Rodent of the Week: How calories affect cancer

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Research published this week in the journal Nature provides a possible explanation for why people who restrict their calories on a daily basis appear to have lower rates of cancer. A story on the scientific evidence supporting caloric restriction and fasting appeared last month in the Los Angeles Times Health section.

Scientists have long known that dietary restriction and tumor growth are somehow linked. The new study, by researchers at Whitehead Institute for Biomedical Research in Cambridge, Mass., showed that a cellular pathway known as PI3K is key to this relationship. Studying mice with cancer, they showed that when this pathway is permanently turned on -- due to a mutation -- tumors grow independent of food consumption. But when this pathway operates normally, dietary restriction (defined in this study as a 60% reduction in normal intake) resulted in smaller tumors. The cancer cells in the mice that were sensitive to dietary restriction were stunted by a lack of insulin and insulin-like growth factor 1. Mice that were resistant to dietary restriction were unaffected by changes in insulin and insulin-like growth factor 1.

‘Our findings indicate that each tumor cell bears a signature that determines whether or not that cell will be affected by dietary restriction,’ said Nada Kalaany, a co-author of the paper, in a news release. ‘We think that mutations in the PI3K pathway are a major determinant of the sensitivity of tumors to dietary restriction.’

The research could lead to cancer treatments that mimic dietary restriction. Those treatments could then be applied based on the characteristics of each person’s unique tumor cells, said David Sabatini, a co-author of the paper. The researchers also plan to study the relationship between consuming too much food and the rate of tumor growth. As people become more obese, perhaps the PI3K pathway is involved in their sensitivity to cancer, he said.

-- Shari Roan