The preparation of the recombinant human CD47 protein involves expressing a plasmid containing the sequence for residues 19-139 of the human CD47 in mammalian cells. The gene fragment is co-expressed with the C-terminal 10xHis-tag gene. The resulting protein CD47's endotoxin levels are less than 1.0 EU/μg as determined by the LAL method. ELISA demonstrates the CD47 protein's functional binding to the human SIRPA protein and the CD47 recombinant antibody (CSB-RA004940MA1HU), yielding an EC50 of 98.73-112.7 ng/mL and 1.343-1.561 ng/mL, respectively.
Human CD47, also known as the don't eat me signal, is a transmembrane protein that plays a critical role in immune evasion, particularly in the context of cancer. It interacts with signal regulatory protein alpha (SIRPα) on macrophages, inhibiting phagocytosis and allowing tumor cells to escape immune surveillance [1][2][3]. CD47 is widely expressed across various human cancers, including breast, colorectal, ovarian, and lung cancers, where its overexpression is often associated with poor prognosis and adverse clinicopathological features [4][5][6][7].
The mechanism by which CD47 contributes to tumor progression involves its ability to inhibit macrophage-mediated phagocytosis. When CD47 binds to SIRPα, it triggers a signaling cascade that results in the phosphorylation of immunoreceptor tyrosine-based inhibition motifs (ITIMs) within SIRPα, effectively dampening the immune response [8][9]. This interaction not only protects tumor cells from being engulfed by macrophages but also impairs the activation of T cells, further contributing to an immunosuppressive tumor microenvironment [10][11].
Research has demonstrated that blocking CD47 can enhance the efficacy of various cancer therapies. For instance, anti-CD47 antibodies have shown promise in promoting phagocytosis of cancer cells and synergizing with other therapeutic agents, such as rituximab, to improve treatment outcomes in non-Hodgkin lymphoma and other malignancies [12][13]. Additionally, CD47 blockade has been associated with increased infiltration of CD8+ T cells into tumors, indicating a potential for restoring anti-tumor immunity [14].
References:
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[2] J. Wu, Z. Li, Z. Yang, L. Guo, Y. Zhang, H. Deng, et al. A glutamine-rich carrier efficiently delivers anti-cd47 sirna driven by a “glutamine trap” to inhibit lung cancer cell growth, Molecular Pharmaceutics, vol. 15, no. 8, p. 3032-3045, 2018. https://doi.org/10.1021/acs.molpharmaceut.8b00076
[3] S. Bang, S. Jee, H. Son, H. Cha, H. Park, J. Myung, et al. Cd47 expression in non-melanoma skin cancers and its clinicopathological implications, Diagnostics, vol. 12, no. 8, p. 1859, 2022. https://doi.org/10.3390/diagnostics12081859
[4] J. Yuan, X. Shi, C. Chen, H. He, L. Liu, J. Wu, et al. High expression of cd47 in triple negative breast cancer is associated with epithelial‑mesenchymal transition and poor prognosis, Oncology Letters, 2019. https://doi.org/10.3892/ol.2019.10618
[5] M. Yang, C. Jiang, L. Lin, H. Xing, & H. Li. Expression of cd47 in endometrial cancer and its clinicopathological significance, Journal of Oncology, vol. 2022, p. 1-10, 2022. https://doi.org/10.1155/2022/7188972
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[8] Y. Lee, E. Ko, Y. Lee, Y. Lee, Z. Bian, Y. Liu, et al. Cd47 plays a role as a negative regulator in inducing protective immune responses to vaccination against influenza virus, Journal of Virology, vol. 90, no. 15, p. 6746-6758, 2016. https://doi.org/10.1128/jvi.00605-16
[9] D. Soto-Pantoja, M. Terabe, A. Ghosh, L. Ridnour, W. DeGraff, D. Wink, et al. Cd47 in the tumor microenvironment limits cooperation between antitumor t-cell immunity and radiotherapy, Cancer Research, vol. 74, no. 23, p. 6771-6783, 2014. https://doi.org/10.1158/0008-5472.can-14-0037-t
[10] J. Sockolosky, M. Dougan, J. Ingram, C. Ho, M. Kauke, S. Almo, et al. Durable antitumor responses to cd47 blockade require adaptive immune stimulation, Proceedings of the National Academy of Sciences, vol. 113, no. 19, 2016. https://doi.org/10.1073/pnas.1604268113
[11] F. Liu, C. Jiang, X. Yan, H. Tseng, C. Wang, X. Zhang, et al. Braf/mek inhibitors promote cd47 expression that is reversible by erk inhibition in melanoma, Oncotarget, vol. 8, no. 41, p. 69477-69492, 2017. https://doi.org/10.18632/oncotarget.17704
[12] L. Liu, L. Zhang, L. Yang, H. Li, R. Li, J. Yu, et al. Anti-cd47 antibody as a targeted therapeutic agent for human lung cancer and cancer stem cells, Frontiers in Immunology, vol. 8, 2017. https://doi.org/10.3389/fimmu.2017.00404
[13] M. Chao, A. Alizadeh, C. Tang, J. Myklebust, B. Varghese, S. Gill, et al. Anti-cd47 antibody synergizes with rituximab to promote phagocytosis and eradicate non-hodgkin lymphoma, Cell, vol. 142, no. 5, p. 699-713, 2010. https://doi.org/10.1016/j.cell.2010.07.044
[14] H. Tao, P. Qian, F. Wang, H. Yu, & Y. Guo. Targeting cd47 enhances the efficacy of anti-pd-1 and ctla-4 in an esophageal squamous cell cancer preclinical model, Oncology Research Featuring Preclinical and Clinical Cancer Therapeutics, vol. 25, no. 9, p. 1579-1587, 2017. https://doi.org/10.3727/096504017x14900505020895
