On January 3, 2024, a recent review titled "Research progress on the role of tumor-associated macrophages in tumor development and their use as molecular targets" sheds light on the pivotal role of tumor-associated macrophages (TAMs) in tumor progression [1]. Notably, the CCR6-CCL20 axis significantly influences the recruitment and polarization of TAMs and Tregs. For instance, in colon cancer, TAM-secreted CCL20 attracts CCR6+ Treg cells, fostering an immunosuppressive microenvironment that fuels tumor advancement.
CCR6, a G-protein-coupled chemokine receptor, forms a highly affinity pair with CCL20, constituting a distinctive chemokine receptor-ligand duo. Multiple studies link CCR6 to various inflammatory diseases and highlight its significance in digestive tumor development. As an exceptional chemokine receptor, CCR6 is poised to offer novel avenues for targeted drug development in the future. Today, let's delve deeper into this distinctively specialized chemokine receptor, CCR6!
1. What is the Chemokine Family?
3. What is the Ligand for CCR6?
6. The Prospects for Clinical Drug Research on CCR6
7. CUSABIO CCR6 Recombinant Proteins & Antibodies for Research Use
The chemokine family, a collection of small active proteins, possesses diverse biological functions and is released by various cells, primarily orchestrating cell movement. Over 50 chemokines have been identified in humans, categorized into four subtypes: C (XCL1-XCL2), CC (CCL1-CCL28), CXC (CXCL1-CXCL17), and CX3C (CX3CL1). These chemokines bind to cell surfaces via specific receptors known as G protein-coupled seven-transmembrane receptors, directing cell migration to precise organism locations. Chemokine receptors fall into four subfamilies: CXC (CXCR1-CXCR7), CC (CCR1-CCR10), XC (XCR1), and CX3C (CX3CR1). Generally, chemokines and receptors exhibit diverse binding relationships, with a chemokine binding to multiple receptors and vice versa. However, six distinct chemokine-chemokine receptor pairs exist in humans: CCL20-CCR6, CCL25-CCR9, CXCL16-CXCR6, CX3CL1-CX3CR1, and CXCL12-CXCR4, as well as CXCL13-CXCR5 [1-5].
CC motif chemokine receptor 6 (CCR6) is a transmembrane G protein-coupled receptor situated on chromosome 6q27, unlike several other CCR genes found on chromosome 3p. It exhibits characteristic features of G protein-coupled chemokine receptors, encompassing potential N-linked glycosylation sites in its acidic N-terminal region, along with glycosylation sites on the first and third extracellular loops. Moreover, CCR6's primary structure contains four conserved cysteine residues, two forming disulfide bridges. Despite this, the three-dimensional spatial arrangement of CCR6 remains undetermined, unlike the well-characterized high-level structures of chemokine receptors like CXCR1 and CXCR4. As a result, further investigation is necessary to comprehensively grasp the structure of the CCR6 chemokine receptor (Figure 1) [6-9].
CCR6 displays widespread expression in both lymphoid and non-lymphoid tissues, notably prominent in the spleen, lymph nodes, appendix, and pancreas. It exhibits lower levels in the thymus, colon, small intestine, fetal liver, and testis. Moreover, CCR6 is present in diverse leukocyte subgroups, including immature dendritic cells (iDCs), B cells, T cells (comprising pro-inflammatory Th17 cells and regulatory Treg cells), NK cells, and neutrophils. Numerous studies underscore the association between aberrant CCR6 expression and various diseases such as inflammatory bowel disease, psoriasis, rheumatoid arthritis, and multiple sclerosis, correlating its expression levels with disease severity. Unlike other chemokine receptors, CCR6 uniquely binds to its ligand, CCL20, forming the CCR6/CCL20 pair. Recent investigations highlight the high expression of CCR6/CCL20 in various human tumor cells, strongly linked to tumor invasion and metastasis [6-9].
