Role of CXC chemokine receptor type 7 in carcinogenesis and lymph node metastasis of colon cancer

The role of CXCL12 axis in pancreatic cancer: New biomarkers and potential targets

Introduction

Chemokines are small, secreted peptides involved in the mediation of the immune cell recruitment. Chemokines have been implicated in several diseases including autoimmune diseases, viral infections and also played a critical role in the genesis and development of several malignant tumors. CXCL12 is a homeostatic CXC chemokine involved in the process of proliferation, and tumor spread. Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive tumors, that is still lacking effective therapies and with a dramatically poor prognosis.

Method

We conducted a scientific literature search on Pubmed and Google Scholar including retrospective, prospective studies and reviews focused on the current research elucidating the emerging role of CXCL12 and its receptors CXCR4 - CXCR7 in the pathogenesis of pancreatic cancer.

Results

Considering the mechanism of immunomodulation of the CXCL12-CXCR4-CXCR7 axis, as well as the potential interaction with the microenvironment in the PDAC, several combined therapeutic approaches have been studied and developed, to overcome the "cold" immunological setting of PDAC, like combining CXCL12 axis inhibitors with anti PD-1/PDL1 drugs.

Conclusion

Understanding the role of this chemokine's axis in disease initiation and progression may provide the basis for developing new potential biomarkers as well as therapeutic targets for related pancreatic cancers.

Inhibition of Angiogenesis by MiR-524-5p through Suppression of AKT and ERK Activation by Targeting CXCR7 in Colon Cancer Cells

Increasing evidence shows that alterations in microRNA (miRNA) expression are involved in the occurrence and development of various malignant tumors, including colon cancer. MiRNA-524-5p has been reported to have anticancer activity in colon cancer. This study explored the influence of the miRNA-524-5p/CXCR7 axis on angiogenesis using colon cancer cells and further studied the mechanisms involved. We found that changing the expression of miRNA-524-5p can affect colonic proliferation, migration, and angiogenesis. Furthermore, angiogenesis induced by miRNA-524-5p overexpression was reversed by overexpression of CXCR7 in HT-29 cells, while the opposite was observed in Caco-2 cells. Furthermore, miRNA-524-5p inhibited the activation of AKT and ERK signaling by targeting CXCR7. Overall, our results indicated that the miRNA-524-5p/CXCR7 axis regulated angiogenesis in colon cancer cells through the AKT and ERK pathways.

CXCL12-CXCR4/CXCR7 Axis in Colorectal Cancer: Therapeutic Target in Preclinical and Clinical Studies

Chemokines are chemotactic cytokines that promote cancer growth, metastasis, and regulate resistance to chemotherapy. Stromal cell-derived factor 1 (SDF1) also known as C-X-C motif chemokine 12 (CXCL12), a prognostic factor, is an extracellular homeostatic chemokine that is the natural ligand for chemokine receptors C-X-C chemokine receptor type 4 (CXCR4), also known as fusin or cluster of differentiation 184 (CD184) and chemokine receptor type 7 (CXCR7). CXCR4 is the most widely expressed rhodopsin-like G protein coupled chemokine receptor (GPCR). The CXCL12-CXCR4 axis is involved in tumor growth, invasion, angiogenesis, and metastasis in colorectal cancer (CRC). CXCR7, recently termed as atypical chemokine receptor 3 (ACKR3), is amongst the G protein coupled cell surface receptor family that is also commonly expressed in a large variety of cancer cells. CXCR7, like CXCR4, regulates immunity, angiogenesis, stem cell trafficking, cell growth and organ-specific metastases. CXCR4 and CXCR7 are expressed individually or together, depending on the tumor type. When expressed together, CXCR4 and CXCR7 can form homo- or hetero-dimers. Homo- and hetero-dimerization of CXCL12 and its receptors CXCR4 and CXCR7 alter their signaling activity. Only few drugs have been approved for clinical use targeting CXCL12-CXCR4/CXCR7 axis. Several CXCR4 inhibitors are in clinical trials for solid tumor treatment with limited success whereas CXCR7-specific inhibitors are still in preclinical studies for CRC. This review focuses on current knowledge of chemokine CXCL12 and its receptors CXCR4 and CXCR7, with emphasis on targeting the CXCL12-CXCR4/CXCR7 axis as a treatment strategy for CRC.

Expression of CXCR7 in colorectal adenoma and adenocarcinoma: Correlation with clinicopathological parameters

Colorectal carcinoma (CRC) is one of the most lethal malignancies, it ranks third in cancer-related morbidity and mortality. Although great progress has been made in early diagnosis and combined treatment of CRC, the prognosis of patients remains poor owing to the high rate of recurrence and distant metastasis. CXCR7 belongs to chemokine receptor family and has been identified as a novel receptor for CXCL12. It plays an important role in development and in progression of cancer to metastatic stage.

