Fig. 1. Cell death induction by combination treatment with a low-dose of STP and IR. A, cell viability in E1A/ras-transformed MEFs was determined by trypan blue exclusion 6 ({square}) and 24 h ({blacksquare}) after treatment with STP (20 nM) and IR (5 Gy) alone or in combination. B, proliferation was assessed with the alamar blue assay 24 h after treatment with STP (20 nM) and IR (5 Gy) alone or in combination.