Down-regulation of CXCR7 inhibits the growth and lung metastasis of human hepatocellular carcinoma cells with highly metastatic potential

The effect of CXCL12 on survival outcomes of patients with viral hepatitis-associated hepatocellular carcinoma after hepatectomy

Background

The CXCL12-CXCR4/CXCR7 axis is garnering growing attention. But the comprehension of its function in the progression of HCC remains controversial. The purpose of this study was to investigate the effects of CXCL12 and its receptor on the prognosis of patients with viral hepatitis-associated HCC after hepatectomy.

Methods

A total of 86 patients had been enrolled who had undergone hepatectomy for HCC and followed up to July 31, 2019, and their clinicopathological and follow-up data were recorded. Tumor and peritumoral tissues were obtained to detect the expression of CXCL12, CXCR4, and CXCR7 using immunohistochemistry. Real-time polymerase chain reaction was utilized to detect hepatitis B or C virus loads, while survival analysis was performed using the Kaplan-Meier method. Furthermore, the Cox proportional hazards regression model was employed to analyze the factors affecting the prognosis.

Results

The results revealed that the CXCL12, CXCR4, and CXCR7 expression in tumor tissues was lower than in the corresponding non-tumor tissues in 20.93 %, 22.09 %, and 23.26 % of the patients, respectively, and that only CXCL12 was found to be related to the extrahepatic invasion of HCC. The survival analysis and Cox regression showed that only CXCL12 was associated with the postoperative survival of patients with HCC, and that it was an independent prognostic risk factor in the CXCL12-CXCR4/CXCR7 axis. The CXCL12low group represented shorter progression-free survival and lower overall survival rates. However, the subgroup analysis displayed that the survival difference associated with CXCL12 was only manifested in patients with higher expression of CXCR4 or CXCR7 in HCC, as compared to the surrounding tissues.

Conclusions

Our findings suggest that, when assessing the prognostic significance of CXCL12 in HCC, it is essential to consider the expression level of its receptor. Nevertheless, CXCL12 can potentially serve as a promising prognostic marker for HCC.

Portal vein tumor thrombosis in hepatocellular carcinoma: molecular mechanism and therapy

Portal vein tumor thrombosis (PVTT), a common complication of advanced hepatocellular carcinoma (HCC), remains the bottleneck of the treatments. Liver cancer cells potentially experienced multi-steps during PVTT process, including cancer cells leave from cancer nest, migrate in extracellular matrix, invade the vascular barrier, and colonize in the portal vein. Accumulated evidences have revealed numerous of molecular mechanisms including genetic and epigenetic regulation, cancer stem cells, immunosuppressive microenvironment, hypoxia, et al. contributed to the PVTT formation. In this review, we discuss state-of-the-art PVTT research on the potential molecular mechanisms and experimental models. In addition, we summarize PVTT-associated clinical trials and current treatments for PVTT and suppose perspectives exploring the molecular mechanisms and improving PVTT-related treatment for the future.

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.

Atypical chemokine receptors in tumor cell growth and metastasis

Atypical chemokine receptors (ACKRs) are seven-transmembrane cell surface protein receptors expressed in immune cells, normal mesenchymal cells, and several tumor cells. As of this writing, six ACKRs have been characterized by diverse activities. They bind both cysteine-cysteine (CC) type and cysteine-X-cysteine (CXC)-type chemokines, either alone, or together with a ligand bound-functional G-protein coupled (typical) chemokine receptor. The major structural difference between ACKRs and typical chemokine receptors is the substituted DRYLAIV amino acid motif in the second intracellular loop of the ACKR. Due to this substitution, these receptors cannot bind Gαi-type G-proteins responsible for intracellular calcium mobilization and cellular chemotaxis. Although initially characterized as non-signaling transmembrane receptors (decoy receptors) that attenuate ligand-induced signaling by GPCRs, studies of all ACKRs have shown ligand-independent and ligand-dependent transmembrane signaling in both non-tumor and tumor cells. The precise function and mechanism of the differential expression of ACKRs in many tumors are not understood well. The use of antagonists of ACKRs ligands has shown limited antitumor potential; however, depleting ACKR expression resulted in a reduction in experimental tumor growth and metastasis. The ACKRs represent a unique class of transmembrane signaling proteins that regulate growth, survival, and metastatic processes in tumor cells, affecting multiple pathways of tumor growth. Therefore, closer investigations of ACKRs have a high potential for identifying therapeutics which affect the intracellular signaling, preferentially via the ligand-independent mechanism.

