You might recognize glucosamine as a popular nutritional supplement, most often touted as a treatment for osteoarthritis. But you may be surprised to find out what researchers have known for decades: It can kill some cancer cells, but leave normal cells unharmed.

Glucosamine is surprisingly simple. It’s the same chemical as the sugar glucose — half of the molecule that makes up the sugar you eat in cookies and candy — but with a single chemical piece swapped out.

Three-dimensional rendering of a glucosamine molecule

Researchers have long known that glucosamine can be toxic to some laboratory-grown cancer cells while leaving normal cells alone, but they didn’t understand how it worked. Until now.

City of Hope molecular biologists Keiichi Itakura, Ph.D., and Viktor Chesnokov, Ph.D., recently found that glucosamine blocks a protein that protects cancer cells.

That guardian protein is called signal transducer and activator of transcription 3, or STAT3.

STAT3 is highly overproduced in many cancer cells. Previous research has shown that activated STAT3 promotes cancer development and shields tumor cells from the immune system. It also helps tumor cells grow.

The City of Hope scientists started their latest study with prostate cancer cells that continuously produce STAT3. They gave them glucosamine in the lab, and then watched what happened.

As they hoped, the cells stopped growing and died. The team found that the glucosamine greatly dropped cells’ production of activated STAT3, as well other proteins that help tumor cells grow. One of these is called survivin.

“Survivin is controlled by STAT3, so it makes sense that we see less of it when STAT3 is suppressed,” explained Chesnokov.

More research is needed, but the scientists suggested that glucosamine might be a potential part of treatment for tumors that continuously produce STAT3.

You can access an interactive, 3D model of glucosamine at 3Dchem.com.