MEMORANDUM FOR: Science Writers and Editors on the Journal Press List: Inactivation of the BRCA1 Gene May Play a Role in Nonhereditary Breast and Ovarian Cancers

Extract

March 30, 2000 (EMBARGOED FOR RELEASE 4 P.M. EST April 4)

New research shows that inactivation of the BRCA1 gene by hypermethylation may be involved in development of some cases of primary breast and ovarian cancers.

Mutation of the BRCA1 gene is often involved in hereditary cases of breast and ovarian cancers, but extensive research has not found BRCA1 to be mutated in any cases of sporadic (nonhereditary) breast cancer and in few cases of sporadic ovarian cancer. Therefore, Manel Esteller, M.D., Ph.D., and James Herman, M.D., at The Johns Hopkins Oncology Center, Baltimore, Md., and colleagues looked for potential inactivation of BRCA1 by hypermethylation in breast and ovarian cancer tissues. Their results appear in the April 5 issue of the Journal of the National Cancer Institute.

Hypermethylation in tumor suppressor genes has been linked to their loss of expression. Methylation patterns in the BRCA1 promoter (sequences regulating gene expression) region were assessed in 21 breast cancer cell lines, human breast cancers grown in mice (xenografts), and 215 primary breast and ovarian carcinomas. A second series of ductal breast cancers and ovarian cancers were analyzed for loss of heterozygosity (LOH—meaning loss of one copy) of the BRCA1 gene.