Previous studies in this laboratory have demonstrated that exposure to 5-Bromo-2- deoxyuridine (BrdU) induces differentiation in the lung epithelial cancer cell lines DLKP and A549. This induction o f differentiation was accompanied by increased protein expression of cytokeratins-8 and -18, a 2Pi integrin, cell-adhesion protein Ep- CAM, eukaryotic initiation factor eIF-4E and the transcription factors c-myc and YY1. Following exposure to BrdU, RT-PCR analysis identified large increases in the mRNA levels of MRP1, MRP3, BCRP, BAXa, MRIT, COX-2 and eIF-2a, together with smaller gene expression increases for MRP2, a-catenin and E-cadherin, in the DLKP cell line. Survivin gene and protein expression was decreased. Increased gene expression of MRP 1 and BCRP, as well as decreased MRP2, MRP4 and mdr-1 gene expression was observed in A549. DNA microarray analysis of BrdU-treated DLKP detected significantly increased gene expression of ETR103, p55CDC, Inil, NSEP, EB1, RPS19 and FNRB, and significantly decreased gene expression o f CREB2, c-myc, RPL6, TBP, CNBP, HIP116 and SOD1. RT-PCR analysis of the DLKP cells identified increased expression of the MRP1, MRP2 and BCRP genes following exposure to cisplatin, o f MRP2, a-catenin and Ecadherin following exposure to taxol and of MRP1, MRP2 and a-catenin following exposure to VP 16. These results suggested that patterns of gene induction following exposure to an inducing agent are specific for that agent. Transfac™ transcription factor analysis of the 5’ promoter regions of MRPs 1-3, BCRP, MRIT, COX-2, eIF-2a, a-catenin and E-cadherin identified seven potentially shared factors. These factors were GATAs 1-3, MZF1, Ik-2, CdxA and AML-la. RT-PCR analysis revealed increased GATA-2 and GATA-3 expression in BrdU-treated DLKP, but no change in BrdU-treated A549. RT-PCR analysis also revealed increased GATA- 2 expression in VP16-treated DLKP. Luciferase reporter plasmids attached to truncated regions of the MRP1 5’ promoter identified the major regulatory region in normal DLKP cells. This region encompassed -91 to +103 bases relative to the transcriptional start site. When the DLKP cells were treated with BrdU, luciferase production increased dramatically in another area of the promoter (beween -91 and -411 bases, relative to the transcriptional start). This region of the MRP1 contains a single GATA-2 transcription factor recognition sequence. A similar result was observed following exposure to VP 16. However, no significant change in luciferase readings was observed between BrdU-treated and untreated cells over the whole 2kb promoter, indicating that the major transcriptional target for BrdU is outside this region of the gene. RT-PCR analysis on a number o f human lung, breast and oesophageal tumour samples was carried out to examine the expression o f MRPs 1-6, BCRP, mdr-1, mdr-3, COX-1, COX-2, MRIT, BAXa, B c I -x l, B c l-x s , Bcl-2a, Survivin, BAG, BAP, eIF-4E, eIF-2a and c,-myc. A novel ribozyme to MRP1 was designed and was observed to cleave its intended target in an in vitro cleavage assay. The ribozyme was successfully transfected into MRP1- expressing DLKP-SQ cells. However, the transfections did not affect significantly neither MRP1 RNA or protein expression nor the drug resistance profiles of the cells. RNaseH activity assays for antisense oligonucleotides analyses were also successfully set up using an mdr-1 antisense. However, the identification of effective MRP1 antisense oligonucleotides was not made by either in vitro or in vivo studies.