The role of chemerin and ChemR23 in stimulating the invasion of squamous oesophageal cancer cells

The Dual Role of Chemerin in Lung Diseases

Chemerin is an atypical chemokine first described as a chemoattractant agent for monocytes, natural killer cells, plasmacytoid and myeloid dendritic cells, through interaction with its main receptor, the G protein-coupled receptor chemokine-like receptor 1 (CMKLR1). Chemerin has been studied in various lung disease models, showing both pro- and anti-inflammatory properties. Given the incidence and burden of inflammatory lung diseases from diverse origins (infectious, autoimmune, age-related, etc.), chemerin has emerged as an interesting therapeutical target due to its immunomodulatory role. However, as highlighted by this review, further research efforts to elucidate the mechanisms governing chemerin's dual pro- and anti-inflammatory characteristics are urgently needed. Moreover, although a growing body of evidence suggests chemerin as a potential biomarker for the diagnosis and/or prognosis of inflammatory lung diseases, this review underscores the necessity for standardizing both sampling types and measurement techniques before drawing definitive conclusions.

Elevated Serum Gastrin Is Associated with Melanoma Progression: Putative Role in Increased Migration and Invasion of Melanoma Cells

Micro-environmental factors, including stromal and immune cells, cytokines, and circulating hormones are well recognized to determine cancer progression. Melanoma cell growth was recently shown to be suppressed by cholecystokinin/gastrin (CCK) receptor antagonists, and our preliminary data suggested that melanoma patients with Helicobacter gastritis (which is associated with elevated serum gastrin) might have an increased risk of cancer progression. Therefore, in the present study, we examined how gastrin may act on melanoma cells. In 89 melanoma patients, we found a statistically significant association between circulating gastrin concentrations and melanoma thickness and metastasis, which are known risk factors of melanoma progression and prognosis. Immunocytochemistry using a validated antibody confirmed weak to moderate CCK2R expression in both primary malignant melanoma cells and the melanoma cell lines SK-MEL-2 and G361. Furthermore, among the 219 tumors in the Skin Cutaneous Melanoma TCGA Pan-Cancer dataset showing gastrin receptor (CCKBR) expression, significantly higher CCKBR mRNA levels were linked to stage III-IV than stage I-II melanomas. In both cell lines, gastrin increased intracellular calcium levels and stimulated cell migration and invasion through mechanisms inhibited by a CCK2 receptor antagonist. Proteomic studies identified increased MMP-2 and reduced TIMP-3 levels in response to gastrin that were likely to contribute to the increased migration of both cell lines. However, the effects of gastrin on tumor cell invasion were relatively weak in the presence of the extracellular matrix. Nevertheless, dermal fibroblasts/myofibroblasts, known also to express CCK2R, increased gastrin-induced cancer cell invasion. Our data suggest that in a subset of melanoma patients, an elevated serum gastrin concentration is a risk factor for melanoma tumor progression, and that gastrin may act on both melanoma and adjacent stromal cells through CCK2 receptors to promote mechanisms of tumor migration and invasion.

Discovery of 3-Phenyl Indazole-Based Novel Chemokine-like Receptor 1 Antagonists for the Treatment of Psoriasis

Chemokine-like receptor 1 (CMKLR1)─a G protein-coupled receptor─has functional roles in the immune system and related diseases, including psoriasis and metabolic diseases. Psoriasis is a chronic inflammatory disease characterized by skin redness, scaliness, and itching. In this study, we sought to develop novel CMKLR1 antagonists by screening our in-house GPCR-targeting compound library. Moreover, we optimized a phenylindazole-based hit compound with antagonistic activities and evaluated its oral pharmacokinetic properties in a murine model. A structure-based design on the human CMKLR1 homology model identified S-26d as an optimized compound that serves as a potent and orally available antagonist with a pIC50 value of 7.44 in hCMKLR1-transfected CHO cells. Furthermore, in the imiquimod-induced psoriasis-like mouse model, oral administration of S-26d for 1 week significantly alleviated modified psoriasis area and severity index scores (severity of erythema, scaliness, skin thickness) compared with the control group.

Prognostic impact of chemerin expression in colorectal cancer: A detailed analysis based on histological components and meta-analysis

This study aimed to elucidate the clinicopathological significance of chemerin immunohistochemical expression in colorectal cancer (CRC) based on histologic components. Immunohistochemistry was performed to detect chemerin in 266 human CRC tissues. Correlation between chemerin expression, clinicopathological characteristics, and survival in CRC. A meta-analysis was performed to claify the prognostic role of chemerin tissue expression in malignant tumors. Chemerin was expressed in 125 of 266 CRC tissues (47.0 %) and was significantly correlated with distant metastasis (P = 0.012). However, no significant correlation was observed between chemerin expression and other clinicopathological parameters. Subgroup analyses based on histological components showed that chemerin expression was significantly higher in CRCs with the mucinous component than in those without the mucinous component (P 0.001). However, there was no significant correlation between chemerin expression and the micropapillary component. Patients with chemerin expression had worse overall and recurrence-free survival rates (P = 0.017 and P = 0.009, respectively). The prognostic significance of chemerin was found in CRCs without the mucinous component but not in those with the mucinous component. Chemerin expression was significantly correlated with poor survival in breast and ovarian cancers in the meta-analysis. Chemerin expression significantly correlated with distant metastasis and poor survival in CRCs. The predictive role of patient prognosis is useful for CRCs, especially those with no mucinous component.

ChemR23 activation reprograms macrophages toward a less inflammatory phenotype and dampens carcinoma progression

Introduction

Tumor Associated Macrophages (TAM) are a major component of the tumor environment and their accumulation often correlates with poor prognosis by contributing to local inflammation, inhibition of anti-tumor immune response and resistance to anticancer treatments. In this study, we thus investigated the anti-cancer therapeutic interest to target ChemR23, a receptor of the resolution of inflammation expressed by macrophages, using an agonist monoclonal antibody, αChemR23.

Methods

Human GM-CSF, M-CSF and Tumor Associated Macrophage (TAM)-like macrophages were obtained by incubation of monocytes from healthy donors with GM-CSF, M-CSF or tumor cell supernatants (Breast cancer (BC) or malignant pleural mesothelioma (MPM) cells). The effects of αChemR23 on macrophages were studied at the transcriptomic, protein and functional level. Datasets from The Cancer Genome Atlas (TCGA) were used to study CMKLR1 expression, coding for ChemR23, in BC and MPM tumors. In vivo, αChemR23 was evaluated on overall survival, metastasis development and transcriptomic modification of the metastatic niche using a model of resected triple negative breast cancer.

Results

We show that ChemR23 is expressed at higher levels in M-CSF and tumor cell supernatant differentiated macrophages (TAM-like) than in GM-CSF-differentiated macrophages. ChemR23 activation triggered by αChemR23 deeply modulates M-CSF and TAM-like macrophages including profile of cell surface markers, cytokine secretion, gene mRNA expression and immune functions. The expression of ChemR23 coding gene (CMKLR1) strongly correlates to TAM markers in human BC tumors and MPM and its histological detection in these tumors mainly corresponds to TAM expression. In vivo, treatment with αChemR23 agonist increased mouse survival and decreased metastasis occurrence in a model of triple-negative BC in correlation with modulation of TAM phenotype in the metastatic niche.

