Prostate cancer occurs in the prostate — a small walnut-shaped gland in men that produces the seminal fluid that nourishes and transports sperm. The causes of prostate cancer are largely unknown. However, certain things can increase your risk of developing the condition. No one knows how to prevent the disease but recent research suggests a particular compound found in coffee may inhibit the growth of the disease. Japanese scientists have studied the effects of two compounds found in coffee, kahweol acetate and cafestol, on prostate cancer cells and in animals, where they were able to inhibit growth in cells which are resistant to common anti-cancer drugs such as Cabazitaxel.

The researchers initially tested six compounds, naturally found in coffee, on the proliferation of human prostate cancers cells in vitro (i.e. in a petri-dish).

They found that cells treated with kahweol acetate and cafestol grew more slowly than controls.

They then tested these compounds on prostate cancer cells which had been transplanted to mice (16 mice).

Four mice were controls, four were treated with kahweol acetate, four with cafestol, with the remaining mice being treated with a combination of kahweol acetate and cafestol.

Study leader, Dr Hiroaki Iwamoto (Department of Integrative Cancer Therapy and Urology, Kanazawa University Graduate School of Medical Science, Japan, first author of the study) said: “We found that kahweol acetate and cafestol inhibited the growth of the cancer cells in mice, but the combination seemed to work synergistically, leading to a significantly slower tumour growth than in untreated mice.

We are currently considering how we might test these findings in a larger sample

Dr Hiroaki Iwamoto, study leader

“After 11 days, the untreated tumours had grown by around three and a half times the original volume (342 percent), whereas the tumours in the mice treated with both compounds had grown by around just over one and a half (167 percent) times the original size.”

Dr Iwamoto acknowledges the study’s limitations, however: “It is important to keep these findings in perspective. This is a pilot study, so this work shows that the use of these compounds is scientifically feasible, but needs further investigation; it does not mean that the findings can yet be applied to humans.

“We also found the growth reduction in transplanted tumour cells, rather than in native tumour cells.”

He added: “What it does show is that these compounds appear to have an effect on drug resistant cells prostate cancer cells in the right circumstances, and that they too need further investigation.

“We are currently considering how we might test these findings in a larger sample, and then in humans.”

Kahweol acetate and cafestol are hydrocarbons, naturally found in Arabica coffee. The coffee-making process has been found to affect whether these compounds remain in coffee after brewing (as with espresso), or whether they are stripped out (as when filtered).

Weighing in on the evidence, Professor Atsushi Mizokami (Department of Integrative Cancer Therapy and Urology, Kanazawa University Graduate School of Medical Science, Japan) added: “These are promising findings, but they should not make people change their coffee consumption.

“Coffee can have both positive and negative effects (for example it can increase hypertension), so we need to find out more about the mechanisms behind these findings before we can think about clinical applications. However, if we can confirm these results, we may have candidates to treat drug-resistant prostate cancer.”

The findings add fresh significance to a study published back in 2011, which found that men who regularly drink coffee had a lower risk of developing the disease, particularly in its most aggressive form.

Commenting on the study’s findings at the time, lead author Kathryn Wilson, a research fellow in epidemiology at HSPH, said: “At present we lack an understanding of risk factors that can be changed or controlled to lower the risk of lethal prostate cancer.

“If our findings are validated, coffee could represent one modifiable factor that may lower the risk of developing the most harmful form of prostate cancer.”

The key findings of the 2011 study included:

• Men who consumed the most coffee (six or more cups daily) had nearly a 20 percent lower risk of developing any form of prostate cancer.
• The inverse association with coffee was even stronger for aggressive prostate cancer. Men who drank the most coffee had a 60 percent lower risk of developing lethal prostate cancer.
• The reduction in risk was seen whether the men drank decaffeinated or regular coffee, and does not appear to be due to caffeine.
• Even drinking one to three cups of coffee per day was associated with a 30 percent lower risk of lethal prostate cancer.
• Coffee drinkers were more likely to smoke and less likely to exercise, behaviours that may increase advanced prostate cancer risk. These and other lifestyle factors were controlled for in the study and coffee still was associated with a lower risk.

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