomas to detect possible expression differences. In addition, the expression of CD34, an endothelial and hematopoietic stem cell marker, was analyzed. We found ARNT to be less frequently expressed in AIPmut+ pituitary adenomas (P = 0.001), suggesting that AIP regulates the ARNT levels. AIP small interfering RNA-treated HeLa, HEK293, or Aip-null mouse embryonic fibroblast cells did not show lowered expression of ARNT. Instead, in the pituitary adenoma cell line GH3, Aip silencing caused a partial reduction of Arnt and a clear increase in cell proliferation. We also observed a trend for increased expression of nuclear AHR in AIPmut+ samples, although the difference was not statistically significant (P = 0.06). The expressions of p27(Kip1), hypoxia-inducible factor 1-alpha, or CD34 did not differ between tumor types. The present study shows that the expression of ARNT protein is significantly reduced in AIPmut+ tumors. We suggest that the down-regulation of ARNT may be connected to an imbalance in AHR/ARNT complex formation arising from aberrant cAMP signaling.

Array comparative genomic hybridization identifies a distinct DNA copy number profile in renal cell cancer associated with hereditary leiomyomatosis and renal cell cancer.

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a tumor predisposition syndrome with cutaneous and uterine leiomyomatosis as well as renal cell cancer (RCC) as its clinical manifestations. HLRCC is caused by heterozygous germline mutations in the fumarate hydratase (fumarase) gene. In this study, we used array comparative genomic hybridization to identify the specific copy number changes characterizing the HLRCC-associated RCCs. The study material comprised formalin-fixed paraffin-embedded renal tumors obtained from Finnish patients with HLRCC. All 11 investigated tumors displayed the papillary type 2 histopathology typical for HLRCC renal tumors. The most frequent copy number changes detected in at least 3/11 (27%) of the tumors were gains in chromosomes 2, 7, and 17, and losses in 13q12.3-q21.1, 14, 18, and X. These findings provide genetic evidence for a distinct copy number profile in HLRCC renal tumors compared with sporadic RCC tumors of the same histopathological subtype, and delineate chromosomal regions that associate with this very aggressive form of RCC.

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

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

Unregulated smooth-muscle myosin in human intestinal neoplasia.

A recent study described a recessive ATPase activating germ-line mutation in smooth-muscle myosin (smmhc/myh11) underlying the zebrafish meltdown (mlt) phenotype. The mlt zebrafish develops intestinal abnormalities reminiscent of human Peutz-Jeghers syndrome (PJS) and juvenile polyposis (JP). To examine the role of MYH11 in human intestinal neoplasia, we searched for MYH11 mutations in patients with colorectal cancer (CRC), PJS and JP. We found somatic protein-elongating frameshift mutations in 55% of CRCs displaying microsatellite instability and in the germ-line of one individual with PJS. Additionally, two somatic missense mutations were found in one microsatellite stable CRC. These two missense mutations, R501L and K1044N, and the frameshift mutations were functionally evaluated. All mutations resulted in unregulated molecules displaying constitutive motor activity, similar to the mutant myosin underlying mlt. Thus, MYH11 mutations appear to contribute also to human intestinal neoplasia. Unregulated MYH11 may affect the cellular energy balance or disturb cell lineage decisions in tumor progenitor cells. These data challenge our view on MYH11 as a passive differentiation marker functioning in muscle contraction and add to our understanding of intestinal neoplasia.

The FH mutation database: an online database of fumarate hydratase mutations involved in the MCUL (HLRCC) tumor syndrome and congenital fumarase deficiency.

BACKGROUND: Fumarate hydratase (HGNC approved gene symbol - FH), also known as fumarase, is an enzyme of the tricarboxylic acid (TCA) cycle, involved in fundamental cellular energy production. First described by Zinn et al in 1986, deficiency of FH results in early onset, severe encephalopathy. In 2002, the Multiple Leiomyoma Consortium identified heterozygous germline mutations of FH in patients with multiple cutaneous and uterine leiomyomas, (MCUL: OMIM 150800). In some families renal cell cancer also forms a component of the complex and as such has been described as hereditary leiomyomatosis and renal cell cancer (HLRCC: OMIM 605839). The identification of FH as a tumor suppressor was an unexpected finding and following the identification of subunits of succinate dehydrogenase in 2000 and 2001, was only the second description of the involvement of an enzyme of intermediary metabolism in tumorigenesis. DESCRIPTION: The FH mutation database is a part of the TCA cycle gene mutation database (formerly the succinate dehydrogenase gene mutation database) and is based on the Leiden Open (source) Variation Database (LOVD) system. The variants included in the database were derived from the published literature and annotated to conform to current mutation nomenclature. The FH database applies HGVS nomenclature guidelines, and will assist researchers in applying these guidelines when directly submitting new sequence variants online. Since the first molecular characterization of an FH mutation by Bourgeron et al in 1994, a series of reports of both FH deficiency patients and patients with MCUL/HLRRC have described 107 variants, of which 93 are thought to be pathogenic. The most common type of mutation is missense (57%), followed by frameshifts & nonsense (27%), and diverse deletions, insertions and duplications. Here we introduce an online database detailing all reported FH sequence variants. CONCLUSION: The FH mutation database strives to systematically unify all current genetic knowledge of FH variants. We believe that this knowledge will assist clinical geneticists and treating physicians when advising patients and their families, will provide a rapid and convenient resource for research scientists, and may eventually assist in gaining novel insights into FH and its related clinical syndromes.

Increased HIF1 alpha in SDH and FH deficient tumors does not cause microsatellite instability.

