Inhibition of androgen receptor promotes CXC-chemokine receptor 7-mediated prostate cancer cell survival

Chemokine receptor CXCR7 activates Aurora Kinase A and promotes neuroendocrine prostate cancer growth

CXCR7 is an atypical chemokine receptor that recruits β-arrestin (ARRB2) and internalizes into clathrin-coated intracellular vesicles where the complex acts as a scaffold for cytoplasmic kinase assembly and signal transduction. Here, we report that CXCR7 was elevated in the majority of prostate cancer (PCa) cases with neuroendocrine features (NEPC). CXCR7 markedly induced mitotic spindle and cell cycle gene expression. Mechanistically, we identified Aurora Kinase A (AURKA), a key regulator of mitosis, as a novel target that was bound and activated by the CXCR7-ARRB2 complex. CXCR7 interacted with proteins associated with microtubules and golgi, and, as such, the CXCR7-ARRB2-containing vesicles trafficked along the microtubules to the pericentrosomal golgi apparatus, where the complex interacted with AURKA. Accordingly, CXCR7 promoted PCa cell proliferation and tumor growth, which was mitigated by AURKA inhibition. In summary, our study reveals a critical role of CXCR7-ARRB2 in interacting and activating AURKA, which can be targeted by AURKA inhibitors to benefit a subset of patients with NEPC.

Myricetin alleviated hydrogen peroxide-induced cellular senescence of nucleus pulposus cell through regulating SERPINE1

BACKGROUND

Myricetin (MYR) is a common plant flavonoid with antioxidant and anticancer properties. However, the anti-aging effect of MYR on nucleus pulposus cells (NPCs) is still unknown. The study aimed to explore the effect of MYR on the senescence of NPCs.

METHODS

Methyl-thiazolyl tetrazolium assay was used to detect NPCs viability. Senescence level was evaluated by senescence-associated β-galactosidase (SA-β-Gal) staining and the expression levels of P21, P16, IL-6 and IL-8. RNA-Sequencing (RNA-seq) technology was used to identify differentially expressed genes (DEGs) between hydrogen peroxide + MYR (HO + MYR) group and HO group, and Gene Ontology (GO) functional was performed to analyze DEGs. A Venn diagram was generated to screen overlapping DEGs related to aging and inflammation, and the role of the promising validated DEG was selected for further investigation by gene functional assays.

RESULTS

HO inhibited NPCs viability and stimulated the senescent phenotype of NPCs, whereas MYR treatment significantly reversed SA-β-gal activity in NPCs. MYR also reduced the expression of p21 and p16 and the secretion of IL-6 and IL-8 induced by HO. RNA-seq screened 421 DEGs. The GO enrichment results showed DEGs were mainly enriched in terms such as "sterol biosynthetic process". We also found SERPINE1 has the highest log2FC abs. Silence of SERPINE1 inhibited HO-induced NPCs senescence, and overexpression of SERPINE1 could limit the anti-aging effect of MYR.

CONCLUSIONS

MYR alleviated HO-induced senescence of NPCs by regulating SERPINE1 in vitro.

Atypical chemokine receptors: emerging therapeutic targets in cancer

Atypical chemokine receptors (ACKRs) regulate the availability of chemokines via chemokine scavenging, while also having the capacity to elicit downstream function through β-arrestin coupling. This contrasts with conventional chemokine receptors that directly elicit immune cell migration through G protein-coupled signaling. The significance of ACKRs in cancer biology has previously been poorly understood, but recent findings have highlighted the multifaceted role of these receptors in tumorigenesis and immune response modulation within the tumor microenvironment (TME). Additionally, recent research has expanded our understanding of the function of several receptors including GPR182, CCRL2, GPR1, PITPNM3, and C5aR2 that share similarities with the ACKR family. In this review, we discuss these recent developments, and highlight the opportunities and challenges of pharmacologically targeting ACKRs in cancer.