Conclusion

These results open an attractive opportunity to target TAM and the resolution of inflammation pathways through ChemR23 to circumvent TAM pro-tumoral effects.

Anti-Tumoral Effect of Chemerin on Ovarian Cancer Cell Lines Mediated by Activation of Interferon Alpha Response

Simple Summary

Chemerin is a multifunctional protein with an important role in the immune system. Recent evidence showed that chemerin also regulates the development of cancer. Ovarian cancer is a common type of tumor in women. In this study, we observed that chemerin decreases the growth of ovarian cancer cell lines in vitro when cultivated in standard cell culture or in globular multicellular aggregates. When we examined the mechanisms involved in this process, we found that treatment of ovarian cancer cells with chemerin led to the activation of genes that are known to mediate the effects of interferon alpha (IFNα). The main effect of IFNα is to defend body cells against viral infections, but it is also able to defeat cancer cells. We observed that this activation of IFNα response by chemerin resulted from the increased production of IFNα protein in ovarian cancer cells, which then reduced cancer cells numbers. However, it remains to be investigated how exactly chemerin might be able to activate interferon alpha and its anti-tumoral actions.

Abstract

The pleiotropic adipokine chemerin affects tumor growth primarily as anti-tumoral chemoattractant inducing immunocyte recruitment. However, little is known about its effect on ovarian adenocarcinoma. In this study, we examined chemerin actions on ovarian cancer cell lines in vitro and intended to elucidate involved cell signaling mechanisms. Employing three ovarian cancer cell lines, we observed differentially pronounced effects of this adipokine. Treatment with chemerin (huChem-157) significantly reduced OVCAR-3 cell numbers (by 40.8% on day 6) and decreased the colony and spheroid growth of these cells by half. The spheroid size of SK-OV-3 ovarian cancer cells was also significantly reduced upon treatment. Transcriptome analyses of chemerin-treated cells revealed the most notably induced genes to be interferon alpha (IFNα)-response genes like IFI27, OAS1 and IFIT1 and their upstream regulator IRF9 in all cell lines tested. Finally, we found this adipokine to elevate IFNα levels about fourfold in culture medium of the employed cell lines. In conclusion, our data for the first time demonstrate IFNα as a mediator of chemerin action in vitro. The observed anti-tumoral effect of chemerin on ovarian cancer cells in vitro was mediated by the notable activation of IFNα response genes, resulting from the chemerin-triggered increase of secreted levels of this cytokine.

Chemerin enhances mesenchymal features of glioblastoma by establishing autocrine and paracrine networks in a CMKLR1-dependent manner

Glioblastoma multiforme (GBM) with mesenchymal features exhibits enhanced chemotherapeutic resistance and results in reduced overall survival. Recent studies have suggested that there is a positive correlation between the GBM mesenchymal status and immune cell infiltration. However, the mechanisms by which GBM acquires its mesenchymal features in a tumor immune microenvironment-dependent manner remains unknown. Here, we uncovered a chemerin-mediated autocrine and paracrine network by which the mesenchymal phenotype of GBM cells is strengthened. We identified chemerin as a prognostic secretory protein mediating the mesenchymal phenotype-promoting network between tumor-associated macrophages (TAMs) and tumor cells in GBM. Mechanistically, chemerin promoted the mesenchymal features of GBM by suppressing the ubiquitin-proteasomal degradation of CMKLR1, a chemerin receptor predominantly expressed on TAMs and partially expressed on GBM cells, thereby enhancing NF-κB pathway activation. Moreover, chemerin was found to be involved in the recruitment of TAMs in the GBM tumor microenvironment. We revealed that chemerin also enhances the mesenchymal phenotype-promoting ability of TAMs and promotes their M2 polarization via a CMKLR1/NF-κB axis, which further exacerbates the mesenchymal features of GBM. Blocking the chemerin/CMKLR1 axis with 2-(α-naphthoyl) ethyltrimethylammonium iodide disrupted the mesenchymal network and suppressed tumor growth in GBM. These results suggest the therapeutic potential of targeting the chemerin/CMKLR1 axis to block the mesenchymal network in GBM.

Chemerin promotes proliferation and migration of ovarian cancer cells by upregulating expression of PD-L1

Ovarian cancer is the third-most-common malignant reproductive tumor in women. According to the American Cancer Society, it has the highest mortality rate of gynecological tumors. The five-year survival rate was only 29% during the period from 1975 to 2008 (Reid et al., 2017). In recent decades, the five-year survival rate of ovarian cancer has remained around 30% despite continuous improvements in surgery, chemotherapy, radiotherapy, and other therapeutic methods. However, because of the particularity of the volume and location of ovarian tissue, the early symptoms of ovarian cancer are hidden, and there is a lack of highly sensitive and specific screening methods. Most patients have advanced metastasis, including abdominal metastasis, when they are diagnosed (Reid et al., 2017). Therefore, exploring the mechanism of ovarian cancer metastasis and finding early preventive measures are key to improving the survival rate and reducing mortality caused by ovarian cancer.

Neutrophils Promote Tumor Progression in Oral Squamous Cell Carcinoma by Regulating EMT and JAK2/STAT3 Signaling Through Chemerin

Oral squamous cell carcinoma (OSCC) is the most common malignancy of the oral cavity. In the tumor microenvironment, tumor-associated neutrophils (TANs) can promote tumor growth, invasion, and metastasis. The aim of our study was to explore the relationship between neutrophils infiltration and Chemerin expression in tumor cells, as well as their relationship with the clinicopathological parameters and clinical prognosis of 74 cases of OSCC. We also explored the role of the interaction between neutrophils and Chemerin in the functions of OSCC cells (Cal27, SCC9, and SCC15) in vitro. Our results showed that in OSCC, Chemerin over-expression may increase neutrophils infiltration in tumor tissues. Chemerin over-expression and neutrophils infiltration were the prognostic factors of poor clinical outcomes. Furthermore, we discovered that neutrophils promoted OSCC migration, invasion, and proliferation and EMT through Chemerin. Neutrophils activated JAK2/STAT3 signaling through Chemerin and then up-regulated its downstream signaling target genes, such as Phospho-Rb, E2F1, CyclinE1, and CyclinD1. Taken together, our results revealed that neutrophils and Chemerin are potentially involved in OSCC progression and metastasis. Neutrophils may promote the JAK2/STAT3 signaling pathway and EMT in OSCC cells through Chemerin.

Chemerin - exploring a versatile adipokine

Chemerin is a small chemotactic protein and a key player in initiating the early immune response. As an adipokine, chemerin is also involved in energy homeostasis and the regulation of reproductive functions. Secreted as inactive prochemerin, it relies on proteolytic activation by serine proteases to exert biological activity. Chemerin binds to three distinct G protein-coupled receptors (GPCR), namely chemokine-like receptor 1 (CMKLR1, recently named chemerin₁), G protein-coupled receptor 1 (GPR1, recently named chemerin₂), and CC-motif chemokine receptor-like 2 (CCRL2). Only CMKLR1 displays conventional G protein signaling, while GPR1 only recruits arrestin in response to ligand stimulation, and no CCRL2-mediated signaling events have been described to date. However, GPR1 undergoes constitutive endocytosis, making this receptor perfectly adapted as decoy receptor. Here, we discuss expression pattern, activation, and receptor binding of chemerin. Moreover, we review the current literature regarding the involvement of chemerin in cancer and several obesity-related diseases, as well as recent developments in therapeutic targeting of the chemerin system.

