Effect of Epidermal Growth Factor (EGF) on a Newly Established Head and Neck Squamous Carcinoma Cell Line

A new cell line designated 584A2 has been recently established from a patient with squamous cell carcinoma of the larynx. Cytogenetic analysis of the cell line revealed multiple copies of chromosome 7, as well as a homogeneous staining region (HSR) on one chromosome 7. Since overexpression of epidermal growth factor (EGF) cell surface receptors (EGFr) often occurs in other squamous carcinoma cell lines, it was predicted that 584A2 might overexpress EFGr. This was confirmed by: (1) metabolic labeling, with subsequent immunoprecipitation of EGFr and comparing autoradiographs to a cell line without an HSR and fewer copies of chromosome 7, and (2) performing EGF binding assays with Scatchard analysis. Since overexpression of EGFr correlates with an inhibitory effect of EGF on cell culture, the biological effects of EGF on 584A2 were examined in this study. At 5 ng/ml (serum-free medium), EFG stimulated incorporation of [3H] thymidine into trichloroacetic acid-precipitable material compared with controls. Incorporation increased between days 0 to 1 and 1 to 2 days with a 6- to 7-fold maximum. Dose-response studies (0 to 100 ng/ml) indicated maximum incorporation (6- to 7-fold) occurred between 0.1 ng/ml and 1.0 ng/ml. Cell growth was monitored over 7 days and, during this time, 5 ng/ml EGF produced a 10- to 12-fold increase in absolute cell numbers when compared with controls. We concluded that, unlike other squamous carcinoma lines with elevated EGFr, EGF stimulates rather than inhibits 584A2 cell proliferation.