Esophageal cancer-related gene 4 at the interface of injury, inflammation, infection, and malignancy

Complex and pleiotropic signaling pathways regulated by the secreted protein augurin

The secreted protein augurin, the product of the tumor suppressor gene Ecrg4, has been identified as a peptide hormone in the human proteome in 2007. Since then, a number of studies have been carried out to highlight its structure and processing and its potential roles in physiopathology. Although augurin has been shown to be implicated in a variety of processes, ranging from tumorigenesis, inflammation and infection to neural stem cell proliferation, hypothalamo-pituitary adrenal axis regulation and osteoblast differentiation, the molecular mechanisms of its biological effects and the signaling pathways it regulates are still poorly characterized. Here we provide a comprehensive overview of augurin-dependent signal transduction pathways. Because of their secreted nature and the potential to be manipulated pharmacologically, augurin and its derived peptides represent attractive targets for diagnostic development and discovery of new therapeutic agents for the human diseases resulting from the deregulation of the signaling cascades they modulate. From this perspective, the characterization of the precise nature of augurin derived peptides and the identification of the receptor(s) on the cell surface conveying augurin signaling to downstream effectors are crucial to develop agonists and antagonists for this protein. Video abstract.

Cardiac Expression of Esophageal Cancer-Related Gene-4 is Regulated by Sp1 and is a Potential Early Target of Doxorubicin-Induced Cardiotoxicity

Esophageal Cancer-Related Gene 4 (Ecrg4) expressed in cardiomyocytes and the cardiac conduction system is downregulated during cardiac ischemia and atrial fibrillation. To explore whether Ecrg4 plays any role in doxorubicin (DOX)-induced cardiotoxicity. Rats and neonatal rat cardiomyocytes (NRCMs) were employed to study the effect of DOX on Ecrg4 transcription. Bioinformatics combined with promoter analysis were used to map the rat Ecrg4 promoter. ChIP assay was used to evaluate the binding of Sp1 to the Ecrg4 promoter. Transient transfection was used to study the effect of Sp1 on the expression of endogenous Ecrg4. DOX decreased endogenous Ecrg4 gene expression in the heart and cultured NRCMs. In silico analysis showed that the 5'UTR immediately upstream of the start codon ATG, harbors a putative promoter that is GC-rich, and contains CpG islands, multiple overlapping Sp1sites. Transcription is initiated mainly on the 'C' at - 15. Serial 5'-deletion combined with dual-luciferase assays showed that the rat Ecrg4 core promoter resides at - 1/- 800. Sp1 transactivated Ecrg4 gene, which was almost abolished by DOX. Furthermore, ChIP assay showed that Sp1 specifically bound to the Ecrg4 promoter was interrupted by DOX. Finally, DOX suppressed Sp1 protein expression, and restoration of Sp1 increased Ecrg4 expression that was resistant to DOX-induced Ecrg4 downregulation. Importantly, cardiomyocyte-specific loss of Ecrg4 significantly enriched the differentially expressed proteins in the signaling pathways commonly involved in DOX-induced cardiotoxicity. Our results indicate that Sp1 mediates DOX-induced suppression of Ecrg4, which may contribute indirectly to its cardiotoxicity.

ECRG4 regulates neutrophil recruitment and CD44 expression during the inflammatory response to injury

The complex molecular microenvironment of the wound bed regulates the duration and degree of inflammation in the wound repair process, while its dysregulation leads to impaired healing. Understanding factors controlling this response provides therapeutic targets for inflammatory disease. Esophageal cancer-related gene 4 (ECRG4) is a candidate chemokine that is highly expressed on leukocytes. We used ECRG4 knockout (KO) mice to establish that the absence of ECRG4 leads to defective neutrophil recruitment with a delay in wound healing. An in vitro human promyelocyte model identified an ECRG4-mediated suppression of the hyaluronic acid receptor, CD44, a key receptor mediating inflammation resolution. In ECRG4 KO mouse leukocytes, there was an increase in CD44 expression, consistent with a model in which ECRG4 negatively regulates CD44 levels. Therefore, we propose a previously unidentified mechanism in which ECRG4 regulates early neutrophil recruitment and subsequent CD44-mediated resolution of inflammation.

