FDC-SM-4G10/CD44 protects L3055 cells from spontaneous apoptosis. (A) HK cells rescue L3055 cells from spontaneous apoptosis. L3055 cells (1 × 104 cells/well) were cultured in the presence of different concentrations of HK cells for 72 hours as indicated. L3055 cells were pulse stained with DiOC6(3) 15 minutes before harvesting. DiOC6(3) staining was analyzed by FACS (▪), and viable L3055 cells were counted by a trypan blue exclusive assay (□). (B) Blocking of CD44 molecule augments L3055 cell apoptosis. L3055 cells (1 × 104 cells/well) were cultured with mAb-pretreated HK cells (2 × 104 cells/well) as indicated. DiOC6(3) staining was performed as described earlier. DiOC6(3)-negative cell percentages from 1 of 3 similar experiments are shown. (C) Localization of GFP-CD44 on HK cells where L3055 cells make contact (arrows). HK cells were transfected with GFP-CD44, and L3055 cells were labeled with SNARF-1 as described in “Materials and methods.” After centrifugation, cell-cell contact was investigated under a deconvolution microscope using SlidBook software. Original magnification, × 630.
