The high amounts of dietary sugar in the typical Western diet may increase the risk of breast cancer and its spread to the lungs, a new study published today has warned.

The findings demonstrated dietary sugar's effect on an enzymatic signalling pathway known as 12-LOX (12-lipoxygenase), researchers said.

"We found that sucrose intake in mice comparable to levels of Western diets led to increased tumour growth and metastasis, when compared to a non-sugar starch diet," said Peiying Yang, assistant professor at The University of Texas MD Anderson Cancer Centre in US.

"This was due, in part, to increased expression of 12-LOX and a related fatty acid called 12-HETE," said Yang.

Previous epidemiological studies have shown that dietary sugar intake has an impact on breast cancer development, with inflammation thought to play a role.

"The current study investigated the impact of dietary sugar on mammary gland tumour development in multiple mouse models, along with mechanisms that may be involved," said Lorenzo Cohen, professor of Palliative, Rehabilitation and Integrative Medicine.

"We determined that it was specifically fructose, in table sugar and high-fructose corn syrup, ubiquitous within our food system, which was responsible for facilitating lung metastasis and 12-HETE production in breast tumours," said Cohen.

Cohen added that the data suggested that dietary sugar induces 12-LOX signalling to increase risks for breast cancer development and metastasis.

Identifying risk factors for breast cancer is a public health priority, researchers said.
"Prior research has examined the role of sugar, especially glucose, and energy-based metabolic pathways in cancer development," said Yang.

"However, the inflammatory cascade may be an alternative route of studying sugar-driven carcinogenesis that warrants further study," Yang said.

The team conducted four different studies in which mice were randomised to different diet groups and fed one of four diets.

At six months of age, 30 per cent of mice on a starch-control diet had measurable tumours, whereas 50 to 58 per cent of the mice on sucrose-enriched diets had developed mammary tumours.

The study also showed that numbers of lung metastases were significantly higher in mice on a sucrose- or a fructose-enriched diet, versus mice on a starch-control diet.

"This study suggests that dietary sucrose or fructose induced 12-LOX and 12-HETE production in breast tumour cells in vivo," said Cohen.

"This indicates a possible signalling pathway responsible for sugar-promoted tumour growth in mice. How dietary sucrose and fructose induces 12-HETE and whether it has a direct or indirect effect remains in question," Cohen added.

The study was published in the journal Cancer Research.