Glucocorticoid/oxysterol-induced DNA lysis in human leukemic cells

Both glucocorticoids and oxysterols, steroids with quite different known transduction pathways, cause the death of lymphoid cells. Dual TUNEL/propidium iodide assays on sensitive human leukemic CEM-C7 clones treated with either steroid were clearly positive by 48 h, consistent with apoptosis. Both steroids evoked two distinctive types of DNA lysis: cleavage into large fragments of several different sizes and the classic “ladders”, multiples of ∼200 base pairs. Conventional gel electrophoresis showed that a small proportion of total DNA had undergone laddering 36–48 h after treatment with glucocorticoid or 24 h after oxysterol exposure. On field inversion gel electrophoresis of cellular DNA both steroids caused an increase in an array of large DNA fragments