Figure 1. The topology diagram of CCR6 [9]
CC motif chemokine ligand 20 (CCL20) exclusively binds to CCR6, facilitating CCR6 cell migration with notable specificity and high affinity. Also recognized as macrophage inflammatory protein 3a (MIP-3a) or liver activation regulator (LARC), CCL20 is primarily produced by epithelial cells and significantly upregulated during inflammatory states. Various cytokines, including IL-1a, IL-1β, IL-17, IL-21, TNF-α, IFN-γ, among others, induce CCL20 expression, while IL-10 downregulates it. Though CCL20 remains the sole known ligand for CCR6, ongoing studies explore potential new ligands like human β-defensin 1 (HBD-1) and 2 (HBD-2) [10-12].
Chemokines exert their function by engaging chemokine receptors, facilitating cell migration across diverse tissue systems and maintaining homeostasis. Research highlights the N-terminal end of CCL20 as a pivotal site for CCR6 activation. This region interacts with ECL2 and R421.28 side chains of CCR6, creating hydrogen bonding and salt bridges. This interaction directly links the N-terminal end of CCL20 to the seven-transmembrane region of CCR6, crucial for CCR6 activation. The activation process involves complex signaling pathways, potentially involving second messengers like Ca2+, P13K/Akt, initiating downstream protein kinase activation and prompting a cascade reaction promoting metastasis in chemokine-expressing cells [13-14].
In a mouse model of subcutaneous transplantation for colon cancer, research revealed a significant presence of regulatory T cells expressing the chemokine receptor CCR6 within the tumor tissue. Both in vitro and in vivo experiments underscored the secretion of CCL20, the unique ligand binding to CCR6, by both mouse CMT93 colon cancer cells and tumor-associated giant cells. The introduction of recombinant CCL20 into the tumor microenvironment of these subcutaneously transplanted tumors successfully attracted a considerable influx of regulatory T cells, substantially enhancing tumor progression [15].
Moreover, employing a CD11b-DTR mouse model with selectively knocked-out macrophages systemically showcased diminished CCL20 secretion in the tumor microenvironment post-subcutaneous tumor transplantation. This decline prevented the migration of regulatory T cells within the tumor microenvironment. Ultimately, the recruitment of CCR6-expressing regulatory T cells by tumor-associated macrophages via CCL20 secretion promoted tumor growth in the mouse colon cancer model. This discovery potentially unveils a therapeutic target for future tumor immunotherapy [15].
Researchers constructed CCR6 knockdown and overexpression colorectal cancer cell lines using lentiviral transfection technology. Results exhibited that reducing CCR6 hampered angiogenesis, while heightened CCR6 expression notably amplified tumor angiogenesis. Additionally, the introduction of recombinant human CCL20 (rhCCL20) further magnified angiogenesis, yet this effect was counteracted by antibodies targeting hCCL20 and CCR6. These findings underscore the pivotal reliance of CCR6-mediated angiogenesis on CCL20 secretion [16].
Deeper molecular investigations revealed upregulation in the expression of key molecules such as VEGF-A, angiopoietin-1, angiopoietin-2, and MMP9, particularly highlighting a substantial increase in VEGF-A expression. This suggested VEGF-A's pivotal role as a mediator in CCR6-driven tumor angiogenesis. Additionally, treatment of tumor cells with an ERK and PI3K pathway inhibitor (LY294002) resulted in the downregulation of VEGFA expression, implicating the involvement of the PI3K/AKT pathway in CCR6-mediated angiogenesis (Figure 2) [16].
Figure 2. CCR6 Promotes Tumor Angiogenesis [16]
Recent extensive research, both domestic and international, has delved into CCR6 and its role in organisms. Studies have primarily focused on the CCR6/CCL20 interaction, a key player in regulating inflammatory diseases, autoimmune conditions, and particularly digestive tumors. These findings provide crucial insights for researchers to better grasp and intervene in disease-related tumor, immune, and inflammatory processes.
