How Many Kinds of Immunotherapy Are There?

This treatment typically involves T cells removed from the patient’s tumor. Those that are most active against the cancer are grown in large quantities for several weeks, then injected back into the patient. A specific kind of adoptive cell transfer is called chimeric antigen receptor (CAR) T-cell therapy. Currently used only in clinical trials for patients whose cancer hasn’t responded to, or has returned after, other treatments, this type of immunotherapy uses T cells that are removed from the patient’s blood and genetically altered in the laboratory to add CARs to their surface. When reintroduced into the patient’s body, they can launch a focused attack against the cancer cells.

BCG is currently used only to treat bladder cancer, though its use against other types of cancer is being studied. The bacillus is a weakened form of the bacteria that causes tuberculosis. When inserted directly into the bladder, it stimulates an immune system response to fight the cancer cells.

Cytokines, which are proteins that affect the interactions and communications between cells, play an important role in the body’s immune response to cancer. The two kinds of cytokines used most often to treat cancer are interleukins and interferons. Scientists have discovered immune system cells inside certain tumors. Called tumor-infiltrating lymphocytes, or TILs, they can be removed from patients, multiplied through treatment with interleukins, and reinjected as invigorated cancer fighters. Interferon can stop cancer cells from growing or multiplying and stimulates the immune system to target cancer cells.

These are drugs that don’t target cancer cells directly, but weaken their ability to withstand immune system attack. The immune system has certain so-called checkpoint proteins that prevent it from attacking healthy cells. Cancer cells sometimes co-opt these proteins to avoid detection. Checkpoint inhibitors in effect strip away the protection the checkpoints were providing, leaving the cancer cells vulnerable to the immune system.

Monoclonal antibodies are immune system proteins produced in the laboratory. They are designed to attach to certain parts of cancer cells, in some cases making them more “visible” to the immune system and thus more easily attacked. One new approach is to combine parts of two antibodies into what is called a bispecific antibody, so that one part attaches to an immune cell and the other to a cancer cell. This brings the two together and excites an immune response.

Oncolytic viruses are those that have been manipulated in the laboratory so that they infect — and kill — cancer cells. They can also stimulate the immune system to attack cancer cells.

Developing a vaccine to prevent cancer has been a dream of researchers for decades, but their quest has thus far proven unsuccessful — due to both the complexity of the immune system and the variety of ways cancer cells have developed to elude it. There are, however, several kinds of vaccines that are being studied as means of treatment. The most successful ones thus far are dendritic cell vaccines. To produce these is a difficult and expensive process. Immune cells are removed from the patient’s blood, then exposed to cancer cells or cancer antigens along with various chemicals to turn them into dendritic cells. These are then returned to the patient’s body. Dendritic cells help the immune system recognize cancer cells and make them more vulnerable to the body’s T cells.