Scientists from the Institute of Cancer Research, London; the Institute of Oncology Research in Bellinzona, Switzerland; and the Swiss Federal Institute of Technology used mice and patient samples to investigate the role of gut bacteria in prostate cancer growth and progression. The scientists discovered that getting rid of all gut bacteria in mice with prostate cancer slowed tumor growth and delayed the emergence of hormone resistance. The findings pave the way for potentially treating advanced or hormone-resistant prostate cancer through manipulation of the microbiome.