CCR6/CCL20 signaling is pivotal in inflammatory diseases, influencing tissue damage and disease severity. Specifically, in intestinal tract inflammatory conditions, CCR6 signaling modulates macrophages and dendritic cells, impacting tissue damage and inflammatory responses. Deleting CCR6 shows promise in countering peritonitis and reducing inflammatory reactions triggered by bacterial infections [9]. Furthermore, CCR6/CCL20 signaling contributes significantly to chronic airway inflammation by affecting immune cell aggregation at inflammatory sites [17].
Notably, this signaling axis also plays a crucial role in atherosclerosis, particularly in monocyte chemotaxis [18]. Studies in CCR6-deficient mice revealed slightly reduced atherosclerosis, suggesting the involvement of CCR6 and CCL20 in the vessel wall's self-regulatory processes [18]. Apart from monocytes, other CCR6+ leukocyte subtypes may also have vital roles in atherosclerosis progression, warranting further investigation [19].
Studies indicate that CCR6-deficient mice experience more pronounced skin contact hypersensitivity reactions, yet reduced reactions to hair loss, acute graft-versus-host disease, and allergic airway inflammation. Correlations of CCR6 have been identified in systemic sclerosis, HIV, and psoriatic dermatitis, wherein both CCR6 and CCL20 are upregulated in affected tissues, correlating with immune cell accumulation. Moreover, CCR6/CCL20 signaling potentially influences T cell migration and activation in models of autoimmune hepatitis and airway allergies. Collectively, CCR6/CCL20 plays a role in regulating immune responses by modulating immune cell accumulation at affected sites, although the precise mechanism remains incompletely understood [10, 20-21].
CCR6/CCL20 expression has been detected in various cancers, particularly those affecting the digestive system such as colon, stomach, pancreas, liver, and esophagus [22-31]. These studies mainly investigate how CCR6/CCL20 interaction impacts tumor cell migration, proliferation, and immune evasion. For instance, research indicates elevated CCR6 levels in distant metastatic primary tumor samples, suggesting a potential association with synchronous metastasis, yet showed no significant variance in liver or lung-specific metastasis [27]. Furthermore, CCR6/CCL20 signaling potentially enhances tumor cell dissemination by promoting Th9 cell migration, an effect reduced by anti-CCL20 inhibition [25]. Additionally, CCR6/CCL20 interactions are implicated in tumor immune evasion, as evidenced by increased Th17 cell types in tumor patients, possibly linked to TGF-β regulation [31]. Despite these insights, the current understanding of CCR6/CCL20 in digestive tumors remains limited. Further exploration of its mechanisms in tumor onset and progression promises novel strategies for drug research in this domain.
Currently, two CCR6-related drugs—PF-07054894 and HG-1112—are under exploration. Pfizer Inc.'s PF-07054894 functions as a CCR6 antagonist, impeding CCR6-mediated inflammatory responses by obstructing the binding between CCR6 and its ligand. This drug is presently undergoing preclinical trials targeting ulcerative colitis. HG-1112, another drug in this category, serves as a dual modulator of CCR6 and TRPV1, displaying anti-inflammatory and analgesic effects; however, its specific investigational indications are undisclosed.
Both PF-07054894 and HG-1112 belong to the category of small molecular drugs with excellent bioavailability and tissue permeability. Several small molecule inhibitors targeting chemokine receptors have advanced into clinical phase I to II studies. Notably, small molecule compounds targeting CXCR4 have been notably applied in AIDS treatment, and more recently, in clinical studies concerning tumor metastasis. Foreseeably, the development of highly specific small molecule compounds targeting CCR6, akin to those for CXCR4, holds promise for ushering in novel research avenues in the realms of inflammatory, autoimmune, and tumor diseases research.
CCR6, a key chemokine receptor, profoundly influences inflammation, immunity, and tumor growth. Its interaction with CCL20 drives immune cell movement during inflammation and plays a significant role in various diseases, including digestive cancers. Potential drugs targeting CCR6, like PF-07054894 and HG-1112, show promise in treating inflammatory conditions and offer potential in diverse diseases from colitis to cancer. A thorough comprehension of CCR6's function might reveal novel therapeutic approaches for numerous diseases research.
