New Pathogenic Germline Variants in Very Early Onset and Familial Colorectal Cancer Patients.

A genetic diagnosis facilitates personalized cancer treatment and clinical care of relatives at risk, however, although 25% of colorectal cancer cases are familial, around 95% of the families are genetically unresolved. In this study, we performed gene panel analysis on germline DNA of 32 established or candidate colorectal cancer predisposing genes in 149 individuals from either families with an accumulation of colorectal cancers or families with only one sporadic case of very early onset colorectal cancer (≤40 years at diagnosis). We identified pathogenic or likely pathogenic genetic variants in 10.1% of the participants in genes such as APC, POLE, MSH2 or PMS2. The MSH2 variant, c.2168C>T, p.(Ser723Phe) was previously described as a variant of unknown significance, but we have now reclassified it to be likely pathogenic. The POLE variant, c.1089C>A, p.(Asn363Lys) was identified in a patient with three metachronous colorectal cancers from age 28 and turned out to be de novo. One pathogenic PMS2 variant was novel. We also identified a number of highly interesting variants of unknown significance in APC, BUB1, TP53 and RPS20. The RPS20 variant is novel and was found in a large Amsterdam I positive family with a multi tumor phenotype including 12 cases of CRC from as early as age 24. This variant was found to segregate with cancer in the family and multiple in silico tools predict it to be pathogenic. Our data further support the shift from phenotypic-based cancer panels to large panels including all established genes involved in hereditary cancer syndromes or (targeted) whole genome sequencing. Additionally, identification of a likely disease-predisposing variant in RPS20 expands the phenotypic spectrum of RPS20-related cancers and emphasize that this gene is relevant to include in colorectal cancer gene panels.

Pannexin-2-deficiency sensitizes pancreatic ß-cells to cytokine-induced apoptosis in vitro and impairs glucose tolerance in vivo.

Pannexins (Panx's) are membrane proteins involved in a variety of biological processes, including cell death signaling and immune functions. The role and functions of Panx's in pancreatic ß-cells remain to be clarified. Here, we show Panx1 and Panx2 expression in isolated islets, primary ß-cells, and ß-cell lines. The expression of Panx2, but not Panx1, was downregulated by interleukin-1ß (IL-1ß) plus interferon-γ (IFNγ), two pro-inflammatory cytokines suggested to contribute to ß-cell demise in type 1 diabetes (T1D). siRNA-mediated knockdown (KD) of Panx2 aggravated cytokine-induced apoptosis in rat INS-1E cells and primary rat ß-cells, suggesting anti-apoptotic properties of Panx2. An anti-apoptotic function of Panx2 was confirmed in isolated islets from Panx2-/- mice and in human EndoC-ßH1 cells. Panx2 KD was associated with increased cytokine-induced activation of STAT3 and higher expression of inducible nitric oxide synthase (iNOS). Glucose-stimulated insulin release was impaired in Panx2-/- islets, and Panx2-/- mice subjected to multiple low-dose Streptozotocin (MLDS) treatment, a model of T1D, developed more severe diabetes compared to wild type mice. These data suggest that Panx2 is an important regulator of the insulin secretory capacity and apoptosis in pancreatic ß-cells.

CTSH regulates ß-cell function and disease progression in newly diagnosed type 1 diabetes patients.

Over 40 susceptibility loci have been identified for type 1 diabetes (T1D). Little is known about how these variants modify disease risk and progression. Here, we combined in vitro and in vivo experiments with clinical studies to determine how genetic variation of the candidate gene cathepsin H (CTSH) affects disease mechanisms and progression in T1D. The T allele of rs3825932 was associated with lower CTSH expression in human lymphoblastoid cell lines and pancreatic tissue. Proinflammatory cytokines decreased the expression of CTSH in human islets and primary rat ß-cells, and overexpression of CTSH protected insulin-secreting cells against cytokine-induced apoptosis. Mechanistic studies indicated that CTSH exerts its antiapoptotic effects through decreased JNK and p38 signaling and reduced expression of the proapoptotic factors Bim, DP5, and c-Myc. CTSH overexpression also up-regulated Ins2 expression and increased insulin secretion. Additionally, islets from Ctsh(-/-) mice contained less insulin than islets from WT mice. Importantly, the TT genotype was associated with higher daily insulin dose and faster disease progression in newly diagnosed T1D patients, indicating agreement between the experimental and clinical data. In line with these observations, healthy human subjects carrying the T allele have lower ß-cell function, which was evaluated by glucose tolerance testing. The data provide strong evidence that CTSH is an important regulator of ß-cell function during progression of T1D and reinforce the concept that candidate genes for T1D may affect disease progression by modulating survival and function of pancreatic ß-cells, the target cells of the autoimmune assault.

