Researchers in Garvan's cancer program have shown that a compound found in the leaves and fruit of the avocado tree can kill breast cancer cells, raising hope for a potential new therapeutic.

The team first began looking at toxins produced by avocados following an observation that lactating cattle who were grazing on the plants developed a type of mastitis. The observation led them to persin.

By studying the effects of persin on breast cancer cells grown in the laboratory, the scientists found that it selectively kills the cancerous cells by raising their levels of a 'killer' protein.

"A lot more work needs to be done before persin's potential as a chemotherapy agent is actualised", says group leader Dr Alison Butt. "This includes testing it in animal models and looking for side effects on other cell types, before trialling it in people," she said.

However, the hope is that if persin could be given together with commonly used breast cancer drugs like tamoxifen, which seem to act in a different way, patients would benefit by needing smaller amounts of each type of medicine. Indeed, in the laboratory, persin and tamoxifen look to be a good combination.

Caroline Roberts, Dr Butt's research assistant, was keen to point out that humans cannot break down plant cell walls and are therefore not exposed to persin when eating avocados.