Biological Therapy Agents
Biological therapy involves the use of biologically derived agents to modify the relationship between tumor and host, altering the host's biologic response to tumor cells, with a resultant therapeutic effect. Most biological therapies are designed to activate the patient's immune system and induce it to attack cancer cells. Common biological agents that have been approved for use in treating specific types of cancer are described below. Some of these are still under investigation.
Interferons are proteins secreted by immune cells that interfere with a virus's ability to reproduce and proliferate. The human body produces interferons as part of the immune response. The name comes from the fact that they literally interfere with virus replication.
Through recombinant DNA technology, various interferons have been genetically engineered for use in the medical treatment of disease. These agents increase the cell-killing activity of the immune system, making tumor cells more vulnerable to immune attack by increasing antigens and blocking the formation of new blood vessels by tumors. They also slow tumor cell replication by inhibiting DNA and protein synthesis.
There are three known classes of interferons: alpha-, beta-, and gamma-interferons. Only alpha-interferon has been approved as a cancer treatment. For example, inteferon alfa-2b (Intron A) is used in conjunction with chemotherapy in patients with follicular lymphoma and has proven to be effective for treating malignant melanoma.
Monoclonal antibodies (MABs)
Monoclonal antibodies are lab-engineered products. They are components of the immune system which are able to recognize and bind to a specific antigen. These lab-made antibodies are designed to react directly against certain tumor-associated proteins. They may be used by themselves or equipped with other molecules, such as toxins, chemotherapy drugs, or radioactive isotopes.
Although MABs hold great potential for cancer treatment, complete success has been elusive.
The only monoclonal antibodies available for routine use are for lymphomas, some types of breast cancer, and occasionally for bladder cancer. The early results of treatment with these therapeutic monoclonal antibodies have been quite promising. Sometimes they have been given on their own, but more commonly in combination with conventional chemotherapy.
Interleukin (abbreviated IL) is a group of bioactive proteins produced by leukocytes, monocytes, and other cells that regulate the immune response. They act like messengers between the white blood cells of the immune system. Interleukin-2 increases the activity of lymphocytes, especially killer T-cells. Recombinant IL-2 is used for cancer therapy and continues to be studied as a biological therapy agent for other diseases.
Growth factors are colony stimulating factors or hematopoietic growth factors. These substances promote the growth and maturation of normal cells. There are two types used in cancer treatment: one type stimulates bone marrow to make normal cells; the other acts as an anticancer agent. Colony stimulating factors are being used increasingly in the treatment of bone marrow transplant patients. They are also used for patients who develop anemia or low white blood cell counts because of cancer or cancer therapy.
Vaccines against viral disease are effective in preventing human infections. They are administered to prevent infections for which effective treatments are not available, especially when active infection is associated with high mortality.
Tumor vaccines are a type of immunotherapy that attempt to stimulate the patient's own immune system to respond to tumor antigens. Melanoma vaccines have been administered to patients for several decades in hopes of boosting immunity to the patient's melanoma, usually as an adjuvant to surgery. Tumor vaccines are still experimental.
With further research and more secrets about the immune system revealed, the prospect of biological therapies looks promising and hopefully the role of biological therapies in the successful treatment of cancer will grow in future years.