Germline mutations in nuclear genes encoding mitochondrial enzymes fumarate hydratase (FH) and succinate dehydrogenase (subunits SDHB/C/D) have been implicated in the development of tumor syndromes referred to as hereditary leiomyomatosis and renal cell cancer (HLRCC) and hereditary paragangliomatosis (HPGL), respectively. FH and SDH are operating in the tricarboxylic acid cycle (the TCA cycle, the Krebs cycle). In the FH and SDH deficient tumors, accumulation of the substrates, fumarate and succinate, has been shown to cause stabilization of hypoxia inducible factor 1 alpha (HIF1 alpha). According to recent studies, HIF1 alpha could contribute to the hypoxia induced genomic instability seen in many cancers, through repression of mismatch repair (MMR) protein MSH2. In this study, in agreement with previous works, we found HIF1 alpha to be moderately or highly stabilized in 67% (16/24) and 77% (48/62) of HLRCC tumors and SDHB/C/D paragangliomas (PGL) and pheochromocytomas (PHEO), respectively. In addition, a set of 54 other familial and nonfamilial PGLs/PHEOs were studied. Moderately or highly stabilized HIF1 alpha was present in 68% (26/38) of the PGLs but in PHEOs (n = 16) no such pattern was observed. We then analyzed the suggested link between HIF1 alpha stabilization and MSH2 repression, in HLRCC and HPGL tumor material. No microsatellite instability (MSI) or lack of MSH2 expression was, however, observed. Thus we failed to provide in vivo evidence for the proposed link between HIF1 alpha stabilization and functional MMR deficiency, in TCAC deficient tumors.

Germline CDKN1B/p27Kip1 mutation in multiple endocrine neoplasia.

CONTEXT: Germline mutations in the MEN1 gene predispose to multiple endocrine neoplasia type 1 (MEN1) syndrome, but in up to 20-25% of clinical MEN1 cases, no MEN1 mutations can be found. Recently, a germline mutation in the CDKN1B gene, encoding p27(Kip1), was reported in one suspected MEN1 family with two acromegalic patients. OBJECTIVE: Our objective was to evaluate the role of CDKN1B/p27(Kip1) in human tumor predisposition in patients clinically suspected of MEN1 but testing negative for MEN1 germline mutation as well as in familial and sporadic acromegaly/pituitary adenoma patients. DESIGN: Genomic DNA was analyzed for germline mutations in the CDKN1B/p27(Kip1) gene by PCR amplification and direct sequencing. SETTING: The study was conducted at nonprofit academic research and medical centers. PATIENTS: Thirty-six Dutch and one German suspected MEN1 patient, who previously tested negative for germline MEN1 gene mutations, were analyzed. In addition, 19 familial and 50 sporadic acromegaly/pituitary adenoma patients from Europe and the United States were included in the study. MAIN OUTCOME MEASURES: We analyzed germline CDKN1B/p27(Kip1) mutations in individuals with pituitary adenoma and MEN1-like features. RESULTS: A heterozygous 19-bp duplication (c.59_77dup19) leading to a truncated protein product was identified in one Dutch patient with suspected MEN1 phenotype, pituitary adenoma, carcinoid tumor, and hyperparathyroidism (one of 36, 2.8%). No mutations were detected in either familial or sporadic acromegaly/pituitary adenoma patients. CONCLUSIONS: Our results support the previous finding that germline CDKN1B/p27(Kip1) mutations predispose to a human MEN1-like condition. However, such mutations appear uncommon in suspected MEN1 cases and rare or nonexistent in familial or sporadic acromegaly/pituitary adenoma patients.

Molecular diagnosis of pituitary adenoma predisposition caused by aryl hydrocarbon receptor-interacting protein gene mutations.

Pituitary adenomas are common neoplasms of the anterior pituitary gland. Germ-line mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene cause pituitary adenoma predisposition (PAP), a recent discovery based on genetic studies in Northern Finland. In this population, a founder mutation explained a significant proportion of all acromegaly cases. Typically, PAP patients were of a young age at diagnosis but did not display a strong family history of pituitary adenomas. To evaluate the role of AIP in pituitary adenoma susceptibility in other populations and to gain insight into patient selection for molecular screening of the condition, we investigated the possible contribution of AIP mutations in pituitary tumorigenesis in patients from Europe and the United States. A total of 460 patients were investigated by AIP sequencing: young acromegaly patients, unselected acromegaly patients, unselected pituitary adenoma patients, and endocrine neoplasia-predisposition patients who were negative for MEN1 mutations. Nine AIP mutations were identified. Because many of the patients displayed no family history of pituitary adenomas, detection of the condition appears challenging. Feasibility of AIP immunohistochemistry (IHC) as a prescreening tool was tested in 50 adenomas: 12 AIP mutation-positive versus 38 mutation-negative pituitary tumors. AIP IHC staining levels proved to be a useful predictor of AIP status, with 75% sensitivity and 95% specificity for germ-line mutations. AIP contributes to PAP in all studied populations. AIP IHC, followed by genetic counseling and possible AIP mutation analysis in IHC-negative cases, a procedure similar to the diagnostics of the Lynch syndrome, appears feasible in identification of PAP.

Conventional renal cancer in a patient with fumarate hydratase mutation.

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

Pituitary adenoma predisposition caused by germline mutations in the AIP gene.

Pituitary adenomas are common in the general population, and understanding their molecular basis is of great interest. Combining chip-based technologies with genealogy data, we identified germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene in individuals with pituitary adenoma predisposition (PAP). AIP acts in cytoplasmic retention of the latent form of the aryl hydrocarbon receptor and also has other functions. In a population-based series from Northern Finland, two AIP mutations account for 16% of all patients diagnosed with pituitary adenomas secreting growth hormone and for 40% of the subset of patients who were diagnosed when they were younger than 35 years of age. Typically, PAP patients do not display a strong family history of pituitary adenoma; thus, AIP is an example of a low-penetrance tumor susceptibility gene.