The power of heteronemin in cancers

Heteronemin (Haimian jing) is a sesterterpenoid-type natural marine product that is isolated from sponges and has anticancer properties. It inhibits cancer cell proliferation via different mechanisms, such as reactive oxygen species (ROS) production, cell cycle arrest, apoptosis as well as proliferative gene changes in various types of cancers. Recently, the novel structure and bioactivity evaluation of heteronemin has received extensive attention. Hormones control physiological activities regularly, however, they may also affect several abnormalities such as cancer. L-Thyroxine (T₄), steroid hormones, and epidermal growth factor (EGF) up-regulate the accumulation of checkpoint programmed death-ligand 1 (PD-L1) and promote inflammation in cancer cells. Heteronemin suppresses PD-L1 expression and reduces the PD-L1-induced proliferative effect. In the current review, we evaluated research and evidence regarding the antitumor effects of heteronemin and the antagonizing effects of non-peptide hormones and growth factors on heteronemin-induced anti-cancer properties and utilized computational molecular modeling to explain how these ligands interacted with the integrin αvβ3 receptors. On the other hand, thyroid hormone deaminated analogue, tetraiodothyroacetic acid (tetrac), modulates signal pathways and inhibits cancer growth and metastasis. The combination of heteronemin and tetrac derivatives has been demonstrated to compensate for anti-proliferation in cancer cells under different circumstances. Overall, this review outlines the potential of heteronemin in managing different types of cancers that may lead to its clinical development as an anticancer agent.

ARRB1 Regulates Metabolic Reprogramming to Promote Glycolysis in Stem Cell-Like Bladder Cancer Cells

Simple Summary

Bladder cancer (BC) ranks second in incidence and mortality among all genitourinary cancers. The high recurrence of BC is attributed to the presence of cancer stem cells (CSCs), which are the driving force behind tumor growth. Increasing evidence suggests that stem cells exhibit a distinct metabolic program compared to differentiated cells. Understanding their metabolic preference for maintaining stem cell properties is essential for developing novel therapeutics targeting CSCs. The current work shows for the first time that the scaffold protein β-arrestin1 (ARRB1) functions as a metabolic switch regulating the metabolic reprogramming of CSC-like cells towards glycolysis by regulating the mitochondrial pyruvate carrier MPC1 and glucose transporter GLUT1. The balance between glycolysis and oxidative phosphorylation plays a crucial role in regulating the fate of stem cells. Our findings will potentially open new therapeutic avenues for targeting bladder cancer cells and/or the CSC-like cells within aggressive bladder tumors.

Abstract

β-arrestin 1 (ARRB1) is a scaffold protein that regulates signaling downstream of G protein-coupled receptors (GPCRs). In the current work, we investigated the role of ARRB1 in regulating the metabolic preference of cancer stem cell (CSC)-like cells in bladder cancer (BC). We show that ARRB1 is crucial for spheroid formation and tumorigenic potential. Furthermore, we measured mitochondrial respiration, glucose uptake, glycolytic rate, mitochondrial/glycolytic ATP production and fuel oxidation in previously established ARRB1 knock out (KO) cells and corresponding controls. Our results demonstrate that depletion of ARRB1 decreased glycolytic rate and induced metabolic reprogramming towards oxidative phosphorylation. Mechanistically, the depletion of ARRB1 dramatically increased the mitochondrial pyruvate carrier MPC1 protein levels and reduced the glucose transporter GLUT1 protein levels along with glucose uptake. Overexpression of ARRB1 in ARRB1 KO cells reversed the phenotype and resulted in the upregulation of glycolysis. In conclusion, we show that ARRB1 regulates the metabolic preference of BC CSC-like cells and functions as a molecular switch that promotes reprogramming towards glycolysis by negatively regulating MPC1 and positively regulating GLUT1/ glucose uptake. These observations open new therapeutic avenues for targeting the metabolic preferences of cancer stem cell (CSC)-like BC cells.

Resistance to Antiandrogens in Prostate Cancer: Is It Inevitable, Intrinsic or Induced?

