Researchers said that the discovery could lead to new therapies for the cancer, called locally advanced breast cancer (LABC). This type of cancer is defined by a large tumour that is about 2 inches or larger in diameter, about the size of a plum, when first diagnosed. The cancer might spread into surrounding lymph nodes or other tissues.
"This disease has not been sufficiently studied, in part because of the social, psychological, economic, and cultural barriers that may stand in the way of obtaining care," said Silvia C. Formenti, M.D., the Sandra and Edward H. Meyer Professor of Radiation Oncology and Chairwoman of Radiation Oncology.
"Our study shows that an unusual molecular switch occurs that is essential for the development of these large tumours. We think that this switch could be a target for new therapies," said Robert J. Schneider, Ph.D., and the Albert B. Sabin Professor of Molecular Pathogenesis. Researchers found in their study that two molecules were unusually abundant or "overexpressed" specifically in locally advanced breast cancers.
Further analysis in mice revealed that the molecules orchestrated a switch in the use of messenger RNA, a kind of ferry service that carries information for making proteins. Researchers found that this switch occurs when tumours become starved for oxygen, a condition known as hypoxia. The switch permits the selective expression of proteins that are required for tumours to carry out angiogenesis, the process of developing a blood supply. It also enables tumours to grow to a large size and to progress.
"The identification of the molecular switch and its importance for development of locally advanced breast cancer reveals realistic targets for the development of new therapeutics to block tumour angiogenesis and progression in breast and possibly other cancers," Dr. Schneider said.
The study is published in the November 9, 2007 issue of the journal Molecular Cell.