Tumor necrosis factor α and γ interferon enhancement of anti-epidermal growth factor receptor monoclonal antibody binding to human melanoma cells

Previous studies have demonstrated that the expression of tumorassociated antigens can be regulated by cytokines. The purpose of this study was to determine whether tumor necrosis factor aα (TNFα) and 7-interferon (IFNγ) were capable of modulating epidermal growth factor receptor (EGFr) immunorecognition on a human melanoma cell line in vitro. DX-3 melanoma cells treated for 24-72 h with various concentrations of each cytokine were incubated with an anti-EGFr monoclonal antibody (Mab) (A108) that recognizes an extracellular domain of the receptor, and differences in binding were analyzed by flow cytometry and radioimmunoassay. A dose- and timedependent enhancement in EGFr immunorecognition was measurable in TNFα- and IFNγ-treated cells. Combinations of these cytokines enhanced the recognition of EGFr on DX-3 cells to a level greater than that achieved with either TNFα or IFNγ alone. Scatchard analysis of receptor binding curves revealed that there was no significant change in Mab affinity between control and cytokine-treated DX-3 melanoma cells, whereas a 1.5- to 1.8-fold enhancement in the number of Mab binding sites was measurable in TNFα- and IFNγ- treated cells, respectively, when compared with controls. Immune complex kinase assay of EGFr showed threefold higher tyrosine kinase activity in TNFα-treated cells, but no change in kinase activity was observed following IFNγ treatment. Similar studies of cytokine action on EGFr expression in squamous A431 cells demonstrated up-regulation of receptor when analyzed by Western blotting and receptor binding studies, but the effects appeared to differ in magnitude and time course of induction when compared to melanoma cells. These studies suggest that cytokines such as TNFα and IFN7 may modulate immunorecognition and expression of EGFr protein on DX-3 melanoma cells and squamous carcinoma A431 cells, but may function through distianct mechanisms and with differential metabolic effects.