[Enhancement of epidermal growth factor receptor (EGF-R) expression on glioma cells by cytokines]

Recombinant tumor necrosis factor alpha (TNF-alpha) significantly enhanced epidermal growth factor receptor (EGF-R) expression in U373-MG glioma cell line as determined by binding of anti-EGF-R monoclonal antibody (MAb) 425. The optimal dose of TNF-alpha was 1000 U/ml of media. When TNF-alpha was combined with recombinant interferon gamma (IFN-gamma), further upregulation of EGF-R was observed. However, IFN-gamma itself did not show any EGF-R enhancement in this cell line. Scatchard analysis of receptor binding revealed that this enhancement of EGF-R expression was due to an increase in the EGF-R density. TNF-alpha did not affect expression of other brain tumor-associated antigens defined by MAb ASHE2, ASHG4 and ASAY1. Cultured fibroblasts showed no upregulation of EGF-R by TNF-alpha, suggesting a differential effect of TNF-alpha on EGF-R expression on glioma cells and normal cells. We investigated whether TNF-alpha treatment of glioma cells increased the tumoricidal effects of radiolabeled MAb 425 which correlate with MAb density on tumor cell surfaces. Growth inhibition of glioma cells in culture by 125I-labeled MAb 425 was significantly enhanced after treatment of the cells with TNF-alpha. In previous clinical trials, 125I-labeled MAb 425 has shown immunotherapeutic effects in glioma patients. The present study provides the basis for considerations of combined immunotherapy of glioma patients with 125I-labeled MAb 425 and cytokines.