The Concentration of CMKLR1 Expression on Clinicopathological Parameters of Colorectal Cancer: A Preliminary Study

Background and Objectives: Colorectal cancer (CRC) is the second-most common cause of cancer-related deaths worldwide. Angiogenesis is crucial for cancer growth, infiltration of surrounding tissues, and metastasis and plays a key role in the pathogenesis of CRC. Chemerin/chemokine-like receptor 1 (CMKLR1) is one of the biochemical pathways involved in the regulation of angiogenesis in solid tumors. The aim of the study was to assess the CMKLR1 level in tumor and margin tissues of CRC in relation to histopathological parameters: microvessel density (MVD), budding, tumor-infiltrating lymphocytes (TILs), TNM scale, and grading. Materials and Methods: The study involved 43 samples of tumor and margin tissues obtained from CRC patients. To assess the concentration of CMKLR1 a commercially available enzyme-linked immunosorbent assay kit was used. For 35 cases, we performed CD34 immunostaining. The MVD, budding, and TILs were assessed using a light microscope. Results: The levels of CMKLR1 in both tumor and margin were negatively correlated with MVD and budding. CMKLR1 concentration in margin was higher in tissues with lymphocytic infiltration. Conclusions: Low vascularity and low budding are associated with higher CMKLR1 expression. CMKLR1 might play a multifunctional role in CRC pathogenesis by influencing tumor budding and peritumoral lymphocytic infiltration.

Chemerin regulates autophagy to participate in polycystic ovary syndrome

OBJECTIVE

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder in women of reproductive age. Chemerin has recently been discovered as a novel adipokine associated with obesity and metabolic syndrome. Excessive autophagy activity and overexpression of autophagy-related genes in follicular granulosa cells are important mechanisms of PCOS. This study aimed to investigate the effect of chemerin on autophagy in PCOS.

METHODS

A rat model of PCOS was established by subcutaneous injection of testosterone propionate under a high-fat diet. Expression levels of chemerin and its receptor CMKLR1 were determined by real-time polymerase chain reaction and western blot. Proliferation and apoptosis of human granulosa cells in vitro and expression of autophagy-related genes were examined using bafilomycin A1 (autophagy inhibitor) and Torin1 (autophagy inducer).

RESULTS

Chemerin and CMKLR1 expression were significantly increased in the ovary in a rat model of PCOS. Ectopic expression of chemerin promoted the proliferation and inhibited the apoptosis of COV434 cells. Ectopic expression of chemerin also induced autophagy by inhibiting the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway.

CONCLUSIONS

Chemerin and CMKLR1 were overexpressed in PCOS rats. Chemerin promoted autophagy through inhibiting the PI3K/Akt/mTOR pathway, and may provide a potential target and biomarker of PCOS.

Resistin Expression in Epithelial Ovarian Cancer promotes the Proliferation and Migration of Ovarian Cancer Cells to Worsen Prognosis

Background: Epithelial ovarian cancer (EOC) is the most common gynecological cancer in women. Resistin, an inflammatory adipocytokine, is associated with obesity, insulin resistance, and various cancer types.

Materials and Methods: We investigated resistin expression in tissues and its association with the clinicopathological characteristics and prognosis of patients with EOC. The SKOV3 and CAOV3 cell lines were treated with exogenous resistin and rapamycin (resistin inhibitor), and the expression of mTOR in SKOV3 and CAOV3 cells was measured. Cell proliferation was measured using the CCK-8 assay. Western blotting analysis was performed to examine the phosphorylation of P70S6K and mTOR. Wound healing and Transwell analyses were conducted to examine the effect of resistin on the migration of SKOV3 and CAOV3 cells.

Results: High resistin expression was positively correlated with the pathological grade (P = 0.017) and lymph node metastasis (P = 0.045). However, resistin expression was not correlated with age, FIGO stage, or residual tumor after initial laparotomy (P > 0.05). Cox multivariate analysis showed that resistin expression was an independent factor for determining disease-free survival, whereas lymph node metastasis, resistin expression, and age (≥55 years) were independent factors affecting overall survival. Exogenous resistin induced ovarian cancer cell proliferation, whereas rapamycin had the opposite effect. Resistin promoted the proliferation of ovarian cancer cells via the mTOR signaling pathway and was associated with phosphorylating P70S6K. Furthermore, resistin promoted the migration of ovarian cancer cells.

Conclusions: Resistin may promote the occurrence of ovarian cancer and is related to the prognosis of patients. This protein may also affect the proliferation of EOC cells through the mTOR signaling pathway. Therefore, resistin shows potential as a molecular therapeutic target in ovarian cancer.

The Role of Kallikrein 7 in Tumorigenesis

Kallikrein 7 (KLK7) is a secreted serine protease with chymotrypsic protease activity. Abnormally high expression of KLK7 is closely related to the occurrence and development of various types of cancer. Therefore, KLK7 has been identified as a potential target for cancer drug development design in recent years. KLK7 mediates various biological and pathological processes in tumorigenesis, including cell proliferation, migration, invasion, angiogenesis, and cell metabolism, by hydrolyzing a series of substrates such as membrane proteins, extracellular matrix proteins, and cytokines. This review mainly introduces the downstream cell signaling pathways involved in the activation of KLK7 and its substrate-related proteins. This review will not only help us to better understand the mechanisms of KLK7 in regulating biological and pathological processes of cancer cells, but also lay a solid foundation for the design of inhibitors targeting KLK7.

Cyclic Derivatives of the Chemerin C-Terminus as Metabolically Stable Agonists at the Chemokine-like Receptor 1 for Cancer Treatment

Chemerin is a small chemotactic protein and a modulator of the innate immune system. Its activity is mainly mediated by the chemokine-like receptor 1 (CMKLR1), a receptor expressed by natural killer cells, dendritic cells, and macrophages. Downregulation of chemerin is part of the immune evasion strategy exploited by several cancer types, including melanoma, breast cancer, and hepatocellular carcinoma. Administration of chemerin can potentially counteract these effects, but synthetically accessible, metabolically stable analogs are required. Other tumors display overexpression of CMKLR1, offering a potential entry point for targeted delivery of chemotherapeutics. Here, we present cyclic derivatives of the chemerin C-terminus (chemerin-9), the minimal activation sequence of chemerin. Chemerin-9 derivatives that were cyclized through positions four and nine retained activity while displaying full stability in blood plasma for more than 24 h. Therefore, these peptides could be used as a drug shuttle system to target cancer cells as demonstrated here by methotrexate conjugates.

