Valérie Schumacher

Frequency and Spectrum of Cancers in the Peutz-Jeghers Syndrome

Background: Although an increased cancer risk in Peutz-Jeghers syndrome is established, data on the spectrum of tumors associated with the disease and the influence of germ-line STK11/LKB1 (serine/threonine kinase) mutation status are limited. Experimental Design: We analyzed the incidence of cancer in 419 individuals with Peutz-Jeghers syndrome, and 297 had documented STK11/LKB1 mutations. Results: Ninety-six cancers were found among individuals with Peutz-Jeghers syndrome. The risk for developing cancer at ages 20, 30, 40, 50, 60, and 70 years was 2%, 5%, 17%, 31%, 60%, and 85%, respectively. The most common cancers represented in this analysis were gastrointestinal in origin, gastroesophageal, small bowel, colorectal, and pancreatic, and the risk for these cancers at ages 30, 40, 50, and 60 years was 1%, 9%, 15%, and 33%, respectively. In women with Peutz-Jeghers syndrome, the risk of breast cancer was substantially increased, being 8% and 31% at ages 40 and 60 years, respectively. Kaplan-Meier analysis showed that cancer risks were similar in Peutz-Jeghers syndrome patients with identified STK11/LKB1 mutations and those with no detectable mutation (log-rank test of difference χ2 = 0.62; 1 df; P = 0.43). Furthermore, the type or site of STK11/LKB1 mutation did not significantly influence cancer risk. Conclusions: The results from our study provide quantitative information on the spectrum of cancers and risks of specific cancer types associated with Peutz-Jeghers syndrome.

Twenty-four new cases of WT1 germline mutations and review of the literature: Genotype/phenotype correlations for Wilms tumor development

We report here 24 new Wilms tumor (WT) patients with germline WT1 alterations and a synopsis of our own previously described and literature cases in whom age of tumor‐onset, gender, and laterality were known. This combined database contains 282 patients, 117 patients with and 165 without WT1 germline alterations. Using this information we have determined the median age of tumor‐onset for patients with (12.5 months) and without WT1 gene alterations (36 months). The earliest onset was in patients with truncation (12 mo, 66 patients), followed by missense mutations (18 mo, 30 patients) and deletions (22 mo, 21 patients). Patients with the two most frequent nonsense mutations R362X and R390X and the Denys–Drash syndrome (DDS) hot spot mutation R394W/Q/L had a very early onset (9, 12, and 18 mo, respectively). The highest number of bilateral tumors was observed in the group of truncation mutations, with a higher percentage of bilateral tumors when truncations occurred in the 5′ half of the WT1 gene. In addition to genital tract anomalies (GU), early onset nephrotic syndrome with diffuse mesangial sclerosis and stromal‐predominant histology, tumor bilaterality, and early age of onset can now be added to the list of risk factors for carrying a germline WT1 mutation.

Copy Number Variation in Patients with Disorders of Sex Development Due to 46,XY Gonadal Dysgenesis

Disorders of sex development (DSD), ranging in severity from mild genital abnormalities to complete sex reversal, represent a major concern for patients and their families. DSD are often due to disruption of the genetic programs that regulate gonad development. Although some genes have been identified in these developmental pathways, the causative mutations have not been identified in more than 50% 46,XY DSD cases. We used the Affymetrix Genome-Wide Human SNP Array 6.0 to analyse copy number variation in 23 individuals with unexplained 46,XY DSD due to gonadal dysgenesis (GD). Here we describe three discrete changes in copy number that are the likely cause of the GD. Firstly, we identified a large duplication on the X chromosome that included DAX1 (NR0B1). Secondly, we identified a rearrangement that appears to affect a novel gonad-specific regulatory region in a known testis gene, SOX9. Surprisingly this patient lacked any signs of campomelic dysplasia, suggesting that the deletion affected expression of SOX9 only in the gonad. Functional analysis of potential SRY binding sites within this deleted region identified five putative enhancers, suggesting that sequences additional to the known SRY-binding TES enhancer influence human testis-specific SOX9 expression. Thirdly, we identified a small deletion immediately downstream of GATA4, supporting a role for GATA4 in gonad development in humans. These CNV analyses give new insights into the pathways involved in human gonad development and dysfunction, and suggest that rearrangements of non-coding sequences disturbing gene regulation may account for significant proportion of DSD cases.

