Macrophage-stimulating protein polymorphism rs3197999 is associated with a gain of function: implications for inflammatory bowel disease

Macrophage-Stimulating 1 Polymorphism rs3197999 in Pediatric Patients with Inflammatory Bowel Disease

Background and Objectives: Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), often necessitates long-term treatment and hospitalizations and also may require surgery. The macrophage-stimulating 1 (MST1) rs3197999 polymorphism is strongly associated with the risk of IBD but its exact clinical correlates remain under investigation. We aimed to characterize the relationships between the MST1 rs3197999 genotype and the clinical characteristics in children and adolescents with IBD within a multi-center cross-sectional study. Materials and Methods: Clinical data included serum C-reactive protein (CRP), albumin, activity indices (PUCAI, PCDAI), anthropometric data, pharmacotherapy details, surgery, and disease severity. Genotyping for rs3197999 was carried out using TaqMan hydrolysis probes. Results: The study included 367 pediatric patients, 197 with Crohn's disease (CD) (40.6% female; a median age of 15.2 years [interquartile range 13.2-17.0]) and 170 with ulcerative colitis (UC) (45.8% female; a median age of 15.1 years [11.6-16.8]). No significant relationships were found between MST1 genotypes and age upon first biologic use, time from diagnosis to biological therapy introduction, PUCAI, PCDAI, or hospitalizations for IBD flares. However, in IBD, the height Z-score at the worst flare was negatively associated with the CC genotype (p = 0.016; CC: -0.4 [-1.2-0.4], CT: -0.1 [-0.7-0.8], TT: 0.0 [-1.2-0.7)]). The TT genotype was associated with higher C-reactive protein upon diagnosis (p = 0.023; CC: 4.3 mg/dL [0.7-21.8], CT 5.3 mg/dL [1.3-17.9], TT 12.2 mg/dL [3.0-32.9]). Conclusions: This study identified links between MST1 rs3197999 and the clinical characteristics of pediatric IBD: height Z-score and CRP. Further studies of the associations between genetics and the course of IBD are still warranted, with a focus on more extensive phenotyping.

Macrophage-stimulating protein is decreased in severe preeclampsia and regulates the biological behavior of HTR-8/SVneo trophoblast cells

Preeclampsia (PE) is a major challenge for obstetricians. There is no effective way to block the development of PE other than terminating the pregnancy. The biological behavior of trophoblast cells, which are similar to cancer cells, may be closely related to the onset of PE. The vital role of macrophage-stimulating protein (MSP) in the development and progression of cancer has been recognized, while a role for this protein in PE has rarely been reported. This study aimed to explore whether MSP affects severe PE (sPE) and, if so, to characterize the mechanism. Patient information, blood samples and/or placental tissues were collected. An enzyme-linked immunosorbent assay (ELISA) was used to determine the plasma MSP concentration. The relationships between the plasma MSP concentration and clinical characteristics were analyzed. Immunofluorescence was performed to localize MSP in placental tissues. Western blotting and reverse transcription quantitative polymerase chain reaction (RT-qPCR) were used to determine MSP protein and mRNA expression in placental tissues. MSP was overexpressed or underexpressed in the trophoblastic cell line HTR-8/SVneo by lentiviral transfection and the proliferation, apoptosis, migration, invasion and angiogenesis of cells were detected. MSP was downregulated in sPE, and the underexpression of MSP inhibited HTR-8/SVneo cell proliferation, migration, invasion and angiogenesis. We further verified that MSP affects the biological behavior of trophoblast cells through the β-catenin/ZEB1 signaling pathway. These results suggest that decreased MSP in the blood and placental tissues of patients with sPE, especially those with early-onset sPE, leads to reduced trophoblast cell invasion, which plays an important role in the pathogenesis of PE.

