Inhibition of Mer expression results in increased induction of apoptotic cell death in response to treatment with chemotherapeutic agents. Cultures of shControl or shMer1A 697 cells were exposed to 6-MP, VP-16, or medium only for 48 hours. Apoptotic and dead cells were identified by flow cytometric analysis of cells stained with YO-PRO-1 and propidium iodide as in Figure 3. (A) Representative flow cytometry profiles are shown. The percentages of apoptotic and dead cells are indicated in bottom right and top right quadrants, respectively. (B) Mean values and standard errors derived from 3 independent experiments are shown. Results were tested for significance using 2-way ANOVA and Bonferroni posttests to compare shControl and shMer1A cells at equivalent drug concentrations. Significant differences in apoptotic cell populations are indicated by asterisks (*P < .05, **P < .001). Significant differences in the number of dead cells were also observed (†P < .05, ‡P < .001).