Figure 4

Effects of MCF7 3-D spheroid formation and hypoxia on Pgp expression. Pgp protein levels were labeled on the surface of non-permeabilized cells and were quantified by FACS analysis as reported in Materials and Methods. A: Pgp protein levels were higher in MCF7 3-D spheroids (Spheroids), in MCF7 hypoxic cells (Monolayer Hypoxia), and in MCF7 cells transfected with MDR-1 gene (Monolayer Normoxia Pgp+) compared to Pgp protein levels in MCF7 control cells (Monolayer Normoxia). The incubation of cells with YC-1 (5 μMol/L for 24 h) decreased the Pgp surface expression in both MCF7 3-D spheroids and MCF7 hypoxic cells, while it had no effect in Pgp + cells. These figure panels are representative of three similar experiments. B: The percentage of positive cells for Pgp in MCF7 cells cultured as monolayers under normoxic conditions (Monolayer Normoxia), 3-D spheroids (Spheroids), monolayers under hypoxic conditions (Monolayer Hypoxia), and transfected with MDR-1 gene (Monolayer Normoxia Pgp+). Cells and spheroids were incubated in the absence (white columns) or in the presence (hatched columns) of 5 μM YC-1 for 24 h. ***, P < 0.0001 versus Monolayer Normoxia without YC-1; °°°, P < 0.0001 versus Spheroids or Monolayer Hypoxia without YC-1.