Cancer immunotherapy is the use of the immune system to treatcancer. Immunotherapies can be categorized as active, passive or hybrid (active and passive). These approaches exploit the fact thatcancer cells often have molecules on their surface that can be detected by the immune system, known as tumour-associated antigens (TAAs); they are often proteins or other macromolecules (e.g. carbohydrates).
Active immunotherapy directs the immune system to attack tumorcells by targeting TAAs. Passive immunotherapies enhance existing anti-tumor responses and include the use of monoclonal antibodies, lymphocytes and cytokines.
Among these, multiple antibody therapies are approved in various jurisdictions to treat a wide range of cancers. Antibodies are proteins produced by the immune system that bind to a target antigen on the cell surface. The immune system normally uses them to fight pathogens. Each antibody is specific to one or a few proteins. Those that bind to tumor antigens treat cancer. Cell surface receptors are common targets for antibody therapies and include CD20, CD274 and CD279. Once bound to a cancer antigen, 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. Approved antibodies include Alemtuzumab, Ipilimumab,Nivolumab, Ofatumumab 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 cultured and returned to the patient where they attack the tumor. Cell types that can be used in this way are natural killer cells, lymphokine-activated killer cells, cytotoxic T cells and dendritic cells. The only US-approved cell-based therapy is Dendreon’s Provenge, for the treatment of prostate cancer.
Interleukin-2 and interferon-α are cytokines, proteins that regulate and coordinate the behaviour of the immune system. They have the ability to enhance anti-tumor activity and thus can be used as passive cancer treatments. Interferon-α is used in the treatment of hairy-cell leukaemia, AIDS-related Kaposi’s sarcoma, follicular lymphoma,chronic myeloid leukaemia and malignant melanoma. Interleukin-2 is used in the treatment of malignant melanomaand renal cell carcinoma.