Mononuclear bone marrow cells were obtained by gradient centrifugation and cultured in agar for 14 days. At days 0 and 7, antisense RB oligonucleotides (AS1) or control oligonucleotides (CO), respectively, were added at the indicated concentrations. At day 14, agar dishes were fixated and stained for unspecific esterase as a marker of monocytic differentiation. A colony (>40 cells) was defined as positive if all of its cells stained and mixed positive if a majority but not all of its cells stained. A colony was defined as negative if none of its cells stained and mixed negative if a minority of its cells stained. Values shown are percentages of colonies. Results shown represent the mean values from 3 separate experiments ± SEM.