Poster abstracts

Poster number 70 submitted by Haritha Mathsyaraja

Identification of microRNA that act in conjunction with Ets2 in tumor associated macrophages

Haritha Mathsyaraja (MCDB, MCB, CCC), Sudarshana S. Sharma (MCB, CCC), Michael C. Ostrowski (MCB, CCC)

Abstract:
MicroRNAs are 20-22nt non-coding RNA that play an important role in the post-transcriptional regulation of gene expression. Over the past few years, there have been several reports linking microRNA to cancer. Most of these suggest that there is microRNA deregulation in tumor cells. However, the role of microRNA in the tumor microenvironment is poorly understood. The aim of our study is to identify microRNA that act synergistically with Ets2, a transcription factor that plays a critical role in tumor stroma. Our study focuses on tumor associated macrophages, where we have seen that Ets2 functions to repress a set of genes involved in ECM remodeling and angiogenesis, thus promoting breast cancer metastasis. Bioinformatics approaches were used to identify microRNAs that target Ets2 repressed genes. miR-29b was selected for further analysis as it had the maximum number of predicted targets. In addition, mir-29b has been reported to be upregulated in invasive breast carcinoma. Biological validation for the predicted targets such as SPARC, Fbn1 and pro-collagen encoding genes was done using luciferase assays. Overexpression of miR-29b in cultured primary bone marrow macrophages resulted in decreased mRNA and protein levels of the predicted target genes. Preliminary in vivo studies carried out in mouse models of breast cancer indicate that there is a correlation between Ets2 and miR-29 expression. Furthermore, promoter analysis of the mouse miR-29b-1 gene revealed the presence of conserved proximal and distal Ets2 binding sites. These taken together suggest that Ets2 is capable of regulating the expression of non-coding RNA in addition to its reported protein-encoding gene targets in the tumor-microenvironment. In the long term, we hope to identify novel microRNA that play an important role in regulating processes in tumor associated macrophages. Eventually, these microRNAs could potentially serve as therapeutic targets.

Keywords: Ets2, microRNA, breast cancer