Cancer immunotherapy

From ArticleWorld

Cancer immunotherapy is a medical practice that uses an individual’s own immune system to fight off cancer cells. This kind of therapy is based on the premise that many cancer cells carry on their surface antigens which are not those that the body sees as “normal”.

Physiology

The ability of an individual to reject and kill a tumor cell depends on the individual’s immune efficiency and on whether or not the tumor cell shows enough difference from the host cells to be recognized as foreign. Because tumor cells are mutations from normal cells they can present a foreign antigen on their surface. Certain antigens, such as the GD2 antigen, is one that is only expressed in fetal cells and is, therefore, a good target for antibody responses.

Other tumor cells reveal particular antigens that normally activate cellular pathways that result in unregulated growth. Because these are not found on normal cells, antibodies can be created. The tumor marker ErbB2, found in breast cancer cells, is one that can generate an immune response as they are seen as foreign.

Therapeutic use

Many recent anti-tumor therapies are actually monoclonal antibodies against specific markers on tumor cells. For example, the drug, Rituximab, is an antibody formulation that targets the CD20 antigen on cells that cause non-Hodgkin’s lymphoma. Similar antibody therapies exist for breast cancer, acute myelogenous leukemia, chronic lymphocytic leukemia and colorectal cancer.

These antibody therapies require that the rest of the immune system, i.e., those cells that destroy cells that have antibodies presented by them, work efficiently to aid the anti-tumor therapy in cell destruction. Unfortunately, the environment in which a tumor cell lives is often somewhat immunosuppressed, so that antibody therapy alone is not completely effective.

The immunochemical, cytokine, is often necessary for the rest of the immune response to occur. Unfortunately the addition of cytokine to antibody therapy often leads to severe side effects and tissue inflammation. Newer therapies are directed at molecules that could be given to partially mimic cytokine’s immune properties.

Another strategy that is being explored is the combination of tumor-cell directed antibodies that carry cytokine with them. The difficulty with this is that the most effective drug would deliver the combined molecule and allow for their separation upon entry into the cell.

Finally, newer therapies against skin lesions such as basal cell cancer and malignant melanoma involve the local use of an interferon producer that allows the body’s killer T cells to destroy the tumor cells. Benign lesions such as warts and actinic keratoses can be destroyed by this method.