PARIS ¿ Researchers at the Institut Curie in Paris have established that medullary-type breast cancer has the particular biological characteristic of being accompanied by a mutation of the p53 gene in 100 percent of cases. It was already known that the p53 gene is altered in 20 to 40 percent of breast cancer cases, but no particular genetic characteristic had been previously identified in medullary breast cancer.
Although this invasive form of breast cancer is characterized by histological anomalies normally found in breast cancers with a poor prognosis, and represents only about 5 percent of total breast cancer cases, it is more common in families with a high risk of breast cancer: those carrying a mutation of the BRCA1 gene, where it accounts for 18 percent of cases.
This discovery was made in the course of specific clinical trials of the p53 gene in breast cancers, in which researchers used a special method for analyzing mutations of the gene developed at the Institut Curie, in particular a molecular test designed to establish the status of the gene. The trials showed not only that the p53 gene is mutated in all medullary breast cancer sufferers, but that there is almost certainly a very close relationship between the functions of the p53 gene, the role of which is to safeguard the integrity of the genome, and those of the BRCA1 gene, which is involved in the DNA repair process.
Researchers at the Institut Curie are now endeavoring to determine the fundamental nature of that relationship. In the longer term, they expect these discoveries to help improve both the diagnosis and prognosis of medullary breast cancers and to contribute to the development of new therapeutic approaches. ¿ James Etheridge