In vitro Repression of Brca1-Associated RING Domain Gene, Bard1, Induces Phenotypic Changes in Mammary Epithelial Cells

• Published in: The Journal of cell biology Vol. 143; no. 5; pp. 1329 - 1339
• Main Authors: Irminger-Finger, Irmgard, Soriano, Jesus V., Vaudan, Geneviève, Montesano, Roberto, Sappino, André-Pascal
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 30.11.1998; The Rockefeller University Press
• Subjects: Animals; B lymphocytes; Base Sequence; Breast cancer; Breast Neoplasms - genetics; Carrier Proteins - genetics; Carrier Proteins - physiology; Cell cycle; Cell growth; Cell lines; Cells; Cellular biology; Cloning, Molecular; Contact Inhibition; Cultured cells; DNA, Complementary - genetics; Epithelial cells; Female; Gene Expression Regulation, Developmental; Genes; Genes, Tumor Suppressor; Hepatocytes; Humans; Mammary Glands, Animal - cytology; Mammary Glands, Animal - growth & development; Mammary Glands, Animal - metabolism; Mammary Neoplasms, Experimental - genetics; Mice; Phenotype; Precancerous Conditions - genetics; Proteins; Repression; S Phase; Tumor Suppressor Proteins; Tumors; Ubiquitin-Protein Ligases
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.143.5.1329

BRCA1-associated RING domain (BARD1) was identified as a protein interacting with the breast cancer gene product BRCA1. The identification of tumorigenic missense mutations within BRCA1 that impair the formation of BARD1-BRCA1 complexes, and of BARD1 mutations in breast carcinomas, sustain the view that BARD1 is involved in BRCA1-mediated tumor suppression. We have cloned the murine Bard1 gene and determined that its expression in different tissues correlates with the expression profile of Brca1. To investigate the function of Bard1, we have reduced Bard1 gene expression in TAC-2 cells, a murine mammary epithelial cell line that retains morphogenetic properties characteristic of normal breast epithelium. Partial repression of Bard1, achieved by the transfection of TAC-2 cells with plasmids constitutively expressing ribozymes or antisense RNAs, resulted in marked phenotypic changes, consisting of altered cell shape, increased cell size, high frequency of multinucleated cells, and aberrant cell cycle progression. Furthermore, Bard1-repressed cell clones overcame contact inhibition of cell proliferation when grown in monolayer cultures and lost the capacity to form luminal structures in three-dimensional collagen gels. These results demonstrate that Bard1 repression induces complex changes in mammary epithelial cell properties which are suggestive of a premalignant phenotype.