A SIMPLE sugar supplement normally prescribed to treat urinary tract infections has been shown to stunt tumour growth and enhance the effectiveness of chemotherapy in a world-first that could transform cancer treatment.
The five-year study by scientists in Glasgow has raised hopes of a potential breakthrough that could see cancer patients survive longer with disease.
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They discovered that mice who were fed mannose - a low-cost sugar supplement freely available on the high street and internet - did not suffer any serious side effects, but did display far slower tumour growth and were much more responsive to chemotherapy.
The findings were particular strong in mice with colorectal cancer, who developed significantly fewer tumours, but survival was also extended in mice with pancreatic, lung or skin cancer.
Mice treated with mannose combined with the common chemotherapy drug, doxorubicin, saw their tumours shrink considerably and recorded "significantly increased life expectancy".
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The researchers are keen to begin clinical trials as soon as possible to test whether the findings can be replicated in humans.
Professor Kevin Ryan, who led the research at the Cancer Research UK Beatson Institute in Glasgow, said: "It's exciting because in a way it's quite simple. We're not saying that what we have here is a cancer cure, because we haven't shown that it eradicates cancer, but we did slow cancer growth and in some cases we get fewer tumours than in those mice without mannose.
"There are many situations where, combined with other therapies, that would be a great benefit.
"Hypothetically, we would be hoping to see an enhanced effectiveness of chemotherapy, or that mannose could be given in between rounds of chemotherapy as a kind of maintenance therapy to keep patients well for longer.
"It could also be given to patients who have a tumour that can't be removed but they would be given mannose to make their tumour as 'lazy' as possible. So I think there would be plenty of instances where people live with cancer, but it doesn't shorten their life."
Prof Ryan stressed that no one should start self-prescribing mannose, however.
He said: "It's very important to stress that it's not been tested in humans yet for the prevention or treatment of cancer, and anybody who's thinking of supplementing their diet in any way - whether they're a cancer patient or a healthy person - should always discuss it with their doctor."
Mannose is extremely similar in structure to glucose, and both sugars share the same molecular weight.
It is already well known that tumours use more glucose than normal, healthy tissues and rely on glucose to grow, but ironically it appears that mannose works by blocking glucose metabolism in certain tumours cells.
The scientists discovered that mannose was most effective in tumours with low levels of an enzyme called phosphomannose isomerase (PMI), which breaks down the mannose into a form that the cells can use for energy.
In tumours with low levels of PMI, mannose accumulates in a form called mannose-6-phosphate which cannot be converted for energy.
When this builds up in cells it is also known to inhibit the activity of other enzymes needed to metabolise glucose, blocking that off as an energy source for the tumour.
When the Glasgow team grew samples of human tumour cells in the lab, including ovarian, renal, breast, prostate, and colorectal cancers, they found that levels of PMI varied but were lowest in the colorectal cancer cells.
Prof Ryan added: “Tumours need a lot of glucose to grow, so limiting the amount they can use should slow cancer progression. The problem is that normal tissues need glucose as well, so we can’t completely remove it from the body.
“In our study, we found a dosage of mannose that could block enough glucose to slow tumour growth in mice, but not so much that normal tissues were affected.
"This is early research, but it is hoped that finding this perfect balance means that, in the future, mannose could be given to cancer patients to enhance chemotherapy without damaging their overall health.”
Dr Helen Rippon, chief executive of Worldwide Cancer Research, said: “It gives a glimmer of hope that this easily available sugar might in future become a cheap and safe addition to cancer treatment.
"This is a brand new discovery and only the first step in working out whether mannose might help treat cancer.”
The study was funded by Cancer Research UK and Worldwide Cancer Research and published in the journal, Nature.
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