Abstract P6-07-06: Post-transcriptional coordination of gene expression during breast cancer tumorigenesis

We investigate mechanisms of RNA regulation central to human breast cancer progression. Aberrant gene expression is known to be an important factor in cancer, yet little is known about the role RNA-binding proteins (RBPs) play in disease onset and progression. Sequence specific RBPs coordinately regulate subsets of functionally related mRNAs within ribonucleoprotein complexes (RNPs), which are remodeled in response to cellular perturbations, allowing for the rapid and coordinated translation of proteins that have common functions. These post-transcriptional events robustly influence expression patterns of proto-oncogenes, growth factors, cytokines, and cell cycle regulators by influencing both mRNA stability and translation. Therefore, understanding the post-transcriptional layer of gene regulation is critical to understanding cancer development and progression. We have identified significant transcriptomic changes during the stepwise transition from primary mammary epithelial cells to a fully malignant state, as well as coordinated RNA dynamics of transient cellular RNP complexes. For this analysis, we generated a model of human breast cancer formation in which normal mammary epithelial cells were first immortalized through the expression of hTERT, p53 DD , Cyclin D1, CDK4 R24C and C-MYC T58A , and then subsequently transformed by the addition of H-RAS G12V . RNA-sequencing analysis demonstrated that the genes most significantly changed in this model are those involved in cell adhesion. In fact, while primary cells have a gene expression pattern typical of normal epithelial cells, both immortalized and transformed cells exhibit an mRNA expression pattern typical of mesenchymal cells. Interestingly, we found that N-cadherin protein, as well as other prototypical mesenchymal proteins, are only robustly expressed in the fully malignant cells, but not in immortalized cells. This suggests coordinated translational regulation of mRNAs that are essential for activating the epithelial-to-mesenchymal transition (EMT). Many of these EMT-related mRNAs are targets of both the HuR protein and microRNAs. HuR is a translational activator that competes with microRNAs and is mislocalized in many cancers. To integrate the quantitative RNA dynamics of HuR and microRNAs on a global scale, we used RNP-Immunoprecipitation followed by high-throughput sequencing to identify and quantify the remodeling of mRNA subsets associated with HuR and the Ago2/RISC complex in our breast cancer progression model. This integrative work provides global information about the underlying biology of carcinogenesis at the level of post-transcriptional coordination of gene expression, resulting in a more comprehensive understanding of the many layers of complex gene regulation. Therefore, the results from this study may ultimately direct our ability to counter the RNA regulatory changes that underlie malignancy. Citation Format: Laura Simone Bisogno, Jack D Keene. Post-transcriptional coordination of gene expression during breast cancer tumorigenesis [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-07-06.