Restricted diet may help slow down breast cancer

Calorie restriction, a kind of dieting in which food intake is decreased by a certain percentage, may help slow down breast cancer, according to a new study.
Researchers found that the triple negative subtype of breast cancer - one of the most aggressive forms - is less likely to spread, or metastasise, to new sites in the body when mice were fed a restricted diet.
"The diet turned on a epigenetic programme that protected mice from metastatic disease," said senior author Nicole Simone, an associate professor in the department of Radiation Oncology at Thomas Jefferson University.
When mouse models of triple negative cancer were fed 30 per cent less than what they ate when given free access to food, the cancer cells decreased their production of microRNAs 17 and 20.

Researchers have found that this group of miRs is often increased in triple negative cancers that metastasise.
The study found that microRNAs - a type of RNA that regulates other genes in the cell - specifically miR 17 and 20, decreased the most when mice were treated with both radiation and calorie restriction.

This decrease in turn increased the production of proteins involved in maintaining the extracellular matrix.
"Calorie restriction promotes epigenetic changes in the breast tissue that keep the extracellular matrix strong," said Simone.
"A strong matrix creates a sort of cage around the tumour, making it more difficult for cancer cells to escape and spread to new sites in the body," Simone said.

Understanding the link to miR 17 also gives researchers a molecular target for diagnosing cancers that are more likely to metastasise and, potentially, for developing a new drug to treat the cancers.
In theory, a drug that decreased miR 17 could have the same effect on the extracellular matrix as calorie restriction.
However, targeting a single molecular pathway, such as the miR17 is unlikely to be as effective as calorie restriction, said Simone.
Triple negative breast cancers tend to be quite different genetically from patient to patient.
If calorie restriction is as effective in women as it is in animal models, then it would likely change the expression patterns of a large set of genes, hitting multiple targets at once without toxicity, researchers said.

The study was published in the journal Breast Cancer Research and Treatment.