Gut Bacteria vs Cancer

The bacterial cells we harbour are estimated to outnumber our human cells by 10 to 1. It therefore seems natural that they have a huge influence upon us, both with respect to health and to disease. However, for years this influence was not appreciated, with the topic of gut bacteria seemingly refined to yoghurt adverts. Now, we are discovering more and more about our microbiota, and two papers in Science this week have revealed interesting links between the bacteria in our gut and cancer.

Researchers at the University of Lille, France, have found that the success of an anti-cancer treatment – ipilimumab – depends on gut flora. Ipilimumab is given to treat advanced melanoma, a later stage of skin cancer. Chamaillard et al found that the drug was less effective in mice lacking gut bacteria and that replenishing certain bacteria restored the drug’s efficacy. Chamaillard now plans to test whether the outcome of treatment can be predicted by the profiles of bacteria within patients’ guts.

In the second study, Gajewski et al noticed the differential growth of tumours in mice with different mirobiota. They noticed that one type of bacteria – Bifidobacteria – was associated with anti-tumour effects, creating a stronger immune response against the tumour cells. This slowed the growth of the tumour to such an extent that oral administration of the bacteria alone was nearly as effective as a current anti-cancer drug being trialed in humans.

More and more studies, like these two, are slowly uncovering the enormous effect gut bacteria have on the development and treatment of disease. While more evidence is required of these effects in humans, it looks likely that microbiota will shape the future of medicine. This could include the introduction of stool transplantation, although that may take some selling.