Open reading frame mining identifies a TLR4 binding domain in the primary sequence of ECRG4

The embedding of small peptide ligands within large inactive pre-pro-precursor proteins encoded by orphan open reading frames (ORFs) makes them difficult to identify and study. To address this problem, we generated oligonucleotide (< 100-400 base pair) combinatorial libraries from either the epidermal growth factor (EGF) ORF that encodes the > 1200 amino acid EGF precursor protein or the orphan ECRG4 ORF, that encodes a 148 amino acid Esophageal Cancer Related Gene 4 (ECRG4), a putative cytokine precursor protein of up to eight ligands. After phage display and 3-4 rounds of biopanning for phage internalization into prostate cancer epithelial cells, sequencing identified the 53-amino acid EGF ligand encoded by the 5' region of the EGF ORF and three distinct domains within the primary sequence of ECRG4: its membrane targeting hydrophobic signal peptide, an unanticipated amino terminus domain at ECRG437-63 and a C-terminus ECRG4133-148 domain. Using HEK-blue cells transfected with the innate immunity receptor complex, we show that both ECRG437-63 and ECRG4133-148 enter cells by interaction with the TLR4 immune complex but neither stimulate NFkB. Taken together, the results help establish that phage display can be used to identify cryptic domains within ORFs of the human secretome and identify a novel TLR4-targeted internalization domain in the amino terminus of ECRG4 that may contribute to its effects on cell migration, immune cell activation and tumor suppression.

Potential functions of esophageal cancer-related gene-4 in the cardiovascular system

Esophageal cancer-related gene-4 (Ecrg4) is cloned from the normal epithelium of the esophagus. It is constitutively expressed in quiescent epithelial cells and downregulated during tumorigenesis, and Ecrg4 expression levels are inversely correlated with the malignant phenotype of tumor cells, validating that Ecrg4 is a real tumor suppressor gene. Unlike other tumor suppressor genes that usually encode membrane or intracellular proteins, Ecrg4 encodes a 148-amino acid pre-pro-peptide that is tethered on the cell surface in epithelial cells, specialized epithelial cells, and human leukocytes, where it can be processed tissue dependently into several small peptides upon cell activation. Ecrg4 is expressed in a wide variety of other cells/tissues, including cardiomyocytes and conduction system of the heart, the glomus cells of the carotid body, adrenal glands, choroid plexus, and leukocytes among others, where it exerts distinct functions, such as promoting/suppressing inflammation, inducing neuron senescence, stimulating the hypothalamus-pituitary-adrenal axis, maintaining the stemness of stem cells, participating in the rhythm and rate control of the heart, and possibly gauging the responsiveness of the cardiovascular system (CVS) to hypoxia, in addition to tumor suppression. Here, we briefly review the latest discoveries on Ecrg4 and its underlying molecular mechanisms as a tumor suppressor and focus on the emerging roles of Ecrg4 in the CVS.

Esophageal cancer related gene-4 inhibits the migration and proliferation of oral squamous cell carcinoma through BC200 lncRNA/MMP-9 and -13 signaling pathway

Esophageal cancer related gene-4 (ECRG4) inhibits the malignant phenotype of oral squamous cell carcinoma. However, the molecular mechanisms remain to be explored. Using the tongue carcinoma cell line, TCA8113 as a cell model, we showed that forced expression of ECRG4 down-regulated the expression of the BC200 long non-coding RNA (lncRNA) and matrix metalloproteinases (MMP-9 and MMP-13). Restoration of BC200 lncRNA rescued ECRG4-mediated down-regulation of MMP-9 and -13. Furthermore, over-expression of Ecrg4 inhibited cell proliferation and migration, which was abolished by forced expression of BC200 lncRNA in TCA8113 cells. Our results indicate that ECRG4 inhibits the malignant phenotype of TCA8113 cells most likely through suppression of BC200 lncRNA/MMPs signaling pathway, rationalizing that BC200 lncRNA may be a potential target for oral squamous cell carcinoma (OSCC) therapy.

