Cancer is one of the most dreaded disease on the planet. Millions of deaths occur worldwide due to cancer, and hence finding novel treatment strategy is one of the major aim of researchers working across the globe. Chemotherapy and radiation therapy are the most commonly used methods which are used to kill cancer cells in the patients. However, gradually tumors develop resistance to these treatments, which leads to relapse of disease. Therefore, new treatment options are required. Immunotherapy has emerged as an alternative strategy for targeting cancers.
The body's immune system comprises of specialized organs and cells which protect the body from all foreign invasions like microbial pathogens, etc. It can be thought of as the army which identifies and wards off any disease-causing attacks. The immune system consists of T cells and B cells. Two types of responses are observed depending on the type of antigen: T cells engulf the antigen, while B cells secrete substances known as antibodies for the neutralization of the antigens. Cancer cells also bear few antigens which can be recognized by immune system. However, cancer cells develop abilities by which they mask themselves to escape from this defense mechanism. Immunotherapy relies on the fact that immunity can again be enhanced for identifying and destroying cancer cells. This can be achieved by inducing the body to produce specific substances which target the tumors, or by administering immune supplements to the cancer patients.
The ways by which the immune system can be enabled to recognize and destroy the tumor cells are administration of either monoclonal antibodies or checkpoint inhibitors, also known as blockade therapy. Monoclonal antibodies attach themselves to cancer cells and ensure that the immune system detects and destroys the cancer cells. Cancer cells hijack the checkpoint mechanisms and utilize them in a way such that it prevent the immune system from destroying them. The checkpoint inhibitors release the "brakes" on the immune system and allow it to identify and attack the tumor cells. The body's immune response can be boosted further by administration of cytokines, therapeutic vaccines or adoptive T cell therapies. Cytokines are small molecules which stimulate T cell growth and bring about the activation of the immune system. Similarly, cancer vaccines can initiate and enhance the activity of the immune system. In T cell therapy, the patient's own T cells are collected and reengineered to identify and fight the cancerous cells.
In a recent report published in journal named "Science Translational Medicine", the researchers utilized the bacteria, Salmonella, which cause food poisoning, for enhancing cancer immunotherapy in mice. A harmless variant of this bacteria was tweaked to express a protein that is recognized by the mouse immune system. The scientists took advantage of the fact that this bacteria invades regions of the body that are deficient of oxygen, which is a hallmark of tumors. Upon infection, the bacteria elicited an immune response which caused the tumors to shrink and also prevented their spread to other organs. This is an exciting discovery, and further studies will have to be performed before it can be extended to human subjects.
Cancer immunotherapy has the advantage of having fewer and less severe side effects as compared to other treatment options. However, at present its success rate is not very high. Not all patients have benefited from this therapy, and among those who were helped by this approach, the extent of benefits vary. Immunotherapy is still in its infancy and cancer researchers admit that there is a long way to go. Nonetheless, immunotherapy is emerging as an important addition to conventional therapies.