High-Throughput Characterization of Blood Serum Proteomics of IBD Patients with Respect to Aging and Genetic Factors

To date, no large scale, systematic description of the blood serum proteome has been performed in inflammatory bowel disease (IBD) patients. By using microarray technology, a more complete description of the blood proteome of IBD patients is feasible. It may help to achieve a better understanding of the disease. We analyzed blood serum profiles of 1128 proteins in IBD patients of European descent (84 Crohn’s Disease (CD) subjects and 88 Ulcerative Colitis (UC) subjects) as well as 15 healthy control subjects, and linked protein variability to patient age (all cohorts) and genetic components (genotype data generated from CD patients). We discovered new, previously unreported aging-associated proteomic traits (such as serum Albumin level), confirmed previously reported results from different tissues (i.e., upregulation of APOE with aging), and found loss of regulation of MMP7 in CD patients. In carrying out a genome wide genotype-protein association study (proteomic Quantitative Trait Loci, pQTL) within the CD patients, we identified 41 distinct proteomic traits influenced by cis pQTLs (underlying SNPs are referred to as pSNPs). Significant overlaps between pQTLs and cis eQTLs corresponding to the same gene were observed and in some cases the QTL were related to inflammatory disease susceptibility. Importantly, we discovered that serum protein levels of MST1 (Macrophage Stimulating 1) were regulated by SNP rs3197999 (p = 5.96E-10, FDR<5%), an accepted GWAS locus for IBD. Filling the knowledge gap of molecular mechanisms between GWAS hits and disease susceptibility requires systematically dissecting the impact of the locus at the cell, mRNA expression, and protein levels. The technology and analysis tools that are now available for large-scale molecular studies can elucidate how alterations in the proteome driven by genetic polymorphisms cause or provide protection against disease. Herein, we demonstrated this directly by integrating proteomic and pQTLs with existing GWAS, mRNA expression, and eQTL datasets to provide insights into the biological processes underlying IBD and pinpoint causal genetic variants along with their downstream molecular consequences.

GWAS have resulted in greater than one hundred susceptibility loci for inflammatory bowel disease (Crohn’s Disease and Ulcerative Colitis). However, the molecular etiology of these diseases is not completely understood. In this study we profiled serum protein levels in IBD and control subjects and demonstrated an association of the levels of some proteins to Crohn’s Disease (CD) as well as aging. For the first time, we report proteomic QTLs (pQTLs) among CD patients, identifying proteomic traits corresponding to 41 distinct genes that were significantly influenced by SNP genotypes in cis. Particularly, we found that a well-known IBD risk locus on chromosome 3 is associated with significant changes of Macrophage Stimulating 1 (MST1) protein levels. As this result is consistent with MST1 eQTLs in liver and adipose tissues (but not whole blood), we believe that one possible mechanism of action of this genetic polymorphism alters expression and translation of MST1 in certain tissues (e.g. liver and adipose), which in turn results in changes of serum levels of the MST1 protein, and ultimately leading to increased risk of IBD.

The Immunogenetics of Autoimmune Cholestasis

The immune-mediated hepatobiliary diseases, primary biliary cirrhosis and primary sclerosing cholangitis are relatively rare, albeit and account for a significant amount of liver transplant activity and liver-related mortality globally. Precise disease mechanisms are yet to be described although a contributory role of genetic predisposition is firmly established. In addition to links with the major histocompatibility complex, a number of associations outside this region harbor additional loci which underscore the fundamental role of breaks in immune tolerance and mucosal immunogenicity in the pathogenesis of autoimmune biliary disease. We provide an overview of these key discoveries before discussing putative avenues of therapeutic exploitation based on existing findings.

Genetics in PSC: what do the "risk genes" teach us?

A role of genetics in primary sclerosing cholangitis (PSC) development is now firmly established. A total of 16 risk genes have been reported at highly robust ("genome-wide") significance levels, and ongoing efforts suggest that the list will ultimately be considerably longer. Importantly, this genetic risk pool so far accounts for less than 10 % of an estimated overall PSC susceptibility. The relative importance of genetic versus environmental factors (including gene-gene and gene-environment interactions) in remaining aspects of PSC pathogenesis is unknown, and other study designs than genome-wide association studies are needed to explore these aspects. For some of the loci, e.g. HLA and FUT2, distinct interacting environmental factors may exist, and working from the genetic associations may prove one valid path for determining the specific nature of environmental triggers. So far the biological implications for PSC risk genes are typically merely hypothesized based on previously published literature, and there is therefore a strong need for dedicated translational studies to determine their roles within the specific disease context of PSC. Apparently, most risk loci seem to involve in a subset of biological pathways for which genetic associations exist in a multitude of immune-mediated diseases, accounting for both inflammatory bowel disease as well as prototypical autoimmunity. In the present article, we will survey the current knowledge on PSC genetics with a particular emphasis on the pathophysiological insight potentially gained from genetic risk loci involving in this profound immunogenetic pleiotropy.