Deep Dive on the Proteome of Human Cerebrospinal Fluid: A Valuable Data Resource for Biomarker Discovery and Missing Protein Identification

Cerebrospinal fluid (CSF) is a body fluid of choice for biomarker studies of brain disorders but remains relatively under-studied compared with other biological fluids such as plasma, partly due to the more invasive means of its sample collection. The present study establishes an in-depth CSF proteome through the analysis of a unique CSF sample from a pool of donors. After immunoaffinity depletion, the CSF sample was fractionated using off-gel electrophoresis and analyzed with liquid chromatography tandem mass spectrometry (MS) using the latest generation of hybrid Orbitrap mass spectrometers. The shotgun proteomic analysis allowed the identification of 20 689 peptides mapping on 3379 proteins. To the best of our knowledge, the obtained data set constitutes the largest CSF proteome published so far. Among the CSF proteins identified, 34% correspond to genes whose transcripts are highly expressed in brain according to the Human Protein Atlas. The principal Alzheimer's disease biomarkers (e.g., tau protein, amyloid-β, apolipoprotein E, and neurogranin) were detected. Importantly, our data set significantly contributes to the Chromosome-centric Human Proteome Project (C-HPP), and 12 proteins considered as missing are proposed for validation in accordance with the HPP guidelines. Of these 12 proteins, 8 proteins are based on 2 to 6 uniquely mapping peptides from this CSF analysis, and 4 match a new peptide with a "stranded" single peptide in PeptideAtlas from previous CSF studies. The MS proteomic data are available to the ProteomeXchange Consortium ( http://www.proteomexchange.org/ ) with the data set identifier PXD009646.

A short synthetic peptide fragment of human C2ORF40 has therapeutic potential in breast cancer

C2ORF40 encodes a secreted protein which is cleaved to generate soluble peptides by proteolytic processing and this process is believed to be necessary for C2ORF40 to exert cell type specific biological activity. Here, we reported a short mimic peptide of human C2ORF40 acts potential therapeutic efficacy in human cancer cells in vitro and in vivo. We synthesized a short peptide of human C2ORF40, named C2ORF40 mimic peptide fragment and assessed its biological function on cancer cell growth, migration and tumorigenesis. Cell growth assay showed that C2ORF40 mimic peptide fragment significantly suppressed cell proliferation of breast and lung cancer cells. Moreover, C2ORF40 mimic peptide fragment significantly inhibited the migration and invasion of breast cancer cells. Furthermore, we showed that this peptide suppressed tumorigenesis in breast tumor xenograft model. Cell cycle assay indicated that the C2ORF40 mimic peptide fragment suppressed the growth of tumor cells through inducing mitotic phase arrest. In conclusion, our results firstly suggested that this short synthetic peptide of human C2ORF40 may be a candidate tumor therapeutic agent.

A Potential Role of Esophageal Cancer Related Gene-4 for Atrial Fibrillation

Epidemiological studies have shown a strong correlation between tumor and AF. However, the molecular link between tumor and AF remains unknown. ECRG4, a tumor suppressor gene that is expressed in the A-V node and in sporadic ventricular myocytes, inhibits tumorigenesis and monitors tissue homeostasis by functioning as a ‘sentinel’ molecule gauging inflammatory and cell proliferative responses. To explore the potential physiological function of Ecrg4 in heart, we evaluated its distribution in heart, analyzed its expression in patients with persistent AF and in a canine AF model, and dissected the molecular events downstream of Ecrg4. The results showed that the level of Ecrg4 expression is homogenously high in atria and the conduction systems and in sporadic ventricular myocytes. Importantly, the expression of Ecrg4 was significantly decreased in atrial appendages of AF patients than patients with SR. Moreover, in rapid pacing canine AF models, the expression of ECRG4 in atria was significantly decreased compared to that of the controls. Mechanistically, knockdown ECRG4 in atrial myocytes significantly shortened the APDs, inhibited the expression of Gja1, and activated pro-inflammatory cascades and genes involved in cardiac remodeling. These results suggest that Ecrg4 may play a critical role in the pathogenesis of AF.

