title: E1A-mediated suppression of EGFR expression and induction of apoptosis in head and neck squamous carcinoma cell lines.
abstract: Previous studies have shown early region 1A (E1A) gene to inhibit the proliferation of tumour cells with wild-type, but not mutant, p53. E1A has also been shown to downregulate c-erb-B-2/neu expression, resulting in inhibition of growth in c-erb-B-2/neu overexpressing tumour cells. In this study, we have investigated the effect of E1A expression on four head and neck squamous cell carcinoma (HNSCC) cell lines that do not overexpress c-erb-B-2/neu. Cell cycle and Western blot analysis show E1A-mediated induction of apoptosis in all cell lines examined. This induction of apoptosis was independent of the p53 status as it occurred in the cell lines with wild-type, mutated or deleted p53. However, there was no evidence of E1A-induced apoptosis in a p53(+ve) normal human fibroblast cell line, 1BR3. Analysis of apoptosis in the SCC cell lines demonstrated E1A-mediated downregulation of EGFR, which was overexpressed in each of these cell lines. Overexpression of an exogenously introduced EGFR, under the control of an E1A-insensitive heterologous promoter, blocked E1A induction of apoptosis in these cells. Therefore, E1A-mediated downregulation of EGFR expression appears to be the cause, rather than a consequence of E1A-induced apoptosis in these SCC cell lines. Previous studies have shown downregulation of EGFR expression by PML. Interestingly, E1A expression in the HNSCC cells altered the pattern of PML distribution and induced the level of PML protein, thus suggesting that E1A-mediated downregulation of EGFR may occur via direct or indirect interactions with PML. These findings demonstrate a novel pathway by which E1A can induce apoptosis and identify EGFR as a potential target for the development of therapeutic strategies against epithelial malignancies, the majority of which have abnormal EGFR expression.
authors.affiliation: Department of Oral Medicine and Pathology, King's College London, The Rayne Institute, UK.
authors.forename: Marcella
authors.initials: M
authors.lastname: Flinterman
authors.forename: Joop
authors.initials: J
authors.lastname: Gäken
authors.forename: Farzin
authors.initials: F
authors.lastname: Farzaneh
authors.forename: Mahvash
authors.initials: M
authors.lastname: Tavassoli
mesh_terms: D017500:Adenovirus E1A Proteins / Q000502:physiology*; D017209:Apoptosis / Q000235:genetics*; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000473:pathology*; D002453:Cell Cycle; D002455:Cell Division; D015536:Down-Regulation; D066246:ErbB Receptors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology; D015972:Gene Expression Regulation, Neoplastic; D006258:Head and Neck Neoplasms / Q000235:genetics / Q000473:pathology*; D006801:Humans; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D000071156:Promyelocytic Leukemia Protein; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015398:Signal Transduction; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D025521:Tumor Suppressor Proteins
chemical_list: D017500:Adenovirus E1A Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D066246:ErbB Receptors