Ligand-binding and -scavenging of the chemerin receptor GPR1

Tight regulation of cytokines is essential for the initiation and resolution of inflammation. Chemerin, a mediator of innate immunity, mainly acts on chemokine-like receptor 1 (CMKLR1) to induce the migration of macrophages and dendritic cells. The role of the second chemerin receptor, G protein-coupled receptor 1 (GPR1), is still unclear. Here we demonstrate that GPR1 shows ligand-induced arrestin3 recruitment and internalization. The chemerin C-terminus triggers this activation by folding into a loop structure, binding to aromatic residues in the extracellular loops of GPR1. While this overall binding mode is shared between GPR1 and CMKLR1, differences in their respective extracellular loop 2 allowed for the design of the first GPR1-selective peptide. However, our results suggest that ligand-induced arrestin recruitment is not the only mode of action of GPR1. This receptor also displays constitutive internalization, which allows GPR1 to internalize inactive peptides efficiently by an activation-independent pathway. Our results demonstrate that GPR1 takes a dual role in regulating chemerin activity: as a signaling receptor for arrestin-based signaling on one hand, and as a scavenging receptor with broader ligand specificity on the other.

Another Weapon against Cancer and Metastasis: Physical-Activity-Dependent Effects on Adiposity and Adipokines

Physically active behavior has been associated with a reduced risk of developing certain types of cancer and improved psychological conditions for patients by reducing anxiety and depression, in turn improving the quality of life of cancer patients. On the other hand, the correlations between inactivity, sedentary behavior, and overweight and obesity with the risk of development and progression of various cancers are well studied, mainly in middle-aged and elderly subjects. In this article, we have revised the evidence on the effects of physical activity on the expression and release of the adipose-tissue-derived mediators of low-grade chronic inflammation, i.e., adipokines, as well as the adipokine-mediated impacts of physical activity on tumor development, growth, and metastasis. Importantly, exercise training may be effective in mitigating the side effects related to anti-cancer treatment, thereby underlining the importance of encouraging cancer patients to engage in moderate-intensity activities. However, the strong need to customize and adapt exercises to a patient’s abilities is apparent. Besides the preventive effects of physically active behavior against the adipokine-stimulated cancer risk, it remains poorly understood how physical activity, through its actions as an adipokine, can actually influence the onset and development of metastases.

Radiolabeled Peptides for SPECT and PET Imaging in the Detection of Breast Cancer: Preclinical and Clinical Perspectives

Breast cancer is the most common cancer in women worldwide. Due to the heterogeneous nature of breast cancer, the optimal treatment and expected response for each patient may not necessarily be universal. Molecular imaging techniques could play an important role in the early detection and targeted therapy evaluation of breast cancer. This review focuses on the development of peptides labeled with SPECT and PET radionuclides for breast cancer imaging. We summarized the current status of radiolabeled peptides for different receptors in breast cancer. The characteristics of radionuclides and major techniques for peptide labeling are also briefly discussed.

Chemerin-156 is the Active Isoform in Human Hepatic Stellate Cells

The chemokine chemerin exists as C-terminally processed isoforms whose biological functions are mostly unknown. A highly active human chemerin variant (huChem-157) was protective in experimental hepatocellular carcinoma (HCC) models. Hepatic stellate cells (HSCs) are central mediators of hepatic fibrogenesis and carcinogenesis and express the chemerin receptors chemokine-like receptor 1 (CMKLR1) and G protein-coupled receptor 1 (GPR1). Here we aimed to analyse the effect of chemerin isoforms on the viability, proliferation and secretome of the human HSC cell line LX-2. Therefore, huChem-157, 156 and 155 were over-expressed in LX-2 cells, which have low endogenous chemerin levels. HuChem-157 produced in LX-2 cells activated CMKLR1 and GPR1, and huChem-156 modestly induced GPR1 signaling. HuChem-155 is an inactive chemerin variant. Chemerin isoforms had no effect on cell viability and proliferation. Cellular expression of the fibrotic proteins galectin-3 and alpha-smooth muscle actin was not regulated by any chemerin isoform. HuChem-156 increased IL-6, IL-8 and galectin-3 in cell media. HuChem-157 was ineffective, and accordingly, did not enhance levels of these proteins in media of primary human hepatic stellate cells when added exogenously. These analyses provide evidence that huChem-156 is the biologic active chemerin variant in hepatic stellate cells and acts as a pro-inflammatory factor.

A Screened GPR1 Peptide Exerts Antitumor Effects on Triple-Negative Breast Cancer

The adipokine chemerin has been considered an important regulator of tumor immune surveillance. Chemerin recruits leukocytes through the receptor CMKLR1 to improve clinical outcomes of tumors and overall patient survival, but the role of GPR1 in tumors has not been widely investigated. Here, we found that GPR1 expression is elevated in breast cancer-especially triple-negative breast cancer (TNBC) tissues and cell lines. Herein, we screened a phage display peptide library to identify LRH7-G5, a peptide antagonist that blocks chemerin/GPR1 signaling. This peptide performed as an anticancer agent to suppress the proliferation of the TNBC cell lines MDA-MB-231 and HCC1937 but has little effect on T47D cells. LRH7-G5 treatment significantly blocked tumor growth in a TNBC cell-bearing orthotopic mouse model. Last, our results showed that this peptide's antitumor role is mediated through the PI3K/AKT signaling pathway. In conclusion, these data collectively suggest that the chemerin receptor GPR1 is a novel target for controlling TNBC progression and establish peptide LRH7-G5 as a new therapeutic agent for suppressing TNBC tumor growth.

Circulating chemerin level and risk of cancer: a systematic review and meta-analysis

Aim: Circulating chemerin level has been reported to be higher in patients with various types of cancer. However, the conclusions obtained are not unified. The aim of present study is to draw an evidence-based conclusion on the relationship between circulating chemerin and risk of cancer. Materials & methods: A systematic search was carried out in PubMed and Web of Science up to 30 June 2019. The random-effects model was applied to calculate summary standardized mean differences with 95% CIs. Results: The meta-analysis included a total of 12 separate studies, 876 cases and 739 healthy controls. The results showed that the expression level of circulating chemerin was significantly higher in cancer patients than that in control group (pooled standardized mean difference = 1.47, 95% CI = 1.03-1.90). Conclusion: This meta-analysis concludes that a high level of circulating chemerin is strongly associated with cancer risk.

Chemerin Treatment Inhibits the Growth and Bone Invasion of Breast Cancer Cells

Chemerin is secreted as prochemerin from various cell types and then cleaved into the bioactive isoform by specific proteases. In various cancer types, chemerin exhibits pro- or antitumor effects. In the present study, chemerin treatment significantly inhibited the viability and invasion of breast cancer cells in the absence or presence of transforming growth factor (TGF)-β and insulin-like growth factor (IGF)-1. The expression levels of E-cadherin and vimentin were reduced in chemerin-treated breast cancer cells. However, chemerin treatment recovered the reduced E-cadherin expression level in breast cancer cells treated with TGF-β or IGF-1. Chemerin treatment inhibited nuclear β-catenin levels in breast cancer cells stimulated with or without TGF-β or IGF-1. In addition, chemerin treatment blocked the increase in the receptor activator of nuclear factor kappa-Β ligand (RANKL)/osteoprotegerin (OPG) ratio in osteoblastic cells exposed to metastatic breast cancer cell-derived conditioned medium. Chemerin treatment inhibited RANKL-induced osteoclast formation and bone resorption by reducing the secretion of matrix metalloproteinase (MMP)-2, MMP-9, and cathepsin K. Intraperitoneal administration of chemerin inhibited tumor growth in MCF-7 breast cancer cell-injected mice and reduced the development of osteolytic lesions resulting from intratibial inoculation of MDA-MB-231 cells. Taken together, chemerin inhibits the growth and invasion of breast cancer cells and prevents bone loss resulting from breast cancer cells by inhibiting finally osteoclast formation and activity.

