ATO enhances the expression of R1 and R2 APO2/TRAIL receptors in IM9 cells.

IM9 cells were cultured for 24 hours with 4 μM ATO. Surface expression of APO2/TRAIL receptors was determined by indirect staining with monoclonal antibodies specific for R1, R2, R3, and R4 APO2/TRAIL receptors. (A) Untreated cells; (B) ATO-treated cells. The thick line is the corresponding antibody, and the thin line is the corresponding immunoglobulin isotype control. For additional experimental details, see “Materials and methods” and the legend to Figure 10. ATO up-regulates the expression of R1 and R2 APO2/TRAIL receptors and down-regulates the expression of R3 and R4 decoy receptors, resulting in a net increase in the number functional TRAIL receptors.