Widespread epidemiological data support the notion that high isoflavoves intake is safe and provides health benefits similar to estrogen. Isoflavones have been reported to regulate genes that are involved in several cellular events, such as control of cell proliferation, cell cycle, cell apoptosis, transcription regulation, cancer invasion and metastasis and so on. Previously, soy isoflavones have been demonstrated to have a tumor suppressor effect on bladder cancer. We earlier identified 71 candidate bladder tumor suppressors by using the isoflavones treatment vs. non-treatment in RT4 (Stage I, TMN) cells in conjunction with the strategy of suppression subtractive cDNA libraries. In a preliminary screening, epithelial membrane protein 2 (EMP2) mRNA was downregulated in higher TMN-grade bladder tumor cells. In this study, we aim at the mechanism of isoflavones upregulation of the candidate bladder tumor suppressor: EMP2. In order to clarify the regulatory mechanism, we have constructed a series of 5¡¦ deletion fragment of EMP2 promoter (-1,420 to +268 bp) into a luciferase reporter plasmid pGL3-baisc and analyzed the promoter activity. The rapidly loss of the promoter activities when the region between pH (-44 to +268) and pI (-24 to +268) is deleted, suggesting that at least one critical transcriptional factor binding site may exist between -44 to -24 bp region. By bioinformatics, the transcription factor CREB1 binding site is predicted in the critical region. The ChIP assay and site-directed mutagenesis of the CREB site reveal its critical role for the EMP2 transcription. The EMP2 mRNA is downregulated after knock-down of CREB1 protein by shCREB1 in J82 cells. It can be evidence for EMP2 transcription is regulated by transcription factor CREB1. In investigations of genistein (one component of isoflavones) up-regulated EMP2 transcripts, we find there are consistent results for genistein upregulated of EMP2 promoter region. In conclusion, transcription factor CREB1 plays an important role in the regulation of EMP2 transcription.