Cell Surface Proteins in Hepatocellular Carcinoma: From Bench to Bedside

Cell surface proteins act as the go-between in carrying the information from the extracellular environment to the intracellular signaling proteins. However, these proteins are often deregulated in neoplastic diseases, including hepatocellular carcinoma. This review discusses several recent studies that have investigated the role of cell surface proteins in the occurrence and progression of HCC, highlighting the possibility to use them as biomarkers of the disease and/or targets for vaccines and therapeutics.

Forkhead box P3 gene silencing inhibits the expression of chemokines and chemokine receptors associated with cell growth, migration, and apoptosis in hepatocellular carcinoma cells

The aberrant expression of forkhead box P3 (FOXP3) leads to the formation of malignant tumors. FOXP3 expression levels are also elevated in hepatocellular carcinoma (HCC). The aim of the present study was to investigate the effects of FOXP3 silencing on cell proliferation, migration, apoptosis and chemokine/chemokine receptor expression in the MHCC-97H HCC cell line. Three FOXP3 short hairpin (sh)RNA constructs were designed: Sh-FOXP3-1-pGreenPuro, sh-FOXP3-2-pGreenPuro, and sh-FOXP3-3-pGreenPuro. MHCC-97H cells were transfected with shRNA-FOXP3, and the mRNA and protein expression levels of C-X-C motif chemokine (CXC) ligand 12 (CXCL12), CXCL11, CXC receptor 4 (CXCR4) and CXCR7 were measured. Cell Counting Kit-8, terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling and Transwell assays were used to evaluate cell proliferation, apoptosis and migration, respectively. Of the three FOXP3 lentivirus carriers constructed, sh-FOXP3-1 significantly reduced FOXP3 expression levels and was chosen for further experiments. sh-FOXP3-1 inhibited cell proliferation, promoted apoptosis and inhibited cell migration compared with the negative control. The mRNA and protein expression levels of CXCL12, CXCL11, CXCR4 and CXCR7 were decreased significantly in response to FOXP3 silencing. FOXP3 silencing may therefore inhibit cell growth, induce apoptosis and inhibit migration in HCC cells, possibly by impairing the chemokine/chemokine receptor axes.

Emerging Roles of G Protein-Coupled Receptors in Hepatocellular Carcinoma

Among a great variety of cell surface receptors, the largest superfamily is G protein-coupled receptors (GPCRs), also known as seven-transmembrane domain receptors. GPCRs can modulate diverse signal-transduction pathways through G protein-dependent or independent pathways which involve β-arrestins, G protein receptor kinases (GRKs), ion channels, or Src kinases under physiological and pathological conditions. Recent studies have revealed the crucial role of GPCRs in the tumorigenesis and the development of cancer metastasis. We will sum up the functions of GPCRs—particularly those coupled to chemokines, prostaglandin, lysophosphatidic acid, endothelin, catecholamine, and angiotensin—in the proliferation, invasion, metastasis, and angiogenesis of hepatoma cells and the development of hepatocellular carcinoma (HCC) in this review. We also highlight the potential avenues of GPCR-based therapeutics for HCC.

CXCR7 regulates breast tumor metastasis and angiogenesis in vivo and in vitro

The chemokine receptor CXCR7 is regarded as a scavenger receptor for CXCL12, and induces numerous key steps in tumor growth and metastasis. However, the exact molecular mechanism of CXCR7 regulation in breast tumor angiogenesis remains unknown. In the present study, the function of CXCR7 in breast tumors was investigated in vitro and in vivo. The breast cancer MDA-MB-231 cell line was used. Pharmacological inhibition of CXCR7 by CCX771 reduced breast tumor invasion, adhesion and metastasis. Furthermore, CXCR7 was essential for the tube formation of HUVECs in vitro, and for blood vessel formation in a Matrigel plug assay in vivo. In addition, vascular endothelial growth factor expression was also decreased in CCX771-treated MDA-MB-231 cells, indicating that CCX771 regulates tumor angiogenesis. The present results indicated that CXCR7 regulated breast cancer metastasis at multiple stages; additional understanding of CXCR7 in tumor environments may develop anti-metastatic therapy.

