Staurosporine induces the cell surface expression of both forms of human tumor necrosis factor receptors on myeloid and epithelial cells and modulates ligand-induced cellular response.

Staurosporine, an inhibitor of protein kinase C, is commonly used to inhibit the growth factor-induced signal transduction pathway at the post-receptor level. In this report, we examined the effect of staurosporine on the constitutive expression of tumor necrosis factor (TNF) receptors in K562, a human erythroblastoid leukemic cell line. Exposure of these cells to staurosporine enhanced cell surface expression of TNF receptors by almost 7-fold in a dose- and time-dependent fashion. Maximum induction occurred at a concentration of 20 nM of the agent for 16 h at 37 degrees C. Induction of the TNF receptor was found to be temperature-dependent. No induction was observed at 22 or at 4 degrees C, suggesting the role of cell metabolism. Scatchard analysis indicated an increase in receptor number without any change in receptor affinity. TNF receptors were induced by staurosporine on a wide variety of human cells of both epithelial (primarily p60 receptors) and myeloid (mainly p80 receptor) origin. Receptor-specific antibodies showed that both TNF receptors were induced. The induction was abolished by inhibitors of protein synthesis, thus suggesting the de novo synthesis of the receptor. Furthermore, we found that staurosporine had no effect on the internalization or shedding of the receptor, but it induced the mRNA for both forms of the TNF receptor. Inhibitors of tyrosine kinases had no effect on the induction of TNF receptors. Modulation of the receptor number by staurosporine correlated with the enhancement of antiproliferative effects of TNF against different tumor cells. Thus, overall these results indicate that protein kinase C may be involved in the signal transduction of TNF not only at the postreceptor level but also at the receptor level.