To fully support researchers and pharmaceutical companies in their research on CCR6 in inflammatory, autoimmune, and tumor diseases, CUSABIO presents CCR6 active proteins & antibodies to support your research on the mechanism of CCR6 or its potential clinical value.
CUSABIO CCR6 Protein
Recombinant Human C-C chemokine receptor type 6(CCR6)-VLPs (Active) Code: CSB-MP004845HU
CSB-MP004845HU is detected by Mouse anti-6*His monoclonal antibody. The two bands respectively correspond to monomer, Homodimer.
Immobilized Human CCR6 at 10μg/mL can bind Anti-CCR6 recombinant antibody (CSB-RA004845MA1HU). The EC50 is 44.79-56.10 ng/mL. VLPs (CSB-MP3838) is negative control.
CUSABIO CCR6 antibody
CCR6 Recombinant Monoclonal Antibody (ELISA) (CSB-RA004845MA1HU)
References
[1] Lu, Chenglin, et al. "Research progress on the role of tumor‑associated macrophages in tumor development and their use as molecular targets." International Journal of Oncology 64.2 (2024): 1-12.
[2] Li, Xian, Jiaqi Peng, and Xiulan Su. "Expression of immune regulatory factors, chemokines and growth factors in differentiated gastric cancer cells treated with an anticancer bioactive peptide combined with oxaliplatin." Molecular and Clinical Oncology 20.1 (2024): 1-10.
[3] Chen, Xuyan, et al. "The role of CXCL chemokine family in the development and progression of gastric cancer." International journal of clinical and experimental pathology 13.3 (2020): 484.
[4] Mamazhakypov, Argen, et al. "The role of chemokines and chemokine receptors in pulmonary arterial hypertension." British journal of pharmacology 178.1 (2021): 72-89.
[5] Do, Ha Thi Thu, Chang Hoon Lee, and Jungsook Cho. "Chemokines and their receptors: multifaceted roles in cancer progression and potential value as cancer prognostic markers." Cancers 12.2 (2020): 287.
[6] Wasilko, David Jonathan, et al. "Structural basis for chemokine receptor CCR6 activation by the endogenous protein ligand CCL20." Nature communications 11.1 (2020): 3031.
[7] Martina, Maria Grazia, et al. "Discovery of small-molecules targeting the CCL20/CCR6 axis as first-in-class inhibitors for inflammatory bowel diseases." European Journal of Medicinal Chemistry 243 (2022): 114703.
[8] Isaikina, Polina, et al. "Structural basis of the activation of the CC chemokine receptor 5 by a chemokine agonist." Science Advances 7.25 (2021): eabg8685.
[9] Gómez-Melero, Sara, and Javier Caballero-Villarraso. "CCR6 as a Potential Target for Therapeutic Antibodies for the Treatment of Inflammatory Diseases." Antibodies 12.2 (2023): 30.
[10] Meitei, Heikrujam Thoihen, Nandadeep Jadhav, and Girdhari Lal. "CCR6-CCL20 axis as a therapeutic target for autoimmune diseases." Autoimmunity reviews 20.7 (2021): 102846.
[11] Reichard, Sherwood. The International Cytokine Conference (11th) Held in Dublin (Ireland) on September 20-24 2003 (European Cytokine Network, Volume 14, Number 3, September 2003). 2003.
[12] Lee, Adrian YS, et al. "The relationship between CCR6 and its binding partners: Does the CCR6–CCL20 axis have to be extended?." Cytokine 72.1 (2015): 97-101.
[13] Liu, Kaiwen, et al. "Structural insights into the activation of chemokine receptor CXCR2." The FEBS Journal 289.2 (2022): 386-393.