CXCR7/CXCL12 axis is involved in lymph node and liver metastasis of gastric carcinoma

AIM

To investigate the role of CXC chemokine receptor (CXCR)-7 and CXCL12 in lymph node and liver metastasis of gastric carcinoma.

METHODS

In 160 cases of gastric cancer, the expression of CXCR7 and CXCL12 in tumor and matched tumor-adjacent non-cancer tissues, in the lymph nodes around the stomach and in the liver was detected using immunohistochemistry to analyze the relationship between CXCR7/CXCL12 expression and clinicopathological features and to determine whether CXCR7 and CXCL12 constitute a biological axis to promote lymph node and liver metastasis of gastric cancer. Furthermore, the CXCR7 gene was silenced and overexpressed in human gastric cancer SGC-7901 cells, and cell proliferation, migration and invasiveness were measured by the MTT, wound healing and Transwell assays, respectively.

RESULTS

CXCR7 expression was up-regulated in gastric cancer tissues (P = 0.011). CXCR7/CXCL12 expression was significantly related to high tumor stage and lymph node (r = 0.338, P = 0.000) and liver metastasis (r = 0.629, P = 0.000). The expression of CXCL12 in lymph node and liver metastasis was higher than that in primary gastric cancer tissues (χ2 = 6.669, P = 0.010; χ2 = 25379, P = 0.000), and the expression of CXCL12 in lymph node and liver metastasis of gastric cancer was consistent with the positive expression of CXCR7 in primary gastric cancer (r = 0.338, P = 0.000; r = 0.629, P = 0.000). Overexpression of the CXCR7 gene promoted cell proliferation, migration and invasion. Silencing of the CXCR7 gene suppressed SGC-7901 cell proliferation, migration and invasion. Human gastric cancer cell lines expressed CXCR7 and showed vigorous proliferation and migratory responses to CXCL12.

CONCLUSION

The CXCR7/CXCL12 axis is involved in lymph node and liver metastasis of gastric cancer. CXCR7 is considered a potential therapeutic target for the treatment of gastric cancer.

ShRNA knock-down of CXCR7 inhibits tumour invasion and metastasis in hepatocellular carcinoma after transcatheter arterial chemoembolization

To investigate the effects of lentiviral vector‐mediated shRNA suppressing CXCR7 on tumour invasion and metastasis in hepatocellular carcinoma (HCC) after transcatheter arterial chemoembolization (TACE). HCCLM3 cell lines were cultured and assigned into the CXCR7‐shRNA, negative control (NC) and blank groups. The qRT‐PCR and Western blotting were applied to detect the mRNA and protein expressions of CXCR7, CXCR4 and MMP‐2 in HCCLM3 cells. Cell proliferation and invasion were evaluated by MTT and Transwell assays. A Buffalo rat model of HCC was established. Fifty model rats were divided into the CXCR7‐shRNA + TACE, CXCR7‐shRNA, TACE, NC and control groups. Immunohistochemistry was performed to detect the expressions of CXCR7, MMP‐2, vascular endothelial growth factor (VEGF) and intratumoral CD31‐positive vessel count in tumour tissues of mice. Compared with the blank and NC groups, the mRNA and protein expressions of CXCR7 and MMP‐2 were decreased in the CXCR7‐shRNA group. The cell proliferation and invasion rates of the CXCR7‐shRNA group were lower than the blank and NC groups. At the 4th week after TACE, tumour weight of the CXCR7‐shRNA + TACE group increased continuously. The CXCR7‐shRNA + TACE group showed longer survival time and smaller tumour sizes than other groups. Compared with other groups, the CXCR7‐shRNA + TACE and CXCR7‐shRNA groups had less number of lung metastatic nodules and lower expressions of CXCR7, MMP‐2, VEGF and CD31‐positive vessel count. CXCR7‐shRNA inhibits tumour invasion and metastasis to improve the efficacy of TACE in HCC by reducing the expressions of CXCR7, MMP‐2 and VEGF.

