Previously, we employed a proteomics-based 2-D gel electrophoresis assay to show that exposure to 10 μM benzo(a)pyrene (BaP) during a 24 h frame can lead to changes in nuclear protein expression and alternative splicing.To further expand our knowledge about the DNA damage response (DDR) induced by BaP, we investigated the nuclear protein expression profiles in HeLa cells treated with different concentrations of BaP (0.1, 1, and 10 μM) using this proteomics-based 2-D gel electrophoresis assay.We found 125 differentially expressed proteins in BaP-treated cells compared to control cells.Among them, 79 (63.2%) were down-regulated, 46 (36.8%) were up-regulated;8 showed changes in the 1 μM and 10 μM BaP-treated groups, 2 in the 0.1 μM and 10 μM BaP-treated groups, 4 in the 0.1 μM and 1 μM BaP-treated groups, and only one showed changes in all three groups.Fifty protein spots were chosen for liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification, and of these, 39 were identified, including subunits of the 26S proteasome and Annexin A1.The functions of some identified proteins were further examined and the results showed that they might be involved in BaP-induced DDR.Taken together, these data indicate that proteomics is a valuable approach in the study of environmental chemical-host interactions, and the identified proteins could provide new leads for better understanding BaP-induced mutagenesis and carcinogenesis.