Identification of novel type 1 diabetes candidate genes by integrating genome-wide association data, protein-protein interactions, and human pancreatic islet gene expression.

Genome-wide association studies (GWAS) have heralded a new era in susceptibility locus discovery in complex diseases. For type 1 diabetes, >40 susceptibility loci have been discovered. However, GWAS do not inevitably lead to identification of the gene or genes in a given locus associated with disease, and they do not typically inform the broader context in which the disease genes operate. Here, we integrated type 1 diabetes GWAS data with protein-protein interactions to construct biological networks of relevance for disease. A total of 17 networks were identified. To prioritize and substantiate these networks, we performed expressional profiling in human pancreatic islets exposed to proinflammatory cytokines. Three networks were significantly enriched for cytokine-regulated genes and, thus, likely to play an important role for type 1 diabetes in pancreatic islets. Eight of the regulated genes (CD83, IFNGR1, IL17RD, TRAF3IP2, IL27RA, PLCG2, MYO1B, and CXCR7) in these networks also harbored single nucleotide polymorphisms nominally associated with type 1 diabetes. Finally, the expression and cytokine regulation of these new candidate genes were confirmed in insulin-secreting INS-1 ß-cells. Our results provide novel insight to the mechanisms behind type 1 diabetes pathogenesis and, thus, may provide the basis for the design of novel treatment strategies.

IL-1 receptor antagonism and muscle gene expression in patients with type 2 diabetes.

BACKGROUND: We have previously reported that systemic blockade of IL-1beta in patients with type 2 diabetes with anakinra (a recombinant human interleukin-1-receptor antagonist, IL-1Ra), lowered glycated hemoglobin improved beta-cell function and reduced circulating levels of IL-6 and CRP (7). To investigate the effects of IL-1Ra in insulin-sensitive tissue, gene expression levels in skeletal muscle from type 2 diabetic patients treated with IL-1Ra were analysed. METHODS: Gene expression profiles in vastus lateralis muscle biopsies from five obese patients (BMI >27) were determined before and after 13 weeks of treatment with IL-1Ra (anakinra) using Affymetrix U133Plus2.0 GeneChips. Microarray data were normalized and analysed independently using four different algorithms; RMA, GCRMA, dChip and GCOS. Hypothesis tests were applied to the microarray data for each gene, and protein network analysis was used to identify biological networks/pathways affected by the treatment. Gene expression levels for candidate genes (COL1A1, CDKN1C, HSP70, HLA-A, IL-1 and IL-6) were determined by qRT-PCR in muscles of placebo- (n = 12) and anakinra-treated patients (n = 11). RESULTS: The concordance of the variations of the transcripts identified as significantly regulated after IL-1Ra treatment was low. No significantly altered expression levels could be demonstrated after false discovery rate correction. The protein interaction network did not reveal any altered networks/pathways. None of the candidate genes, quantified by qRT-PCR, were significantly altered when comparing the number of transcripts before and after treatment for each individual. conclusion: Treatment with IL-1Ra did not significantly affect gene expression levels in skeletal muscle in this limited and selected sample of obese patients with type 2 diabetes. Larger studies might confirm the lack of effect of anakinra on muscle tissue gene expression.

Cytokines and beta-cell biology: from concept to clinical translation.

The tale of cytokines and the beta-cell is a long story, starting with in vitro discovery in 1984, evolving via descriptive and phenomenological studies to detailed mapping of the signalling pathways, gene- and protein expression patterns, molecular and biochemical effector mechanisms to in vivo studies in spontaneously diabetic and transgenic animal models. Only very recently have steps been taken to translate the accumulating compelling preclinical data into clinical trials. The aim of this chapter is to present an overview of early and recent key observations from our own groups as well as other laboratories that serve to illuminate the road from concept to clinical translation.