A Brock research team has uncovered the mechanisms of how a chemical contained within a common household herb can stop the growth of prostate cancer cells.

According to the Canadian Cancer Society, about one in eight Canadian men will develop prostate cancer during their lifetime, with prostate cancer being the third leading cause of death from cancer in men in Canada.

“While treatments exist for prostate cancer, novel therapeutic agents are needed to target aggressive and treatment-resistant forms of prostate cancer,” says Professor of Health Sciences Evangelia Tsiani. “Plant-derived chemicals, through research, could be developed into successful and highly effective chemotherapy drugs.”

Following previous studies by Tsiani’s research group that found rosemary extract kills prostate cancer cells, the researchers set out to uncover the specific chemical found in rosemary extract that was responsible.

The team ended up studying carnosic acid based on other evidence from the literature and Tsiani’s past lung cancer research.

“Although, in limited studies, carnosic acid has been shown to have anticancer properties, its effects in prostate cancer and its mechanisms of action have not been well examined,” she says.

At the core of Tsiani’s research is understanding cancer cell biology and cell signalling — a complex communications system that regulates basic activities and co-ordinates actions within a cell.

Cancer cells are created due to mutations resulting in major alterations in cell signaling leading to defective cells that grow and multiply uncontrollably.

Tsiani and her team were interested in seeing what would happen when carnosic acid was introduced into prostate cancer cells.

Carnosic acid belongs to the polyphenolic class of chemicals. Polyphenols, chemical compounds that are mostly found in plants people eat, are believed to help prevent diabetes, cancer, heart disease and other degenerative conditions.

Using various human prostate cancer cells representing the different tumors seen in prostate cancer patients, the researchers found carnosic acid inhibited the cells’ growth. The team found the inhibitory effect of carnosic acid was similar to that seen with the chemotherapy drug docetaxel.

While toxic to cancer cells, carnosic acid has little toxicity to normal cells, potentially targeting cancer cells while sparing normal cells, Tsiani says.

But Tsiani cautions against eating rosemary leaves as a cure for prostate cancer.

“We can’t just give patients carnosic acid at this point,” she says. “More research is needed to gather evidence that this will be an effective treatment.”

She says that, if successfully developed into a drug, carnosic acid may have less side effects than conventional treatments or may boost chemotherapy and radiation therapies.

The team reported their results, including identifying the specific signaling cascades involved, in their study “Inhibition of Prostate Cancer Cell Survival and Proliferation by Carnosic Acid Is Associated with Inhibition of Akt and Activation of AMPK Signaling,” published in Nutrients in March.

This research was funded by the Canadian Prostate Cancer Fight Foundation/Ride For Dad (PCFF/RFD) grant.

In addition to Tsiani, the team included master’s student Matteo Nadile, Professor of Health Sciences and Canada Research Chair in Mechanisms of Health and Disease Newman Sze, and Associate Professor of Kinesiology and Canada Research Chair in Tissue Re-modelling and Plasticity throughout the Lifespan Val Fajardo.