Cancers and Immune System

Tumor antigen

Antigen is a foreign material is know and is a target that will be destroyed by the immune system. Antigen found on the surface of all cells, but in normal circumstanes, a person's immune system does not react to the itself.

If a cell becomes malignant, the new antigen ( which is not recognized by the immune system ) appears in the cell surface. The immune system may recognize new antigens, called tumor antigens, as foreign and can transport or destroy cancer cells. Butwell-functioning immune system was not always able to destroy all cancer cells.

Tumor antigens have been found in several types of cancer, malignant melanoma, bone cancer ( osteosarcoma ) and some gastrointestinal cancers. Cancer patients have antibodies against tumor antigens. Antigens immune responses are usually not sufficient to control cancer. It seems that the antibodies are not able to destroy cancer and sometimes even stimulate growth.

Antigens is released into the blood vessel by some cancers can be found in blood tests. Antigens is sometimes called tumor markers.

More widely used tumor marker in the diagnosis and treatment of cancer. For example, blood test can help explain whether or not an effective cancer treatment. If tumor markers are no longer found in blood samples, the possibility of treatment has been successful. If the tumor markers disappear and then reappear , the possibility of recurrence of cancer has returned.

Antigens Carcinoembryonik ( CEA ), is a tumor antigens that is found in the blood of patients with colon cancer, breast, pancreas, bladder, ovary or cervix. High levels of antigen can also be found in heavy cigarette smokers and patient eith liver cirrhosis or ulcerative colitis. High CEA levels do not always indicate cancer. Measurement of CEA levels in someone who has been undergoing treatment for cancer, would help to know the recurrence of cancer.

Alpha-fetoprotein ( AFP ) is normally produced by liver cells, are found in the blood of patients with liver cancer (hepatoma). AFP is often found in people with certain ovarian cancer or cancer of the testicles and in children and young adults who suffer from pituitary gland tumor.

Human Chorionic Gonadotropin (HCG) is a hormone produced during pregnancy, which is the basis for prenatal care. This hormone ia also found in women who have cancer that originates from testiculer cancer. HCG is a highly sensitive tumor markers. Its use in monitoring the effects of treatment has helped improve the cure rates of cancer until more than 95%.

Levels of prostate specific antigens (PSA) higher in men with benign prostate enlargement and very high in men with prostate cancer. What causes high level of this antigens, remains, unclear, but men with elevated PSA levels should undergo further examination for prostate cancer. Monitoring of PSA levels after a cancer treatment can be explained whether the cancer has returned or not.

CA-125 levels in the blood increased in women with ovarian disease, including cancer. Because ovarian cancer is often difficult to diagnose, some cancer experts recommend to perform screening test on the CA-125 in women over 40 years. But screening test are less reliable because it is less sensitive and less specific.

In breast cancer, increased levels of CA 15-3:on pancreatic cancer increased levels of CA 19-5;in multiple myeloma, microglobulin levels increased and at the scrotal cancer, increased levels of lactate dehydrogenase. But none of that can be used for cancer screening. This check is used to monitor response to treatment in cancerpatients.

Immunotherapy

To improve the immune system's ability to find and destroy cancer, researchers have create a biological response modifier.

Materials used for the following functions :

1. Stimulate anti-tumor response of the body by increasing the number of killer cells to tumors or produce 1 or more chemical messenger.
2. Directly function as a tumor killer agent or chemical messenger.
3. Reducing the body's normal mechanism in suppressing the immune response
4. Change the tumor cells to increase their chances of triggering an immune response or to make tumor cells more likely destroyed by the immune system.
5. Fix the body tolerance to radiation therapy or the chemical used in chemotherapy.

Biologic response modifier of the best know and most widely used is interferon. Under normal circumstances, almost all human cells to produce interferon, but interferon can also be made with recombinant moleculer biology technicques.

Although the mechanism of action is not entirely clear, interferon play a role in the treatment of some cancers. Outstanding response (including healing) had occurred at about 30%  of patients with Kaposi's sarcoma, 20% of young people with chronic leukemia mielogenous and 15% of patients with renal cell carcinoma.

Interferon extend the expected disease-free period in patients who experience healing from multiple myoloma and some forms of lymphoma.

In cell therapy killer , lymphocytes from cancer patients are remove from blood samples. In the laboratory , carried out the exposure of lymphocytes with interleukin-2, to create cell-lymphokine activated killer cells, which will be injected into the patient through his veins. These cells are better trained than the natural cels of the body in finding and destroying cancer cells.

Approximately 25-30% patients with malignant melanoma or kidney cancer respond well to lymphokine activated killer cell therapy, but treatment is still under research.

Materials such as tuberculosis bacteria are attenuated, that are know to increase the immune response, were tested on several cancers. Tuberculosis bacteria inject directly into a melanoma is almost always cause the shrinking of cancer. Sometimes the effect is spread to tumors that have the body (metastasis).

Bacterium tuberculosis has also been successfully used to control bladder cancer has not spread to the bladder wall.

Other experimental approaches  linking the tumor specific antibodies with anticancer drugs. Antibodies are made in the laboratory and injected to the patient, will bring the drug into cancer cells.

Another option is an antibody made in a laboratory that can be attached to both cancer cells and killer lymphocytes as well as to unify the two cells so that killer lymphocytes to destroy cancer cells.

New research give hope for new treatment. Some of them use part of the oncogene, which is important in the regulation and cell growth.

Posted in: cancer