Downregulated ECRG4 is correlated with lymph node metastasis and predicts poor outcome for nasopharyngeal carcinoma patients

OBJECTIVE

Esophageal cancer-related gene 4 (ECRG4) is a new candidate tumor suppressor gene. In this retrospective study, we evaluated ECRG4 protein expression in patients with nasopharyngeal carcinoma (NPC) under curative treatment and examined its association with pathological features and clinical outcomes as a possible biomarker for diagnosis and prognosis of NPC.

METHODS

We enrolled 122 patients with a first diagnosis between January 2001 and December 2003. Tumor tissue and control tissue from biopsies underwent immunohistochemical staining for ECRG4. ECRG4 expression was analyzed by clinicopathological variables. After Kaplan-Meier survival analysis, we used Cox proportional hazards regression to estimate the predictive effect of ECRG4 expression on overall survival.

RESULTS

ECRG4 protein level was lower in NPC than control tissue (P < 0.01). It was inversely related to node status (P < 0.001) and clinical stage (P = 0.027). ECRG4 expression was associated with overall survival, and downregulated ECRG4 expression was an independent prognostic factor of poor survival (hazard ratio = 0.677, 95 % confidence interval 0.463-0.989, P = 0.044).

CONCLUSIONS

A significant NPC patients showed downregulated ECRG4 expression, which is correlated with lymph node metastasis. The marker could be an independent prognostic factor for NPC patients. The precise function of ECRG4 in the progression of NPC, especially for lymphatic metastasis, deserves further investigation, which would bring a new target for personalized therapy.

Soluble purified recombinant C2ORF40 protein inhibits tumor cell growth in vivo by decreasing telomerase activity in esophageal squamous cell carcinoma

The chromosome 2 open reading frame 40 (C2ORF40) gene is a candidate tumor suppressor gene for a variety of tumors. Previous results by the present authors revealed that the C2ORF40 protein is a secreted protein. However, the exact biological function of secreted C2ORF40 protein in carcinogenesis has not been thoroughly investigated. In the present study, the signal peptide sequence of the C2ORF40 cDNA was initially removed to produce secreted recombinant human C2ORF40 protein (rhC2ORF40). Soluble rhC2ORF40 was successfully expressed and purified, which was evaluated for the first time, to the best of our knowledge, for tumor-suppressing function in vivo in esophageal cancer. The present results revealed that soluble purified rhC2ORF40 was concentrated with a purity of >95%. Furthermore, rhC2ORF40 inhibited esophageal cancer cell growth in vivo in a dose-dependent manner compared with a control group (P<0.05). In addition, the present study demonstrated for the first time that rhC2ORF40 decreased telomerase activity using telomeric repeat amplification protocol-enzyme-linked immunosorbent assay (P<0.05), without affecting the expression levels of telomerase-component RNA (P>0.05), as shown with polymerase chain reaction. Overall, the present results demonstrated that soluble rhC2ORF40 inhibited tumor cell growth in vivo by decreasing telomerase activity in esophageal squamous cell carcinoma. Therefore, soluble rhC2ORF40 with a high purity and biological activity may be a potential biological therapy drug for esophageal cancer.

