Overexpression of ECRG4 enhances chemosensitivity to 5-fluorouracil in the human gastric cancer SGC-7901 cell line

A potential role of human esophageal cancer-related gene-4 in cardiovascular homeostasis

Human esophageal cancer related gene-4 (ECRG-4) encodes a 148-aminoacid pre-pro-peptide that can be processed tissue-dependently into multiple small peptides possessing multiple functions distinct from, similar to, or opposite to the tumor suppressor function of the full-length Ecrg4. Ecrg-4 is covalently bound to the cell surface through its signal peptide, colocalized with the innate immunity complex (TLR4-CD14-MD2), and functions as a 'sentinel' molecule in the maintenance of epithelium and leukocyte homeostasis, meaning that the presence of Ecrg-4 on the cell surface signals the maintained homeostasis, whereas the loss of Ecrg-4 due to tissue injury activates pro-inflammatory and tissue proliferative responses, and the level of Ecrg-4 gradually returns to its pre-injury level upon wound healing. Interestingly, Ecrg-4 is also highly expressed in the heart and its conduction system, endothelial cells, and vascular smooth muscle cells. Accumulating evidence has shown that Ecrg-4 is involved in cardiac rate/rhythm control, the development of atrial fibrillation, doxorubicin-induced cardiotoxicity, the ischemic response of the heart and hypoxic response in the carotid body, the pathogenesis of atherosclerosis, and likely the endemic incidence of idiopathic dilated cardiomyopathy. These preliminary discoveries suggest that Ecrg-4 may function as a 'sentinel' molecule in cardiovascular system as well. Here, we briefly review the basic characteristics of ECRG-4 as a tumor suppressor gene and its regulatory functions on inflammation and apoptosis; summarize the discoveries about its distribution in cardiovascular system and involvement in the development of CVDs, and discuss its potential as a novel therapeutic target for the maintenance of cardiovascular system homeostasis.

A potential link between aberrant expression of ECRG4 and atrial fibrillation

Esophageal cancer-related gene-4 (ECRG4), a 148-amino acid propertied and new tumor suppressor, is initially cloned from the normal esophageal epithelium. ECRG4 was found to be expressed not only in esophageal tissues but also in cardiomyocytes. Previous studies demonstrated that ECRG4 is constitutively expressed in esophageal epithelial cells, and its degree of downregulation is directly proportional to prognosis in patients with esophageal cancer. In the heart, ECRG4 shows greater expression in the atria than in the ventricles, which accounts for its heterogeneity. Downregulation of ECRG4 expression level correlates with esophageal cancer, as well as myocardial injuries and arrhythmias. As a result, this review summarizes the possible susceptibility gene, ECRG4 and its associated molecular mechanisms in cancer patients with atrial fibrillation and myocardial injury. The review begins by describing ECRG4's biological background, discusses its expression in the cardiovascular system, lists the clinical and animal research related to the downregulation of ECRG4 in atrial fibrillation, and focuses on its potential role in atrial fibrillation. Downregulation of ECRG4 may increase the risk of atrial fibrillation by affecting ion channels, MMPs expression and inflammatory response. We will then discuss how ECRG4 can be used in the treatment of tumors and arrhythmias, and provide a novel possible strategy to reduce the occurrence of perioperative cardiovascular adverse events in patients with tumors such as esophageal cancer and gastric cancer.

Aberrant expression of the esophageal carcinoma related gene 4 as a prognostic signature for hepatocellular carcinoma

BACKGROUND AND OBJECTIVE

Hepatocellular carcinoma (HCC) is a lethal cancer with increasing incidence, yet the molecular biomarkers that have strong prognostic impact and also hold great therapeutic promise remain elusive.

METHODS

Data mining approaches with a set of publicly accessible databases and immunohistochemistry were used to provide a novel insight into the expression pattern and prognostic significance of the esophageal cancer-related gene (ECRG) family members in HCC.

