Epidermal growth factor receptors in the human glioblastoma cell line SF268 differ from those in epidermoid carcinoma cell line A431

Two established human tumor cell lines, epidermoid carcinoma line A431 and glioblastoma line SF268, were studied to compare the interaction of each with epidermal growth factor (EGF). SF268 cells bound [ 125I] EGF with 35–40 fold higher affinity than did the A431 cells. The EGF binding sites of both lines were photoaffinity labeled using 2,4-NAPS-[ 125I] EGF, a photoreactive derivative of EGF. Extracts of photolysed cells analyzed by SDS-PAGE showed a difference between the two cell lines in the high molecular weight component corresponding to the EGF receptor. EGF in a dose range from 0.3–200 nM had no effect on thymidine incorporation by SF268 cells, whereas thymidine incorporation by A431 cells was markedly inhibited by EGF.