Figure 6

Effects of 3-D spheroid formation and hypoxia on the doxorubicin accumulation in MCF7 cells. A: Cells and spheroids were incubated with 3 μMol/L doxorubicin for 18 h, in the absence (white columns) or in the presence (hatched columns) of 5 μmol/L YC-1 for 24 h (6 h alone and 18 h together with doxorubicin). Drug accumulation was then measured in MCF7 cell monolayers under normoxic conditions (Monolayer Normoxia), MCF7 3-D spheroids (Spheroids), MCF7 cell monolayers under hypoxic conditions (Monolayer Hypoxia), and MCF7 cells transfected with MDR-1 gene (Monolayer Normoxia Pgp+). ***, P < 0.0001 versus Monolayer Normoxia without YC-1; *, P < 0.05 versus Monolayer Normoxia without YC-1; °°°, P < 0.0001 versus Spheroids or Monolayer Hypoxia without YC-1. B: Cells and spheroids were transfected with 400 nM/L of HIF-1α (hatched columns) or transfected with vehicle alone (white columns), and incubated with 3 μMol/L doxorubicin for 18 h. Drug accumulation was then measured in MCF7 cell monolayers under normoxic conditions (Monolayer Normoxia), MCF7 3-D spheroids (Spheroids), MCF7 cell monolayers under hypoxic conditions (Monolayer Hypoxia), and MCF7 cells transfected with MDR-1 gene (Monolayer Normoxia Pgp+). ***, P < 0.0001 versus Monolayer Normoxia transfected with vehicle alone; *; °°°, P < 0.0001 versus Spheroids or Monolayer Hypoxia transfected with vehicle alone.