RESULTS

We found that elevated mRNA expression levels of ECRG factors were correlated with better overall survival, relapse-free survival and progression-free survival rates in patients with HCC. Subgroup analyses showed significant associations between ECRG expression and survival outcome in select HCC patients. In addition, immunohistochemical and multivariate analysis confirmed increased ECRG4 expression as an independent prognostic indicator for survival.

CONCLUSIONS

Our data suggest that ECRG factors have significant impacts on the survival of HCC patients. The expression of ECRG factors may be involved in HCC progression and could serve as novel biomarkers for predicting more accurate prognosis.

ECRG4 acts as a tumor suppressor in nasopharyngeal carcinoma by suppressing the AKT/GSK3β/β-catenin signaling pathway

Nasopharyngeal carcinoma (NPC) is a malignant tumor with a poor prognosis. Studies have shown that esophageal carcinoma related gene 4 (ECRG4) is hypermethylated and significantly downregulated in NPC tissues. However, the role of ECRG4 in NPC, and in particular the underlying molecular mechanism, is largely unclear. In this study, using immunohistochemical staining of ECRG4 in NPC and normal specimens, we confirmed that ECRG4 was downregulated in human NPC tissues. In addition, various biological and molecular studies were carried out and the results showed that ECRG4 exerted anticancer effect in NPC, including inhibiting cell growth, migration, and invasion of NPC cells in vitro. Moreover, restoring ECRG4 expression suppressed the in vivo tumorigenesis of CNE2 cells. ECRG4 inhibited AKT/GSK3β/β-catenin signaling, as well as the downstream targets of β-catenin. LiCl treatment, which reduced GSK3β phosphorylation and upregulated β-catenin expression, restored the invasive ability of ECRG4-overexpressing NPC cells. Furthermore, we showed that the DNA methylation inhibitor 5-aza-dC reduced ECRG4 methylation and the invasive ability of negative control cells, but not that of ECRG4-overexpressing cells, suggesting that the inhibitory effect of 5-aza-dC depends on low expression of ECRG4. Collectively, our results demonstrated that ECRG4 downregulation contributed to NPC growth and invasion by activating AKT/GSK3β/β-catenin signaling pathway. ECRG4 could be a promising therapeutic target for the treatment of NPC.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10616-022-00520-8.

NHE1 Mediates 5-Fu Resistance in Gastric Cancer via STAT3 Signaling Pathway

BACKGROUND

Several recent studies have addressed the role of Na+/H+ exchanger isoform 1 (NHE1) in tumor cell growth and apoptosis, including in gastric cancer. However, the role of NHE1 expression related to the 5-Fu resistance in gastric cancer has not been investigated.

METHODS

The expression of NHE1 was examined by qPCR in the SGC7901/5-FU cell line and its parental cell line. pcDNA3.1-NHE1 and NHE1-siRNA were transfected to SGC7901/5-FU resistance cells and cell apoptosis was detected via TUNEL assay. The upstream activators in NHE1 mediated 5-Fu resistant gastric cancer cells were detected by Western blot and immunofluorescent.

RESULTS

A significant increase of the expression of NHE1 was observed in SGC7901 5-FU resistance cells compared to the GES-1 and SGC7901 cell line. NHE1 can suppress the cell apoptosis of SGC7901 5-FU resistance cells and involved in cell cycle. Also, the migration and invasion of SGC7901 5-FU resistance cells were promoted by NHE1. NHE1 also increases the intracellular pH. The results of Western blot analysis showed that NHE1 overexpression induced an increase in the expression of phosphorylated activator transcription factor 3 (pSTAT3). The more obvious phosphorylated level was shown in the phosphorylated STAT3 at pSTAT3tyr705. Further investigations revealed that the constitutive activation of STAT3 may be induced by JAK1 and JAK2, and thus effect the 5-FU resistance by regulating NHE1.

