Japan research uncovers how coffee constituent limits growth of colorectal cancer cells

KYOTO — A team of researchers in Japan has uncovered the mechanism by which caffeic acid, a polyphenol found in coffee, suppresses the growth of colorectal cancer cells, offering hope for the development of cancer treatment and prevention strategies.

Recent epidemiological research has reported a link between coffee consumption and reduced risk of developing colorectal cancer, but it wasn’t clear which specific components of coffee were responsible, or how they worked in the body. The researchers, including Motoki Watanabe of the Graduate School of Medical Science at Kyoto Prefectural University of Medicine and Shogen Boku of the Department of Clinical Oncology at Kansai Medical University Hospital, focused on the fact that polyphenols such as chlorogenic acid, which is abundant in coffee, are broken down through hydrolysis in the intestines and exist as caffeic acid. They then analyzed what caffeic acid does to colorectal cancer cells at the molecular level.

First, they confirmed that when caffeic acid was added to colorectal cancer cells, it significantly suppressed the formation of “colonies” of cancer cells. They additionally found that caffeic acid binds to a protein called “RPS5,” which is known to be associated with a poor outlook for recovery in colorectal cancer patients.

Furthermore, they found that suppressing the expression of RPS5 — the process where gene information is turned into a function — caused the cell cycle of cancer cells to halt at the preparatory stage before copying their DNA.

Both adding caffeic acid and suppressing RPS5 expression limited the expression of a protein called cyclin D1, which is important for pushing cells through the growth cycle. The team’s analysis suggests that RPS5 regulates the amount of cyclin D1 by controlling the quantity of messenger RNA produced from genes. This kind of control is known as “post-transcriptional regulation.”

Taken together, these findings suggest a molecular mechanism in which caffeic acid directly binds to RPS5, blocking its function and reducing cyclin D1 levels to inhibit the growth of colorectal cancer cells.

Watanabe said he hopes the findings will “lead to derivatives based on the structure of caffeic acid and the development of new cancer prevention and treatment strategies targeting RPS5.”

At the same time, he cautioned, “This is mainly basic research using cell experiments and does not directly show a relationship between coffee intake and colorectal cancer prevention. Coffee also contains caffeine and other components and may not suit everyone’s constitution. Drinking coffee in excessively large amounts is not recommended.”

The Japanese researchers’ findings were published in the British scientific journal Scientific Reports on March 5.

(Japanese original by Hiroyuki Ota, Kyoto Bureau)