4T1 SP cells are more chemoresistant than non-SP cells. (A-C) 4T1 cells were cultured in the presence of DMSO, Dox, or CDDP for 24 hours, followed by staining with Hoechst 33342 dye, and analyzed by FACS. Gates represent the SP and non-SP in each figure. (D-F) In addition to Hoechst 33342 dye, cells were also stained with the CaspaTag pan-caspase inhibitor FLICA to determine the extent of apoptosis occurring in each compartment by FACS. (G) Doxorubicin-treated cells were analyzed by FACS to quantitate the level of intracellular doxorubicin within each compartment. Each figure represents 1 of 3 experiments.