DISCUSSION

In summary, our findings provided evidence that NHE1 contributed to 5-Fu resistance in gastric cancer cells by regulating the JAK/STAT3 pathway. Therefore, NHE1 can be a useful marker for predicting and monitoring 5-Fu resistance.

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.

Downregulation and DNA methylation of ECRG4 in gastric cancer

Background

Esophageal cancer-related gene 4 (ECRG4) is a novel candidate tumor suppressor gene. Our study investigated the expression and function of ECRG4 in gastric cancer and highlighted the role of DNA hypermethylation at the promoter in silencing the ECRG4 expression.

Methods

The GSE63089 data set was obtained from the Gene Expression Omnibus and analyzed for differentially expressed genes. Carcinoma and para-carcinoma tissues of 102 patients with gastric cancer were collected from January 2010 to July 2011. Immunohistochemistry, real-time polymerase chain reaction (PCR), and western blot analyses were performed to evaluate the expression of ECRG4. After measuring the change in the level of ECRG4 expression, CCK-8, Transwell, and flow cytometric cell cycle assays were performed. In addition, methylation-specific PCR was performed to detect the methylation state of ECRG4, and 5-aza-2′-deoxycytidine was used for demethylation of ECRG4. All statistical analyses were performed using the SPSS 17.0 software.

Results

We found that ECRG4 expression was downregulated in gastric cancer, and this was closely related to lymph node metastasis. After ECRG4 was silenced using a specific small interfering RNA, the BGC-823 cell line became highly aggressive and proliferative. In addition, we verified whether downregulation of ECRG4 was highly correlated with DNA methylation of the ECRG4 promoter and found that the demethylating agent 5-aza-2′-deoxycytidine could effectively enhance ECRG4 expression.

Conclusion

The aberrant expression of ECRG4 is associated with hypermethylation in the promoter region and plays an important role in the malignancy of gastric cancer. Therefore, ECRG4 may be a potential biomarker for molecular diagnosis of gastric cancer, and the use of 5-Aza-dC to reverse the hypermethylation of ECRG4 may be a new approach to the treatment of gastric cancer.

ECRG4: a new potential target in precision medicine

Given the rapid development in precision medicine, tremendous efforts have been devoted to discovering new biomarkers for disease diagnosis and treatment. Esophageal cancer-related gene-4 (ECRG4), which is initially known as a new candidate tumor suppressor gene, is emerging as a sentinel molecule for gauging tissue homeostasis. ECRG4 is unique in its cytokine-like functional pattern and epigenetically-regulated gene expression pattern. The gene can be released from the cell membrane upon activation and detected in liquid biopsy, thus offering considerable potential in precision medicine. This review provides an updated summary on the biology of ECRG4, with emphasis on its important roles in cancer diagnosis and therapy. The future perspectives of ECRG4 as a potential molecular marker in precision medicine are also discussed in detail.

UBR5 Contributes to Colorectal Cancer Progression by Destabilizing the Tumor Suppressor ECRG4

BACKGROUND

The E3 ligase UBR5 is aberrantly expressed in diverse types of cancer. However, its expression pattern and biological function in colorectal cancer (CRC) remain unclear.

METHODS

We used RT-PCR, Western blot, and immunohistochemistry to measure UBR5 expression in CRC tissues and corresponding non-tumor tissues. The expression pattern of UBR5 in CRC tissues was determined by scoring system of immunohistochemical analysis and mRNA level by RT-PCR. The statistical analyses were applied to evaluate the associations of UBR5 expression with survival rate of patients. The UBR5 gene was overexpressed or silenced with lentiviral vectors in CRC cells. And, cell proliferation and apoptosis were measured using CCK8 assay and flow cytometry.