Silencing of CXCR4 and CXCR7 expression by RNA interference suppresses human endometrial carcinoma growth in vivo

In this paper, the effect of silencing the expression of CXCR4 and CXCR7 by RNAi on the growth of endometrial carcinoma (EC), in vivo, was evaluated. To establish endometrial carcinoma model, thirty nude mice were subcutaneously inoculated with 1 × 10⁷ Ishikawa cells. All tumor-bearing mice were randomly assigned to five groups (six mice in each group) when the tumor xenografts reached 5-7 mm in diameter, and treated with CXCR4-siRNA (5 nmol), CXCR7-siRNA (5 nmol), CXCR4-siRNA (5 nmol) plus CXCR7-siRNA (5 nmol), negative-siRNA (5 nmol) and normal saline, respectively. Following intra-tumor injection, the growth rate of tumor xenografts in the three treatment groups was significantly delayed compared with those in Ne-si and NS group (P<0.05). The results of QRT-PCR and immunohistochemical assessment showed that the expression levels of CXCR4 and CXCR7 could be down regulated by RNA interference. We also observed that treatment with CXCR4-siRNA and CXCR7-siRNA reduced cell proliferation, but there was no significant difference in apoptosis among the five groups. CXCR4 and CXCR7 silencing by RNAi inhibit the growth of human endometrial carcinoma xenografts by inhibiting cancer cell proliferation, in vivo. These results indicate that CXCR4 and CXCR7 could serve as potential alternative targets for gene therapy in endometrial carcinoma.

miR-100 suppresses the proliferation and tumor growth of esophageal squamous cancer cells via targeting CXCR7

MicroRNAs are highly conserved non-coding RNAs that regulate gene expression at the post-transcriptional level, and play pivotal roles in cancer development and progression. miR-100 has been reported to be significantly downregulated in a variety of cancers, including esophageal cancer. However, the role of miR-100 in human esophageal cancer has not been fully elucidated. We demonstrated that overexpression of miR-100 in esophageal cancer cells markedly inhibited cell proliferation, migration and invasion as well as tumor growth. We subsequently showed that CXCR7 is a direct target gene of miR-100. Our results indicated that miR-100 plays a tumor-suppressor role in esophageal cancer and suggest its potential application for esophageal cancer treatment.

The chemokine receptor CXCR7 is a critical regulator for the tumorigenesis and development of papillary thyroid carcinoma by inducing angiogenesis in vitro and in vivo

Papillary thyroid carcinoma (PTC) is a well-differentiated neoplasm, but it can transfer early to cervical lymph nodes. Accumulating evidences have confirmed the important roles of CXCR7 in tumor cell proliferation, invasion, metastasis, and angiogenesis. Our previous study demonstrated CXCR7 modulated proliferation, apoptosis, and invasion of PTC cells. In this study, we evaluated the effect of expression of CXCR7 in PTC cells on angiogenesis and whether its expression had an influence on the tumor growth of PTC in vivo. We evaluated the effect of CXCR7 on interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF) secretion, angiogenesis, and tumor growth by ELISA, endothelial tube formation assay, and a xenograft tumor model in nude mice. Immunohistochemistry was used to assess expression of CD34 in tumor of mice. In vitro and in vivo studies in PTC cells suggested that the alteration of CXCR7 expression was correlated with angiogenesis and tumor growth. Moreover, CXCR7 mediated the expression of IL-8 and VEGF, which might be involved in the regulation of tumor angiogenesis. These findings suggest that CXCR7 affects the growth of PTC cells and participates in the tumorigenesis of PTC, probably through regulating angiogenesis by the proangiogenic VEGF or IL-8.

Endothelial CXCR7 regulates breast cancer metastasis

Atypical chemokine receptor CXCR7 (ACKR3) functions as a scavenger receptor for chemokine CXCL12, a molecule that promotes multiple steps in tumor growth and metastasis in breast cancer and multiple other malignancies. While normal vascular endothelium expresses low levels of CXCR7, marked upregulation of CXCR7 occurs in tumor vasculature in breast cancer and other tumors. To investigate effects of endothelial CXCR7 in breast cancer, we conditionally deleted this receptor from vascular endothelium of adult mice, generating CXCR7^ΔEND/ΔEND animals. CXCR7^ΔEND/ΔEND mice appeared phenotypically normal, although these animals exhibited a modest 35 ± 3% increase in plasma CXCL12 as compared with control. Using two different syngeneic, orthotopic tumor implant models of breast cancer, we discovered that CXCR7^ΔEND/ΔEND mice had significantly greater local recurrence of cancer following resection, elevated numbers of circulating tumor cells, and more spontaneous metastases. CXCR7^ΔEND/ΔEND mice also showed greater experimental metastases following intracardiac injection of cancer cells. These results establish that endothelial CXCR7 limits breast cancer metastasis at multiple steps in the metastatic cascade, advancing understanding of CXCL12 pathways in tumor environments and informing ongoing drug development targeting CXCR7 in cancer.

