Cancer immunotherapy

It seems that these days nearly everyone has a friend or family member who has battled cancer. Unfortunately, however, not all of these battles end the way we would hope, and often times the cancer wins. Cancer is a tricky beast and even with all the money and time funneled into cancer research the disease usually seems to evade our best efforts.

This happens because our immune system is designed to attack cells that are foreign to our bodies; cancer cells are not. Cancer cells develop when our own cells mutate and begin to replicate out of control. The reason our body does not recognize the disease is because it is built to seek out foreign cells for destruction and a very important system of checks and balances is in place to make sure that it does not attack our own cells. Sometimes the cancer cells themselves may secrete substances that prevent the immune system from identifying the tumors. Other times, the immune system does recognize these cells as harmful but may not be strong enough to fight off the cancer.

Immunotherapy is a new, and very promising, approach to fighting cancer by stimulating the individual’s immune system in a novel way. This can be done by boosting the entire immune system to respond more readily or by helping the immune system identify and specifically attack cancer cells.

One type of immunotherapy utilizes monoclonal antibodies. Monoclonal antibodies (mAbs) are commonly used in treating autoimmune diseases and are becoming a popular therapeutic option across all medical specialties. Monoclonal antibodies are humanized antibodies that are developed in a lab setting. By tailoring these antibodies to bind particular protein sequences, scientists are able to target cells with incredible specificity allowing the immune system to mount an attack against these cells. In cancer immunotherapy three types of monoclonal antibodies are used; naked, conjugated, and bispecific.

Conjugated monoclonal antibodies are monoclonal antibodies with some sort of pharmaceutical attached; this can be chemotherapy or radiation. These antibodies target cancer cells, attach to them, and deliver the treatment directly to the cell itself. Both chemotherapy and radiation therapy can be very damaging to the body; being able to target cancer cells specifically for treatment greatly reduces the damage inflicted on surrounding cells.

Naked monoclonal antibodies are the most commonly used mAbs in cancer treatment. These monoclonal antibodies function on their own by targeting cancer cells, attaching to them, and marking them for destruction by the immune system. These antibodies can also function by attaching to a specific point on the cancer cell and reducing the ability of these cells to grow and multiply.

Naked monoclonal antibodies are also able to target immune system checkpoints, those substances secreted by cancer cells that can prevent the body from identifying tumors, thus boosting the immune system. PD-1 is a checkpoint protein that inactivates T cells. When the PD-1 protein on a T cell binds to the PD-L1 protein on another cell a signal is sent to the T cell telling it not to attack. While this can be useful in preventing our T cells from attacking our own cells, cancer cells originate from our own cells and many of them carry PD-L1 molecules. Monoclonal antibodies that bind to either the PD-1 protein or the PD-L1 protein prevent the two from binding to one another, allowing the T cells to recognize and attack the cancer cells.

Another form of cancer immunotherapy is through vaccination. Vaccines can be administered to prevent viruses known to cause cancer or to treat the cancer itself. Preventative vaccinations have proven to be beneficial in reducing the likelihood of cervical, anal, and throat cancer caused by the human papilloma virus (HPV) and liver cancer cancer caused by hepatitis B. In these viruses chronic infection damages the cells which can lead to the formation of cancerous tumors over time. By preventing these infections one can prevent potential damage to the cells. Vaccines that target and treat cancer itself are much less common, in fact, there is only one that is approved for use in the United States (Provenge, which fights against prostate cancer). The development of these vaccines is ongoing and will hopefully provide another means of initiating the immune system to specifically target cancer cells.

Immunotherapy has become a powerful new tool in treating cancer. By manipulating the body’s own defense system and finding ways to specifically target cancer cells many patients have seen better disease outcomes and fewer side-effects; some effectively “cured” of their disease. This exciting new field in cancer research may be the key to finally winning the battle against cancer.

Margo Henkhaus