¹Department of Surgery, Johns Hopkins University School of Medicine; Baltimore, Maryland, MD 21231, USA

²Department of Oncology, Johns Hopkins University School of Medicine; Baltimore, Maryland, MD 21231, USA

³Department of Pathology, Johns Hopkins University School of Medicine; Baltimore, Maryland, MD 21231, USA

⁴Molecular Devices Corp., Sunnyvale, California, CA 94085, USA

⁵Duke University Medical Center, Durham, North Carolina, NC 27710, USA

Correspondence to: S Sukumar, Breast Cancer Program, Johns Hopkins Oncology Center, CCRB Room 410, 1650 Orleans Street, Baltimore, MD 21231-1000, USA

We have identified 14-3-3 ( ) as a gene whose expression is lost in breast carcinomas, primarily by methylation-mediated silencing. In this report, we investigated the timing of loss of gene expression during breast tumorigenesis in vivo. We analysed the methylation status of in breast cancer precursor lesions using microdissection for selective tissue sampling. We found hypermethylation of in 24 of 25 carcinomas (96%), 15 of 18 (83%) of ductal carcinoma in situ, and three of eight (38%) of atypical hyperplasias. None of the five hyperplasias without atypia showed -hypermethylation. Unexpectedly, patients with breast cancer showed hypermethylation in adjacent histologically normal breast epithelium, while this was never observed in individuals without evidence of breast cancer. Also, samples of periductal stromal breast tissue were consistently hypermethylated, underscoring the importance of selective tissue sampling for accurate assessment of 14-3-3- methylation in breast epithelium. These results suggest that hypermethylation of 14-3-3- occurs at an early stage in the progression to invasive breast cancer, and may occur in apparently normal epithelium adjacent to breast cancer. These results provide evidence that loss of expression of is an early event in neoplastic transformation. Oncogene (2001) 20, 3348-3353.

breast cancer; 14-3-3 ; methylation; MSP; DCIS; preneoplasia