C-X-C motif receptor 7 in gastrointestinal cancer

Chemokine receptors are key mediators of normal physiology and numerous pathological conditions, including inflammation and cancer. This receptor family is an emerging target for anticancer drug development. C-X-C motif receptor 7 (CXCR7) is an atypical chemokine receptor that was first cloned from a canine cDNA library as an orphan receptor and was initially named receptor dog cDNA 1 (RDC1). Shortly after demonstrating that RDC1 binds with its ligand, stromal cell-derived factor-1α and interferon-inducible T-cell α chemoattractant, RDC1 was officially deorphanized and renamed CXCR7, as the seventh receptor in the CXC class of the chemokine receptor family. Recent accumulating evidence has demonstrated that CXCR7 expression is augmented in the majority of tumor cells compared with their normal counterparts and is involved in cell proliferation, survival, migration, invasion and angiogenesis during the initiation and progression of breast, lung and prostate cancer. In the present review, the expression and role of CXCR7, as well as its clinical relevance in cancer of the gastrointestinal system, were investigated. In addition, the potential of this chemokine receptor as a therapeutic target in the treatment of gastrointestinal cancer was discussed.

Chemokines and their receptors play important roles in the development of hepatocellular carcinoma

The chemokine system consists of four different subclasses with over 50 chemokines and 19 receptors. Their functions in the immune system have been well elucidated and research during the last decades unveils their new roles in hepatocellular carcinoma (HCC). The chemokines and their receptors in the microenvironment influence the development of HCC by several aspects including: inflammation, effects on immune cells, angiogenesis, and direct effects on HCC cells. Regarding these aspects, pre-clinical research by targeting the chemokine system has yielded promising data, and these findings bring us new clues in the chemokine-based therapies for HCC.

Sex-determination gene SRY potentially associates with poor prognosis but not sex bias in hepatocellular carcinoma

BACKGROUND

Gender disparity is well known in hepatocellular carcinoma (HCC). SRY is a critical sex-determination gene involved in embryonic development.

AIM

The potential relevance of SRY to HCC progression was evaluated.

METHODS

SRY expression in HCC cell lines and tissues was evaluated. Invasion and wound healing assays were used to evaluate the role of SRY in HCC cell migration. The prognostic value of SRY for HCC patient survival was evaluated.

RESULTS

SRY was highly expressed in HCC cell lines and tumor tissues. Downregulation of SRY expression decreased migration and invasion potential of HCC cells. High SRY levels correlated with poor HCC patient survival. Additionally, neither spatial position nor expression intensity of SRY was correlated with HCC gender disparity.

CONCLUSIONS

High levels of SRY expression correlated with cancer progression and poor HCC patient survival. However, high SRY levels are not significantly correlated with HCC sex bias.

Goosecoid promotes the metastasis of hepatocellular carcinoma by modulating the epithelial-mesenchymal transition

The homeobox gene, goosecoid (GSC), is a transcription factor that participates in cell migration during embryonic development. Because cell migration during development has characteristics similar to cell invasion during metastasis, we evaluated the potential role of GSC in the metastasis of hepatocellular carcinoma (HCC). GSC expression in HCC cell lines and tissues was evaluated, and its effects on the migration potential of HCC cells were determined by GSC knock-down and overexpression methods. In addition, the prognostic role of GSC expression in the metastasis of cancer cells in HCC patients was determined. Our data showed that GSC was highly expressed in several HCC cell lines, particularly in a highly metastatic HCC cell line. Overexpression of GSC promoted cell migration and invasion of HCC cells in vitro. Gain-of-function induced the epithelial-mesenchymal transition but not collective cell migration, whereas loss-of-function induced the reverse change. High-level expression of GSC correlated closely with poor survival and lung metastasis in HCC patients; lung metastases showed more upregulated GSC expression than the primary tumor. We conclude that GSC promotes metastasis of HCC potentially through initiating the epithelial-mesenchymal transition. GSC is also a prognostic factor for poor survival and metastasis of HCC, which suggests its potential as a therapeutic target for metastatic HCC.