Increasingly sophisticated therapies for chemical castration dominate first-line treatments for locally advanced prostate cancer. However, androgen deprivation therapy (ADT) offers little prospect of a cure, as resistant tumors emerge rather rapidly, normally within 30 months. Cells have multiple mechanisms of resistance to even the most sophisticated drug regimes, and both tumor cell heterogeneity in prostate cancer and the multiple salvage pathways result in castration-resistant disease related genetically to the original hormone-naive cancer. The timing and mechanisms of cell death after ADT for prostate cancer are not well understood, and off-target effects after long-term ADT due to functional extra-prostatic expression of the androgen receptor protein are now increasingly being recorded. Our knowledge of how these widely used treatments fail at a biological level in patients is deficient. In this review, I will discuss whether there are pre-existing drug-resistant cells in a tumor mass, or whether resistance is induced/selected by the ADT. Equally, what is the cell of origin of this resistance, and does it differ from the treatment-naïve tumor cells by differentiation or dedifferentiation? Conflicting evidence also emerges from studies in the range of biological systems and species employed to answer this key question. It is only by improving our understanding of this aspect of treatment and not simply devising another new means of androgen inhibition that we can improve patient outcomes.

Promotion of epithelial hyperplasia by interleukin-8-CXCR axis in human prostate

BACKGROUND

The clinical manifestation of benign prostatic hyperplasia (BPH) is causally linked to the inflammatory microenvironment and proliferation of epithelial and stromal cells in the prostate transitional zone. The CXC-chemokine interleukin-8 (IL-8) contributes to inflammation. We evaluated the expression of inflammatory cytokines in clinical specimens, primary cultures, and prostatic lineage cell lines. We investigated whether IL-8 via its receptor system (IL-8 axis) promotes BPH.

METHODS

The messenger RNA and protein expression of chemokines, including components of the IL-8 axis, were measured in normal prostate (NP; n = 7) and BPH (n = 21), urine (n = 24) specimens, primary cultures, prostatic lineage epithelial cell lines (NHPrE1, BHPrE1, BPH-1), and normal prostate cells (RWPE-1). The functional role of the IL-8 axis in prostate epithelial cell growth was evaluated by CRISPR/Cas9 gene editing. The effect of a combination with two natural compounds, oleanolic acid (OA) and ursolic acid (UA), was evaluated on the expression of the IL-8 axis and epithelial cell growth.

RESULTS

Among the 19 inflammatory chemokines and chemokine receptors we analyzed, levels of IL-8 and its receptors (CXCR1, CXCR2), as well as, of CXCR7, a receptor for CXCL12, were 5- to 25-fold elevated in BPH tissues when compared to NP tissues (P ≤ .001). Urinary IL-8 levels were threefold to sixfold elevated in BPH patients, but not in asymptomatic males and females with lower urinary tract symptoms (P ≤ .004). The expression of the IL-8 axis components was confined to the prostate luminal epithelial cells in both normal and BPH tissues. However, these components were elevated in BPH-1 and primary explant cultures as compared to RWPE-1, NHPrE1, and BHPrE1 cells. Knockout of CXCR7 reduced IL-8, and CXCR1 expression by 4- to 10-fold and caused greater than or equal to 50% growth inhibition in BPH-1 cells. Low-dose OA + UA combination synergistically inhibited the growth of BPH-1 and BPH primary cultures. In the combination, the drug reduction indices for UA and OA were 16.4 and 7852, respectively, demonstrating that the combination was effective in inhibiting BPH-1 growth at significantly reduced doses of UA or OA alone.

CONCLUSION

The IL-8 axis is a promotor of BPH pathogenesis. Low-dose OA + UA combination inhibits BPH cell growth by inducing autophagy and reducing IL-8 axis expression in BPH-epithelial cells.

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.

Modulation of CXC-motif chemokine receptor 7, but not 4, expression is related to migration of the human prostate cancer cell LNCaP: regulation by androgen and inflammatory stimuli

OBJECTIVE

To elucidate the regulation, function of the chemokine CXC-motif ligand 12 (CXCL12) and its receptors (CXCR) 4 and 7 in prostate cancer tumor microenvironment.

