Epidermal growth factor (EGF), which stimulates tyrosine-specific protein kinase activity both in vivo and in vitro, inhibits proliferation of A431 human epidermoid carcinoma cells.
In this study, a variety of squamous cell carcinomas were examined and one, SCC-15, contained high levels of the EGF receptor as determined by immunoprecipitation via an EGF receptor-specific polyclonal antibody.
Thus, the protein products of the amplified c-erbB-2 gene may have a role in the evolution of adenocarcinomas, as does the EGF receptor in some squamous-cell carcinomas.
Six cell lines (3 adenocarcinomas, 2 squamous cell carcinomas and 1 small cell carcinoma) expressed EGF receptor gene and its product to a significant level without gene amplification, and the other three cell lines were found to be negative as regards expression.
Enhanced mRNA expression was found only in one squamous cell carcinoma cell line, which is known to have high levels of epidermal growth factor receptor.
Southern blot analysis of a subset of the tumours detected amplification of the EGF receptor gene in squamous cell carcinomas but not in adenocarcinomas.
Interestingly, DNA from both primary and secondary transformants of one particular human squamous cell carcinoma contained highly amplified copies of the Ha-ras oncogene.
This study presents the results of cytophotometric (CPM) and flow cytometric (FCM) DNA ploidy measurements in cervical intraepithelial neoplasias grade III (CIN III) with and without synchronous invasive squamous cell carcinoma.
PMA elevates EGF receptor mRNA levels in human KB epidermoid carcinoma cells, but does not significantly affect the half-life of this mRNA when its decay is examined after the addition of actinomycin D. In contrast, EGF greatly prolongs the half-life of EGF receptor mRNA suggesting a possible mechanism for the stimulatory effect of EGF on EGF receptor mRNA levels.
We have studied in vitro transcription of the human epidermal growth factor (EGF) receptor proto-oncogene using nuclear extracts of A431 human epidermoid carcinoma cells, which overproduce the EGF receptor.