Analysis of the bacterial microbiome from prostate tissue of South African men

Abstract

Cancer is a major cause of death globally and the incidence of the disease is expected to increase in coming years. It is predicted that 20 million new cases of cancer will be observed annually as early as 2025, rising from 14.1 million new cases in 2012. Prostate Cancer (PCa) was found to have the second highest incidence among male cancers globally, and it is expected that the absolute number of men with PCa will increase. Contrary to global trends, PCa has a higher incidence and mortality rate than lung cancer in Sub-Saharan African men. According to the National Cancer Registry of South Africa, the incidence of PCa was three times greater than the incidence of lung cancer amongst men in 2010. Furthermore, disparities have been reported in the presentation and outcomes of PCa between racial groups. PCa has been found to be more common amongst men with African ancestry, and Black South African men have been shown to present a more aggressive disease phenotype. The South African Prostate Cancer Study (SAPCS) was established in 2008 to investigate clinical presentation, epidemiological risk factors, and associated microbial pathogenic contributions to PCa within Black South Africans from rural and urban localities. Chronic inflammation has been associated with the development of cancer. Inflammatory responses include increased cellular proliferation, the production of growth factors, as well as factors that are known to damage DNA. Together, these responses create an environment which can promote the development of neoplasia. With regard to PCa in particular, chronic inflammation of benign prostate tissue has been associated with high-grade PCa. Bacterial infection represents one potential source of such long term inflammation. Studies on mouse models have found bacteria to be capable of inducing chronic inflammation with prostatitis which can still be detected in 40% of the subjects up to 1 year post-infection. The present study investigated the bacterial communities identified from prostate biopsy tissue taken from South African men suffering from prostate cancer or benign prostatic hyperplasia (BPH). A population of 50 men were enrolled in the study representing 26 BPH patients and 24 PCa patients. Bacterial communities were shown to be highly diverse for each patient, but the total bacterial communities did not differ significantly between the PCa group and the BPH group. However, significant associations were identified between specific taxa and the two patient groups. These taxa included known pathogens, and bacteria previously associated with diseases of the prostate and various cancers. Taken together, these results suggest a contribution of specific bacterial taxa, to the aggressive PCa disease observed amongst South African men.