Radioactivity seems to be a concept that is shrouded in mystery and perceived with a mix of fear and wonder. We hear folktales of radioactivity causing monstrous abnormalities in humans, wilting and decaying lush green fields with a single touch, or, maybe when exposed via venomous insects, creating our friendly neighborhood Spider-Man. After taking a few surveys, I heard repeatedly that though someone might not know exactly what chemical radiation is, he would avoid radioactivity because it might give him cancer. Spider-Man may not be real, but cancer caused by radiation, unfortunately, is. People correctly cited the explosion at Chernobyl or the atomic bombing of Hiroshima (as well as incorrectly cited FM radio waves!) as potential culprits. Ionizing energy emitted from decaying atoms – radioactivity – is indeed a hazard to human health. But recently, we’ve found a new way to use it to treat cancer.

Cancer, a devastating disease that has touched every one of our lives in some way, is marked by the abnormal, uncontrolled division of cells that destroys surrounding tissue. Just as radioactivity can destroy healthy cells by damaging DNA, cancer cells are similarly affected. The concern here is: how do we kill just the cancer cells with radioactivity while leaving the healthy cells intact? As you may know, radiation therapy is already in use. However, despite the current precision technology that uses an external source of X-rays to target specific areas of the body, healthy cells near the target site are not spared. In addition, tumors in certain hard-to-reach areas of the body cannot be accessed with typical radiotherapy, and it is particularly unhelpful when cancer has spread throughout the body. Thus, it is often combined with chemotherapy drugs. From these treatments, people often experience unpleasant side effects that result from the inability to address the aforementioned concern. Our inability to kill solely the cancer cells means that we may end up fatigued, nauseated, experiencing hair loss, and even unable to fight off other diseases when we undergo rigorous cancer treatment due to the loss of healthy cells. Radioligand therapy, or RLT, is an up-and-coming solution. It can be used on its own and provides access to cancer types that are hard to treat with standard radiation therapy technology.

In RLT, radioactive molecules, such as Radium-223, are attached to molecules that are specific to a certain kind of receptor on the surface of our cells. Receptors can be thought of as a ‘lock’ that a specific ‘key’ has to fit into to gain access to the cell. In certain cancers, a specific kind of receptor is present in abnormally large numbers. By attaching a radioactive atom to a molecule that only binds that particular receptor, we can localize damaging radiation to that one particular type of cell! This level of specificity is exceptional for cancer treatment and has the potential to greatly reduce the painful burden of cancer treatment side effects. Moreover, the nature of the damage by radioactivity means that resistance is hard to develop compared to other cancer treatments – radiation damage doesn’t depend on activity downstream of receptor binding. Other cancer treatments such as chemotherapy drugs which depend on a sequence of cellular events after binding may be eventually rendered ineffective by cancer cells adapting to the drug.

The only current FDA-approved RLT treatment is for prostate cancer and uses an antibody as the ligand for the radioligand therapy. Antibodies are the perfect tool for this treatment as they are specifically manufactured by the body’s immune system to bind to only one specific molecule. This strictly limits the damage to cells that can be recognized in large numbers by the antibody, due to having a cancer specific pattern of receptors. This type of targeted therapy has the potential to revolutionize cancer treatment, and we have much to look forward to in the field of targeted cancer therapeutics.

Peer editor: Caitlyn Molloy

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