Cancer immunotherapy

Cancer immunotherapy (sometimes called immuno-oncology) is the artificial stimulation of the immune system to treat cancer, improving on the immune system's natural ability to fight cancer. It is an application of the fundamental research of cancer immunology and a growing subspeciality of oncology. It exploits the fact that cancer cells often have tumor antigens, molecules on their surface that can be detected by the antibody proteins of the immune system, binding to them. The tumor antigens are often proteins or other macromolecules (e.g. carbohydrates). Normal antibodies bind to external pathogens, but the modified immunotherapy antibodies bind to the tumor antigens marking and identifying the cancer cells for the immune system to inhibit or kill. In 2018 James Allison and Tasuku Honjo received the Nobel Prize in Physiology or Medicine for their discovery of cancer therapy by inhibition of negative immune regulation. Immunotherapies can be categorized as active, passive or hybrid (active and passive). Active immunotherapy directs the immune system to attack tumor cells by targeting tumor antigens. Passive immunotherapies enhance existing anti-tumor responses and include the use of monoclonal antibodies, lymphocytes and cytokines. A wide range of cancers can be treated by various immunotherapy medicines that have been approved in many jurisdictions around the world. Passive antibody therapies commonly involve the targeting of Cell surface receptors and include CD20, CD274 and CD279 antibodies. Once bound to a cancer antigen, the modified antibodies can induce antibody-dependent cell-mediated cytotoxicity, activate the complement system, or prevent a receptor from interacting with its ligand, all of which can lead to cell death. Apart from classical immunomodulatory receptors, cell surface proteoglycans are an emerging class of targets for cancer immunotherapy. Approved immunotherapy antibodies include alemtuzumab, ipilimumab, nivolumab, ofatumumab, pembrolizumab and rituximab. Active cellular therapies usually involve the removal of immune cells from the blood or from a tumor. Those specific for the tumor are grown in culture and returned to the patient where they attack the tumor; alternatively, immune cells can be genetically engineered to express a tumor-specific receptor, cultured and returned to the patient. Cell types that can be used in this way are natural killer (NK) cells, lymphokine-activated killer cells, cytotoxic T cells and dendritic cells. Dendritic cell therapy provokes anti-tumor responses by causing dendritic cells to present tumor antigens to lymphocytes, which activates them, priming them to kill other cells that present the antigen. Dendritic cells are antigen presenting cells (APCs) in the mammalian immune system. In cancer treatment they aid cancer antigen targeting. The only approved cellular cancer therapy based on dendritic cells is sipuleucel-T. One method of inducing dendritic cells to present tumor antigens is by vaccination with autologous tumor lysates or short peptides (small parts of protein that correspond to the protein antigens on cancer cells). These peptides are often given in combination with adjuvants (highly immunogenic substances) to increase the immune and anti-tumor responses. Other adjuvants include proteins or other chemicals that attract and/or activate dendritic cells, such as granulocyte macrophage colony-stimulating factor (GM-CSF). The most common source of antigens used for dendritic cell vaccine in Glioblastoma (GBM) as an aggressive brain tumor were whole tumor lysate, CMV antigen RNA and tumor associated peptides like EGFRvIII.