A consortium of Cancer Research UK scientists and doctors has discovered a new gene for breast and ovarian cancer - providing a missing link in an enduring medical mystery.

The gene, which they have named EMSY, finally joins the dots between hereditary breast cancers and sporadic, non-inherited forms.

While inheriting faulty BRCA genes can trigger hereditary breast and ovarian cancer, no one could find a role for these genes within sporadic tumors.

But the new study, published in the journal Cell, finally provides a solution, suggesting EMSY shuts down the action of functional BRCA2 to fuel cancer's development.

It is not only a key advance in understanding how and why cancers develop, but may pave the way for new types of tests to predict how the disease may progress.

Cancer Research UK's Professor Tony Kouzarides, who led the project at the Wellcome Trust/Cancer Research UK Institute, University of Cambridge, says: "Discovering such an important new gene is very exciting and gives us the piece in the jigsaw we've been looking for. It's taken us six years to get here, but it's been well worth the effort.

"We'll now have a much more sophisticated image of the genetic changes triggering breast and ovarian cancer in women who haven't inherited a high risk of cancer, but develop it anyway. It's going to give us new lines of investigation and potentially exciting angles of attack."

Inheriting faulty BRCA genes gives women a high risk of breast and ovarian cancer, but only five percent of breast cancers run in families like this.

Scientists have been hunting for the genes that cause sporadic breast cancers - the other 95 percent of cases - ever since the BRCA genes were discovered, eight years ago.

They had long suspected BRCA2 might play a role in sporadic breast and ovarian cancers, despite the fact that the gene is very rarely damaged within these tumors.

Professor Kouzarides' team searched for sequences of DNA that interact with BRCA2 and were able to describe and isolate a brand new gene.

They decided to call the gene EMSY after cancer nurse Emma Hughes-Davies - the sister of Dr. Luke Hughes-Davies, the discoverer of the gene and a Cancer Research UK clinical fellow.

Scientists found that EMSY has a role in turning genes on and off and in repairing damaged DNA. It is highly effective at switching off BRCA2, raising suspicions that it might be an important cancer gene.

Colleagues at the Cancer Research UK Department of Oncology, University of Cambridge, were convinced they were on the right track to a new cancer gene when they found extra copies of EMSY in the first few tumor samples they tested.

Working with a team from the British Columbia Cancer Agency in Canada, they then analyzed the gene in nearly 551 breast and 360 ovarian tumors.

Their suspicions were confirmed - they found extra copies of the gene in 13 percent of breast cancers and 17 percent of ovarian cancers, but never in normal tissue and hardly ever in other types of tumor.

Professor Carlos Caldas, leading the team in the Cancer Research UK Department of Oncology, says: "We've always thought factors that are important in inherited breast cancers should also be playing a role in other kinds, and it's heartening to know that we hadn't been barking up the wrong tree.

"It should help us in the development of new, targeted treatments against breast and ovarian cancer, particularly as cancers with high levels of the new gene seem to behave in a similar way to inherited forms. EMSY could also form the basis for new types of predictive test."

EMSY seems to play a particularly important role in aggressive forms of breast cancer. Women whose tumors had extra copies of the EMSY gene survived for 6.4 years on average, compared with 14 years for those whose breast cancers had normal amounts of EMSY.

The difference in survival was particularly great among women who at diagnosis had not suffered any spread of the cancer to their lymph nodes, suggesting it might be possible to test for EMSY early on in a woman's course of treatment, in order to predict how aggressive their disease is likely to become.

SOURCES:
Cell, November 26, 2003
Cancer Research UK (http://www.cancerresearchuk.org)