Altered expression of genes in AP4 knockdown and overexpression

The transcription factor AP4/TFAP4/AP-4 is a ubiquitously expressed basic helix-loop-helix leucine-zipper (bHLH-LZ) transcription factor, which forms homodimer that binds to the consensus E-box motif 5-CAGCTG-3. Prostatic adenocarcinoma (PAC), also known as prostate cancer, is the second most common malignancy of men with 914,000 new cases and approximately 258,000 deaths worldwide in 2008. The goal of this study is to identify the target genes of AP4 in prostate cancer. Our results demonstrated that the genes regulated by AP4 are involved in a variety of biological functions, such as proliferation and invasion. We used microarrays to detail the different expression of genes in AP4 knockdown and overexpression and identified distinct classes of up-regulated genes during this process. Prostate cancer cell line PC-3 was transfected with the control siRNA or AP4 siRNA for 48h. In addition, we applied with AP4, AP4△bHLH adenovirus and empty vector virus transfected PC-3 cell. The RNA of the transfected cells was extracted and hybridized on Affymetrix microarrays. We identified the putative target genes of AP4 in both knockdown and overexpression by comparing the different expressed genes among si-NC vs. si-AP4; AP4 vs. AP4△bHLH vs. vector. We further validated the data of microarray in PC-3 and LNCaP by qPCR and Western blotting.