Some forms of active immunotherapy are not considered cancer vaccines. Vaccines try to get the body's immune system to react to specific antigens, while these other therapies try to boost specific parts of the immune system.
Lymphokine-activated killer cell therapy
Scientists can make large numbers of active, cancer-fighting T cells in the lab by treating a small number of killer T cells in a test tube with a cytokine (an immune system growth factor) called interleukin-2 (IL-2). After being returned to a patient's bloodstream, these special cells, now called lymphokine-activated killer cells (or LAK cells), are more effective against cancer cells. Researchers are now testing several ways to use these very active cancer-fighting cells.
LAK cell therapy has shown promising results in animal studies, where it shrunk tumors in animals with lung, liver, and other cancers. Although clinical trials in humans have not yet been as successful, researchers are constantly improving LAK cell techniques. They are testing these newly improved methods against melanoma, brain tumors, and other cancers.
Tumor-infiltrating lymphocyte vaccine with interleukin-2
Researchers have found immune system cells deep inside some tumors and have named these cells tumor-infiltrating lymphocytes (TILs). These cells can be removed from tumor samples taken from patients and made to reproduce in the lab by treating them with IL-2. When injected back into the patient, these cells can be active cancer fighters. This is a type of autologous vaccine (the same person is the donor and the recipient).
Success with TILs in lab animals has led researchers to try to increase the anti-tumor activity of TILs. Treatments using TILs are being tested in clinical trials in people with melanoma, kidney cancer, and other cancers.
In one study, researchers from the National Cancer Institute used a newer technique with TILs in patients with advanced melanoma. After removing TILs from the body and increasing their numbers, the researchers treated the patients with chemotherapy to reduce the numbers of other white blood cells in the body. When the TILs were given back into the body, the tumors shrank in about half of the patients, and almost all of the patients lived longer than expected. The results were promising, but the researchers weren't able to get TILs from all of the patients. This limited the treatment's effectiveness, in that it couldn't be used for everyone.
More recently, the researchers took T cells from the blood of patients with advanced melanoma. In the lab, they inserted genes into them that made them more likely to recognize melanoma cells. When the T cells were injected back into the patients, 5 of 11 had their tumors shrink, 2 of which went away completely for at least a year.
Suppressing regulatory T cells
Regulatory T cells normally act as brakes to help keep the immune system in check. They help keep it from overreacting and attacking normal cells in the body. But they may also slow the immune system's ability to attack cancer cells. Researchers have studied whether suppressing these cells might allow the immune system to be more effective against cancer. This is, in part, how ipilimumab (Yervoy) works. Ipilimumab is a monoclonal antibody that targets CTLA-4, a protein on some T-cells that normally helps them suppress the immune response. This drug suppresses regulatory T cells and activates cytotoxic T cells. In studies of advanced melanoma, it caused tumors to shrink and helped patients live longer. Still, taking some of the brakes off the immune system can lead to some serious side effects, such as autoimmune diseases.
Feedback
