The tumor suppression activity of E1A in HER-2/neu-overexpressing breast cancer

Oncogene. 1997 Feb 6;14(5):561-8. doi: 10.1038/sj.onc.1200861.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenovirus E1A Proteins / biosynthesis
  • Adenovirus E1A Proteins / metabolism*
  • Adenoviruses, Human
  • Adipose Tissue
  • Animals
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology*
  • Cell Division
  • Cell Line
  • Female
  • Genes, Reporter
  • Genetic Vectors
  • Humans
  • Mammary Glands, Animal
  • Mice
  • Mice, Nude
  • Receptor, ErbB-2 / biosynthesis*
  • Recombinant Proteins / biosynthesis
  • Transfection
  • Transplantation, Heterologous
  • Tumor Cells, Cultured
  • beta-Galactosidase / biosynthesis


  • Adenovirus E1A Proteins
  • Recombinant Proteins
  • Receptor, ErbB-2
  • beta-Galactosidase