CXCR7 correlates with the differentiation of hepatocellular carcinoma and suppresses HNF4α expression through the ERK pathway

Hepatocellular carcinoma (HCC) is a malignancy with dysregulated differentiation. However, effective differentiation therapy for HCC is lacking. Previous evidence suggests that CXCR7 is associated with the differentiation of embryonic stem cells. Here, we evaluated the potential role of CXCR7 in the differentiation of HCC. In HCC cell lines, the expression of cancer stem cell-related markers was assessed by flow cytometry and confirmed by western blot and immunofluorescence analyses. Dimethyl sulfoxide, oncostatin M and dexamethasone were used to induce the differentiation of HCC. Immunohistochemical assay was performed on a tissue microarray based on 112 HCC cases that received hepatectomy. Ligand activation, inhibition assays and RNA interference were used to analyze the regulation of hepatocyte nuclear factor 4α (HNF4α) by the CXCR7 pathway. Huh7 and HCCLM3 cell lines were screened for differentiation induction based on biomarkers of hepatic cancer stem cells. CXCR7 was found to be closely associated with the differentiation of HCC, and an inverse expression trend between CXCR7 and HNF4α was found upon induced differentiation. Clinically, high CXCR7 expression was negatively correlated with HNF4α expression in patients with relatively well-differentiated HCC. Moreover, high CXCR7 expression was correlated with poor overall survival and accelerated post-resection metastasis in HCC with a low HNF4α level. Mechanistically, CXCR7 signaling inhibited HNF4α through extracellular regulated protein kinase (ERK) activation, which was inhibited by U0126, an inhibitor of MAPK/ERK kinases 1 and 2. Knockdown of CXCR7 further confirmed that CXCR7 signaling can regulate HNF4α expression. Taken together, our findings indicate that CXCR7 participates in the differentiation of HCC by regulating HNF4α. The CXCR7-ERK-HNF4α cascade represents a new target for the differentiation therapy of HCC.

Insights on the CXCL12-CXCR4 axis in hepatocellular carcinoma carcinogenesis

Chemokines, a group of small chemotactic cytokines, and their G-protein-coupled receptors were originally identified for their ability to mediate various pro- and anti-inflammatory responses. Beyond the influence of chemokines and their cognate receptors in several inflammatory diseases, several malignancies have been shown to be dependent of chemokines for progression, tumor growth, cellular migration and invasion, and angiogenesis; those later facilitating the development of distant metastases. In hepatocellular carcinoma (HCC), chemokines were shown to affect leukocyte recruitment, neovascularization and tumor progression. CXCL12 (stromal-derived factor 1 alpha- SDF-1) is the primary ligand for the seven transmembrane G-protein coupled receptor CXCR4. The CXCR4/CXCL12 axis exerts a variety of functions at different steps of HCC tumor progression, using autocrine and/or paracrine mechanisms to sustain tumor cell growth, to induce angiogenesis and to facilitate tumor escape through evasion of immune surveillance. In this review, we have comprehensively described the role of CXCR4/CXCL12 in HCC and also investigated the role of CXCR7, an alternative receptors that also binds CXCL12 with potentially distinct downstream effects. Preclinical data converge to demonstrate that inhibition of the CXCR4/CXCL12 axis may lead to direct inhibition of tumor migration, invasion, and metastases. This pathway is under investigation to identify potential novel treatments in HCC and other cancers. However, one of the major challenges faced in this emerging field targeting the CXCR4/CXCL12 signaling pathway, is the translation of current knowledge into the design and development of effective inhibitors of CXCR4 and/or CXCL12 for cancer therapy.

The role of chemoattractant receptors in shaping the tumor microenvironment

Chemoattractant receptors are a family of seven transmembrane G protein coupled receptors (GPCRs) initially found to mediate the chemotaxis and activation of immune cells. During the past decades, the functions of these GPCRs have been discovered to not only regulate leukocyte trafficking and promote immune responses, but also play important roles in homeostasis, development, angiogenesis, and tumor progression. Accumulating evidence indicates that chemoattractant GPCRs and their ligands promote the progression of malignant tumors based on their capacity to orchestrate the infiltration of the tumor microenvironment by immune cells, endothelial cells, fibroblasts, and mesenchymal cells. This facilitates the interaction of tumor cells with host cells, tumor cells with tumor cells, and host cells with host cells to provide a basis for the expansion of established tumors and development of distant metastasis. In addition, many malignant tumors of the nonhematopoietic origin express multiple chemoattractant GPCRs that increase the invasiveness and metastasis of tumor cells. Therefore, GPCRs and their ligands constitute targets for the development of novel antitumor therapeutics.