[14] Murugesan, Vidya, and Senthilkumar Rajagopal. "Modulatory effects of G protein–coupled receptor in hepatocellular carcinoma." Theranostics and Precision Medicine for the Management of Hepatocellular Carcinoma. Academic Press, 2022. 81-95.
[15] Liu, Jinlin, et al. "Tumor-associated macrophages recruit CCR6+ regulatory T cells and promote the development of colorectal cancer via enhancing CCL20 production in mice." PloS one 6.4 (2011): e19495.
[16] Zhu, Cong-cong, et al. "CCR6 promotes tumor angiogenesis via the AKT/NF-κB/VEGF pathway in colorectal cancer." Biochimica et Biophysica Acta (BBA)-Molecular Basis of Disease 1864.2 (2018): 387-397.
[17] Bracke, Ken R., et al. "Cigarette smoke-induced pulmonary inflammation and emphysema are attenuated in CCR6-deficient mice." The Journal of Immunology 177.7 (2006): 4350-4359.
[18] Wan, Wuzhou, et al. "Genetic deletion of chemokine receptor Ccr6 decreases atherogenesis in ApoE-deficient mice." Circulation research 109.4 (2011): 374-381.
[19] Wan, Wuzhou, and Philip M. Murphy. "Regulation of atherogenesis by chemokine receptor CCR6." Trends in cardiovascular medicine 21.5 (2011): 140-144.
[20] Comerford, Iain, et al. "An immune paradox: how can the same chemokine axis regulate both immune tolerance and activation? CCR6/CCL20: a chemokine axis balancing immunological tolerance and inflammation in autoimmune disease." Bioessays 32.12 (2010): 1067-1076.
[21] Chung, So-Hyang, et al. "The CC chemokine receptor 6 (CCR6) is crucial for Th2-driven allergic conjunctivitis." Clinical Immunology 161.2 (2015): 110-119.
[22] Nandi, Bisweswar, et al. "Stromal CCR6 drives tumor growth in a murine transplantable colon cancer through recruitment of tumor-promoting macrophages." Oncoimmunology 5.8 (2016): e1189052.
[23] Ohtani, Haruo, Takashi Nakayama, and Osamu Yoshie. "In situ expression of the CCL20–CCR6 axis in lymphocyte‐rich gastric cancer and its potential role in the formation of lymphoid stroma." Pathology international 61.11 (2011): 645-651.
[24] Nandi, Bisweswar, et al. "CCR6, the sole receptor for the chemokine CCL20, promotes spontaneous intestinal tumorigenesis." PloS one 9.5 (2014): e97566.
[25] Kadomoto, Suguru, Kouji Izumi, and Atsushi Mizokami. "The CCL20-CCR6 axis in cancer progression." International journal of molecular sciences 21.15 (2020): 5186.
[26] Cook, Katherine W., et al. "CCL20/CCR6-mediated migration of regulatory T cells to the Helicobacter pylori-infected human gastric mucosa." Gut (2014): gutjnl-2013.
[27] Dellacasagrande, J., et al. "Liver metastasis of cancer facilitated by chemokine receptor CCR6." Scandinavian journal of immunology 57.6 (2003): 534-544.
[28] Rubie, Claudia, et al. "CCL20/CCR6 expression profile in pancreatic cancer." Journal of translational medicine 8 (2010): 1-8.
[29] Lian, Jingyao, et al. "Eomes promotes esophageal carcinoma progression by recruiting Treg cells through the CCL20‐CCR6 pathway." Cancer Science 112.1 (2021): 144-154.
[30] Zhang, X. G., et al. "CCR6 overexpression predicted advanced biological behaviors and poor prognosis in patients with gastric cancer." Clinical and Translational Oncology 18 (2016): 700-707.
[31] Xu, Lin, et al. "In situ prior proliferation of CD4+ CCR6+ regulatory T cells facilitated by TGF-β secreting DCs is crucial for their enrichment and suppression in tumor immunity." PLoS One 6.5 (2011): e20282.
Comments
Leave a Comment