Primer on Immunotherapy - The New Frontier
Radiation, Chemotherapy and Surgery are considered to be the three frontline weapons in a conventional war against cancer. A fourth weapon, largely considered experimental, is "immunotherapy." Immunotherapy seeks to use the body's immune system to fight against cancer. In the abstract, the theory sounds elegant, useful and realistic. But the devil is in the details. Putting the theories into practice will take much time, money, blood, sweat and tears.
The body is blessed with natural defense mechanisms the guard against foreign invaders, like bacteria, viruses and cancer cells. Research has found that the body can distinguish between healthy cells and cancer cells and eliminate the cancer cells. Full blown cancer develops when the body's immune system is overwhelmed. Immunotherapy is designed to rebuild or stimulate the immune system to fight back.
The body's internal army that fights against the foreign invaders is spearheaded by the white blood cell, or lymphocyte. The lymphocytes search for the invader, and once identified, unleash little sharpshooters called T cells or B cells. The T cells are generated in the body's thymus gland high in the chest. The thymus gland is like a munitions dump. The Killer T cells, once unleashed and after locking onto their enemy target, destroy the invader directly. Another weapon in the T Cell arsenal is the lymphokine-producing T cell. It releases a protein called a lymphokine, which includes interferons and interleukin -2. These proteins speed up and bolster the immune system's force field against foreign attack.
The strategy is to create an "immune response" against the cancer cell. Each cell in your body has an identical copy of your unique DNA code. The DNA molecule is like your own personal identity card, which screens all sister and brother cells to see if they belong. Cells that do not contain your unique DNA code are redlined as invaders. The surfaces of these invader cells are studded with molecules called "antigens". The scientists in the lab coats try to develop vaccines or antibodies that are programmed to recognize and defend against certain antigens.
Biological therapies include interferons, interleukins, tumor necrosis factors, monoclonal antibodies and cancer vaccines. These may prove beneficial when used in combination with each other and/or with conventional treatments.
Interferons are types of cytokines (cancer cell killing proteins) that occur naturally in the body. There are three kinds, of which interferon alpha is currently the most widely used (for hairy cell leukemia ). Interferons can improve a patient's immune response against cancer cells by inhibiting the cancer cell's growth or promoting their development into normally behaving cells. The FDA has approved their use for hairy cell leukemia, kaposi's sarcoma (which often arises in AIDS patients), and chronic myelogenous leukemia.
Interleukins are also cytokines that occur naturally in the body. They can also be created in a test tube. Interleukin-2 (IL-2) has been the most widely studied interleukin. IL-2 stimulates the growth of many immune cells, such as lymphocytes (and Killer T cells). Lymphocytes that have been supercharged with IL-2 have been shown effective in destroying certain tumors. The game plan is to remove the lymphocytes from the cancer patient's blood, boost them with IL-2 in the test tube, and re-inject the cancer killing cocktail in the patient. The goal is to fortify the besieged patient's anticancer immune response. IL-2 therapy has worked best with metastatic kidney cancer.
Monoclonal Antibodies (MOABs) were originally lauded back in the late 1970s by cancer researchers as the "magic bullet." These antibodies are made in the laboratory and are cloned from the same living parent cell. MOAB are specific for a particular cancer cell membrane antigen. MOABs are made by injecting human cancer cells into mice so that their immune systems will manufacture antibodies against these cancer cells. The mouse cells that are producing the antibodies are then removed and fused with a hybrid cell (a hybridoma). Hybridomas are like factories that pump out large quantities of pure MOABs.
MOABS are being tested in clinical trials in patients with lymphomas, colorectal cancer, lung cancer, and leukemia.
Like other forms of treatment, immunotherapies can cause serious side effects. They are normally administered by injection, which may engender swelling and rashes at the site of the shot. Interferons and interleukins can cause flu- like symptoms. They may affect blood pressure. Side effects with IL-2 can be severe and patients need to be closely monitored. Most trials require the patient's doctor to obtain the immunotherapy agent and inject same in the doctor's office. You can learn more about a particular therapy and the logistics by calling the National Cancer Institute's toll free number at 1-800-422-6237.
Also contact:
National Cancer Institute, wwwicic.nci.nih.gov
For a listing of clinical trials: www.centerwatch.com (listing over 1,400 current trials, with information about the researchers and the medical facilities).
MedWeb: Oncology: neuro-www.mgh.harvard.edu/hospital-web.nclk
National Comprehensive Cancer Center Network www.cancer.med.umich.edu/NCCN/NCCN.html
