Cell-cycle arrest–based antagonistic interaction between irradiation and VCR. CEM cells were irradiated with 6 Gy for 24 hours. Cell-cycle analysis was performed (left panel), and cells were stimulated with VCR for another 48 hours (right panel). *P < .05 (ANOVA). NS indicates not significant. The concentration of VCR, measurement of apoptosis, presentation of data, and statistical analysis were performed as described in Figure 1A.