Role of the CXCL8-CXCR1/2 Axis in Cancer and Inflammatory Diseases.
ABSTRACT: The chemokine receptors CXCR1/2 and their ligand CXCL8 are essential for the activation and trafficking of inflammatory mediators as well as tumor progression and metastasis. The CXCL8-CXCR1/2 signaling axis is involved in the pathogenesis of several diseases including chronic obstructive pulmonary diseases (COPD), asthma, cystic fibrosis and cancer. Interaction between CXCL8 secreted by select cancer cells and CXCR1/2 in the tumor microenvironment is critical for cancer progression and metastasis. The CXCL8-CXCR1/2 axis may play an important role in tumor progression and metastasis by regulating cancer stem cell (CSC) proliferation and self-renewal. During the past two decades, several small-molecule CXCR1/2 inhibitors, CXCL8 releasing inhibitors, and neutralizing antibodies against CXCL8 and CXCR1/2 have been reported. As single agents, such inhibitors are expected to be efficacious in various inflammatory diseases. Several preclinical studies suggest that combination of CXCR1/2 inhibitors along with other targeted therapies, chemotherapies, and immunotherapy may be effective in treating select cancers. Currently, several of these inhibitors are in advanced clinical trials for COPD, asthma, and metastatic breast cancer. In this review, we provide a comprehensive analysis of the role of the CXCL8-CXCR1/2 axis and select genes co-expressed in this pathway in disease progression. We also discuss the latest progress in developing small-molecule drugs targeting this pathway.
Project description:It is well established that chronic inflammation underpins the development of a number of human cancers, with pro-inflammatory signaling within the tumor microenvironment contributing to tumor progression and metastasis. CXCL8 is an ELR+ pro-inflammatory CXC-chemokine which mediates its effects via signaling through two G protein-coupled receptors, CXCR1 and CXCR2. Elevated CXCL8-CXCR1/2 signaling within the tumor microenvironment of numerous cancers is known to enhance tumor progression via activation of signaling pathways promoting proliferation, angiogenesis, migration, invasion and cell survival. This review provides an overview of established roles of CXCL8-CXCR1/2 signaling in cancer and subsequently, discusses the possible strategies of targeting CXCL8-CXCR1/2 signaling in cancer, covering indirect strategies (e.g., anti-inflammatories, NF?B inhibitors) and direct CXCL8 or CXCR1/2 inhibition (e.g., neutralizing antibodies, small molecule receptor antagonists, pepducin inhibitors and siRNA strategies). Reports of pre-clinical cancer studies and clinical trials using CXCL8-CXCR1/2-targeting strategies for the treatment of inflammatory diseases will be discussed. The future translational opportunities for use of such agents in oncology will be discussed, with emphasis on exploitation in stratified populations.
Project description:In humans, Interleukin-8 (IL-8 or CXCL8) is a granulocytic chemokine with multiple roles within the tumor microenvironment (TME), such as recruiting immunosuppressive cells to the tumor, increasing tumor angiogenesis, and promoting epithelial-to-mesenchymal transition (EMT). All of these effects of CXCL8 on individual cell types can result in cascading alterations to the TME. The changes in the TME components such as the cancer-associated fibroblasts (CAFs), the immune cells, the extracellular matrix, the blood vessels, or the lymphatic vessels further influence tumor progression and therapeutic resistance. Emerging roles of the microbiome in tumorigenesis or tumor progression revealed the intricate interactions between inflammatory response, dysbiosis, metabolites, CXCL8, immune cells, and the TME. Studies have shown that CXCL8 directly contributes to TME remodeling, cancer plasticity, and the development of resistance to both chemotherapy and immunotherapy. Further, clinical data demonstrate that CXCL8 could be an easily measurable prognostic biomarker in patients receiving immune checkpoint inhibitors. The blockade of the CXCL8-CXCR1/2 axis alone or in combination with other immunotherapy will be a promising strategy to improve antitumor efficacy. Herein, we review recent advances focusing on identifying the mechanisms between TME components and the CXCL8-CXCR1/2 axis for novel immunotherapy strategies.
