Exposure of M1.WT1 +KTS cells to LIF results in the rapid onset of apoptotic cell death. M1 cell populations were cultured in the presence or absence of LIF (1 ng/mL) for the indicated timepoints and assessed for chromosomal DNA fragmentation by electrophoresis of the extracted DNA on 2% agarose gels, with the size and position of the ◊X174/HaeIII molecular weight markers indicated to the left of the gels.