Chemerin in immune response and gastrointestinal pathophysiology

Chemerin is a multifunctional protein involved among others in adipogenesis, angiogenesis and lipid as well as glucose metabolism. Chemerin is an essential factor in promotion of chemotaxis of numerous immune cell types and plays an important role in several pathophysiologic conditions. Chemerin receptors are present on monocytes/macrophages, T cells, natural killer and dendritic cells as well as neutrophils. However, the role of chemerin and chemerin receptors in immune response and gastrointestinal diseases is still poorly understood. Accumulating, clinical and experimental studies observed disturbation of chemerin and chemerin receptors in a number of disorders including Barrett's esophagus, esophageal cancer, gastric cancer, hepatic dysfunction, irritable bowel syndrome, inflammatory bowel disease and colorectal cancer. Moreover, chemerin and chemerin receptors have been shown to regulate proliferation, migration and invasion of gastrointestinal and immune cells as well as cancer-associated fibroblasts. In this review we present the current state of knowledge about the contribution of chemerin to immune response and gastrointestinal disorders.

Assessment of CMKLR1 level in colorectal cancer and its correlation with angiogenic markers

INTRODUCTION

Colorectal cancer (CRC) is the second most common malignant neoplasm in men and third in women. It is also the third leading cause of cancer-related death, killing annually >700,000 patients in the world. The global burden of CRC is expected to increase by 60% to >2.2 million new cases and 1.1 million deaths by 2030. The pathogenesis of cancer mainly depends on angiogenesis. This process plays a key role in the growth and infiltration of tumors which is essential for distant metastases. A large number of biochemical pathways is involved in the regulation of angiogenesis. As a subject of our study, we chose chemerin/chemokine-like receptor 1 (CMKLR1) pathway which is responsible for the angiogenic processes in malignant neoplasms.

AIM OF THE STUDY

To assess the CMKLR1 level and the concentrations of the two markers of angiogenesis, matrix metalloproteinase (MMP)-9 and vascular cell adhesion molecule (VCAM)-1, in tumor and margin tissues of CRC in relation to histological grade and TNM classification.

MATERIALS AND METHODS

The study used 47 samples of tumor and margin tissues derived from CRC patients. To determine the concentration of CMKLR1, MMP-9, and VCAM-1, we used the commercially available enzyme-linked immunosorbent assay kit.

RESULTS

We found a significantly higher concentration of CMKLR1 and MMP-9 in tumor tissue compared to margin. There was no difference in VCAM-1 concentration between tumor and margin. The margin concentration of CMKLR1 was significantly correlated with that of both MMP-9 and VCAM-1. The margin concentration of VCAM-1 was correlated with that of MMP-9. Additionally, we observed that the tumor levels of CMKLR1 and MMP-9 were positively correlated with the tumor size (T parameter).

CONCLUSION

CMKLR1 activity may be associated with the angiogenic process in CRC via MMP-9 activity. Further research, involving a larger sample, may verify whether chemerin/CMKLR1 axis could be considered as a suitable target in novel molecular therapies.

Overexpression of Hepatocyte Chemerin-156 Lowers Tumor Burden in a Murine Model of Diethylnitrosamine-Induced Hepatocellular Carcinoma

The tumor inhibitory potential of the highly active chemerin-156 isoform was described in orthotopic models of hepatocellular carcinoma (HCC). The majority of HCC arises in the fibrotic liver, which was not reproduced in these studies. Here, a potential therapeutic activity of chemerin-156 was evaluated in diethylnitrosamine (DEN)-induced liver cancer, which mimics fibrosis-associated HCC. Mice were infected with adeno-associated virus (AAV) six months after DEN injection to overexpress chemerin-156 in the liver, and animals injected with non-recombinant-AAV served as controls. Three months later, the animals were killed. Both groups were comparable with regard to liver steatosis and fibrosis. Of note, the number of very small tumors was reduced by chemerin-156. Anyhow, the expression of inflammatory and profibrotic genes was similar in larger tumors of control and chemerin-156-AAV-infected animals. Although genes with a role in lipid metabolism, like 3-hydroxy-3-methylglutaryl-coenzym-A--reductase, were overexpressed in tumors of animals with high chemerin-156, total hepatic cholesterol, diacylglycerol and triglyceride levels, and distribution of individual lipid species were normal. Chemerin-156-AAV-infected mice had elevated hepatic and systemic chemerin. Ex vivo activation of the chemerin receptor chemokine-like receptor 1 increased in parallel with serum chemerin, illustrating the biological activity of the recombinant protein. In the tumors, chemerin-155 was the most abundant variant. Chemerin-156 was not detected in tumors of the controls and was hardly found in chemerin-156-AAV infected animals. In conclusion, the present study showed that chemerin-156 overexpression caused a decline in the number of small lesions but did not prevent the growth of pre-existing neoplasms.

More Than an Adipokine: The Complex Roles of Chemerin Signaling in Cancer

Chemerin is widely recognized as an adipokine, with diverse biological roles in cellular differentiation and metabolism, as well as a leukocyte chemoattractant. Research investigating the role of chemerin in the obesity-cancer relationship has provided evidence both for pro- and anti-cancer effects. The tumor-promoting effects of chemerin primarily involve direct effects on migration, invasion, and metastasis as well as growth and proliferation of cancer cells. Chemerin can also promote tumor growth via the recruitment of tumor-supporting mesenchymal stromal cells and stimulation of angiogenesis pathways in endothelial cells. In contrast, the majority of evidence supports that the tumor-suppressing effects of chemerin are immune-mediated and result in a shift from immunosuppressive to immunogenic cell populations within the tumor microenvironment. Systemic chemerin and chemerin produced within the tumor microenvironment may contribute to these effects via signaling through CMKLR1 (chemerin₁), GPR1 (chemerin₂), and CCLR2 on target cells. As such, inhibition or activation of chemerin signaling could be beneficial as a therapeutic approach depending on the type of cancer. Additional studies are required to determine if obesity influences cancer initiation or progression through increased adipose tissue production of chemerin and/or altered chemerin processing that leads to changes in chemerin signaling in the tumor microenvironment.

