Marrow stromal cells protect MCL cells from 4-HC-induced cytotoxicity. The mean viability of SP-53 cells (A) and MINO cells (B) treated with 4-HC is presented at the different time points displayed on the horizontal axis. MCL cell viability was increased when MCL cells were cocultured with M2-10B4 (), compared with MCL in suspension and without stromal cell support (). Results are presented as mean relative viability compared with untreated controls (100%) and are the mean ± SEM of triplicates. *Protection of MCL cells from 4-HC-induced cytotoxicity with significantly higher viabilities compared with controls (P < .05). (C) Contour plots that depict the viability of MINO MCL cells, as detected by staining with DiOC₆ and PI after 24 hours of culture with 10 μM 4-HC, in the presence or absence of M2-10B4 stromal cells, as indicated above each of the plots. The proportion of viable cells is indicated above each of the gates that define viable cells by bright DiOC₆ staining and PI exclusion.