THE AIM OF STUDY

To evaluate the immunohistochemical expression of CXCR7 in colorectal adenoma and carcinoma and to analyze its correlation with clinicopathological factors. This is retrospective study including 58 colonic adenocarcinoma specimens and 18 cases of colonic adenoma.

RESULTS

CXCR7 showed positive cytoplasmic expression in two out 18 cases of colorectal adenoma (11%) and 42 out of 58 cases of CRC (72.4%) with a significant difference between both (p < 0.001). We found a significant correlation between upregulation of CXCR7 and presence of lymphovascular tumor emboli, presence of lymph node metastasis and advanced TNM stage of the CRC. The association of the CXCR7 with patient age, sex, tumor size, depth of invasion and tumor cell differentiation was found to be non-significant. Regarding colonic adenoma, we found no significant association between CXCR7 expression on one hand and patient age, sex, tumor size, histologic type and degree of dysplasia on the other hand.

CONCLUSION

CXCR7 in CRC may act as a novel predictive indicator for prognosis and even be a potential molecular target for anticancer therapies.

Functions and mechanisms of chemokine receptor 7 in tumors of the digestive system

Chemokine (C-X-C motif) receptor 7 (CXCR7), recently termed ACKR3, belongs to the G protein-coupled cell surface receptor family, binds to stromal cell-derived factor-1 [SDF-1, or chemokine (C-X-C motif) ligand 12] or chemokine (C-X-C motif) ligand 11, and is the most common chemokine receptor expressed in a variety of cancer cells. SDF-1 binds to its receptor chemokine (C-X-C motif) receptor 4 (CXCR4) and regulates cell proliferation, survival, angiogenesis and migration. In recent years, another new receptor for SDF-1, CXCR7, has been discovered, and CXCR7 has also been found to be expressed in a variety of tumor cells and tumor-related vascular endothelial cells. Many studies have shown that CXCR7 can promote the growth and metastasis of a variety of malignant tumor cells. Unlike CXCR4, CXCR7 exhibits a slight modification in the DRYLAIV motif and does not induce intracellular Ca²⁺ release following ligand binding, which is essential for recruiting and activating G proteins. CXCR7 is generally thought to work in three ways: (1) Recruiting β-arrestin 2; (2) Heterodimerizing with CXCR4; and (3) Acting as a “scavenger” of SDF-1, thus lowering the level of SDF-1 to weaken the activity of CXCR4. In the present review, the expression and role of CXCR7, as well as its prognosis in cancers of the digestive system, were investigated.

Expression and regulation effects of chemokine receptor 7 in colon cancer cells

In China the incidence and mortality rates of colon cancer have been increasing annually. Studies have revealed that CXCR7 is expressed in many tumors. The aim of the present study was to investigate the function of CXCR7 in colon cancer. The expression level of chemokine receptor 7 (CXCR7) in Caco-2 and HCT116 cells was investigated to elucidate the effect of CXCR7 on cell biological behavior. Reverse transcription-quantitative PCR and western blot analysis were used to detect the expression level of CXCR7 in Caco-2 and HCT116 cells after transfection with small interfering (si)RNA. To analyze the in vitro biological function of CXCR7, cell proliferation was measured using a Cell Counting Kit-8 assay, and cell invasion and migration were measured using Matrigel, and Transwell and wound healing assays. siRNAs were successfully transfected into Caco-2 and HCT116 cells and resulted in a decrease in CXCR7 protein and mRNA expression. Downregulation of CXCR7 inhibited Caco-2 and HCT116 cell proliferation, invasion, and migration. Regulation of CXCR7 expression may affect the biological behavior of Caco-2 and HCT116 cells, suggesting that CXCR7 has a potential role in molecular therapy in colon cancer.

Chemokine receptor 7 targets the vascular endothelial growth factor via the AKT/ERK pathway to regulate angiogenesis in colon cancer

Background

Studies have shown that CXCR7 is expressed in many tumors. The aim of the present study was to investigate the function of CXCR7 in colon cancer. Although evidence indicates that CXCR7 promotes angiogenesis in colon cancer, the mechanism involved in this process remains unclear.

Methods

The expression of CXCR7 in colon cancer was evaluated by quantitative reverse‐transcription polymerase chain reaction and western blotting. After transfection, cell proliferation, migration, and lumen formation were measured in vitro. Immunohistochemistry and western blotting were used to identify the functional target of CXCR7 in vivo and in vitro.

