Treatment of the DF cells with doxorubicin (DOX). The number of surviving cells was greatly reduced as the duration of DOX (1 µM) incubation was increased from 2 hrs (B), to 4 hrs (C), and to 6 hrs (D), as compared with the control without DOX treatment (A). The placement of cells treated with DOX for 4 hrs in an adipogenesis induction medium resulted in the majority of the cells forming Oil Red O-positive adipocytes (arrow) (E), whereas in the controls not treated with DOX, but placed in adipogenesis induction medium, the majority of the cells remained undifferentiated, with only a few forming adipocytes (arrow) (F). The results suggest that DOX kills the non-stem cells, and that adipocytes are derived from the stem cells. (This Figure appears in color in the online version.)