Project description:Tumor-associated macrophages (TAMs) are involved in tumor progression and poor prognosis in several malignancies. We previously demonstrated the interaction between high numbers of infiltrating TAMs and poor prognosis in esophageal squamous cell carcinomas (ESCCs). To investigate the significance of TAMs in ESCC, we conducted a cDNA microarray analysis of peripheral blood monocytes (PBMo)-derived macrophages and PBMo-derived macrophages stimulated with conditioned media of TE-series ESCC cell lines (TAM-like PBMo-derived macrophages). C-X-C motif chemokine ligand 8 (CXCL8) was up-regulated in the TAM-like PBMo-derived macrophages. Here we confirmed a high expression level of CXCL8 in TAM-like PBMo-derived macrophages and the expression of CXCR1/2, known as CXCL8 receptors, in TE-series ESCC cell lines. Recombinant human CXCL8 induced the ESCC cell lines' migration and invasion by the phosphorylation of Akt and Erk1/2. In indirect co-cultures, not only signal pathway inhibitors but also neutralizing antibodies against CXCL8, CXCR1 and CXCR2 suppressed these phenotypes induced by TAM-like PBMo-derived macrophages. Immunohistochemical analysis of 70 resected ESCC samples showed that high expression levels of CXCL8 in ESCC tissues were significantly associated with lymph node metastasis and poor prognosis. These results suggest that CXCL8 up-regulated in the microenvironment may contribute to ESCC progression by promoting cancer cells' migration and invasion.
Project description:Persistent infection or chronic inflammation contributes significantly to tumourigenesis and tumour progression. C-X-C motif ligand 8 (CXCL8) is a chemokine that acts as an important multifunctional cytokine to modulate tumour proliferation, invasion and migration in an autocrine or paracrine manner. Studies have suggested that CXCL8 and its cognate receptors, C-X-C chemokine receptor 1 (CXCR1) and C-X-C chemokine receptor 2 (CXCR2), mediate the initiation and development of various cancers including breast cancer, prostate cancer, lung cancer, colorectal carcinoma and melanoma. CXCL8 also integrates with multiple intracellular signalling pathways to produce coordinated effects. Neovascularisation, which provides a basis for fostering tumour growth and metastasis, is now recognised as a critical function of CXCL8 in the tumour microenvironment. In this review, we summarize the biological functions and clinical significance of the CXCL8 signalling axis in cancer. We also propose that CXCL8 may be a potential therapeutic target for cancer treatment.
Project description:CXCR1, a receptor for CXCL8/IL-8, has recently been demonstrated to be associated with cancer stem cell (CSC) populations in certain types of human cancers. However, the effect of CXCR1 on CSC and its prognostic value in human pancreatic cancer remain unknown. In this study, we evaluated the expression of CXCR1 in human pancreatic duct adenocarcinoma (PDAC) and found that positive CXCR1 expression correlated with lymph node metastasis (P = 0.017) and a poor survival rate (HR, 3.748; 95% CI, 1.822 to 7.712; P < 0.001) in patients with PDAC. In addition, we identified significant positive correlations between CXCR1 and CD44 (P = 0.002) and CD133 (P = 0.017). Further functional studies confirmed that IL-8 addition increased sphere formation, CSC populations, and cell invasion of pancreatic cancer cells and that these effects could be reversed by antagonizing CXCR1 with a CXCR1-specific antibody. Therefore, our study demonstrated that the IL-8/CXCR1 axis is associated with the CSC-like properties of pancratic cancer cells and prognosis in human pancreatic cancer. This suggested a way of targeting pancreatic CSCs by disrupting IL-8/CXCR1 axis.
