Cytokines modulate expression of cell-membrane complement inhibitory proteins in human lung cancer cell lines

Human lung cancers overexpress several cell-membrane complement inhibitory proteins (CIP). These complement inhibitory proteins are membrane cofactor protein (CD46), decay-accelerating factor (DAF; CD55), and CD59 (protectin). These cell-membrane proteins have a wide normal tissue distribution, are known to protect normal host cells from homologous complement-mediated lysis, and are thought to facilitate tumor escape from immunosurveillance. To study whether proinflammatory cytokines that are involved in cancer growth can modulate cell-membrane CIP expression in lung cancer cells, we studied the effect of interleukin (IL)-1alpha, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma on two human lung cancer cell lines. ChaGo K-1 and NCI-H596 cell lines, undifferentiated carcinoma and lung adenosquamous carcinoma, respectively, were stimulated with different cytokines, and the effects of incubation time and cytokine concentration on cell-membrane CIP expression were studied. Cell-membrane CIP expression was evaluated using flow cytometry and cytokine effect was calculated as percent change in mean fluorescence intensity of each CIP molecule from its untreated control. We found that DAF was the lung cancer cell-membrane CIP molecule that was the most responsive to cytokine stimulation. Maximal stimulatory effect was usually noted 72 h after a cytokine was introduced. In ChaGo K-1 and NCI-H596 lung cancer cell lines, IL-1alpha and TNF-alpha increased DAF expression. IL-1alpha (100 U/ml/72 h) increased DAF expression up to a maximal mean of 45 and 48%, respectively, in comparison with untreated cells. TNF-alpha (1, 000 U/ml/72 h) increased DAF expression up to a mean of 131 and 46%, respectively. IFN-gamma (1 U/ml/72 h) increased DAF expression in NCI-H596 cells up to a mean of 100%, but had a slight inhibitory effect on DAF expression in ChaGo K-1 cells, decreasing expression by a mean of 17% in comparison with untreated cells. We conclude that cell-membrane DAF expression in the studied human lung cancer cell lines is modulated by IL-1alpha, TNF-alpha, and IFN-gamma, and speculate that cytokine-mediated modulation of cell-membrane DAF in human lung cancer cells might affect lung cancer cell biology.