The Tragedy of Comorbidity: What You Need to Know About Cancer and DiabetesKatie Taylor
Would you rather have cancer or diabetes? It’s not a choice anyone should have to make. Cancer patients rejoice when new drugs are developed that can increase their life expectancy or beat their cancer altogether. But some treatments may come with a heavy pricetag.
A new type of cancer drug, called checkpoint inhibitors, comes with dire potential side effects. They may cause autoimmune disorders such as type 1 diabetes to develop in recovering cancer patients.
Checkpoint inhibitors work by essentially retraining the body’s immune system. The immune system is designed to attack foreign cells and leave healthy cells alone. Immune system cells distinguish between foreign and healthy cells using “checkpoints.” These checkpoints are molecules that are activated or deactivated by proteins. When certain proteins attach to the proteins on the checkpoint cells, the immune system knows that a cell is safe and doesn’t need to be destroyed.
PD-1 is a protein that lives on the immune system’s T-cells. When PD-1 attaches to PD-L1, the T-cell thinks it has come into contact with a healthy cell and leaves that cell alone. PD-L1 is a protein that is found on healthy cells, and it’s a signal to the immune system that all is well. However, the problem is that PD-L1 cells are found on some cancer cells, so the immune system doesn’t recognize the cancer as dangerous.
Checkpoint inhibitors prevent PD-1 and PD-L1 proteins from connecting which means that cancer cells no longer have a free pass and the body’s immune system attacks them. This is great news for cancer patients because checkpoint inhibitors allow the powerful immune system to do what it does best: fight foreign cells. Checkpoint inhibitor drugs are truly life-saving for people with deadly forms of cancer.
So What’s the Catch?
Since the immune system’s normal way of distinguishing between benign and dangerous cells has been inhibited, it can start to attack healthy cells, which is the signature starting point of many autoimmune disorders. Checkpoint inhibitors have been known to lead to thyroid disease, colitis, and type 1 diabetes in cancer patients.
“When you stop and think about it, you think, ‘Oh of course this would happen,'” Yale University immunologist Kevan Herold said. Herold is currently treating patients who have developed type 1 diabetes after using checkpoint inhibitors, and experts around the country are working on building a network of people who have developed other autoimmune disorders after taking the drug. Doctors want to better understand the connection between the drug and the disorders, identify genetic predisposition, and determine who is most susceptible to developing an autoimmune disorder after using checkpoint inhibitors. Not everyone who takes checkpoint inhibitors will develop an autoimmune disease.
Type 1 diabetes is caused when the body’s immune system attacks insulin-producing beta cells in the pancreas, destroying the body’s ability to create its own insulin. Type 1 diabetics must regularly inject insulin in order to regulate blood sugar levels. The condition requires constant management, may cause a host of serious complications, and currently has no cure. Type 1 diabetes typically develops in children or young adults, but checkpoint inhibitors may cause adult onset. A type 1 diabetes diagnosis would be a grave side effect for cancer patients.
Doctors are looking to better understand the risk factors so they can predict who might have a negative response to checkpoint inhibitors. They also want to better understand the relationship between PD-1 and PD-L1. Understanding this relationship may help them better understand autoimmune disorders in general and, more importantly, how to overcome them.
For now, oncologists are attempting to navigate the narrow channel between treating cancer and potentially causing disorders. For those with cancers needing checkpoint inhibitor drugs, the benefit is likely worth the risk. But doctors and patients alike can hope for a day when treatment is nimble enough to treat disease without the risk of causing a new one.