Results

In this study, CXCR7 was differentially expressed in four colon cancer cell lines. The proliferation and migration experiments showed that overexpression of CXCR7 enhanced cell growth and migration. Moreover, the tube formation assays showed that co‐culture of colon cancer cells overexpressing CXCR7 with human umbilical vein endothelial cells significantly promoted tube formation in the latter cells. Conversely, the stable knockdown of CXCR7 significantly reduced this malignant activity. In addition, we found that CXCR7 activates the AKT and ERK pathways in colon cancer cells. The phosphorylation of AKT and ERK, as well as the expression of the vascular endothelial growth factor, can be inhibited using the LY294002 and U0126 inhibitors. Furthermore, the angiogenic ability of CXCR7‐induced colon cancer cells was eliminated.

Conclusion

Expression of CXCR7 contributes to colon cancer growth and angiogenesis, by activating the AKT and ERK pathways. CXCR7 provides a potential therapeutic target against colon cancer.

Role of CXCR7 as a Common Predictor for Prognosis in Solid Tumors: a Meta-Analysis

Background: Accumulating evidence indicated that the CXC chemokine receptor (CXCR) 7 (CXCR7) was overexpressed in a variety of tumors. However, the value of the CXCR7 expression in predicting prognosis in solid tumors remains controversial. Therefore, we performed this meta-analysis to evaluate the correlation between CXCR7 expression and lymph node metastasis (LNM), tumor pathological grade and survival, including overall survival (OS), disease-free survival (DFS) and recurrence-free survival (RFS). Methods: Eligible studies were searched in PubMed, Web of Science, and PMC up to April 2018. A total of 27 studies were included in this meta-analysis. Odds ratio (OR), hazard ratio (HR) and 95 % confidence intervals (CI) were used as effect measures. Results: The meta-analysis showed that high expression of CXCR7 predicted a high risk of LNM (pooled OR = 2.22, 95%CI: 1.41-3.50), high tumor grade (pooled OR = 1.94, 95%CI: 1.20-3.13), poor OS (pooled HR = 1.66, 95%CI: 1.30-2.03), and poor DFS/RFS (pooled HR = 1.82, 95%CI: 1.21-2.43). Subgroup analysis showed that CXCR7 expression had a positive correlation with LNM in pan-adenocarcinoma subgroup (pooled OR = 3.73, 95%CI: 2.21-6.30), while no correlation was found in pan-squamous cancer subgroup (pooled OR = 1.29, 95%CI: 0.56-2.96). Subgroup analysis of tumor grade revealed that high expression of CXCR7 predicted high tumor grade both in pan-squamous cancer and pan-adenocarcinoma (pooled OR = 3.58, 95%CI: 1.39-9.22, pooled OR = 2.25, 95%CI: 1.20-4.20). As in OS group, we divided the data based on analysis method and it turned out that overexpressed CXCR7 predicted worse OS both in multivariate analysis (pooled HR =1.57, 95%CI: 1.12-2.01) and univariate analysis subgroup (pooled HR =1.86, 95%CI: 1.23-2.49). Conclusions: Our meta-analysis revealed that high expression of CXCR7 predicted unfavorable prognosis and may serve as potential targets of cancer therapy.

CXCR7 as a chemokine receptor for SDF-1 promotes gastric cancer progression via MAPK pathways

OBJECTIVE

As the alternate receptor for stromal cell-derived factor-1 (SDF-1) except CXCR4, CXCR7 has been shown to be involved in the progression of some malignancies. However, the role of SDF-1/CXCR7 in gastric cancer (GC) remains unclear.

MATERIALS AND METHODS

CXCR7 expression was examined in 83 human GC tissues and adjacent non-cancer tissues (ANCTs) by immunohistochemistry, in three human GC cell lines (MGC-803, BGC-823 and SGC-7901) by reverse transcription-PCR and western blot. CXCR7 was stably knocked down via lentiviral vectors. The cells proliferation was evaluated using CCK-8 and colony formation assay; MAPK pathways (ERK1/2, p38 and SAPK/JNK) were detected using western blot. Besides, the xenograft model of nude mice for GC growth was performed.

RESULTS

CXCR7 expression in GC tissues was significantly higher than that in ANCTs and associated with tumor size, TNM stage and lymph node metastasis. CXCR7 and CXCR4 were both detectable in three GC cell lines and SGC-7901 cells expressed CXCR7 the most abundantly. SDF-1 promoted the proliferation of SGC-7901 cells, the phosphorylation of ERK1/2, p38 and CXCR7 knockdown distinctly reversed these changes; the proliferation stimulated with SDF-1 was attenuated by U0126 (MEK1/2 inhibitor). Furthermore, CXCR7 knockdown inhibited the growth of GC subcutaneous xenografts and decreased the microvessel density and VEGF expression in vivo.

CONCLUSION

CXCR7 was identified as a novel promoter in GC initiation and progression.