RESULTS

We found that UBR5 is abundantly overexpressed in CRC tissues than adjacent non-cancerous tissues. We also found that high UBR5 level is positively correlated with progression and poor survival in CRC patients. In addition, further multivariate analysis indicated that UBR5 and TNM stage were independent prognostic factors for overall survival in patients with CRC. Furthermore, we demonstrated that the expression of UBR5 was significantly elevated in CRC cell lines. Overexpression of UBR5 enhanced in vitro cell proliferation and promoted in vivo tumor growth, whereas silencing UBR5 suppressed growth of CRC cells. Moreover, our findings show that UBR5 promotes CRC cell proliferation by inducing cell cycle progression and suppressing cell apoptosis. Finally, we found that UBR5 directly binds to the tumor suppressor esophageal cancer-related gene 4 (ECRG4) and increased its ubiquitination to reduce the protein stability of ECRG4.

CONCLUSIONS

We identified a tumorigenic role of UBR5 in CRC and provided a novel therapeutic target for CRC patients.

Downregulation of esophageal cancer-related gene 4 promotes proliferation and migration of hepatocellular carcinoma

Esophageal cancer-related gene 4 (ECRG4) is a candidate tumor suppressor gene, which is involved in cell apoptosis, migration, infection and inflammation responsiveness; however, its expression level and clinical significance in hepatocellular carcinoma (HCC) remains unclear. In the present study, the authors aim to evaluate the clinical significance and potential role of ECRG4 in HCC. Level of ECRG4 protein expression in HCC and peripheral tissues was investigated in tissue specimens obtained from 56 consecutive HCC patients by immunohistochemistry. Cell proliferation, cell migration and invasion regulations were examined by MTT curves, flow cytometry, Transwell assays and western blotting. ECRG4 expression was weak positive in normal liver cells but was downregulated in HCC cells in vivo or in vitro. A decreased expression of ECRG4 was associated with the age of the patients, metastasis and Ki-67 proliferation index. However, decreased ECRG4 expression was not associated with differentiation, tumor size, the presence of portal vein tumor thrombosis, satellite lesions, tumor relapse or mortality. Further investigations revealed that ectopic expression of ECRG4 inhibited cell proliferation, migration and invasion and promoted cell apoptosis in SMMC-7721 cells, which was mediated by the regulation of BAX and B cell lymphoma-2, in addition to the upregulation of epithelial-mesenchymal transition markers. In conclusion, the results of the present study indicated that ECRG4 was downregulated in HCC and served important roles in promoting cell proliferation and migration.

Antitumor effects and the underlying mechanism of licochalcone A combined with 5-fluorouracil in gastric cancer cells

Licochalcone A (LCA) is a flavonoid extracted from licorice root that has antiparasitic, antibacterial and antitumor properties. Previous studies have revealed that LCA may be a novel treatment for gastric cancer. The present study further assessed the potential antitumor effects of LCA alone or in combination with 5-fluorouracil (5-FU), and the underlying mechanisms responsible for those effects in gastric cancer cells. The effects of LCA alone or in combination with 5-FU on SGC7901 and MKN-45 gastric cancer cell lines were studied using Cell Counting Kit-8, cell cycle, apoptosis and western blot analyses of cell check points and apoptosis-associated proteins. The results revealed that LCA inhibited cell proliferation, blocked cell cycle progression at the G₂/M transition and induced apoptosis. Western blot analysis demonstrated that LCA treatment increased the levels of tumor proteins 21 and 27, as well as mouse double minute 2 homolog in gastric cancer cells. In addition, LCA treatment increased the expression levels of Bax, cleaved-poly ADP ribose polymerase, tumor protein 53 and caspase 3, and decreased the expression levels of Bcl-2. Therefore, the present study demonstrated that LCA alone or in combination with 5-FU may have significant anticancer effects on gastric cancer cells, and may be a novel therapeutic for the treatment of gastric cancer in the future.

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.

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.

