Figure 4

Assessment of the viability of the caspase-8^+/+ and caspase-8^−/− mouse embryonic fibroblasts (MEFs) in agar tests. (a) Cell viability in the soft agar test. MEFs that were suspended in agar as described for Figure 3, and then showed positive staining with the vital dye calcein-AM in a representative pair of WT (empty squares), and KO (filled squares) MEFs in at least four randomly chosen microscopic fields (× 10) were counted. In each case the value (mean±S.D.) of the obtained count, relative to that determined immediately after plating (day 0), was plotted as a function of the time following seeding in agar. (b, c) Cell viability in a semi-solid agar test. (b) Representative histogram of annexin-V staining of a pair of WT and KO MEFs, before and after growth for 3 days in semi-solid agar culture. The extent of cell death (% of annexin-V-positive cells) is indicated at the top of the histograms. (c) Quantification of the annexin-V-staining level, assessed as in (b), for a number of independent MEF strains (indicated by ‘n’) having either the WT (empty squares) or the KO (filled squares) genotype, grown in semi-solid soft agar cultures (broken gray lines). Mean values±S.D. are indicated by a solid line