Dietary restriction of the amino acid methionine can reduce tumour growth and improve the outcome of chemotherapy and radiation treatments in mice, according to a paper published online in Nature this week. In a proof-of-principle study in humans, a reduction in dietary methionine levels had a similar effect on metabolism to that seen in mice, which may suggest a conserved response between humans and mice to dietary restriction of this amino acid.
Methionine is an essential amino acid (the body is unable to produce it) and plays a critical role in metabolism. It is metabolized as part of a group of reactions called one-carbon metabolism, which are also targeted by a number of cancer treatments involving chemotherapy and radiation. However, it is unclear whether specific dietary interventions could influence the metabolic pathways that are targeted by these therapies.
Jason Locasale and colleagues investigated whether dietary restriction of methionine could have anti-cancer properties through interaction with other therapies that target one-carbon metabolism. In a series of cancer models in mice, the authors found that restricting levels of methionine in the diets of the mice resulted in inhibition of tumour growth. When used in combination with the chemotherapy drug 5-fluorouracil, or radiation therapy, tumour growth was also reduced.
In a preliminary clinical study, six healthy middle-aged individuals received a low methionine diet (equivalent to an 83% reduction in daily methionine intake) for three weeks. The authors found that metabolite levels in the study participants correlated with those seen in mice on the same dietary restriction. They propose that the findings provide evidence that a specific dietary manipulation may influence cancer outcomes.