Inflammatory bowel disease (IBD) locus 12: is glutathione peroxidase-1 (GPX1) the relevant gene?

Genome-wide association studies have identified and repeatedly confirmed the association of rs3197999 in MST1 with inflammatory bowel disease (IBD). However, the underlying pathophysiology remains unclear. rs3197999 is a non-synonymous single-nucleotide polymorphism which modifies the function of macrophage stimulating protein-1 (MST1). We show by haplotyping that rs3197999 is in linkage disequilibrium with rs1050450 in GPX1, with almost complete cosegregation of the minor alleles. As shown by immunoassay, rs3197999 influences the MST-1 level in serum. But also rs1050450 causes an amino acid exchange in glutathione peroxidase 1 (GPx-1) and reduced activity of this antioxidant enzyme. The association of GPx deficiency and IBD in mice was already shown. We propose that GPx-1 is a better candidate than MST1 for the pathophysiologic link between IBD locus 12 and IBD.

Functional consequences of the macrophage stimulating protein 689C inflammatory bowel disease risk allele

Background

Macrophage stimulating protein (MSP) is a serum growth factor that binds to and activates the receptor tyrosine kinase, Recepteur d'Origine Nantais (RON). A non-synonymous coding variant in MSP (689C) has been associated with genetic susceptibility to both Crohn's disease and ulcerative colitis, two major types of inflammatory bowel disease (IBD) characterized by chronic inflammation of the digestive tract. We investigated the consequences of this polymorphism for MSP-RON pathway activity and IBD pathogenesis.

Methods

RON expression patterns were examined on mouse and human cells and tissues under normal and disease conditions to identify cell types regulated by MSP-RON. Recombinant MSP variants were tested for their ability to bind and stimulate RON and undergo proteolytic activation. MSP concentrations were quantified in the serum of individuals carrying the MSP 689R and 689C alleles.

Results

In intestinal tissue, RON was primarily expressed by epithelial cells under normal and disease conditions. The 689C polymorphism had no impact on the ability of MSP to bind to or signal through RON. In a cohort of normal individuals and IBD patients, carriers of the 689C polymorphism had lower concentrations of MSP in their serum.

Conclusions

By reducing the quantities of circulating MSP, the 689C polymorphism, or a variant in linkage disequilibrium with this polymorphism, may impact RON ligand availability and thus receptor activity. Given the known functions of RON in regulating wound healing and our analysis of RON expression patterns in human intestinal tissue, these data suggest that decreased RON activity may impact the efficiency of epithelial repair and thus underlie the increased IBD susceptibility associated with the MSP 689C allele.

From genetics of inflammatory bowel disease towards mechanistic insights

Advancements in human genetics now poise the field to illuminate the pathophysiology of complex genetic disease. In particular, genome-wide association studies (GWAS) have generated insights into the mechanisms driving inflammatory bowel disease (IBD) and implicated genes shared by multiple autoimmune and autoinflammatory diseases. Thus, emerging evidence suggests a central role for the mucosal immune system in mediating immune homeostasis and highlights the complexity of genetic and environmental interactions that collectively modulate the risk of disease. Nevertheless, the challenge remains to determine how genetic variation can precipitate and sustain the inappropriate inflammatory response to commensals that is observed in IBD. Here, we highlight recent advancements in immunogenetics and provide a forward-looking view of the innovations that will deliver mechanistic insights from human genetics.

Macrophage stimulating protein variation enhances the risk of sporadic extrahepatic cholangiocarcinoma

BACKGROUND

Primary sclerosing cholangitis confers risk of cholangiocarcinoma. Here, we assessed the primary sclerosing cholangitis-associated variant rs3197999 in the MST1 gene, coding for RON receptor tyrosine kinase ligand macrophage stimulating protein, in a large European cholangiocarcinoma cohort.