The Orphan C2orf40 Gene is a Neuroimmune Factor in Alzheimer's Disease

Expression of the orphan C2orf40 gene is associated with the aggregation of the neurofibrillary tangle-protein tau in transgenic mice, tumor suppression, the induction of senescence in CNS, and the activation of microglia and peripheral mononuclear leukocytes. This gene also encodes several secreted pro- and anti-inflammatory neuropeptide-like cytokines, suggesting they might be implicated in the inflammatory component(s) of Alzheimer's disease (AD). Accordingly, we evaluated human AD and control brains for expression changes by RT-qPCR, Western blot, and histological changes by immunolabeling. RT-qPCR demonstrated increased cortical gene expression in AD. The molecular form of Ecrg4 detected in cortex was 8-10 kDa, which was shown previously to interact with the innate immunity receptor complex. Immunocytochemical studies showed intensely stained microglia and intravascular blood-borne monocytes within cerebral cortical white matter of AD patients. Staining was diminished within cortical neurons, except for prominent staining in neurofibrillary tangles. Choroid plexuses showed a decreasing trend. These findings support our hypothesis that c2orf40 participates in the neuroimmune response in AD.

Down-regulated ECRG4 expression in breast cancer and its correlation with tumor progression and poor prognosis--A short Report

BACKGROUND

Recently, we identified the esophageal carcinoma related gene 4 (ECRG4) as a novel candidate tumor suppressor gene and a promising therapeutic target in nasopharyngeal carcinoma (NPC). In addition, we found that reduced ECRG4 expression in NPC was associated with promoter hypermethylation. The aim of the current study was to assess the expression status of the ECRG4 protein in breast cancer and to clarify its clinicopathological significance and potential prognostic implications.

METHODS

Western blotting was used to examine ECRG4 protein levels in 20 paired breast cancer tissues and adjacent noncancerous tissues. In addition, we performed ECRG4 immunohistochemistry on 113 clinicopathologically well-characterized breast cancer samples and assessed putative associations between its expression and overall patient survival rates.

RESULTS

We found that ECRG4 protein expression was significantly reduced in the breast cancer tissues compared to the noncancerous tissues. Clinicopathological analyses revealed that loss of ECRG4 protein expression, observed in 41.6 % (47/113) of the primary breast cancer tissues tested, was significantly correlated with lymph node metastasis (P = 0.026), advanced tumor stage (P = 0.042) and unfavorable overall survival (P = 0.004). Additional multivariate analyses revealed that ECRG4 protein expression may serve as an independent prognostic factor for the prediction of patient survival (P = 0.033).

CONCLUSION

Our data suggest that loss of ECRG4 protein expression may be involved in tumor progression and may serve as a prognostic biomarker for breast cancer.

Monitoring Neutrophil-Expressed Cell Surface Esophageal Cancer Related Gene-4 after Severe Burn Injury

BACKGROUND

We identified recently esophageal cancer related gene-4 (ECRG4) as a candidate cytokine that is expressed on the surface of quiescent polymorphonuclear leukocytes (PMNs) and shed in response to ex vivo treatment with lipopolysaccharide. To investigate the potential biologic relevance of changes in cell surface ECRG4 in human samples, we performed a pilot study to examine a population of burn patients in whom blood could be analyzed prospectively. We hypothesized that cutaneous burn injury would alter cell surface expression of ECRG4 on PMNs.

METHODS

Patients admitted with more than 20% total burn surface area (TBSA) (n = 10) had blood collected at the time of admission and weekly thereafter. For comparison, blood was obtained from a control group of healthy human volunteers (n = 4). We used flow cytometry to measure changes in ECRG4(+) PMNs from patients during recovery from injury. Esophageal cancer related gene-4 expression at each time point was compared with the patient's clinical status based on a Multiple Organ Dysfunction (MOD) score.

RESULTS

Esophageal cancer related gene-4 was detected on the PMN surface of cells collected from healthy volunteers, however, within 48 h of admission after burn injury (n = 10 patients), the number of PMNs with cell surface ECRG4 was decreased. Esophageal cancer related gene-4 expression in PMNs was re-established over the course of patient recovery, unless complications occurred. In this case, the decrease in cell surface ECRG4(+) PMNs preceded the clinical diagnosis of infectious complications and was reflected by increased organ injury scores.

