NORMALIZATION OF EGFR MESSENGER-RNA LEVELS FOLLOWING RESTORATION OF WILD-TYPE P53 IN A HEAD AND NECK SQUAMOUS-CELL CARCINOMA CELL-LINE

Head and neck squamous cell carcinoma (HNSCC) is frequently characteri zed by mutation of the p53 tumor suppressor gene and increased express ion of the epidermal growth factor receptor (EGFR). To determine the p otential link between p53 and EGFR expression, we examined the effect of overexpressing wild-type p53 on EGFR mRNA levels in HNSCC. In these studies, a temperature-sensitive (ts) p53 mutant was transfected into an HNSCC line which contained a deletion of one allele of the p53 gen e and a mutation of the remaining allele. Following selection, six clo nes were isolated, characterized by Southern blot analysis, and stable expression of mutant p53 protein was confirmed by immunoblotting of c lones grown at the mutant temperature. Total RNA was isolated from tra nsfectants grown at both wild-type or mutant temperatures followed by Northern blot analysis to determine levels of EGFR mRNA expression at the two p53 conformations. Clones grown at the wild-type temperature ( 32.5 degrees C) demonstrated a 69%+/-13% decrease in EGFR mRNA compare d with the same cells grown at the mutant temperature (39.5 degrees C; p=0.006) indicating that restoration of wild-type p53 reduces EGFR mR NA levels in this HNSCC cell line. These findings suggest that abnorma lities in p53 may contribute to activation of EGFR gene transcription.