Role of Podocyte B7-1 in Diabetic Nephropathy

Podocyte injury and resulting albuminuria are hallmarks of diabetic nephropathy, but targeted therapies to halt or prevent these complications are currently not available. Here, we show that the immune-related molecule B7-1/CD80 is a critical mediator of podocyte injury in type 2 diabetic nephropathy. We report the induction of podocyte B7-1 in kidney biopsy specimens from patients with type 2 diabetes. Genetic and epidemiologic studies revealed the association of two single nucleotide polymorphisms at the B7-1 gene with diabetic nephropathy. Furthermore, increased levels of the soluble isoform of the B7-1 ligand CD28 correlated with the progression to ESRD in individuals with type 2 diabetes. In vitro, high glucose conditions prompted the phosphatidylinositol 3 kinase-dependent upregulation of B7-1 in podocytes, and the ectopic expression of B7-1 in podocytes increased apoptosis and induced disruption of the cytoskeleton that were reversed by the B7-1 inhibitor CTLA4-Ig. Podocyte expression of B7-1 was also induced in vivo in two murine models of diabetic nephropathy, and treatment with CTLA4-Ig prevented increased urinary albumin excretion and improved kidney pathology in these animals. Taken together, these results identify B7-1 inhibition as a potential therapeutic strategy for the prevention or treatment of diabetic nephropathy.

STK11 genotyping and cancer risk in Peutz-Jeghers syndrome

Peutz-Jeghers syndrome (PJS; OMIM #175200) is an autosomal dominant disorder characterised by mucocutaneous melanin pigmentation, gastrointestinal hamartomatous polyposis, and an increased risk for the development of various neoplasms.1,2 Malignancies occur both in the gastrointestinal tract and in extraintestinal sites such as the pancreas, the breast, and reproductive organs. The estimated relative cancer risk may be 15 fold higher than in the general population1 and appears to be particularly high in women (20 fold) because of an increased risk of development of breast cancer and gynaecological malignancies.2 Germline mutations in the STK11/LKB1 gene on 19p13.3 are found in 30–70% of PJS cases, depending on the screening method, with considerable uncharacterised genetic heterogeneity remaining in this syndrome.3,4 The disease causing gene has been identified by two independent groups.5,6 Human STK11 encodes a serine/threonine protein kinase that is highly homologous to the mouse protein Lkb1 and the Xenopus kinase XEEK1,7,8 and is expressed in all human tissues.9 The kinase domain of the human 433 amino acid protein is localised between residues 49 and 309,7 and shows homology to the conserved catalytic core of the kinase domain common to both serine/threonine and tyrosine protein kinase family members.10 Most mutations found in PJS patients are small deletions/insertions or single base substitutions leading to an abnormal truncated/kinase inactive protein. Loss of the wild type allele in hamartomas and adenocarcinomas occurring in patients with PJS suggests that STK11 is a tumour suppressor gene. Several studies have described a role in cell cycle arrest,11 p53 mediated apoptosis,12 Wnt signalling,13,14 TGF-β signalling,15 Ras induced cell transformation,16 and cell polarity.17–20 Growth suppression requires phosphorylation of STK1121,22 and was found to be caused by activation of the CDK …

Reference Gene Validation for RT-qPCR, a Note on Different Available Software Packages

Background An appropriate normalization strategy is crucial for data analysis from real time reverse transcription polymerase chain reactions (RT-qPCR). It is widely supported to identify and validate stable reference genes, since no single biological gene is stably expressed between cell types or within cells under different conditions. Different algorithms exist to validate optimal reference genes for normalization. Applying human cells, we here compare the three main methods to the online available RefFinder tool that integrates these algorithms along with R-based software packages which include the NormFinder and GeNorm algorithms. Results 14 candidate reference genes were assessed by RT-qPCR in two sample sets, i.e. a set of samples of human testicular tissue containing carcinoma in situ (CIS), and a set of samples from the human adult Sertoli cell line (FS1) either cultured alone or in co-culture with the seminoma like cell line (TCam-2) or with equine bone marrow derived mesenchymal stem cells (eBM-MSC). Expression stabilities of the reference genes were evaluated using geNorm, NormFinder, and BestKeeper. Similar results were obtained by the three approaches for the most and least stably expressed genes. The R-based packages NormqPCR, SLqPCR and the NormFinder for R script gave identical gene rankings. Interestingly, different outputs were obtained between the original software packages and the RefFinder tool, which is based on raw Cq values for input. When the raw data were reanalysed assuming 100% efficiency for all genes, then the outputs of the original software packages were similar to the RefFinder software, indicating that RefFinder outputs may be biased because PCR efficiencies are not taken into account. Conclusions This report shows that assay efficiency is an important parameter for reference gene validation. New software tools that incorporate these algorithms should be carefully validated prior to use.