MATERIALS AND METHODS

223 cholangiocarcinoma patients including three primary sclerosing cholangitis individuals and 355 cancer- and primary sclerosing cholangitis-free controls were genotyped for MST1 rs3197999.

RESULTS

The cancer group departed from Hardy-Weinberg equilibrium (p = 0.022) and exhibited a trend for rs3197999 [A] overrepresentation (31% vs. 26%: p = 0.10). Homozygous rs3197999 [AA] carrier status significantly increased overall (OR = 1.97; p = 0.023) and primary sclerosing cholangitis-unrelated biliary tract cancer risk (OR = 1.84; p = 0.044), relative to homozygous common allele carriers. The association was most pronounced in patients with extrahepatic tumours. This finding was robust to multivariate analysis (p < 0.05), validating the [AA] genotype as an independent cholangiocarcinoma risk factor.

CONCLUSIONS

These results suggest that the [AA] genotype of the common MST1 variant rs3197999 enhances genetic risk of sporadic extrahepatic cholangiocarcinoma irrespective of primary sclerosing cholangitis status, presumably by modulating inflammatory responses and/or altered MSP/RON signalling.

MSP-RON signalling in cancer: pathogenesis and therapeutic potential

Since the discovery of MSP (macrophage-stimulating protein; also known as MST1 and hepatocyte growth factor-like (HGFL)) as the ligand for the receptor tyrosine kinase RON (also known as MST1R) in the early 1990s, the roles of this signalling axis in cancer pathogenesis has been extensively studied in various model systems. Both in vitro and in vivo evidence has revealed that MSP-RON signalling is important for the invasive growth of different types of cancers. Currently, small-molecule inhibitors and antibodies blocking RON signalling are under investigation. Substantial responses have been achieved in human tumour xenograft models, laying the foundation for clinical validation. In this Review, we discuss recent advances that demonstrate the importance of MSP-RON signalling in cancer and its potential as a therapeutic target.

Gene network analysis of small molecules with autoimmune disease associated genes predicts a novel strategy for drug efficacy

Numerous genes/SNPs in autoimmune diseases (ADs) are identified through genome-wide association studies (GWAS) and likely to contribute in developing autoimmune phenotypes. Constructions of biologically meaningful pathways are necessary to determine how these genes interact with each other and with other small molecules to develop various complex AD phenotypes prior to beginning time-consuming rigorous experimentation. We have constructed biological pathways with genetically identified genes leading to shared AD phenotypes. Various environmental and endogenous factors interact with these AD associated genes suggesting their critical role in developing diseases and further association studies could be designed for assessing the role of these factors with risk allele in a specific gene. Additionally, existing drugs that have been used long before the identification of these genetically associated genes also interact with these newly associated genes. Thus advanced therapeutic strategies could be designed by grouping patients with risk allele(s) in particular genes that directly or closely interact with the specified drugs. This drug-susceptible gene network will not only increase our understanding about the additional molecular basis for effectiveness against these diseases but also indicate which drug could be more effective for those patients carrying risk allele(s) in that gene. Additionally, we have also identified several interlinking genes in the pathways that could be used for designing future association studies.

Ron receptor tyrosine kinase signaling as a therapeutic target

INTRODUCTION

Since its discovery nearly 20 years ago, the Ron receptor tyrosine kinase has been extensively studied. These studies have elucidated many of the major signaling pathways activated by Ron. In the context of the inflammation and cancer, studies have shown that Ron plays differential roles; Ron activation limits the inflammatory response, whereas in cancer, Ron activation is associated with increased metastases and poor prognosis.

AREAS COVERED

This review discusses the current literature with regard to Ron signaling and consequences of its activation in cancer as well as its role in cancer therapy. Further, we discuss the mechanisms by which Ron influences the inflammatory response and its role in chronic inflammatory diseases. Finally, we discuss Ron's connection between chronic inflammation and progression to cancer.

EXPERT OPINION

The complex nature of Ron's signaling paradigm necessitates additional studies to understand the pathways by which Ron is functioning and how these differ in inflammation and cancer. This will be vital to understanding the impact that Ron signaling has in disease states. Additional studies of targeted therapies, either alone or in conjunction with current therapies are needed to determine if inhibition of Ron signaling will provide long-term benefits to cancer patients.