Project description:A role for the collagen-derived tripeptide, N-acetyl proline-glycine-proline (NAc-PGP), in neutrophil recruitment in chronic airway inflammatory diseases, including COPD and cystic fibrosis, has recently been delineated. Due to structural similarity to an important motif for interleukin-8 (CXCL8) binding to its receptor, NAc-PGP binds to CXCR1/2 receptors, leading to neutrophil activation and chemotaxis. In an effort to develop novel CXCL8 antagonists, we describe the synthesis of four chiral isomers of NAc-PGP (NAc-L-Pro-Gly-L-Pro (LL-NAc-PGP), NAc-L-Pro-Gly-D-Pro (LD-NAc-PGP), NAc-D-Pro-Gly-L-Pro (DL-NAc-PGP), and NAc-D-Pro-Gly-D-Pro (DD-NAc-PGP)), characterize them by circular dichroism and NMR spectroscopy, compare their structures to the equivalent region of CXCL8, and test them as potential antagonists of ll-NAc-PGP and CXCL8. We find that LL-NAc-PGP superimposes onto the CXCR1/2 contacting E(29)S(30)G(31)P(32) region of CXCL8 (0.59A rmsd for heavy atoms). In contrast, DD-NAc-PGP has an opposing orientation of key functional groups as compared to the G(31)P(32) region of CXCL8. As a consequence, DD-NAc-PGP binds CXCR1/2, as demonstrated by competition with radiolabeled CXCL8 binding in a radioreceptor assay, yet acts as a receptor antagonist as evidenced by inhibition of CXCL8 and LL-NAc-PGP mediated neutrophil chemotaxis. The ability of DD-NAc-PGP to prevent the activation of CXC receptors indicates that DD-NAc-PGP may serve as a lead compound for the development of CXCR1/2 inhibitors. In addition, this study further proves that using a different technical approach, namely preincubation of NAc-PGP instead of simultaneous addition of NAc-PGP with radiolabeled CXCL8, the direct binding of NAc-PGP to the CXCL8 receptor is evident.
Project description:Chemokine CXCL8 and its receptor CXCR1 are key mediators in combating infection and have also been implicated in the pathophysiology of various diseases including chronic obstructive pulmonary disease (COPD) and cancer. CXCL8 exists as monomers and dimers but monomer alone binds CXCR1 with high affinity. CXCL8 function involves binding two distinct CXCR1 sites - the N-terminal domain (Site-I) and the extracellular/transmembrane domain (Site-II). Therefore, higher monomer affinity could be due to stronger binding at Site-I or Site-II or both. We have now characterized the binding of a human CXCR1 N-terminal domain peptide (hCXCR1Ndp) to WT CXCL8 under conditions where it exists as both monomers and dimers. We show that the WT monomer binds the CXCR1 N-domain with much higher affinity and that binding is coupled to dimer dissociation. We also characterized the binding of two CXCL8 monomer variants and a trapped dimer to two different hCXCR1Ndp constructs, and observe that the monomer binds with ?10- to 100-fold higher affinity than the dimer. Our studies also show that the binding constants of monomer and dimer to the receptor peptides, and the dimer dissociation constant, can vary significantly as a function of pH and buffer, and so the ability to observe WT monomer peaks is critically dependent on NMR experimental conditions. We conclude that the monomer is the high affinity CXCR1 agonist, that Site-I interactions play a dominant role in determining monomer vs. dimer affinity, and that the dimer plays an indirect role in regulating monomer function.
Project description:Dysfunctional inflammatory pathways are associated with an increased risk of cancer, including colorectal cancer. We have previously identified and enriched for a self-renewing, colon cancer stem cell (CCSC) subpopulation in primary sporadic colorectal cancers (CRC) and a related subpopulation in ulcerative colitis (UC) patients defined by the stem cell marker, aldehyde dehydrogenase (ALDH). Subsequent work demonstrated that CCSC-initiated tumors are dependent on the inflammatory chemokine, CXCL8, a known inducer of tumor proliferation, angiogenesis and invasion. Here, we use RNA interference to target CXCL8 and its receptor, CXCR1, to establish the existence of a functional signaling pathway promoting tumor growth initiated by sporadic and colitis CCSCs. Knocking down either CXCL8 or CXCR1 had a dramatic effect on inhibiting both in vitro proliferation and angiogenesis. Likewise, tumorigenicity was significantly inhibited due to reduced levels of proliferation and angiogenesis. Decreased expression of cycle cell regulators cyclins D1 and B1 along with increased p21 levels suggested that the reduction in tumor growth is due to dysregulation of cell cycle progression. Therapeutically targeting the CXCL8-CXCR1 signaling pathway has the potential to block sustained tumorigenesis by inhibiting both CCSC- and pCCSC-induced proliferation and angiogenesis.