CMKLR1-targeting peptide tracers for PET/MR imaging of breast cancer

Background: Molecular targeting remains to be a promising approach in oncology. Overexpression of G protein-coupled receptors (GPCRs) in human cancer is offering a powerful opportunity for tumor-selective imaging and treatment employing nuclear medicine. We utilized novel chemerin-based peptide conjugates for chemokine-like receptor 1 (CMKLR1) targeting in a breast cancer xenograft model. Methods: By conjugation with the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), we obtained a family of five highly specific, high-affinity tracers for hybrid positron emission tomography/magnetic resonance (PET/MR) imaging. A xenograft model with target-positive DU4475 and negative A549 tumors in immunodeficient nude mice enabled CMKLR1-specific imaging in vivo. We acquired small animal PET/MR images, assessed biodistribution by ex vivo measurements and investigated the tracer specificity by blocking experiments. Results: Five CMKLR1-targeting peptide tracers demonstrated high biological activity and affinity in vitro with EC₅₀ and IC₅₀ values below 2 nM. Our target-positive (DU4475) and target-negative (A549) xenograft model could be validated by ex vivo analysis of CMKLR1 expression and binding. After preliminary PET imaging, the three most promising tracers [⁶⁸Ga]Ga-DOTA-AHX-CG34, [⁶⁸Ga]Ga-DOTA-KCap-CG34 and [⁶⁸Ga]Ga-DOTA-ADX-CG34 with best tumor uptake were further analyzed. Hybrid PET/MR imaging along with concomitant biodistribution studies revealed distinct CMKLR1-specific uptake (5.1% IA/g, 3.3% IA/g and 6.2% IA/g 1 h post-injection) of our targeted tracers in DU4475 tumor tissue. In addition, tumor uptake was blocked by excess of unlabeled peptide (6.4-fold, 5.5-fold and 3.4-fold 1 h post-injection), further confirming CMKLR1 specificity. Out of five tracers, we identified these three tracers with moderate, balanced hydrophilicity to be the most potent in receptor-mediated tumor targeting. Conclusion: We demonstrated the applicability of ⁶⁸Ga-labeled peptide tracers by visualizing CMKLR1-positive breast cancer xenografts in PET/MR imaging, paving the way for developing them into theranostics for tumor treatment.

Chemerin and Cancer

Chemerin is a multifunctional adipokine with established roles in inflammation, adipogenesis and glucose homeostasis. Increasing evidence suggest an important function of chemerin in cancer. Chemerin's main cellular receptors, chemokine-like receptor 1 (CMKLR1), G-protein coupled receptor 1 (GPR1) and C-C chemokine receptor-like 2 (CCRL2) are expressed in most normal and tumor tissues. Chemerin's role in cancer is considered controversial, since it is able to exert both anti-tumoral and tumor-promoting effects, which are mediated by different mechanisms like recruiting innate immune defenses or activation of endothelial angiogenesis. For this review article, original research articles on the role of chemerin and its receptors in cancer were considered, which are listed in the PubMed database. Additionally, we included meta-analyses of publicly accessible DNA microarray data to elucidate the association of expression of chemerin and its receptors in tumor tissues with patients' survival.

Chemerin Suppresses Breast Cancer Growth by Recruiting Immune Effector Cells Into the Tumor Microenvironment

Infiltration of immune cells into the tumor microenvironment (TME) can regulate growth and survival of neoplastic cells, impacting tumorigenesis and tumor progression. Correlations between the number of effector immune cells present in a tumor and clinical outcomes in many human tumors, including breast, have been widely described. Current immunotherapies utilizing checkpoint inhibitors or co-stimulatory molecule agonists aim to activate effector immune cells. However, tumors often lack adequate effector cell numbers within the TME, resulting in suboptimal responses to these agents. Chemerin (RARRES2) is a leukocyte chemoattractant widely expressed in many tissues and is known to recruit innate leukocytes. CMKLR1 is a chemotactic cellular receptor for chemerin and is expressed on subsets of dendritic cells, NK cells, and macrophages. We have previously shown that chemerin acts as a tumor suppressive cytokine in mouse melanoma models by recruiting innate immune defenses into the TME. Chemerin/RARRES2 is down-regulated in many tumors, including breast, compared to normal tissue counterparts. Here, using a syngeneic orthotopic EMT6 breast carcinoma model, we show that forced overexpression of chemerin by tumor cells results in significant recruitment of NK cells and T cells within the TME. While chemerin secretion by EMT6 cells did not alter their phenotypic behavior in vitro, it did significantly suppress tumor growth in vivo. To define the cellular effectors required for this anti-tumor phenotype, we depleted NK cells or CD8+ T cells and found that either cell type is required for chemerin-dependent suppression of EMT6 tumor growth. Finally, we show significantly reduced levels of RARRES2 mRNA in human breast cancer samples compared to matched normal tissues. Thus, for the first time we have shown that increasing chemerin expression within the breast carcinoma TME can suppress growth by recruitment of NK and T cells, thereby supporting this approach as a promising immunotherapeutic strategy.

The serum biomarker chemerin promotes tumorigenesis and metastasis in oral squamous cell carcinoma

Chemerin, which is encoded by retinoic acid receptor responder 2 (RARRES2), has been found to be related to malignant tumours, but its role in the development of oral squamous cell carcinoma (OSCC) is largely unexplored. In the present study, a higher serum level of chemerin was evident in patients with OSCC than in healthy individuals, and this high level of chemerin significantly decreased after tumour resection. In addition, high chemerin levels were positively associated with advanced tumour stage and lymph node metastasis. The expression levels of chemerin and Chemerin Receptor 23 (ChemR23) were positively correlated with the migration and invasion of OSCC cell lines. Recombinant chemerin (R-chemerin) enhanced the in vitro migration, invasion and proliferation of OSCC cells in a concentration-dependent manner, and short hairpin RNAs (shRNAs) targeting RARRES2 decreased chemerin expression and inhibited OSCC cell metastasis and proliferation both in vitro and in vivo Additionally, R-chemerin activated manganese superoxide dismutase (SOD2) and increased the amount of intracellular hydrogen peroxide (H₂O₂), leading to a significant decrease in E-cadherin expression and dramatic increase in the expression of phosphorylated ERK1/2 (p-ERK1/2), Slug, Vimentin and N-cadherin, but shRNAs targeting RARRES2 reversed these effects. Moreover, knockdown of ChemR23 with small interfering RNAs (siRNA) significantly inhibited chemerin-induced OSCC cell migration/invasion and SOD2 activity. Our results revealed that chemerin is a novel biomarker for OSCC. Chemerin/ChemR23 promotes tumorigenesis and metastasis in OSCC and may be a new therapeutic target for OSCC.

Chemerin acts via CMKLR1 and GPR1 to stimulate migration and invasion of gastric cancer cells: putative role of decreased TIMP-1 and TIMP-2

The chemokine-like peptide, chemerin, stimulates chemotaxis in several cell types. In this study we examined the expression of putative chemerin receptors in gastric cancer and the action of chemerin on cancer cell migration and invasion. Immunohistochemical studies of gastric tumors identified expression of two putative receptors, chemokine-like receptor-1 (CMKLR1) and G-protein coupled receptor 1(GPR1), in cancer cells; there was also some expression in stromal myofibroblasts although generally at a lower intensity. The expression of both receptors was detected in a gastric cancer cell line, AGS; chemerin itself was expressed in cultured gastric cancer myofibroblasts but not AGS cells. Chemerin stimulated (a) morphological transformation of AGS cells characterized by extension of processes and cell scattering, (b) migration in scratch wound assays and (c) both migration and invasion in Boyden chamber chemotaxis assays. These responses were inhibited by two putative receptor antagonists CCX832 and α-NETA. Inhibition of receptor expression by siRNA selectively reduced CMKLR1 or GPR1 and inhibited the action of chemerin indicating that both receptors contributed to the functional response. Using a proteomic approach employing stable isotope dynamic labeling of secretomes (SIDLS) to selectively label secreted proteins, we identified down regulation of tissue inhibitors of metalloproteinease (TIMP)1 and TIMP2 in media in response to chemerin. When cells were treated with chemerin and TIMP1 or TIMP2 the migration response to chemerin was reduced. The data suggest a role for chemerin in promoting the invasion of gastric cancer cells via CMKLR1 and GPR1at least partly by reducing TIMP1 and TIMP2 expression. Chemerin receptor antagonists have potential in inhibiting gastric cancer progression.

