What is Immunotherapy of Cancer?
Cancer Immunotherapy is a type of treatment that promotes the effect of the immune system in attacking cancer. For this purpose, it relies on several types of applications, including immune system modulators, checkpoint inhibitors, monoclonal antibodies, and adoptive cell transfer.
Immune system modulators
This type of immunotherapy aims to boost the number of white blood cells, including killer T cells and natural killer cells, and relies on interleukins and interferons. Interleukins, such as interleukin 2 (IL-2), are a type of cytokine produced by leukocytes and other cells in the body, promoting communication between immune cells [1]. Interferons, such as interferon-alpha, are also cytokines produced by fibroblasts, monocytes, and cytotoxic T cells and play an important role in the activation of immune cells [2].
Checkpoint inhibitors
Checkpoint inhibitors are a type of targeted immunotherapy that blocks proteins that stop the immune system from attacking the cancer cells. For instance, cancer cells express on their cell surface a protein known as PDL-1 (programmed death ligand-1) which binds and inhibits the receptor PD-1 (programmed cell death protein-1) on the cell surface of lymphocytes T, preventing their anti-tumor activity. Treatments with checkpoint inhibitors rely on the use of monoclonal antibodies that inhibit PDL-1 or PD1 to promote the activity of immune cells [3].
Monoclonal Antibodies
Antibodies are naturally produced by a type of white blood cell known as a B cell (B lymphocyte) in the presence of a foreign antigen. They help the immune system recognize pathogens that cause diseases and tag them for destruction [4]. However, monoclonal antibodies are generated in the lab to recognize specific targets, including cancer cells and the pathways that promote their growth within the tumor microenvironment, such as angiogenesis, proliferation, invasion, and metastasis. For instance, checkpoint inhibitors are monoclonal antibodies that target proteins that inhibit the activity of the immune cells [3].
Adoptive cell transfer
Adoptive T cell transfer is a therapy that uses the immune system to fight cancer by increasing the number of lymphocytes T that attack cancer cells. It relies on three main therapeutic strategies: 1) isolation of tumor-infiltrating lymphocytes (TILs) from cancer patients, their expansion outside the body and their transfer back into the patient; 2) isolation of T cells, genetically engineer their expression of the T-cell receptor (TCR) which recognizes cancer cells, and then their transfer back into the patient; 3) isolation of T cells, genetically engineer their expression of chimeric antigen receptor (CAR), which recognizes a specific antigen on cancer cells and then their transfer back into the patient [6].
Conclusion
Immunotherapy is a treatment that promotes the immune response in fighting diseases, such as cancer, through the stimulation of the natural defenses of the immune system to work harder and smarter in finding and attacking cancer cells. Recent advances in cellular immunology and tumor biology are very promising and have led to significant results in the treatment of cancer patients, particularly using checkpoint inhibitors. Advances using other applications of monoclonal antibodies, such as bispecific monoclonal antibodies [6], should lead to further efficacy in treating cancer patients.
References
[2] Borden, E.C., 2002. Interferons. In Melanoma (pp. 235-258). Humana Press, Totowa, NJ.