Project description:Interleukin-8 (CXCL8), a potent neutrophil-activating chemokine, exerts its function by activating the CXCR1 receptor that belongs to class A G protein-coupled receptors (GPCRs). Receptor activation involves interactions between the CXCL8 N-terminal loop and CXCR1 N-terminal domain (N-domain) residues (Site-I) and between the CXCL8 N-terminal and CXCR1 extracellular/transmembrane residues (Site-II). CXCL8 exists in equilibrium between monomers and dimers, and it is known that the monomer binds CXCR1 with much higher affinity and that Site-I interactions are largely responsible for the differences in monomer vs. dimer affinity. Here, using backbone 15N-relaxation nuclear magnetic resonance (NMR) data, we characterized the dynamic properties of the CXCL8 monomer and the CXCR1 N-domain in the free and bound states. The main chain of CXCL8 appears largely rigid on the picosecond time scale as evident from high order parameters (S²). However, on average, S² are higher in the bound state. Interestingly, several residues show millisecond-microsecond (ms-?s) dynamics only in the bound state. The CXCR1 N-domain is unstructured in the free state but structured with significant dynamics in the bound state. Isothermal titration calorimetry (ITC) data indicate that both enthalpic and entropic factors contribute to affinity, suggesting that increased slow dynamics in the bound state contribute to affinity. In sum, our data indicate a critical and complex role for dynamics in driving CXCL8 monomer-CXCR1 Site-I interactions.
Project description:Impaired PTEN function is a genetic hallmark of aggressive prostate cancers (CaP) and is associated with increased CXCL8 expression and signaling. The current aim was to further characterize biological responses and mechanisms underpinning CXCL8-promoted progression of PTEN-depleted prostate cancer, focusing on characterizing the potential interplay between CXCL8 and other disease-promoting chemokines resident within the prostate tumor microenvironment. Autocrine CXCL8-stimulation (i) increased expression of CXCR1 and CXCR2 in PTEN-deficient CaP cells suggesting a self-potentiating signaling axis and (ii) induced expression of CXCR4 and CCR2 in PTEN-wild-type and PTEN-depleted CaP cells. In contrast, paracrine CXCL8 signaling induced expression and secretion of the chemokines CCL2 and CXCL12 from prostate stromal WPMY-1 fibroblasts and monocytic macrophage-like THP-1 cells. In vitro studies demonstrated functional co-operation of tumor-derived CXCL8 with stromal-derived chemokines. CXCL12-induced migration of PC3 cells and CCL2-induced proliferation of prostate cancer cells were dependent upon intrinsic CXCL8 signaling within the prostate cancer cells. For example, in co-culture experiments, CXCL12/CXCR4 signaling but not CCL2/CCR2 signaling supported fibroblast-mediated migration of PC3 cells while CXCL12/CXCR4 and CCL2/CCR2 signaling underpinned monocyte-enhanced migration of PC3 cells. Combined inhibition of both CXCL8 and CXCL12 signaling was more effective in inhibiting fibroblast-promoted cell motility while repression of CXCL8 attenuated CCL2-promoted proliferation of prostate cancer cells. We conclude that tumor-derived CXCL8 signaling from PTEN-deficient tumor cells increases the sensitivity and responsiveness of CaP cells to stromal chemokines by concurrently upregulating receptor expression in cancer cells and inducing stromal chemokine synthesis. Combined chemokine targeting may be required to inhibit their multi-faceted actions in promoting the invasion and proliferation of aggressive CaP.