Immunotherapies are a type of treatment designed to boost the body’s natural defences. They use substances either made by the body or in a laboratory to improve or restore immune system function. Some immunotherapies elicit or enhance the immune response whilst others suppress the immune response. There are three main types, namely antimicrobial immunotherapies such as immunisation; allergen immunotherapies which expose people to larger and larger amounts of allergens to restore tolerance to the allergen; and cancer immunotherapies which attempt to stimulate the immune system to reject and destroy tumours.
Antibodies are produced by the immune cells called B cells. Antibodies recognise, bind with and destroy specific antigens i.e. molecules or cells that are “foreign” and might be harmful. For every antigen there is a specific antibody. Of the three types of cancer immunotherapies, antibody therapies are the most successful, treating a wide range of cancers with monoclonal antibodies. Monoclonal antibodies are produced in the laboratory using hybridoma cells made by fusing B cells with cancerous bone marrow (myeloma) cells. Hybridoma cells can multiply indefinitely and create cultures that produce large amounts of an antibody that responds to a specific antigen. Monoclonal antibodies can be developed that target and bind with specific proteins found on cancer cells. Toxic drugs can be attached to the monoclonal antibodies to produce a targeted form of chemotherapy.
Modern-day cancer immunotherapeutic approaches do not directly target cancer cells, but harness the power of the immune system to combat cancer. This way might have long-lasting benefits, if the immune system can ‘remember’ the cancer and stop it.
In June 2015, the Royal Marsden Hospital published results of a clinical trial in which 945 patients considered to be terminally ill with advanced melanoma were treated with a combination therapy using two monoclonal antibody drugs, ipilimumab and nivolumab. In 58% of patients the tumours shrank and it ishoped they might disappear. It appears that cancer cells can “hide” from immune cells called T- cells through a “secret handshake”. Some cancer cells have molecules on their surface which bind with the T cell preventing it from recognising the cancer cells as a threat and allowing the cancer to grow. Nivolumab attaches itself to the T cells blocking its ability to hide and the cancer is then attacked and destroyed. Ipilimumab allows the T cells to multiply.
Research has proven this immunotherapeutic approach can be effective against a wide range of hard-to-treat advanced cancers previously considered intractable. The clinical development of immunotherapies is undoubtedly one of the hottest areas in cancer research today