“Cancer immunotherapy” was hailed as 2013’s Breakthrough of the Year by Science and the American Society of Clinical Oncology’s Advancement of the Year for 2 years in a row [1, 2]. But the advances so far have only begun to scratch the surface.
Immunotherapy is geared towards boosting the body’s immune system to fight cancer. From the first groundbreaking success of ipilimumab in advanced melanoma, immunotherapy can now be employed to treat a range of cancers with relatively milder adverse effects as compared with chemotherapy. Mainly, immunotherapy may lead to an overactive immune system resulting in excessive inflammation and development of autoimmune disorders.
Immunotherapy may work by:
• Inhibiting or slowing the growth of cancer cells
• Preventing cancer metastasis
• Helping the immune system recognize and destroy cancer cells 
The main types of immunotherapy include:
Monoclonal antibodies: Such antibodies are designed to bind to specific targets found on cancer cells so that they are detected and destroyed by the immune system. Mechanisms include mediation of cellular cytotoxicity of tumour cells, targeting of Fc receptors on dendritic cells to promote antigen presentation and induction of adaptive immune responses, and triggering of the idiotypic network to elicit tumour-antigen-specific immune responses. 
Immune checkpoint inhibitors: The PD-1/PD-L1 and CTLA-4 pathways, called immune checkpoints, negatively regulate immune response by inhibiting the activation and proliferation of T lymphocytes and decreasing production of cytokines. Immune checkpoint blockade removes inhibitory signals of T-cell activation, which enables tumor-reactive T cells to overcome regulatory mechanisms and mount an effective antitumor response. [5, 6]
Adoptive cell transfer (CAR T Cell Therapy): T cells are collected from a patient via apheresis and reengineered in a laboratory to produce chimeric antigen receptors (CARs) on their surface that allow them to recognize an antigen on targeted tumor cells. The reengineered CAR T cells are then multiplied and eventually infused into the patient. [3, 6, 7]
Cancer vaccines: Prevention vaccines expose the immune system to an antigen which triggers the immune system to identify and eliminate the antigen. Treatment vaccines work against cancer by boosting the immune system’s response to cancer cells. [3, 5] For example, immunoenhancing agents are locally injected into a tumor site; the triggered T cell immune response locally subsequent attacks cancer throughout the body. 
Interferons: IFNs, which are secreted by immune cells, regulate different aspects of cancer cells’ behavior, including proliferation and metastatic spread. [3, 9]
Interleukins: Aldesleukin, human recombinant IL-2, promotes proliferation, differentiation, and recruitment of T and B cells, induces killer cell (lymphokine-activated (LAK) and natural (NK)) activity, and stimulates interferon-gamma production. It is used to treat kidney cancer and melanoma. [3, 10, 11]
BCG: Bacillus Calmette-Guérin, an attenuated form of M. tuberculosis, is an intravesical immunotherapy for early-stage bladder cancer. The live organisms enter macrophages, where they induce an immunologic reaction, and bladder cancer cells, where the proteins are broken down to combine with histocompatibility antigens and be displayed on the cell surface. This induces a cytokine and direct cell-to-cell cytotoxicity response, which causes destruction of these cells. [3, 12]
Oncolytic virus therapy: The locally injected virus selectively enters cancer cells and makes copies of itself. As the cells die, they release antigens that trigger the patient’s immune system to target all the cancer cells that display those antigens. 
Which type of immunotherapy do you find most interesting and promising?
1. Couzin-Frankel J. Breakthrough of the year 2013. Cancer immunotherapy. Science. 2013;342(6165):1432–1433.
2. Guthrie G. Immunotherapy 2.0: The 2017 Clinical Cancer Advance of the Year. Cancer.Net. https://www.cancer.net/blog/2017-02/immunotherapy-20-2017-clinical-cancer-advance-year. Published February 1, 2017. Accessed January 13, 2019
3.! Understanding Immunotherapy. Cancer.Net. https://www.cancer.net/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/understanding-immunotherapy. Published May 2018. Accessed January 13, 2019
4. Weiner, L. M., Dhodapkar, M. V., & Ferrone, S. (2009). Monoclonal antibodies for cancer immunotherapy. The Lancet, 373(9668), 1033-1040.
5. Immunotherapy. National Cancer Institute. https://www.cancer.gov/about-cancer/treatment/types/immunotherapy#1. Published November 28, 2018. Accessed January 13, 2019.
6. Yang, Y. (2015). Cancer immunotherapy: harnessing the immune system to battle cancer. The Journal of clinical investigation, 125(9), 3335-3337.
7. Guthrie G. CAR T-Cell Immunotherapy: The 2018 Advance of the Year. Cancer.Net. https://www.cancer.net/blog/2018-01/car-t-cell-immunotherapy-2018-advance-year. Published March 2, 2018. Accessed January 13, 2019
8. Sagiv-Barfi, I., Czerwinski, D. K., Levy, S., Alam, I. S., Mayer, A. T., Gambhir, S. S., & Levy, R. (2018). Eradication of spontaneous malignancy by local immunotherapy. Science translational medicine, 10(426), eaan4488.
9. Di Franco, S., Turdo, A., Todaro, M., & Stassi, G. (2017). Role of type I and II interferons in colorectal cancer and melanoma. Frontiers in immunology, 8, 878.
10. Doyle MV, Lee MT, Fong S. Comparison of the biological activities of human recombinant interleukin-2125 and native interleukin-2. J Biol Response Mod 1985; 4:96-109.
11. Ralph P, Nakoinz I, Doyle M, et al. Human B and T lymphocyte stimulating properties of interleukin-2 (IL-2) muteins. In: Immune Regulation By Characterized Polypeptides. Alan R. Liss, Inc. 1987; 453-62
12. Steinberg GD. Bacillus Calmette-Guérin Immunotherapy for Bladder Cancer Overview of BCG Immunotherapy. Sickle Cell Anemia Differential Diagnoses. https://emedicine.medscape.com/article/1950803-overview#a2. Published June 6, 2018. Accessed January 13, 2019.