MATERIAL

In-silico-analysis of expression in prostate cancer tissues. In-vitro comparison, testing of regulation in human prostate cancer cells LNCaP, DU145, and PC3.

TREATMENT

Dihydrotestosterone (DHT) treatments (0-10 nM) were for 0-48 h. The inflammatory agent Flagellin treatment (20 ng/ml) was for 2 h. Migration assays were performed for 24 h using 10 ng/ml CXCL12.

METHODS

Real-time PCR, western analysis, and migration assays were used to determine mRNA, protein, and functional changes, respectively.

RESULTS

Malignant prostate cancer tissues exhibit higher CXCR4/7 mRNA ratio, and higher CXCR7 mRNA levels were detected in the androgen-responsive LNCaP cells. Putative androgen-responsive elements were identified in CXCR4, 7 gene, and exposure to DHT, flagellin increased CXCR4 mRNA but decreased CXCR7 mRNA levels in LNCaP cells. Androgen receptor siRNA significantly attenuated the effects of DHT on CXCR4, 7 mRNA in LNCaP cells. However, DHT and flagellin only decrease CXCR7 protein and additively increased migration of LNCaP cells towards CXCL12.

CONCLUSIONS

Down regulation of CXCR7 protein by DHT and flagellin increased migration, supporting CXCR7 as decoy receptor counteracting CXCL12/CXCR4-mediated migration in prostate cancer cells.

CXCR7, a Prognostic Biomarker in Cervical Squamous Cell Carcinoma, May Be a Screening Index for Treatment Options at Stages IB1 and IIA1

Purpose

Recent studies indicate that CXC chemokine receptor type 7 (CXCR7) is associated with tumorigenesis, progression, and metastasis of various cancers, but its roles and molecular mechanisms of action in cervical squamous cell carcinoma (CSCC) remain unclear. Our purpose was to explore the expression patterns of CXCR7 and epidermal growth factor receptor (EGFR) in CSCC and to identify possible correlations with clinical characteristics. We also tested whether CXCR7 can be a screening index for treatment options for CSCC stages IB1 and IIA1.

Methods

Expression of CXCR7 and EGFR in tumors from 165 patients with CSCC was evaluated by immunohistochemistry and compared with the clinical data including survival.

Results

Patients at CSCC stages IB1 and IIA1 received different treatment options, including radical hysterectomy, pelvic lymph node dissection, and para-aortic lymph node sampling (RH group, 67 patients) or pelvic external-beam radiation therapy with brachytherapy (EBRT group, 34 patients). Disease-free survival (DFS) and overall survival (OS) were compared between two groups at different CXCR7 expression levels. Immunohistochemical staining showed that CXCR7, EGFR, phospho-ERK, and phospho-AKT amounts increased from normal cervical epithelia and cervical intraepithelial neoplasia to CSCC, and CXCR7 was associated with the disease stage, lymph node metastasis, tumor size ≥40 mm, and EGFR expression. Kaplan–Meier analysis revealed that CXCR7 and EGFR expression was associated with shorter DFS and OS. Multivariate analysis suggested that CXCR7 was independently associated with DFS and OS. Prevalence of recurrence and distant metastasis was significantly lower in the EBRT group than in the RH group during CXCR7 expression. Besides, CXCR7 knockdown significantly decreased the proliferation and invasion of CSCC cells.

Conclusion

CXCR7 is coexpressed with EGFR, which may be involved in ERK or AKT pathway activation. CXCR7 may be a screening index for treatment options at CSCC stages IB1 and IIA1.