Extraintestinal polyps in Peutz-Jeghers syndrome: presentation of four cases and review of the literature

Abstract Peutz-Jeghers syndrome (PJS) is a rare hereditary disorder characterized by hamartomatous polyps in the gastrointestinal tract and typical pigment lesions. Extraintestinal polyps have rarely been reported. Possible sites include the respiratory tract, urogenital tract, and gallbladder. We here describe four cases of extraintestinal polyps in PJS patients and review the literature on the need for operative therapy of extraintestinal polyps in PJS. Three nonrelated patients were examined who had PJS and polyps in the gallbladder; the fourth patient had PJS and recurrent choanal polyps. Surgery has so far been performed only for symptomatic polyps: one laparoscopic cholecystectomy and removal of the choanal polyps for recurrent infections of the respiratory tract. The remaining two patients reported no symptoms from the extraintestinal polyps. No malignant transformation was found in these patients, nor has such been reported in the literature on PJS. The frequent observation of this manifestation in our patients raises the question of clinical management: Is prophylactic surgery indicated? Since malignant transformation of PJS polyps in the intestine is extremely rare we see no reason for operative therapy as long as the polyps are small and asymptomatic. Regular sonographic controls are recommended since the risk of malignant transformation cannot be ruled out at present.

Evidence for susceptibility genes to familial Wilms tumour in addition to WT1, FWT1 and FWT2

Three loci have been implicated in familial Wilms tumour: WT1 located on chromosome 11p13, FWT1 on 17q12-q21, and FWT2 on 19q13. Two out of 19 Wilms tumour families evaluated showed strong evidence against linkage at all three loci. Both of these families contained at least three cases of Wilms tumour indicating that they were highly likely to be due to genetic susceptibility and therefore that one or more additional familial Wilms tumour susceptibility genes remain to be found.

Gain-of-function mutations in transient receptor potential C6 (TRPC6) activate extracellular signal-regulated kinases 1/2 (ERK1/2).

Background: Signaling events affected by disease-associated mutations in TRPC6 are poorly defined. Results: Expression of mutant TRPC6 induces ERK1/2 activation via both cell-autonomous and non-cell-autonomous mechanisms. Conclusion: Mutant TRPC6 activates complex signaling pathways that lead to the release of paracrine factors activating ERK. Significance: Understanding the signaling pathways downstream of gain-of-function TRPC6 is crucial for understanding TRPC6-mediated biology and pathology. Gain-of-function mutations in the canonical transient receptor potential 6 (TRPC6) gene are a cause of autosomal dominant focal segmental glomerulosclerosis (FSGS). The mechanisms whereby abnormal TRPC6 activity results in proteinuria remain unknown. The ERK1/2 MAPKs are activated in glomeruli and podocytes in several proteinuric disease models. We therefore examined whether FSGS-associated mutations in TRPC6 result in activation of these kinases. In 293T cells and cultured podocytes, overexpression of gain-of-function TRPC6 mutants resulted in increased ERK1/2 phosphorylation, an effect dependent upon channel function. Pharmacologic inhibitor studies implicated several signaling mediators, including calmodulin and calcineurin, supporting the importance of TRPC6-mediated calcium influx in this process. Through medium transfer experiments, we uncovered two distinct mechanisms for ERK activation by mutant TRPC6, a cell-autonomous, EGF receptor-independent mechanism and a non-cell-autonomous mechanism involving metalloprotease-mediated release of a presumed EGF receptor ligand. The inhibitors KN-92 and H89 were able to block both pathways in mutant TRPC6 expressing cells as well as the prolonged elevation of intracellular calcium levels upon carbachol stimulation seen in these cells. However, these effects appear to be independent of their effects on calcium/calmodulin-dependent protein kinase II and PKA, respectively. Phosphorylation of Thr-70, Ser-282, and Tyr-31/285 were not necessary for ERK activation by mutant TRPC6, although a phosphomimetic TRPC6 S282E mutant was capable of ERK activation. Taken together, these results identify two pathways downstream of mutant TRPC6 leading to ERK activation that may play a role in the development of FSGS.

Clinical relevance of mutations in the Wilms tumor suppressor 1 gene WT1 and the cadherin‐associated protein β1 gene CTNNB1 for patients with Wilms tumors

Mutations in the Wilms tumor (WT) suppressor 1 gene (WT1) and the cadherin‐associated protein β1 gene (CTNNB1) are found predominantly in stromal type WT, defining a genetic subgroup. The clinical relevance of these mutations remains to be determined.