CONCLUSION

From a small sample set, we were able to determine that PMN cell surface ECRG4 expression was decreased after burn injury and returned to baseline during recovery from injury. Although larger studies are needed to define the role of ECRG4 in human PMNs further, this report is the first assessment of cell surface ECRG4 protein in a patient population to support analogous findings in animal studies.

ECRG4 expression in normal rat tissues: expression study and literature review

The Esophageal Cancer Related Gene 4 (ECRG4) is a highly conserved tumour suppressor gene encoding various peptides (augurin, CΔ16 augurin, ecilin, argilin, CΔ16 argilin) which can be processed and secreted. In the present work, we examined ECRG4 expression and location in a wide range of rat organs and reviewed the available literature. ECRG4 mRNA was identified in all examined tissues by quantitative PCR (qPCR). ECRG4 immunoreaction was mainly cytoplasmic, and was detected in heart and skeletal muscles, smooth muscle cells showing only weak reactions. In the digestive system, ECRG4 immunostaining was stronger in the esophageal epithelium, bases of gastric glands, hepatocytes and pancreatic acinar epithelium. In the lymphatic system, immunoreactive cells were detectable in the thymus cortex, lymph node medulla and splenic red pulp. In the central and peripheral nervous systems, different neuronal groups showed different reaction intensities. In the endocrine system, ECRG4 immunoreaction was detected in the hypothalamic paraventricular and supraoptic nuclei, hypophysis, thyroid and parathyroid glands, adrenal zona glomerularis and medulla and Leydig cells, as well as in follicular and luteal cells of the ovary. In the literature, ECRG4 has been reported to inhibit cell proliferation and increase apoptosis in various cell types. It is down-regulated, frequently due to hypermethylation, in esophageal, prostate, breast and colon cancers, together with glioma (oncosuppressor function), although it is up-regulated in papillary thyroid cancer (oncogenic role). ECRG4 expression is also higher in non-proliferating cells of the lymphatic system. In conclusion, our identification of ECRG4 in many structures suggests the involvement of ECRG4 in the tumorigenesis of other organs and also the need for further research. In addition, on the basis of the location of ECRG4 in neurons and endocrine cells and the fact that it can be secreted, its role as a neurotransmitter/neuromodulator and endocrine factor must be examined in depth in the future.

ECRG4 acts as a tumor suppressor and as a determinant of chemotherapy resistance in human nasopharyngeal carcinoma

BACKGROUND

Human nasopharyngeal carcinoma (NPC) is a malignant type of cancer with an increasing incidence. As yet, however, molecular biomarkers with a strong diagnostic impact and a major therapeutic promise have remained elusive. Here, we identified the esophageal carcinoma related gene 4 (ECRG4) as a novel candidate tumor suppressor gene and a promising therapeutic target for NPC.

METHODS

RT-PCR, Western blotting, methylation-specific PCR and bisulfite sequencing were performed to assess the expression and methylation status of the ECRG4 gene in primary NPC samples, NPC-derived cell lines and patient-derived peripheral blood samples. The NPC-derived cell line CNE1 was selected for treatment with a methylation inhibitor to restore ECRG4 expression. In addition, cell proliferation, invasion and colony formation assays were performed to assess the inhibitory effects of exogenous ECRG4 expression in CNE1 cells.

RESULTS

Down-regulated ECRG4 expression was found to occur in 82.5% (33/40) of the primary NPC biopsies tested. This down-regulation was significantly correlated with its tumor-specific promoter methylation status (72.5%, 29/40) and was also observed in the matching peripheral blood samples from the NPC patients (57.5%, 23/40). Pharmacologic demethylation through 5-aza-dC treatment led to gene reactivation in ECRG4 methylated and silenced NPC cell lines. Moreover, exogenous expression of ECRG4 in the CNE1 cell line strongly inhibited its growth and invasive capacities, as well as its enhanced chemosensitivity to cisplatin through autophagy induction.

