How boosting gut bacteria may help to battle cancer by stimulating the body to create specialist immune cells that can attack tumours
- Oncologists at University College London are testing probiotic strain of bacteria
- 120 patients with conditions such as breast and kidney cancer will be studied
- There is ‘some evidence’ probiotics help in preventing diarrhoea when taking antibiotics, according to NHS guidance
Could simply swallowing a pill containing probiotic bacteria help destroy lethal cancers? That’s the hope of a new clinical trial being run by a British bioscience company at a leading London university.
Probiotic yoghurts, which promise to promote healthy gut bacteria, have been in UK shops since the Nineties, but scientists are divided about whether commercially sold probiotics can deliver real benefits.
NHS guidance says there is ‘some evidence’ probiotics help in preventing diarrhoea when taking antibiotics, and may ease some symptoms of irritable bowel syndrome (IBS).
But there is little to support many of the other health claims made about them — for example, that they can help treat eczema.
Oncologists at University College London are testing a probiotic strain of bacteria in 120 patients with conditions such as breast, prostate, bladder, lung and kidney cancer (file picture)
However, emerging scientific knowledge shows that having a diverse array of microbes in our gut, sourced from food, encourages the immune system to operate more effectively.
It is on this theory — that microbes can be harnessed to improve cancer care — that the new British trial is based.
Scientists at 4D Pharma Plc and oncologists at University College London are testing a probiotic strain of bacteria, Enterococcus gallinarum, in 120 patients with conditions such as breast, prostate, bladder, lung and kidney cancer.
The bacterium is found in the bowel and in foods such as cheese and olives. The drug version, called MRx0518, was made from samples taken from healthy guts.
Researchers say that it seems E. gallinarum can stimulate the body to secrete specialist immune cells that can attack tumours.
This is crucial, as MRx0518 is designed to be used with a cancer treatment called immunotherapy, which helps patients’ own immune systems identify cancer cells and destroy them. This approach has taken decades to refine, as learning how to manipulate the immune system without harming patients has proved a challenge.
Immunotherapy drugs such as pembrolizumab (Keytruda) have scored some notable successes against melanoma, non small-cell lung cancer, kidney cancer, bladder cancer, head and neck cancers and Hodgkin lymphoma.
Recent figures show that nearly 25 per cent of patients who received pembrolizumab as an initial treatment for advanced non small-cell lung cancer were still alive after five years — a huge gain over the historical five-year survival rate of only 5 per cent.
However, despite such success, many patients’ immune systems do not respond effectively to the therapy or are stimulated for only a limited time before the benefit fades and the cancer returns.
It is hoped a targeted probiotic could improve these outcomes. Patients will be given the probiotic in the month or so between them being diagnosed with cancer and undergoing surgery to remove the tumour. Biopsies at these points will be compared to see how much the tumour has or hasn’t shrunk.
Trials have previously flagged the potential benefit of healthy gut bacteria in defeating cancers (file picture)
The trial will also see if MRx0518 can reactivate pembrolizumab’s effects in cancer patients who initially showed a benefit, but then stopped responding to the drug.
Already, trials have flagged the potential benefit of healthy gut bacteria in defeating cancers. In 2017, the journal Science reported patients with melanoma who had more diverse beneficial bacteria in their guts had better success with their cancer treatment.
However, earlier this year, U.S. scientists warned against taking over-the-counter probiotics to boost immunotherapy because they actually appear to hinder its effects by disrupting the patients’ healthy balance of gut bacteria.
Their study of 113 patients with metastatic melanoma found that those who regularly took over-the-counter probiotics had a 70 per cent lower than normal chance of responding to immunotherapy.
‘The general perception is [that probiotics] make your gut microbiome healthier,’ reports the study, which was presented at the American Association for Cancer Research conference.
‘Our data suggest that may not be the case for cancer patients.’
These differing results might be explained by a study, published in the journal Cell Host & Microbe in March, which suggests that, under certain conditions, probiotics can be harmful due to their ability to evolve.
Scientists from Washington University School of Medicine in St Louis, in the U.S., investigated the behaviour of a strain of E. coli (believed to have anti-diarrhoeal properties) in mice. After five weeks, the bacterium had evolved to become harmful in mice with low levels of bacterial diversity in their guts, eating the protective layer that lines the intestine.
Aura Ferreiro, who led the study, warns: ‘Quite often, we use probiotics in sick people who have a low-diversity, unhealthy microbiome. That seems to be the condition when the probiotic is most likely to evolve.’
Rather than buying probiotics, cancer patients may be better off eating as healthy a diet as possible, as this may best foster a healthy balance of bacteria in their guts.
Jane Clarke, a leading dietitian, told Good Health: ‘Probiotics are an exciting area of research. But the answers are never going to be as easy as just taking a pill.’
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