Investigating the characteristics of intestinal flora of patients with high-Gleason prostate cancer

Through joint research with the Graduate School of Medicine at Osaka University, the research team led by Associate Professor Kazutoshi Fujita of the Department of Urology of the Faculty of Medicine at Kindai University and others discovered an intestinal flora complex that is characteristic of Japanese patients with high-Gleason prostate cancer.

With the aging of the Japanese population, the number of prostate cancer cases has increased in recent years, and it has become the most common cancer among men in Japan. This form of cancer is closely related to dietary habit, and the increase in its morbidity in Japan is thought to be partly owing to the spread of western-style dietary habits. In contrast, it has been recently reported that intestinal flora and their metabolites are involved in various diseases, such as colorectal cancer, and have taken the spotlight as potential new therapeutic targets.

In a recent study, the research team found that the administration of antibiotics to mice fed a high-fat diet, which altered their intestinal flora, suppressed the growth of prostate cancer. However, the intestinal flora is known to vary greatly depending on race, region, and dietary habits, and an examination of the Japanese population was needed for healthcare in the country.

To investigate further, the research team collected stool samples from 152 Japanese individuals with suspected prostate cancer living in Osaka and analyzed the genes of their intestinal bacteria to detect intestinal flora characteristic of high-Gleason prostate cancer. First, examination of the stool samples from 114 individuals found that bacteria, such as Rikenellaceae, Alistipes, and Lachnospiraceae, were abundant in those with prostate cancer. Because these bacteria are known to produce short-chain fatty acids, intestinal bacteria producing short-chain fatty acids may affect prostate cancer in humans, as was also suggested in previous studies in mice.

In addition, the diagnosis of prostate cancer using the fecal microbiome prostate index (FMPI) in stool samples based on 18 bacterial species showed a sensitivity of 81% and a specificity of 66% when evaluating the accuracy of the test , indicating that it is more useful than the PSA test, which is a test for early detection of prostate cancer.

Furthermore, in the examination of the stool samples from the remaining 38 individuals, the diagnosis of high-Gleason prostate cancer by FMPI had a sensitivity of 79% and a specificity of 63%, confirming its usefulness over the PSA test. In addition, the AUC index, an index for cancer discrimination, was 0.85 points, which was higher than the 0.74 points of the PSA test, indicating its usefulness.

These results suggest that the intestinal bacteria in humans, similar to those in the prostate cancer onset model mice, are associated with high-Gleason prostate cancer and that they may cause the onset and progression of prostate cancer.

Associate Professor Fujita spoke about the findings, "We will validate the results of this study by investigating the gut microbiota of patients with suspected prostate cancer nationwide in the future. By examining the gut microbiota, we aim to identify men who are at high risk of developing high-Gleason prostate cancer and to detect prostate cancer efficiently at an early stage. We will also aim to prevent the onset of prostate cancer by improving the lifestyle of patients with gut microbiota involved in the progression of prostate cancer and by altering the gut microbiota present in these individuals."