February 15, 2016

expert reaction to study looking at probiotics, gut microbes and liver carcinoma in mice

The potential health benefits of probiotics (mixtures of live microbes used with the aim of aiding digestion) is the subject of a paper published in the journal PNAS, with the authors reporting that, in their mouse model, a probiotic mixture reduced growth and size of liver tumours, which they suggest could be due to a reduction in certain immune cells.

Prof. David Dearnaley, Professor of Uro-Oncology at The Institute of Cancer Research, London, said:

“In humans the gut microbiota weigh about as much as the brain but until relatively recently was a neglected ‘organ’. Very considerable interest now surrounds the role of microbiota in human health and disease with associations between dysbiosis and not only inflammatory gastointestinal disorders, such as ulcerative colitis and Crohn’s disease, but a wide range of non-gut related auto-immune disease. Gut microbiota may also play an important role in explaining individual variations of drug metabolism, efficacy and side effects, as well as radiation enteropathy.

“This report suggests a mechanism for immune modulation by gut microbiota using a novel pro-biotic mixture that impacts on the establishment of hepato-cellular carcinoma (HCC) in a mouse model.  The relevance to human cancer has to be speculative but the research is thought provoking, and may lead to testable hypothesis related to carcinogenesis and possibly novel immunotherapy approaches.”

Dr Marcus Dorner, Non-Clinical Lecturer in Immunology, Imperial College London, said:

“The gut microbiome is a major player in shaping the immune system (see reviewed in Hooper et al. 2012 Science). Most of these studies have been undertaken in germ-free animals, which can be transplanted with different gut microbiomes. Even though our understanding of this complex interplay has yielded striking results, including the dependence of anti-cancer treatments on gut microbiota (Vétizou et al. 2015 Science & Viaud et al. 2013 Science), data on a direct contribution of probiotics affecting the gut microbiome, and in terms cancer progression, are rare.

“The present study aims at addressing the impact of alterations in the gut microbiome, by means of probiotic treatment, on progression of hepatocellular carcinoma in mice. The presented data suggest that probiotic treatments do not only slow progression of hepatocellular carcinoma in a preventative manner but exhibit the same effect when given therapeutically following induction of tumourigenesis.

“However, the model employed uses a mouse hepatoma cell line in wild-type mice to mimic tumour formation. This leaves the important question unanswered as to whether altering the gut microbiome can effectively prevent cancer formation. Additionally, this study uses wild-type mice with a murine gut microbiome, which is different from that observed in humans. Further studies will be needed to demonstrate that altering the gut microbiome has a direct impact on development and progression of hepatocellular carcinoma in humans.”

‘Probiotics modulated gut microbiota suppresses hepatocellular carcinoma growth in mice’ by Jun Lia et al. published in PNAS on Monday 15 February 2016.

Declared interests

Dr Marcus Dorner: “I do not have anything to declare in terms of interests.”

No others received.