The compound, called caffeic acid phenethyl ester or CAPE, is made from propolis, the resin honeybees use to patch holes in their hives. The product has been known and used for centuries as a natural remedy for teeth and skin, as well as a defense against viruses and bacteria.
When the researchers fed CAPE to mice that had early stages of the human form of prostate cancer, it seemed to stop the cancer in its tracks.
"Their tumors simply stopped growing," said Richard Jones, the study's author and a cancer researcher at the University of Chicago. "When we stopped feeding the mice CAPE, their tumors returned."
After six weeks, the tumors in mice eating CAPE were 50 percent smaller than the tumors in mice not getting the compound, whose tumors kept growing unchecked. The CAPE mice also didn't lose any weight during the treatment, which researchers said indicated that the compound was not overly toxic.
The researchers said the compound didn't kill the cancer, but it appeared to stop the growth of the cancer cells by masking their ability to use a system of signals to detect nutrition. If cells don't sense the presence of the food they need, such as glucose, they will stop growing.
The study was only in mice, and the compound has not yet been tested in human cancer patients. But Jones said the cell pathways targeted by CAPE are found in all mammal cells. He said he is hopeful that CAPE will prove useful against cancer in humans, most likely in combination with other available cancer therapies.
"One can imagine in the context of cancer prevention or early stage cancer, administering this molecule as a natural low-risk way to reduce proliferation of this and other types of cancer cells," Jones said.
A next step will be for clinicians to test the compound in human patients.