Aims of this study are to investigate the differential gene expression caused by a carcinogen. the hypothesis is that by employing suppressive subtractive hybridization PCR (SSH PCR), we may identify novel rare up- and down-regulated transcripts that are missed in conventional microarray and proteomic analyses. the authors exposed a non-cytotoxic dose of benzo[a]pyrene (BaP) . to AhR-deficient Jurkat cells and investigated the cellular response in genome-wide gene expression. After treating the cells with 2.5 pM BaP for 48h, the authors isolated mRNA for SSH PCR analysis. the authors screened approximately 15,000 clones to obtain a final of 41 positive clones (20 up- and 21 down-regulated clones). The use of this approach to identify the regulated transcripts which was validated by real-time qPCR. Among these 41 transcripts, the authors observed that 27 of them are related to cell growth, DNA repair, and gene regulation
3 of them (TCF7, DOCK2, and ZAP70) are related to immune response. Two ot'the down-regulated transcripts BCL2 and TCF7 have been reported to be also down-regulated by cigarette smoke and the rest are novel BaP-regulated transcripts. the data suggested that Jurkat cells are sensitive to DNA damage at a non-cytotoxic dose of BaP because of Jurkat cells down-regulate genes (SART1, SNRK, HIRA, and BCL2) that promote cell growth and up-regulate DNA repair related genes (GTF2H2 and RNASEH1). In addition, immune response is suppressed even though no apparent change in morphology has been observed when comparing the BaP-treated cells with the untreated cells.