Intragenic mutation analysis of the human epidermal growth factor receptor(EGFR) gene in malignant human oral keratinocytes

Alteration in epidermal growth factor receptor (EGFR) expression is frequen tly associated with malignant transformation of epithelial tissues, includi ng oral mucosa, This study examines the mutations in the coding region of t he human EGFR gene in normal and malignant human oral keratinocytes, To exa mine the intragenic mutations in the human EGFR gene, a panel of normal and malignant human oral keratinocytes were examined by a nonisotopic RNase cl eavage assay. Two consistent alterations were detected, First, a polymorphi sm, which generates a unique BsrI. restriction site, was detected at positi on 2073, This BsrI polymorphism was present only in malignant keratinocytes , Second, Southern blot hybridization of PCR products revealed that there i s a truncated EGFR mRNA (similar to 1.5-kb) in oral squamous cell carcinoma cell lines. Similar analysis in normal cell lines revealed that this trunc ated EGFR transcript is also present, Immunoblotting revealed the presence of this truncated form of EGFR in all keratinocyte cell lines. These data p ermit us to conclude that there exists a novel truncated form of EGFR in hu man oral keratinocytes, Furthermore, there exists a tumor-associated EGFR p olymorphic site at position 2073, The potential biological relevance of the truncated receptor and the utility of the BsrI polymorphic site for diagno stic applications are currently being explored.