A low calorie diet could help prevent an aggressive form of cancer from spreading around the body.
Scientists have found that cutting calories reduces the likelihood of one type of breast cancer migrating to other organs.
They were looking at triple negative breast cancer – one of the most life threatening forms that is aggressive and least responsive to standard treatment. It affects about one in five women with the disease.
One theory is that dieting may decrease chance of cancer spreading by strengthening the tissue surrounding the tumour.
Many breast cancer patients are treated with hormonal therapy to block tumour growth and steroids to counteract the side effects of chemotherapy.
But both treatments can alter the metabolism – which in turn, can trigger weight gain, with the average woman gaining 10lb in the first year of treatment.
Previous studies have shown that being overweight makes breast cancer treatment less effective, and those who gain weight during treatment have worse cancer outcomes.
‘That’s why it’s important to look at metabolism when treating women with cancer,’ said study leader Dr Nicole Simone, from the department of Radiation Oncology at Thomas Jefferson University, Philadelphia.
The study involved feeding one group of mice a third less than another group.
‘We found that the diet turned on a programme that protected mice from metastatic disease,’ explained Dr Simone.
The study, published in the journal Breast Cancer Research and Treatment, found that in the dieting mice, cancer cells decreased their production of microRNAs 17 and 20 (miR 17/20).
These are molecules that play a vital role in influencing the pathways responsible for many disease processes.
Researchers have found that in triple negative cancers that spread, this group of microRNAs is often increased.
Dr Simone has previously discovered that calorie restriction boosts the effectiveness of radiation therapy.
The new study set out to examine which molecular pathways were involved in this effect.
The researchers found that the microRNAs decreased the most when mice were treated with both radiation and calorie restriction.
This decrease in turn increased the production of proteins involved in strengthening the tissue surrounding the tumour
Dr Simone said: ‘Calorie restriction promotes epigenetic changes in the breast tissue that keep the extracellular matrix strong.
This is a scaffold that provides support to the cells.
Dr Simone added: ‘A strong matrix creates a sort of cage around the tumor, making it more difficult for cancer cells to escape and spread to new sites in the body.’
The findings should help pave the way for new drugs to treat cancer. In theory, a drug that decreased miR 17 could have the same effect on the extracellular matrix as calorie restriction.
However, the researchers say that targeting a single molecular pathway, such as the miR17, is unlikely to be as effective as calorie restriction.