Close correlation between CXCR4 and VEGF expression and frequent CXCR7 expression in rhabdomyosarcoma

CXC chemokine receptor 4 (CXCR4) expression is reportedly correlated with both vascular endothelial growth factor (VEGF) expression and poor prognosis in a variety of cancers. Its relation to CXC chemokine receptor 7 (CXCR7) is also noted in several malignancies, including rhabdomyosarcoma (RMS) cell lines. However, the correlations between these chemokine receptors and angiogenic factors have not yet been adequately investigated in RMS clinical specimens. By immunohistochemistry, we assessed CXCR4, CXCR7, CC chemokine receptor 6, CC chemokine receptor 7, VEGF expression, microvessel density, and MIB-1 labeling index in 82 formalin-fixed RMS specimens, including 34 primary alveolar RMS and 44 primary embryonal RMS (ERMS). Twenty-six frozen samples were available for investigation by quantitative reverse transcription polymerase chain reaction to detect the messenger RNA expression levels of these molecules. We also evaluated their significance with respect to clinicopathological factors and patient survival rates. Primary RMS showed high expression of CXCR7 (83.1%) regardless of the histologic subtype. High cytoplasmic CXCR4 and high VEGF expression revealed significant correlations in both ERMS and alveolar RMS (P = .0051 and P = .0003, respectively). By univariate analysis of ERMS cases, the tumors with high VEGF expression showed significantly poor prognoses (P = .0017). High VEGF expression also was the independent adverse prognostic factor for ERMS. Because CXCR4, CXCR7, and VEGF are widely expressed in RMS, the combination of these antagonists may provide a potential target for molecular therapy.

SDF-1/CXCR7 axis enhances ovarian cancer cell invasion by MMP-9 expression through p38 MAPK pathway

Ovarian cancer is an aggressive gynecological malignancy with high metastatic potential. Recently, the CXC receptor (CXCR7) has been identified as a new receptor for stromal-derived factor-1 (SDF-1), and exerts important roles in cancer development. However, its effect on ovarian cancer and the underlying mechanism remain unknown. In this study, we detected abundant CXCR7 expression in ovarian cancer tissues and cells. Moreover, SDF-1 induced dramatically upregulation of CXCR7 mRNA and protein levels, indicating that the SDF-1/CXCR7 axis existed in ovarian cancer. Further analysis confirmed that SDF-1 enhanced cell adhesion and subsequent invasion, which were significantly attenuated when pretreated with CXCR7 small interference RNA (siRNA), indicating the critical function of SDF-1/CXCR7 in cell invasion. Further mechanistic analysis indicated that SDF-1/CXCR7 enhanced cell invasion by matrix metalloproteinase (MMP)-9, as pretreatment with MMP-9 siRNA significantly abrogated a number of invading cells. Additionally, SDF-1/CXCR7 induced phosphorylation of the p38 MAPK pathway, which was accounted for MMP-9 expression as preconditioning with the p38 MAPK inhibitor SB203580 obviously decreased MMP-9 expression. Together, our data implied that SDF-1/CXCR7 enhanced ovarian cancer cell invasion by MMP-9 expression through the p38 MAPK pathway. Thus, these findings confirmed the critical role of SDF-1/CXCR7 during the pathological processes of ovarian cancer and supported its potential targets for further development of antiovarian cancer therapy.

The involvement of CXCR7 in modulating the progression of papillary thyroid carcinoma

BACKGROUND

Although papillary thyroid carcinoma (PTC) has favorable prognosis, it is prone to cervical lymph node metastasis. Chemokine receptors play a role in metastasis of tumor cells, and accumulating evidence suggests an important role for the chemokine receptor CXCR7 in cancer development. We previously demonstrated high expression of CXCR7 protein in PTC tissue. In this study, we further evaluated the role of CXCR7 in PTC.

METHODS

The expression of CXCR7 messenger RNA and protein in 79 cases of PTC and peritumoral tissues was detected by real-time quantitative polymerase chain reaction and Western blot. The association between CXCR7 expression and clinicopathologic characteristics in PTC was analyzed. Stable CXCR7 overexpression and knockdown PTC cells were constructed and used to examine proliferation, cell cycle, apoptosis and invasion of PTC cells by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, propidium iodide staining, 7-amino-actinomycin D staining, and invasion assay. We examined cell cycle regulatory protein levels by Western blot.

