http://www.topix.com/wire/health/breast-cancer

Hopes high as breast tumours are put to sleep

The study, published today in PNAS, the journal of the Proceedings of the National Academy of Sciences, found that Id1, a gene which is normally produced only in embryonic development, is reactivated in many solid cancers, such as those found in the breast, causing them to be highly aggressive and spread rapidly.

Cancers driven by Id1, which occur in about 4500 people each year, do not have oestrogen receptors and cannot be treated with Tamoxifen, which interferes with the action of oestrogen.

Women with these tumours have a much poorer prognosis and must be treated with high levels of toxic chemotherapy.

When Id1 was switched off in mice, tumours went into senescence, a form of sleep where the cells lose their ability to divide and spread.

"You induce a terminal sleep, and then the immune system just gobbles them up," the study's author, Alex Swarbrick, said yesterday. "Those mice live much longer than mice with continual Id1 expression in their tumour … … About 40 per cent were cured and the tumours … shrank away."

Dr Swarbrick, a scientist at the Garvan Institute, spent three years studying the Id1 gene with Professor Mike Bishop, of the University of California, San Francisco.

"We happened to ask the right questions about the right gene. Up to that point, no one else had asked whether or not Id1 actually contributed to the origin and behaviour of breast cancer," he said.

"But by artificially activating the Id1 protein in mouse mammary glands, we demonstrated that Id1 contributes to cancer - and that mammary cancers with high levels of Id1 become very aggressive and highly metastatic."

Dr Swarbrick said the discovery was exciting because most cancers "mutate the genes involved in cell death, so it's hard to kill them.

"Our results suggest that in the future if we can therapeutically target the genes controlling senescence, such as Id1, we can force these tumours to senesce."

Sandra O'Toole, a pathologist at St Vincent's Hospital, in Darlinghurst, and a clinical research fellow at the Garvan Institute, said the finding would give hope to women forced to undergo chemotherapy.

"Up to 40 per cent of breast cancers lack the oestrogen receptors which respond to Tamoxifen, and at the moment the only treatment we have is aggressive chemotherapy, which attacks fast-growing cancer cells, but also kills off all other fast-growing cells in the body, causing hair loss, diarrhoea and blood problems. It's exciting that this finding could lead to the development of a drug which offers an alternative."

Dr O'Toole said she expected the discovery would attract pharmaceutical companies, making a new treatment possible in five to 10 years.