Immunofluorescence analysis in NB4 (a through c) and Zn-induced U937/PR9 cells (e through g) using the PG-M3 anti-PML monoclonal antibody. Control cells (a and d) and cells treated for 96 hours with 1 μmol/L RA (b and e) or 1 μmol/L RA + 100 μmol/L DEVD (c and f).