The Effect of Androgens on Proinflammatory Cytokine Secretion from Human Ocular Surface Epithelial Cells

Purpose: The purpose of this study is to explore the effects of dihydrotestosterone (DHT) on lipopolysaccharide (LPS)-induced proinflammatory cytokine release in human ocular surface epithelial cells exposed to LPS and LPS-binding protein (LBP).Methods: Immortalized human corneal, conjunctival, and meibomian gland epithelial cells were cultured in keratinocyte-free medium. After confluency, they were exposed to a stratification medium Dulbecco's modified Eagle medium (DMEM)/F12 in the presence of fetal bovine serum and were exposed to vehicle, LPS + LBP, or DHT. Culture media were processed for multiplex-bead analysis of specific proinflammatory cytokines including interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-2, IL-4, IL-8, IL-6, IL-10, IL-1β, vascular endothelial growth factor (VEGF)-A. Cytokine concentrations were compared by analysis of variance with Tukey post hoc testing. p < 0.05 was considered statistically significant.Results: The results are LPS + LBP-induced the secretion of IFN-γ, IL-6, IL-10, IL-1β, VEGF-A cytokines in corneal epithelial cells; TNF-α, IL-2, IL-8, IL-6, IL-1β, VEGF-A cytokines in conjunctival epithelial cells; and IL-8, IL-6, IL-1β, VEGF-A cytokines in meibomian gland epithelial cells. When these LPS + LBP-stimulated cells were exposed to DHT for 2 days, it was found that DHT suppressed the secretion of IL-6, IL-10, IL-1β, VEGF-A cytokines in corneal epithelial cells; TNF-α, IL-6, IL-1β, VEGF-A cytokines in conjunctival epithelial cells; and IL-6, IL-1β, VEGF-A cytokines in meibomian gland epithelial cells.Conclusion: LPS + LBP is shown to induce the secretion of certain proinflammatory cytokines from ocular surface and adnexal epithelial cells. DHT showed anti-inflammatory activity by suppressing some of those cytokines in these cell lines.

Androgen receptor promotes oral squamous cell carcinoma cell migration by increasing EGFR phosphorylation

Objectives: This study is aimed to investigate the role of androgen receptor (AR) in regulating oral squamous cell carcinoma (OSCC) cells migration.

Materials and methods: Tumors from 23 patients with OSCC and five OSCC cell lines were used for analyzing AR expression. The effects of AR agonist and antagonist were used to examine the role of AR in regulating the migration of OSCC cells.

Results: Ten of 23 tumors from patients with OSCC were AR positive. There was no significant difference in total EGFR (tEGFR) expression between AR-positive tumors and AR-negative tumors. However, the expression of phosphorylated EGFR (pEGFR) in AR-positive tumors was significantly higher than that in AR-negative tumors (p<0.01). Stimulation of AR by dihydrotestosterone in SCC9 (AR-positive OSCC cell) caused an increase in pEGFR and pAKT expression and promoted cell migration without changed tEGFR expression, whereas treatment with bicalutamide led to a decrement in pEGFR expression and pAKT and inhibited cell migration. No effects were found in SCC25 cell line (AR-negative) either treated by dihydrotestosterone or bicalutamide. Furthermore, SCC9 cell line treated by EGF or cetuximab (EGFR inhibitor) significantly promoted or inhibited cell migration.

Conclusion: Our data indicate that OSSC tumors and OSCC cell lines express AR which is critical for promoting cell migration by increasing EGFR phosphorylation.

Activation of MAPK Signaling by CXCR7 Leads to Enzalutamide Resistance in Prostate Cancer