Downregulated ECRG4 is associated with poor prognosis in renal cell cancer and is regulated by promoter DNA methylation

Esophageal cancer-related gene 4 (ECRG4) has been proposed as a putative tumor suppressor gene in several tumors. However, the role and regulation of ECRG4 in the pathogenesis of human renal cancer remain largely unknown. Our current study revealed that expression of ECRG4 is downregulated in renal cell lines and renal cancer tissues. ECRG4 expression was significantly associated with histological grade of tumors (p < 0.001), primary tumor stage (p = 0.017), and distant metastasis (p = 0.017). Low expression of ECRG4 was an independent prognostic indicator for survival of renal cancer patients. Silencing of ECRG4 expression in renal cell lines was associated with its promoter methylation. Moreover, ectopic expression of ECRG4 markedly inhibited cell proliferation and invasion in renal cancer cell lines. These results indicated that ECRG4 is frequently silenced by the methylation of promoter in renal cell cancers. ECRG4 may be a tumor suppressor in renal cancer and serve as a prognostic marker.

A preliminary study of the effect of ECRG4 overexpression on the proliferation and apoptosis of human laryngeal cancer cells and the underlying mechanisms

Human esophageal cancer-related gene 4 (ECRG4) is a potential tumor suppressor gene isolated from human esophageal epithelial cells. Studies have shown that ECRG4 effectively inhibits the proliferation of tumor cells and induces apoptosis. However, the role of ECRG4 in laryngeal cancer has not yet been clearly defined. In this study, a human laryngeal cancer cell line stably overexpressing ECRG4 was established. The effect of ECRG4 on the proliferation and apoptosis of laryngeal cancer cells and the associated mechanisms were investigated. The Hep-2 human laryngeal carcinoma cell line exhibited a low basal level of ECRG4 expression and was selected for the present study. The eukaryotic expression plasmid pcDNA3.1-ECRG4 was constructed and introduced into Hep-2 cells by transfection reagents. Western blot analysis, reverse transcription-quantitative polymerase chain reaction and immunofluorescence staining confirmed high-level expression of ECRG4. The 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and colony formation assay showed that ECRG4 over-expression suppressed the proliferative capacity of laryngeal cancer cells in vitro. Cell cycle analysis showed that ECRG4 induced cell cycle arrest at the G0/G1 phase. Flow cytometric analysis and Hoechst staining demonstrated that overexpres-sion of ECRG4 significantly induced apoptosis. Western blot analysis confirmed that Bcl-2-associated X protein, cleaved-caspase-3 and cleaved-poly (ADP-ribose) polymerase were upregulated in the apoptotic process, whereas B-cell lymphoma 2 was downregulated. In conclusion, overexpression of ECRG4 inhibited laryngeal cancer cell proliferation and induced cancer cell apoptosis. Therefore, ECRG4 exhibits potential as an effective target in gene therapy for laryngeal cancer.

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.

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

In humans, esophageal cancer-related gene 4 (ECRG4) is encoded by four exons in the c2orf40 locus of chromosome 2. Translation of ECRG4 messenger ribonucleic acid produces a 148 amino acid-secreted 17 KDa protein that is then processed to 14, ten, eight, six, four, and two KDa peptides, depending on the cell in which the gene is expressed. As hypermethylation at the c2orf40 locus inhibits ECRG4 gene expression in many epithelial cancers, several investigators have speculated that ECRG4 is a candidate tumor suppressor. Indeed, overexpression of ECRG4 inhibits cell proliferation in vitro, but it also has a wide range of effects in vivo beyond its antitumor activity. ECRG4 overexpression affects apoptosis, senescence, cell migration, inflammation, injury, and infection responsiveness. ECRG4 activities also depend on its cellular localization, secretion, and post-translational processing. These cytokine/chemokine-like characteristics argue that ECRG4 is not a traditional candidate tumor suppressor gene, as originally predicted by its downregulation in cancer. We review how insights into the regulation of ECRG4 gene expression, knowledge of its primary structure, and the study of its emerging physiological functions come together to support a much more complex role for ECRG4 at the interface of inflammation, infection, and malignancy.