Chemokine receptor 7 (CCR7) is a G-protein coupled receptor (GPCR) that binds chemokine ligand 19 (CCL19) and chemokine ligand 21 (CCL21) and, together, this receptor-ligand interaction functions in inflammatory and adaptive immune response (1,2). The CCR7 protein contains 7-transmembrane spanning alpha helices and is 378 amino acids (aa) in length, with a theoretical molecular weight of 42.8 kDa (3,4). CCR7 is expressed on several cells within the immune system, including naive T cells, central memory T cells, regulatory T cells, naive B cells, a subset of double negative and single positive thymocytes, and mature dendritic cells (DCs) (1, 3).
The primary role of the CCR7/CCL19/CCL21 chemokine signaling axis is homing T cells and DCs to lymph nodes and lymphoid tissues to initiate an immune response (1,2,5,6). In the context of cancer, the CCR7 signaling axis appears to have two opposing roles (2). Downregulation of CCR7 on CD8+ T cells contributes to effector cell migration and anti-cancer activities via cytotoxic tumor-infiltrating lymphocytes (2). However, upregulation of CCR7 by cancer cells can result in cancer cell migration and metastasis (2). Overexpression of CCR7 has been implicated in a variety of cancers including breast, cervical, gastric, head and neck cell carcinoma, and prostate (1,2,7). Studies in breast cancer have found that hypoxia increases CCR7 expression, and this activation can affect cancer cell invasion, extravasation, proliferation, angiogenesis, and metastasis through induction of multiple signaling transduction pathways such as PI3K/AKT, MAPK, and JAK/STAT (5,7).
Given its important role in inflammation and immune response, several strategies have been employed to target the CCR7 signaling axis for cancer immunotherapy (2). Some cancer immunotherapies under investigation include intra-tumoral administration of CCL19 and CCL21, introduction of patient-derived cells transfected to express CCR7 or its ligands, and vaccines (2). Further interrogation of CCR7/CCL19/CCL21 signaling axis is required to develop better therapeutic strategies for cancer treatment.
References:
1. Comerford, I., Harata-Lee, Y., Bunting, M. D., Gregor, C., Kara, E. E., & McColl, S. R. (2013). A myriad of functions and complex regulation of the CCR7/CCL19/CCL21 chemokine axis in the adaptive immune system. Cytokine & growth factor reviews, 24(3), 269-283. https://doi.org/10.1016/j.cytogfr.2013.03.001
2. Salem, A., Alotaibi, M., Mroueh, R., Basheer, H. A., & Afarinkia, K. (2021). CCR7 as a therapeutic target in Cancer. Biochimica et biophysica acta. Reviews on cancer, 1875(1), 188499. https://doi.org/10.1016/j.bbcan.2020.188499
3. Yan, Y., Chen, R., Wang, X., Hu, K., Huang, L., Lu, M., & Hu, Q. (2019). CCL19 and CCR7 Expression, Signaling Pathways, and Adjuvant Functions in Viral Infection and Prevention. Frontiers in cell and developmental biology, 7, 212. https://doi.org/10.3389/fcell.2019.00212
4. Uniprot (P32248)
5. Korbecki, J., Grochans, S., Gutowska, I., Barczak, K., & Baranowska-Bosiacka, I. (2020). CC Chemokines in a Tumor: A Review of Pro-Cancer and Anti-Cancer Properties of Receptors CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10 Ligands. International journal of molecular sciences, 21(20), 7619. https://doi.org/10.3390/ijms21207619
6. Sanchez-Sanchez, N., Riol-Blanco, L., & Rodriguez-Fernandez, J. L. (2006). The multiple personalities of the chemokine receptor CCR7 in dendritic cells. Journal of immunology (Baltimore, Md. : 1950), 176(9), 5153-5159. https://doi.org/10.4049/jimmunol.176.9.5153
7. Rizeq, B., & Malki, M. I. (2020). The Role of CCL21/CCR7 Chemokine Axis in Breast Cancer Progression. Cancers, 12(4), 1036. https://doi.org/10.3390/cancers12041036
