MicroRNAs (miRNAs) are short-stranded, non-coding RNAs that regulate gene expression. The expression of miRNAs is often deregulated in breast cancer. Epigenetic modifications, such as DNA methylation, have been shown to regulate miRNA gene expression in breast cancer. In our study, we set out to analyze the role that differentially expressed miRNAs play in pregnancy associated breast cancer (PABC) amongst a Hispanic population within the Ella Binational Breast Cancer study. PABC is defined as cancer that arises within a time-frame of 10 years after pregnancy. Previous studies have shown that women diagnosed with PABC do far worse than women diagnosed with non-PABC. Our hypothesis is that the epigenetic regulation of miRNA genes contributes to poor survival in PABC. We are testing our hypothesis using a cohort of post-partum formalin fixed, paraffin embedded (FFPE) breast cancer tissues from a Hispanic population. Using Exiqon miRCURY LNA™ Universal RT microRNA PCR panels we were able to test for the expression of 360 human miRNAs, which our laboratory previously identified as miRNAs that are specific for human mammary cells. Preliminary data from a small subset of samples showed six miRNAs that were differentially expressed (having > 4-fold expression and a p-value ≤ 0.05) between PABC and non-PABC (hsa-miR-876-5p; hsa-miR-299-3p; hsa-miR-137; hsa-miR-187; hsa-miR-873; hsa-miR-190b ). Several of these miRNAs have been implicated in carcinogenesis. Our goals are to identify differentially expressed miRNAs and to determine the extent of the epigenetic regulation of those miRNAs. These miRNAs will be evaluated for their potential utility as targets of epigenetic regulation and targets for therapeutic interventions. In addition, our studies will be the first to look at epigenetic mechanisms related to PABC in Hispanics. Hispanics have one of the highest fertility rates and an early breast cancer diagnosis. Therefore, our results will elucidate factors associated with this PABC disparity.

Citation Format: Jose Luis Munoz-Rodriguez, Lukas Vrba, Patricia A. Thompson-Carino, Maria Elena Martinez, Bernard W. Futscher. Pregnancy-associated breast cancer and differentially expressed microRNAs. [abstract]. In: Proceedings of the Fifth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2012 Oct 27-30; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(10 Suppl):Abstract nr B34.