A new study co-led by researchers at the USC School of Pharmacy, among others, has found that suppressing the enzyme monoamine oxidase A (MAO-A) reduced or even eliminated prostate tumor growth and metastasis in mice.

The finding opens the door for physicians to possibly use the antidepressant drugs that had targeted MAO-A as a cancer-suppressant as well.

Jean C.  Shih, PhD, University Professor at the USC School of Pharmacy, said, “This is the first paper showing that MAO-A plays an important role in prostate cancer progression and metastasis. MAO-A inhibitors may provide an unmet need in cancer treatment.”

Shih, who is co-corresponding author of a paper on the research that was published on May 27 in the Journal of Clinical Investigation, has studied MAO-A for 30 years. She collaborated with fellow co-corresponding author Leland Chung, PhD, a prostate cancer expert from Cedars-Sinai Medical Center.Their team included researchers from the Keck School of Medicine of USC and the Fourth Military Medical University in China. The first author, Boyang Wu, PhD, was Shih’s doctoral student at USC.

Chung, director of the Uro-Oncology Research Program at the Cedars-Sinai Samuel Oschin Comprehensive Cancer Institute, said that when this enzyme is not suppressed, it produces a tumor-rich environment that fuels the growth and metastasis of prostate cancer cells.

“Suppressing this enzyme and combining it with current therapies may provide a better way to manage and cure men with metastatic prostate cancer,” he said.

MAO-A  regulates the amount of neurotransmitters in the central nervous system by deactivating some — breaking them down. Like all enzymes in the brain, MAO-A is needed in optimum quantities to keep a person healthy. Too much MAO-A has been linked with depression, while too little with autistic behaviors, aggression and anxiety.

Recently, scientists noticed that MAO-A levels were especially high in individuals suffering from prostate cancer, but were unable to determine why. Shih, Chung, and their team found that MAO-A produces an oxygen-rich, free-radical environment for cancer cells to thrive in — promoting stronger growth and invasiveness. They were able to control this effect in mice, strongly suggesting that the drugs already in existence to inhibit MAO-A for mental depression can do double-duty to suppress prostate cancer.

— Kukla Vera