Kinetics of ATO-induced up-regulation of R1 and R2 APO2/TRAIL receptors in HS-Sultan cells.
HS-Sultan cells were cultured (0.4 × 106/mL) in RPMI medium plus 15% FCS for 0, 6, and 12 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. The thin dotted line is the immunoglobulin isotype-matched control (C); the dashed line represents time 0; the thin solid line represents 6 hours with ATO; and the thick solid line represents 12 hours with ATO. R1 to R4 are antibodies to the various APO2/TRAIL receptors; 10 000 cells were analyzed in the live cells gate determined by light scatter. For additional experimental details, see “Materials and methods.” It is clear that ATO up-regulates the expression of R1 and R2 APO2/TRAIL receptors as early as 6 to 12 hours after induction.