Mechanisms and Functions of Chemerin in Cancer: Potential Roles in Therapeutic Intervention

Chemerin [RARRES2 [retinoic acid receptor responder 2], TIG2 [tazarotene induced gene 2 (TIG2)]] is a multifunctional cytokine initially described in skin cultures upon exposure to the synthetic retinoid tazarotene. Its secreted pro-form, prochemerin, is widely expressed, found systemically, and is readily converted into active chemerin by various proteases. Subsequent studies elucidated major roles of chemerin as both a leukocyte chemoattractant as well as an adipokine. Chemerin's main chemotactic receptor, the G-protein coupled receptor CMKLR1, is expressed on macrophages, dendritic, and NK cells. With respect to its role in immunology, chemerin mediates trafficking of these cells to sites of inflammation along its concentration gradient, and likely helps coordinate early responses, as it has been shown to have antimicrobial and angiogenic properties, as well. Recently, there has been mounting evidence that chemerin is an important factor in various cancers. As with its role in immune responses-where it can act as both a pro- and anti-inflammatory mediator-the potential functions or correlations chemerin has in or with cancer appears to be context dependent. Most studies, however, suggest a downregulation or loss of chemerin/RARRES2 in malignancies compared to the normal tissue counterparts. Here, we perform a comprehensive review of the literature to date and summarize relevant findings in order to better define the roles of chemerin in the setting of the tumor microenvironment and tumor immune responses, with an ultimate focus on the potential for therapeutic intervention.

Expression of chemerin correlates with a poor prognosis in female breast cancer patients

Objective

Chemerin was reported to regulate adipogenesis, metabolism, and immunity. But, its relation to cancer remains controversial. In breast cancer, chemerin expression has only been studied in serum, however, its expression in tissue, to our knowledge, has not been studied. The aim of this study was to investigate chemerin expression in breast cancer tissue in comparison to the adjacent normal tissue, and to assess its relationship to disease prognosis.

Methods

We examined chemerin expression in tissue with immunohistochemistry and analyzed the association of chemerin expression with the patients’ clinical and pathological characteristics to determine its role as a predictor of the disease and its relation to disease prognosis.

Results

We detected a significantly higher expression of chemerin in the malignant vs the non-cancerous tissue specimens in 30/53, (56%) patients, (P=0.001). Moreover, its expression was significantly higher in the metastatic lymph nodes in comparison to the tumor tissues, (P=0.01). Chemerin expression was significantly correlated with weight (r=0.256, P=0.04), body mass index (r=0.233, P=0.03), tumor size (r=0.235, P=0.03), lymph node metastasis (r=0.265, P=0.045), distant metastasis (r=0.267, P=0.02), and tumor grading, (r=0.421, P=0.004), while it was inversely significantly correlated with estrogen receptor and progesterone receptor expression in malignant breast tissues (P=0.038, r=−0.437, and P=0.047, r=–0.316), respectively. The area under the receiver operating characteristic curve for chemerin as a predictor of breast cancer was 0.82, (P<0.001, sensitivity 89%, and specificity 69%). The Kaplan–Meier survival curves revealed that patients with higher chemerin expression had worse overall survival in comparison to those with a lower chemerin expression, (P=0.001).

Conclusion

Our results revealed higher chemerin expression in malignant vs adjacent normal breast tissue and lend support to a presumable role of chemerin tissue expression as an independent predictor of poor prognosis in breast cancer patients.

Upregulation of Nrf2 and Decreased Redox Signaling Contribute to Renoprotective Effects of Chemerin Receptor Blockade in Diabetic Mice

Chemerin, acting through its receptor ChemR23, is an adipokine associated with inflammatory response, glucose and lipid metabolism and vascular function. Although this adipokine has been associated with the development and progression of kidney disease, it is not clear whether the chemerin/ChemR23 system plays a role in renal function in the context of diabetes. Therefore, we sought to determine whether ChemR23 receptor blockade prevents the development and/or progression of diabetic nephropathy and questioned the role of oxidative stress and Nrf2 in this process. Renal redox state and function were assessed in non-diabetic lean db/m and diabetic obese db/db mice treated with vehicle or CCX832 (ChemR23 antagonist). Renal reactive oxygen species (ROS) production, which was increased in diabetic mice, was attenuated by CCX832. This was associated with an increase in Nox 4 expression. Augmented protein oxidation in db/db mice was not observed when mice were treated with CCX832. CCX832 also abrogated impaired Nrf2 nuclear activity and associated downregulation in antioxidants expression in kidneys from db/db mice. Our in vivo findings highlight the role of the redox signaling and Nrf2 system as renoprotective players during chemerin receptor blockade in diabetic mice. The chemerin/ChemR23 system may be an important target to limit renal dysfunction associated with obesity-related diabetes.

Assessment of Serum Levels of the Adipocytokine Chemerin in Colorectal Cancer Patients

Background

Colorectal cancer (CRC) is one of the most common cancers worldwide. The tumor microenvironment is very important for determining cancer cell growth and spreading. Chemerin, a newly identified adipokine secreted by adipose tissue, is known to be associated with obesity, metabolic syndrome, and insulin resistance. The present study was carried out to investigate the association between serum levels of chemerin and colorectal cancer.

Methods

Thirty-two patients with colorectal cancer aged 57.6±6.5 years, and twenty age, sex and BMI matched healthy controls were included in the study. Serum che me rin levels were determined using enzyme linked immuno sorbent assay. C-reactive protein (CRP) levels were determined using a turbidimetric immunoassay. Carcino embryonic antigen (CEA) and carbohydrate antigen (CA 19-9) were measured by radioimmunoassay.

Results

Chemerin levels were found to be significantly higher in patients relative to the controls (P<0.001) and gradually increased with the TNM tumor stage progression. The mean CRP, CEA and CA 19-9 levels were also significantly higher in patients (P<0.001). There was a significant correlation between the serum levels of chemerin and the other measured parameters in CRC patients. The area under receiver operating characteristic curve (ROC) for serum chemerin was 1 at a cut-off value ≥ 161.5 with 100% sensitivity and 100% specificity.

Conclusions

Conclusions: The observed results suggest that chemerin may have a potential role in the pathogenesis and progression of colorectal malignancy and may be a good biomarker of colorectal cancer and stage progression.

