title: The tumor suppression activity of E1A in HER-2/neu-overexpressing breast cancer.
abstract: The HER-2/neu proto-oncogene is frequently amplified or overexpressed in human breast and ovarian cancers, and is significantly correlated with shorter survival. We have previously reported that the adenovirus type 5 early region 1A (E1A) gene product can repress HER-2/neu overexpression by repressing HER-2/neu promoter activity, and suppress the tumorigenic potential of HER-2/neu-overexpressing ovarian cancer cells. To examine E1A tumor suppressor function in breast cancer, we transduced E1A in vitro by adenovirus into both HER-2/neu-overexpressing and low expressing human breast cancer cell lines. In HER-2/neu-overexpressing cells, E1A greatly inhibited tumor cell growth in vitro. However, in HER-2/neu low expressing cancer cell lines, E1A had no significant effect on cell growth in culture medium. To test the therapeutic efficacy of E1A, we used both adenovirus-mediated and cationic liposome-mediated E1A gene delivery systems in an orthotopic breast cancer animal model. An advanced breast cancer model was established by inoculation of HER-2/neu-overexpressing human breast cancer cells in mammary fat pad and treated by local injections of either replication-deficient adenovirus expressing E1A, Ad.E1A(+) or a liposome-E1A DNA complex. As controls, mice bearing tumors were also treated with Ad.E1A(-) which is virtually the same adenovirus as Ad.E1A(+) except that E1A is deleted, a liposome-E1A frame-shift mutant DNA complex, or just PBS. In mice bearing a HER-2/neu-overexpressing breast cancer cell line, E1A delivered either by adenovirus or liposome significantly inhibited tumor growth and prolonged mouse survival compared with the controls. In fact, 60-80% of E1A-treated mice lived longer than 2 years versus only 0-20% of control mice (P<0.05). Western blot analysis showed that E1A protein was expressed in tumor tissue and immunohistochemical analysis showed that HER-2/neu p185 protein expression was suppressed. Taken together, our results indicated that both adenovirus and cationic liposome delivery systems were effective in transfering E1A gene for tumor suppression in a HER-2/neu-overexpressing breast cancer model.
authors.affiliation: Department of Tumor Biology and Breast Cancer Basic Research Program, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: J Y
authors.initials: JY
authors.lastname: Chang
authors.forename: W
authors.initials: W
authors.lastname: Xia
authors.forename: R
authors.initials: R
authors.lastname: Shao
authors.forename: F
authors.initials: F
authors.lastname: Sorgi
authors.forename: G N
authors.initials: GN
authors.lastname: Hortobagyi
authors.forename: L
authors.initials: L
authors.lastname: Huang
authors.forename: M C
authors.initials: MC
authors.lastname: Hung
mesh_terms: D017500:Adenovirus E1A Proteins / Q000096:biosynthesis / Q000378:metabolism*; D000260:Adenoviruses, Human; D000273:Adipose Tissue; D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D002455:Cell Division; D002460:Cell Line; D005260:Female; D017930:Genes, Reporter; D005822:Genetic Vectors; D006801:Humans; D008321:Mammary Glands, Animal; D051379:Mice; D008819:Mice, Nude; D000090063:Proto-Oncogene Mas; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000096:biosynthesis; D014162:Transfection; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured; D001616:beta-Galactosidase / Q000096:biosynthesis
chemical_list: D017500:Adenovirus E1A Proteins; D000090063:Proto-Oncogene Mas; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins; D001616:beta-Galactosidase; C000715470:MAS1 protein, human