Common gut bacteria can fuel the growth of prostate cancers and allow them to evade the effects of treatment, scientists have found.
Hormone therapy is the standard of care for advanced prostate cancer and works by lowering levels of androgens – male hormones.
But researchers have found low levels of these hormones in patients can drive the expansion of gut bacteria, which can become hormone factories to sustain prostate cancer growth.
Scientists have identified what they describe as bacterial fingerprints, which may help pick out patients at high risk of developing resistance to treatment.
These men could benefit from strategies to manipulate their microbiome – bacteria, they suggest.
For example, men could undergo a faecal transplant or researchers hope to produce yoghurt drink enriched with favourable bacteria.
Study author Professor Johann de Bono is professor of experimental cancer medicine at The Institute of Cancer Research, London (ICR), and consultant medical oncologist at the Royal Marsden NHS Foundation Trust.
He said: “Our findings reveal that the initiation of hormone therapy for prostate cancer can trigger ‘gut bugs’ to start producing androgen hormones.
“These androgens can then sustain prostate cancer’s growth and drive resistance to hormone therapy – worsening men’s survival outcomes.”
Prof de Bono added: “The next step will be to further explore how we apply these signatures in patients, with the aim of devising tests to pick out men who would benefit from faecal transplants, antibiotic therapy and other strategies to manipulate the microbiome.
“In the long-term, our aim would be to produce a ‘yoghurt’ enriched with favourable bacteria to prevent resistance to treatment.”
Gut bacteria are part of our microbiome and are usually valuable to humans.
However, cancer and other diseases can ruin this mutually beneficial balance – for example, by promoting the expansion of gut bacteria and encouraging them to release toxins or other molecules that affect cancer cells.
Once further validated in the clinic, the findings could provide new opportunities for the treatment of prostate cancer through manipulation of the microbiome.
The study found that getting rid of all gut bacteria in mice with prostate cancer slowed tumour growth and delayed the emergence of hormone resistance.
It further revealed that transplanting faeces from mice with hormone-resistant prostate cancer into mice with low androgen levels that had not yet developed resistance encouraged tumour growth.
Researchers also analysed gut bacteria from patients who were being treated at the Royal Marsden NHS Foundation Trust.
They looked at 19 men whose cancers were still responding to hormone therapy and 55 men with advanced hormone-resistant prostate cancer.
Transplanting stools from patients with hormone-resistant prostate cancer, into mice whose cancers were not resistant, promoted tumour growth and hormone resistance.
Professor Kristian Helin, chief executive of the ICR, said: “The influence of the gut microbiome on cancer is a fascinating new area of science that we are just beginning to understand.
“These exciting findings are the first to unveil a mechanism through which the gut microbiome can drive prostate cancer growth and resistance to hormone therapy.”
The study, published in the journal Science, was funded by the Prostate Cancer Foundation, Movember, Prostate Cancer UK, Cancer Research UK and The John Black Charitable Foundation.