Underrated enemy - from nonalcoholic fatty liver disease to cancers of the gastrointestinal tract

Nonalcoholic fatty liver disease (NAFLD) is intrahepatic ectopic lipid deposition which is present despite a lack of other causes of secondary hepatic fat accumulation. It is the most common chronic liver disorder in the welldeveloped countries. NAFLD is a multidisciplinary disease that affects various systems and organs and is inextricably linked to simple obesity, metabolic syndrome, insulin resistance and overt diabetes mellitus type 2. The positive energy balance related to obesity leads to a variety of systemic changes including modified levels of insulin, insulin- like growth factor-1, adipokines, hepatokines and cytokines. It is strongly linked to carcinogenesis and new evidence proves that NAFLD is associated with higher risk of all-cause mortality and cancer-specific mortality among cancer survivors. This article focuses on the association between NAFLD and extrahepatic gastrointestinal tract cancers, aiming to shed light on the pathomechanism of changes leading to the development of tumors.

Senescent fibroblast-derived Chemerin promotes squamous cell carcinoma migration

Aging is associated with a rising incidence of cutaneous squamous cell carcinoma (cSCC), an aggressive skin cancer with the potential for local invasion and metastasis. Acquisition of a senescence-associated secretory phenotype (SASP) in dermal fibroblasts has been postulated to promote skin cancer progression in elderly individuals. The underlying molecular mechanisms are largely unexplored. We show that Chemerin, a previously unreported SASP factor released from senescent human dermal fibroblasts, promotes cSCC cell migration, a key feature driving tumor progression. Whereas the Chemerin abundance is downregulated in malignant cSCC cells, increased Chemerin transcripts and protein concentrations are detected in replicative senescent fibroblasts in vitro and in the fibroblast of skin sections from old donors, indicating that a Chemerin gradient is built up in the dermis of elderly. Using Transwell^® migration assays, we show that Chemerin enhances the chemotaxis of different cSCC cell lines. Notably, the Chemerin receptor CCRL2 is remarkably upregulated in cSCC cell lines and human patient biopsies. Silencing Chemerin in senescent fibroblasts or the CCRL2 and GPR1 receptors in the SCL-1 cSCC cell line abrogates the Chemerin-mediated chemotaxis. Chemerin triggers the MAPK cascade via JNK and ERK1 activation, whereby the inhibition impairs the SASP- or Chemerin-mediated cSCC cell migration.

Taken together, we uncover a key role for Chemerin, as a major factor in the secretome of senescent fibroblasts, promoting cSCC cell migration and possibly progression, relaying its signals through CCRL2 and GPR1 receptors with subsequent MAPK activation. These findings might have implications for targeted therapeutic interventions in elderly patients.

International Union of Basic and Clinical Pharmacology CIII: Chemerin Receptors CMKLR1 (Chemerin1) and GPR1 (Chemerin2) Nomenclature, Pharmacology, and Function

Chemerin, a chemoattractant protein and adipokine, has been identified as the endogenous ligand for a G protein–coupled receptor encoded by the gene CMKLR1 (also known as ChemR23), and as a consequence the receptor protein was renamed the chemerin receptor in 2013. Since then, chemerin has been identified as the endogenous ligand for a second G protein–coupled receptor, encoded by the gene GPR1. Therefore, the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification recommends that the official name of the receptor protein for chemokine-like receptor 1 (CMKLR1) is chemerin receptor 1, and G protein–coupled receptor 1 is chemerin receptor 2 to follow the convention of naming the receptor protein after the endogenous ligand. Chemerin receptor 1 and chemerin receptor 2 can be abbreviated to Chemerin₁ and Chemerin₂, respectively. Chemerin requires C-terminal processing for activity, and human chemerin21–157 is reported to be the most active form, with peptide fragments derived from the C terminus biologically active at both receptors. Small-molecule antagonist, CCX832, selectively blocks CMKLR1, and resolvin E1 activation of CMKLR1 is discussed. Activation of both receptors by chemerin is via coupling to G_i/o, causing inhibition of adenylyl cyclase and increased Ca²⁺ flux. Receptors and ligand are widely expressed in humans, rats, and mice, and both receptors share ∼80% identity across these species. CMKLR1 knockout mice highlight the role of this receptor in inflammation and obesity, and similarly, GPR1 knockout mice exhibit glucose intolerance. In addition, the chemerin receptors have been implicated in cardiovascular disease, cancer, steroidogenesis, human immunodeficiency virus replication, and neurogenerative disease.

Cell cycle dependent expression of the CCK2 receptor by gastrointestinal myofibroblasts: putative role in determining cell migration

The well‐known action of the gastric hormone gastrin in stimulating gastric acid secretion is mediated by activation of cholecystokinin‐2 receptors (CCK2R). The latter are expressed by a variety of cell types suggesting that gastrin is implicated in multiple functions. During wound healing in the stomach CCK2R may be expressed by myofibroblasts. We have now characterized CCK2R expression in cultured myofibroblasts. Immunocytochemistry showed that a relatively small proportion (1–6%) of myofibroblasts expressed the receptor regardless of the region of the gut from which they were derived, or whether from cancer or control tissue. Activation of CCK2R by human heptadecapeptide gastrin (hG17) increased intracellular calcium concentrations in a small subset of myofibroblasts indicating the presence of a functional receptor. Unexpectedly, we found over 80% of cells expressing CCK2R were also labeled with 5‐ethynyl‐2′‐deoxyuridine (EdU) which is incorporated into DNA during S‐phase of the cell cycle. hG17 did not stimulate EdU incorporation but increased migration of both EdU‐labeled and unlabelled myofibroblasts; the migratory response was inhibited by a CCK2R antagonist and by an inhibitor of IGF receptor tyrosine kinase; hG17 also increased IGF‐2 transcript abundance. The data suggest myofibroblasts express CCK2R in a restricted period of the cell cycle during S‐phase, and that gastrin accelerates migration of these cells; it also stimulates migration of adjacent cells probably through paracrine release of IGF. Together with previous findings, the results raise the prospect that gastrin controls the position of dividing myofibroblasts which may be relevant in wound healing and cancer progression in the gastrointestinal tract.

Inhibition of chemerin/CMKLR1 axis in neuroblastoma cells reduces clonogenicity and cell viability in vitro and impairs tumor growth in vivo

Pro-inflammatory cells, cytokines, and chemokines are essential in promoting a tumor supporting microenvironment. Chemerin is a chemotactic protein and a natural ligand for the receptors CMKLR1, GPR1, and CCRL2. The chemerin/CMKLR1 axis is involved in immunity and inflammation, and it has also been implicated in obesity and cancer. In neuroblastoma, a childhood tumor of the peripheral nervous system we identified correlations between high CMKLR1 and GPR1 expression and reduced overall survival probability. CMKLR1, GPR1, and chemerin RNA and protein were detected in neuroblastoma cell lines and neuroblastoma primary tumor tissue. Chemerin induced calcium mobilization, increased MMP-2 synthesis as well as MAP-kinase- and Akt-mediated signaling in neuroblastoma cells. Stimulation of neuroblastoma cells with serum, TNFα or IL-1β increased chemerin secretion. The small molecule CMKLR1 antagonist α-NETA reduced the clonogenicity and viability of neuroblastoma cell lines indicating the chemerin/CMKLR1 axis as a promoting factor in neuroblastoma tumorigenesis. Furthermore, nude mice carrying neuroblastoma SK-N-AS cells as xenografts showed impaired tumor growth when treated daily with α-NETA from day 1 after tumor cell injection. This study demonstrates the potential of the chemerin/CMKLR1 axis as a prognostic factor and possible therapeutic target in neuroblastoma.