Castration-resistant prostate cancer (CRPC) that has developed resistance to the new-generation androgen receptor (AR) antagonist enzalutamide is a lethal disease. Transcriptome analysis of multiple prostate cancer models identified CXCR7, an atypical chemokine receptor, as one of the most upregulated genes in enzalutamide-resistant cells. AR directly repressed CXCR7 by binding to an enhancer 110 kb downstream of the gene and expression was restored upon androgen deprivation. We demonstrate that CXCR7 is a critical regulator of prostate cancer sensitivity to enzalutamide and is required for CRPC growth in vitro and in vivo. Elevated CXCR7 activated MAPK/ERK signaling through ligand-independent, but β-arrestin 2-dependent mechanisms. Examination of patient specimens showed that CXCR7 and pERK levels increased significantly from localized prostate cancer to CRPC and further upon enzalutamide resistance. Preclinical studies revealed remarkable efficacies of MAPK/ERK inhibitors in suppressing enzalutamide-resistant prostate cancer. Overall, these results indicate that CXCR7 may serve as a biomarker of resistant disease in patients with prostate cancer and that disruption of CXCR7 signaling may be an effective strategy to overcome resistance. SIGNIFICANCE: These findings identify CXCR7-mediated MAPK activation as a mechanism of resistance to second-generation antiandrogen therapy, highlighting the therapeutic potential of MAPK/ERK inhibitors in CRPC.

CXCR7 promotes melanoma tumorigenesis via Src kinase signaling

Chemokine receptors have been documented to exert critical functions in melanoma progression. However, current drugs targeting these receptors have limited efficacy in clinical applications, suggesting the urgency to further explore the roles of chemokine receptors in melanoma. Here we found that C–X–C chemokine receptor 7 (CXCR7) was the most highly expressed chemokine receptor in murine melanoma cell lines. In addition, the expression level of CXCR7 was positively correlated with melanoma progression in the clinical samples. High CXCR7 expression was associated with shorter overall survival in melanoma patients. Increased expression of CXCR7 augmented melanoma proliferation in vitro and tumor growth in vivo, whereas knockout of CXCR7 exhibited significant inhibitory effects. Moreover, our data elucidated that CXCR7 activated Src kinase phosphorylation in a β-arrestin2-dependent manner. The administration of the Src kinase inhibitor PP1 or siRNA specific for β-arrestin2 abolished CXCR7-promoted cell proliferation. Importantly, CXCR7 also regulated melanoma angiogenesis and the secretion of vascular endothelial growth factor (VEGF). Subsequent investigations revealed a novel event that the activation of the CXCR7-Src axis stimulated the phosphorylation of eukaryotic translation initiation factor 4E (eIF4E) to accelerate the translation of hypoxia-inducible factor 1α (HIF-1α), which enhanced the secretion of VEGF from melanoma cells. Collectively, our results illuminate the crucial roles of CXCR7 in melanoma tumorigenesis, and indicate the potential of targeting CXCR7 as new therapeutic strategies for melanoma treatment.

β-Arrestins Regulate Stem Cell-Like Phenotype and Response to Chemotherapy in Bladder Cancer

β-Arrestins are classic attenuators of G-protein-coupled receptor signaling. However, they have multiple roles in cellular physiology, including carcinogenesis. This work shows for the first time that β-arrestins have prognostic significance for predicting metastasis and response to chemotherapy in bladder cancer. β-Arrestin-1 (ARRB1) and β-arrestin-2 (ARRB2) mRNA levels were measured by quantitative RT-PCR in two clinical specimen cohorts (n = 63 and 43). The role of ARRBs in regulating a stem cell-like phenotype and response to chemotherapy treatments was investigated. The consequence of forced expression of ARRBs on tumor growth and response to Gemcitabine in vivo were investigated using bladder tumor xenografts in nude mice. ARRB1 levels were significantly elevated and ARRB2 levels downregulated in cancer tissues compared with normal tissues. In multivariate analysis only ARRB2 was an independent predictor of metastasis, disease-specific-mortality, and failure to Gemcitabine + Cisplatin (G+C) chemotherapy; ∼80% sensitivity and specificity to predict clinical outcome. ARRBs were found to regulate stem cell characteristics in bladder cancer cells. Depletion of ARRB2 resulted in increased cancer stem cell markers but ARRB2 overexpression reduced expression of stem cell markers (CD44, ALDH2, and BMI-1), and increased sensitivity toward Gemcitabine. Overexpression of ARRB2 resulted in reduced tumor growth and increased response to Gemcitabine in tumor xenografts. CRISPR-Cas9-mediated gene-knockout of ARRB1 resulted in the reversal of this aggressive phenotype. ARRBs regulate cancer stem cell-like properties in bladder cancer and are potential prognostic indicators for tumor progression and chemotherapy response.

