FACTORS AFFECTING TOPOTECAN-INDUCED PROGRAMMED CELL-DEATH - ADHESION PROTECTS CELLS FROM APOPTOSIS AND IMPAIRS CLEAVAGE OF POLY(ADP-RIBOSE)POLYMERASE

We have evaluated the influence of anchorage status together with endo genous Levels of bcl-2 family members on the ability of the topoisomer ase I inhibitor, topotecan (TPT), to induce programmed cell death (PCD ) in human colon, breast, lymphoid, and cervical cancer cell lines, As part of this study, we assessed the use of measuring poly(ADP-ribose) polymerase (PARP) cleavage by Western blot, as an index of apoptosis, relative to measuring chromatin condensation by acridine orange analy sis, Our results show a strong correlation between both assays, indica ting that PARP cleavage is an accurate method to examine PCD, We have encountered a strong association between cell attachment and sensitivi ty to TPT-induced PCD. Cells growing attached to flasks appear to be r elatively more resistant than suspension-growing cells in spite of end ogenous bcl-2, bar, or bcl-x levels, Furthermore, we demonstrate that interference with attachment status alters the sensitivity of cells to TPT-induced PCD, Although cell attachment to ProNectin F confers prot ection against TPT-induced chromatin condensation and cleavage of PARP , cell detachment by poly(2-hydroxyethyl methacrylate) stimulates TPT- induced PCD and PARP cleavage.