Comprehensive genomic analysis of breast tumors has revealed four main subclasses of breast cancer, each of which has extensive genetic heterogeneity, said an international consortium of scientists in The Cancer Genome Atlas Network that includes scientists from the Baylor College of Medicine (BCM), and from 90 other institutions around the world. The result were published in an open article online on September 23, 2012 in Nature. "In the last 10 years, new technologies have allowed us to look at these tumors at a variety of different levels," said Dr. Chad Creighton, an associate professor in the National Cancer Institute-designated Dan L. Duncan Cancer Center at BCM, who worked on the analysis of the various genomic datasets, which included, for all genes, the sequence, expression, copy number, and any epigenetic silencing. Dr. Lawrence Donehower, professor of molecular virology and microbiology at BCM, concentrated on analysis involving a particular tumor suppressor gene called p53. "We took all these data and used them together to identify these four basic subtypes of tumors that we’ve known about for some time," said Dr. Creighton. "Among other things, this study aimed to get at the fundamental question of just how many subtypes of breast cancer there are, because that can determine treatment." "This is one of the largest multi-institutional and multi-platform efforts of this kind to date," said Dr. Donehower. For this report, members of the consortium evaluated tumors and tissue samples from 825 patients with breast cancer. Of these, 510 tumors from 507 patients underwent sequencing of the whole exome (the protein-coding portion of the genome) and identified 30,626 somatic mutations.
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