RESULTS

CXCR7 messenger RNA and protein levels were markedly increased in PTC and correlated with tumor progression. CXCR7 could regulate proliferation, cell cycle, apoptosis, invasion, and the expression of cell cycle regulatory proteins involved in the S-G2 phase transition. Knockdown of CXCR7 in PTC cells suppressed cell proliferation and invasion, decreased expression of cyclin A, CDK2 and PCNA, increased expression of p21 and p57, induced S phase arrest, and promoted apoptosis.

CONCLUSIONS

CXCR7 plays an important role in regulating growth and metastasis ability of PTC cell and provides a potential target for therapeutic interventions in PTC.

S100A14 promotes the growth and metastasis of hepatocellular carcinoma

BACKGROUND

S100A14 has recently been implicated in the progress of several types of cancers. This study aimed to investigate the clinical significance and possible mechanisms of action of S100A14 in the invasion and metastasis of hepatocellular carcinoma (HCC).

METHODS

S100A14 expression in HCC was detected at mRNA and protein levels and its prognostic significance was assessed. Functional roles of S100A14 in HCC were investigated using MTT, BrdU, wound healing, transwell invasion assay and HCC metastatic mouse model.

RESULTS

S100A14 was significantly elevated in HCC tissues, correlated with multiple tumor nodes, high Edmondson-Steiner grade and vascular invasion. Multivariate Cox analysis showed that the S100A14 expression level was a significant and independent prognostic factor for overall survival (OS) of HCC patients (hazard ratio=1.98, 95% confidence interval=1.14-3.46, P=0.013). S100A14 promoted cell proliferation, invasion and metastasis of HCC in vitro and in vivo.

CONCLUSION

These results suggest S100A14 is a novel prognostic marker and therapeutic target for HCC.

Immune regulation by atypical chemokine receptors

Chemokines have fundamental roles in regulating immune and inflammatory responses, primarily through their control of leukocyte migration and localization. The biological functions of chemokines are typically mediated by signalling through G protein-coupled chemokine receptors, but chemokines are also bound by a small family of atypical chemokine receptors (ACKRs), the members of which are unified by their inability to initiate classical signalling pathways after ligand binding. These ACKRs are emerging as crucial regulatory components of chemokine networks in a wide range of developmental, physiological and pathological contexts. In this Review, we discuss the biochemical and immunological properties of ACKRs and the potential unifying themes in this family, and we highlight recent studies that identify novel roles for these molecules in development , homeostasis, inflammatory disease, infection and cancer.

Transmembrane receptor CXCR7 increases the risk of extrahepatic metastasis of relatively well-differentiated hepatocellular carcinoma through upregulation of osteopontin

Recurrence and metastasis are the main obstacles to improving the survival of patients with post-resective hepato-cellular carcinoma (HCC). Our previous study suggests a critical role of CXCR7 in the metastasis of HCC. In the present study, the effect of CXCR7 as a risk factor for metastasis of HCC was evaluated. Immunohistochemical assay was performed on tissue microarrays based on HCC with extrahepatic metastases after hepatectomy. Two categories based on staining scores were used to evaluate the risk effect of CXCR7, respectively. The effect of CXCR7 on osteopontin (OPN) was explored by RNA interference. Based on the results, in both categories, highly expressed CXCR7 was a dependent risk factor for extrahepatic metastasis because of the potential association with relatively good cell differentiation. Stratification analyses indicated that CXCR7 was a strong independent risk factor (OR, 3.40; 95% CI, 1.07-18.84; P=0.038 in category 1 and OR, 6.40; 95% CI, 1.64-24.92; P=0.007 in category 2, respectively) in patients with Edmondson grade 1/2. Furthermore, CXCR7 correlated well and positively with expression of OPN (P=0.019 and P<0.001 in two categories, respectively) in HCC cases with Edmondson grade 1/2. Immunocytochemistry and RT-PCR demonstrated downregulation of OPN in a highly metastatic HCC cell line following knockdown of CXCR7. Taken together, these findings suggest that high expression of CXCR7 increases the risk of metastasis in post-resective HCC patients with relatively good differentiated tumors, potentially through upregulation of OPN. This group of patients may acquire a survival benefit from early detection and treatment of recurrence and metastasis.