Heterologous Epidermal Growth Factor Receptor (EGF-R) Expression in Larynx Cancer Cell Lines: Evidence for the Existence of Structurally Modified Receptors

Abstract

Overexpression of epidermal growth factor receptor (EGF-R) is a common characteristic of epidermoid tumors and its expression in head and neck squamous cell carcinoma biopsies and cell lines has been reported previously by several authors. With the aim to provide more structural and functional details about the protein overexpression of EGF-R in head and neck squamous cell carcinomas, the expression of this molecule was studied in four larnyx carcinoma cell lines (HLaC-78, HLaC-79, UM-SCC-17A and UM-SCC-17B). The results were compared with those from a spontaneously immortalized aneuploid human keratinocyte cell line (HaCaT) and cultured fresh skin keratinocytes. The EGF-R identification was performed using two well characterized monoclonal antibodies (MoAb) which recognize antigen determinants located on the extracellular domain of the receptor: EGF-R I and 29.1.1. Cytocentrifuge smears and cell suspensions were prepared for flow cytometric analysis. With the monoclonal antibody EGF-R I the highest EGF-R expression was obtained in the cell line UM-SCC-17A, whereas the cell line with the highest EGF-R overexpression was the HLaC-78 if the monoclonal antibody 29.1.1 was used. The cultured keratinocytes always showed a histogram similar to the control sample (cells were incubated with the second antibody alone). These results could be explained by the existence of structurally modified EGF-receptors. Further studies including possible differences in both the autophospho-rylization and the kinase activities are in progress to clarify the functional repercussions of these observed structural defects.

Key Words:

• epidermal growth factor receptor
• head and neck squamous cell carcinoma
• flow cytometric analysis