ATF3 mediates, in part, the enhanced cytotoxicity between M344 and cisplatin. A, A549 cells treated with cisplatin alone (0-10 μg/ml), or with M344 (1 μM) for 48 hrs were assessed for cell viability as measured by MTT activity. Data is represented as a percentage of MTT activity where untreated cells were taken to be 100%. Error bars are representative of six replicates of two independent experiments. B, A549 cells treated with solvent control, M344 alone (1 and 5 μM), cisplatin (2 μg/ml) alone or in combination with M344 (1 and 5 μM) were analyzed by Western blotting for ATF3, PARP and actin.