October 15, 2021 – A key element in the treatment of prostate cancer is to deprive it of androgens, the hormones that make it grow. The testicles are the main source of these hormones, so treatment may consist of either surgical removal of these organs or the use of drugs to block hormone production.
Over time, some types of prostate cancer become resistant to these treatments and begin to spread again. As with many cancers that show this behavior, finding exactly what makes them resilient can be difficult.
The culprit may be the bacteria that live in the gut. The researchers found that in castrated mice and in androgen-treated humans, some of these intestinal bacteria began to produce androgens that were easily absorbed into the bloodstream. According to these new discoveries,published in the journal Science, androgens appear to support the growth of prostate cancer and its resistance to treatment.
This study is the first to show that bacteria can produce testosterone, although researchers are still unsure what makes them start doing so. Androgen deprivation treatment can also lead to more of these germs producing hormones in the gut, the results show. Faecal bacteria in people with resistant prostate cancer have also been shown to be associated with lower life expectancy.
Fecal transplants from mice with treatment-resistant prostate cancer may cause resistance in animals with a disease susceptible to these hormones. When these mice received fecal transplants from people with resistant cancer, the effect was the same: a shift to treatment resistance.
But the opposite was also true: Fecal transplants from mice or people with hormone-sensitive cancer helped to limit tumor growth.
The findings may suggest new therapeutic targets: germs living in the gut. In studies in mice, the researchers found that when they killed these bacteria, the cancer progressed much more slowly to resistance to treatment. The authors of a commentary accompanying the study say there are other places to look for bacteria that could also produce these hormones, including the urinary tract or even the tumor itself.