PRSS23 Is an Estrogen Induced, AP-1-Dependent Gene in MCF-7 Breast Cancer Cells.
Authors: Mayer J. , Wang C. , Rodenberg J. , Brown P. 
Published: December 2010

Background: Breast cancer is the second leading cause of cancer related deaths among women in the United States. While estrogens have been documented to play a role in the etiology and progression of breast cancer through a “classical” pathway by binding to the estrogen receptor which in turn binds at estrogen response elements (EREs) within gene promoters, the mechanisms by which estrogens stimulate breast cancer growth are poorly understood. Estrogens have also been shown to stimulate transcription by interacting with other transcription factors such as AP-1, SP-1 or NFκB through a “non-classical” pathway. We have shown previously that estrogen can stimulate breast cancer cell growth by activating gene expression independently of ERα binding directly to the DNA. We also previously used microarray analysis to identify a set of genes that are induced by estrogen and that are dependent on AP-1 for their induction. One of these ER and AP-1-dependent genes is PRSS23. We hypothesized that many growth regulatory estrogen-induced genes are induced through these non-classical pathways via crosstalk with the AP-1 transcription factor. To test this hypothesis, we investigated the role of AP-1 in the up-regulation of one estrogen responsive gene, PRSS23.Methods: qPCR was used to establish the estrogen and AP-1 responsiveness of PRSS23 following treatment of MCF7 cells with 1nM estradiol (E2) and 100nM TPA respectively. Antibodies specific to ERα (Santa Cruz), cJun/AP-1 (Oncogene), cFos (Santa Cruz), and pan-Fos (Santa Cruz), with rabbit IgG (Santa Cruz) as a control, were used in chromatin immunoprecipitation (ChIP) assays to identify the transcription factors recruited to the PRSS23 promoter after estrogen stimulation. siRNA knockdown studies were used to assess the requirement of specific transcription factors for estrogen-induction of PRSS23.Results: qPCR analysis confirmed that PRSS23 mRNA levels are induced following both E2 and TPA stimulation. These studies also demonstrated that the induction of PRSS23 by estrogen mRNA is reduced by expression of a dominant-negative form of cJun (TAM67), showing that estrogen induction of PRSS23 is AP-1-dependent. siRNA experiments identified that members of both ERα and AP-1 (cFos and Jun) are required for estrogen induction of PRSS23 mRNA expression. ChIP assays demonstrated that estrogen induces ERα recruitment to an upstream enhancer region. We are now investigating the location of recruitment of the AP-1 transcription factors to the PRSS23 promoter after estrogen stimulation.Conclusion: Our results demonstrate that PRSS23 is a “non-classical”, estrogen-induced gene that requires ERα and AP-1 family members for its induction by estrogen. The mechanism by which ER and these AP-1 proteins cooperate to induce the expression of this gene is now being investigated. Data generated from this study may yield a new therapeutic target that could have a broad application to the diagnosis and treatment of breast cancer. Support: NCI R01 CA123246 (PHB), NIH/NCI T32 CA909221 (JAM)

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1131.