Prognostic significance of CXCR7 in cancer patients: a meta-analysis

Background

CXC chemokine receptor 7 (CXCR7) is frequently overexpressed in a variety of tumors. Nevertheless, whether CXCR7 can be used as a tumor prognosis marker has not been systematically assessed. The current meta-analysis was performed to obtain an accurate evaluation of the relationship between CXCR7 level and the prognosis of cancer patients.

Methods

Embase, Web of Science, and PubMed were systematically searched according to a defined search strategy up to June 11, 2018. Then, the required data were extracted from all qualified studies which were screened out based on the defined inclusion and exclusion criteria. Finally, the hazard ratios (HR) with 95% confidence intervals (CI) were used to evaluate the prognostic significance of CXCR7 in tumor patients.

Results

A total of 28 original research studies comprising 33 cohorts and 5685 patients were included in this meta-analysis. The results showed that CXCR7 overexpression was significantly related to worse overall survival (OS) (HR 1.72; 95% CI 1.49–1.99), disease-free survival (DFS) (HR 5.58; 95% CI 3.16–9.85), progression-free survival (PFS) (HR 2.83; 95% CI 1.66–4.85) and recurrence-free survival (RFS) (HR 1.58; 95% CI 1.34–1.88) in cancer patients. Furthermore, for certain types of cancer, significant associations between higher CXCR7 expression and worse OS of glioma (HR 1.77; 95% CI 1.43–2.19), breast cancer (HR 1.45; 95% CI 1.28–1.63), esophageal cancer (HR 2.72; 95% CI 1.11–6.66) and pancreatic cancer (HR 1.46; 95% CI 1.12–1.90) were found. However, for lung cancer and hepatocellular cancer, there was no significant relationship between CXCR7 expression level and OS, (HR 2.40; 95% CI 0.34–17.07) and (HR 1.37; 95% CI 0.84–2.24) respectively.

Conclusions

Increased CXCR7 level could predict poor prognosis of tumor patients and might be regarded as a novel prognostic biomarker for tumor patients.

Targeting the MIF/CXCR7/AKT Signaling Pathway in Castration-Resistant Prostate Cancer

Although androgen deprivation therapy (ADT) is an effective treatment for metastatic prostate cancer, incurable castration-resistant prostate cancer (CRPC) inevitably develops. Importantly, androgen receptor (AR) continues to be critical for prostate cancer growth and progression after ADT. One of the underlying molecular mechanisms is derepression of AR-repressed genes involved in cell cycle and proliferation after ADT. Here, the data demonstrate that C-X-C chemokine receptor type 7 (CXCR7), a seven-transmembrane G-protein-coupled chemokine receptor, is an AR-repressed gene and is upregulated after ADT. AR directly regulates CXCR7 using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) gene editing. Macrophage migration inhibitory factor (MIF) was identified as a ligand for CXCR7, which induces expression of cell-cycle genes through activating AKT signaling pathway. Previous studies have been focused on chemokine CXCL12 and its receptor CXCR4 in mediating metastasis of various cancer types, including prostate cancer. The critical roles of CXCL12/CXCR4 axis in the interaction between cancer cells and their microenvironment render it a promising therapeutic target in cancer treatment. The data suggest that the MIF/CXCR7/AKT pathway drives CRPC growth and metastasis independent of the CXCL12/CXCR4 axis. Furthermore, CXCR7 blockade in combination with anti-androgen enzalutamide inhibits CRPC tumor growth and potentially prevents metastasis. Notably, both MIF and CXCR7 are overexpressed in CRPC patient specimens and therefore are attractive therapeutic targets for these patients. IMPLICATIONS: This work suggests that CXCR7 plays more important roles than CXCR4 in CRPC progression; thus, targeting CXCR7 in combination with anti-androgen is a promising therapeutic approach for metastatic CRPC.