CONCLUSION

Our data suggest that methylation-mediated suppression of the ECRG4 gene occurs frequently in NPC and that restoration of its expression may have therapeutic benefits.

Pulmonary preconditioning, injury, and inflammation modulate expression of the candidate tumor suppressor gene ECRG4 in lung

PURPOSE

The human c2orf40 gene encodes a candidate tumor suppressor called Esophageal Cancer-Related Gene-4 (ECRG4) that is a cytokine-like epigenetically-regulated protein that is characteristically downregulated in cancer, injury, inflammation, and infection. Here, we asked whether ECRG4 gene expression is detectable in lung epithelial cells and if its expression changes with inflammation, infection, and/or protective preconditioning.

MATERIALS AND METHODS

We used immunoblotting, PCR, and quantitative PCR to measure ECRG4 and either inhalation anesthesia preconditioning, lipopolysaccharide injection, or laparotomy to modulate lung inflammation.

RESULTS

Immunoblotting establishes the presence of the full-length 14 kDa ECRG4 peptide in mouse lung. Immunohistochemistry localizes ECRG4 to type l alveolar epithelial cells. Basal ECRG4 mRNA is greater than TNF-α, IL-1β, and IL-6 but following inflammatory lung injury, TNF-α, IL-1β, IL-6, and IL-10 are upregulated while ECRG4 gene expression is decreased. Similar findings are observed after an intravenous administration of lipopolysaccharide. In contrast, lung preconditioning with isoflurane anesthesia increases lung ECRG4 gene expression. Over-expression of ECRG4 in human lung epithelial cells in vitro decreases cell proliferation implying that a loss of ECRG4 in vivo would be permissive to cell growth.

CONCLUSIONS

This study supports the hypothesis that ECRG4 acts as a sentinel growth inhibitor in lung alveolar epithelial cells. Its downregulation by injury, infection, and inflammation and upregulation by preconditioning supports a role for ECRG4 in regulating the alveolar epithelium response to injury and inflammation. By extension, the findings support a functional consequence to its inhibition by promoter hypermethylation (i.e. lung cancer) and suggest potential benefits to its upregulation.

Esophageal cancer-related gene-4 (ECRG4) interactions with the innate immunity receptor complex

OBJECTIVE AND DESIGN

The human c2orf40 gene encodes a tumor suppressor gene called esophageal cancer-related gene-4 (ECRG4) with pro- and anti-inflammatory activities that depend on cell surface processing. Here, we investigated its physical and functional association with the innate immunity receptor complex.

METHODS

Interactions between ECRG4 and the innate immunity receptor complex were assessed by flow cytometry, immunohistochemistry, confocal microscopy, and co-immunoprecipitation. Phage display was used for ligand targeting to cells that overexpress the TLR4-MD2-CD14.

RESULTS

Immunoprecipitation and immunohistochemical studies demonstrate a physical interaction between ECRG4 and TLR4-MD2-CD14 on human granulocytes. Flow cytometry shows ECRG4 on the cell surface of a subset of CD14(+) and CD16(+) leukocytes. In a cohort of trauma patients, the C-terminal 16 amino acid domain of ECRG4 (ECRG4(133-148)) appears to be processed and shed, presumably at a thrombin-like consensus sequence. Phage targeting this putative ligand shows that this peptide sequence internalizes into cells through the TLR4/CD14/MD2 complex, but modulates inflammation through non-canonical, NFκB signal transduction.

CONCLUSIONS

ECRG4 is present on the surface of human monocytes and granulocytes. Its interaction with the human innate immunity receptor complex supports a role for cell surface activation of ECRG4 during inflammation and implicates this receptor in its mechanism of action.