Abstract 5325: Co-culture induced EMT in breast tumor cells is mediated through MAPK signaling and microRNA regulation.
Authors: Miller Philip C. , Shah Sanket , Lairet Stephania , Steinberg Alana , Heyn Alexandra , Benito Daniel , El-Ashry Dorraya 
Published: August 2014

Understanding how components of the microenvironment cooperate with tumor cells to facilitate tumor progression, metastasis, and clinical outcome is an important aspect of breast tumor biology that remains incompletely understood. We have previously identified a microRNA (miRNA) signature indicative of hyperactive MAPK signaling (hMAPK) in primary human breast tumors. This hMAPK-miRNA signature is significantly associated with poor clinical outcome and increased tumor aggressiveness. As the hMAPK-miRNA signature as well as associations with gene and protein expression were generated from primary tumor specimens comprised not only of tumor cells but also stromal cells, here we undertook to further elucidate unique contributions of stromal cells and tumor cells to this hMAPK-miRNA signature, and to investigate whether these miRNAs facilitate EMT and subsequent invasion and aggressiveness in the tumor cell population.

Informatic analysis reveals that this hMAPK-miRNA signature contains several miRNAs which are known and predicted to regulate modulators of EMT. mRNA expression analysis as well as analysis of RPPA protein expression data from primary tumors bearing this hMAPK-miRNA signature reveals increased expression of EMT markers at the protein level. These data suggest that activation of MAPK signaling may contribute to breast tumor cell EMT in part through miRNA-mediated regulation of EMT-related genes.

To examine the contributions of tumor cells and stromal cells to the hMAPK miRNA signature and associated EMT gene and protein expression, we utilized a panel of primary cultures from ER-negative breast tumors (DTs) and CAFs derived from dissociated tumors (CAF-DTs). miRNA expression analysis of DTs and CAF-DTs indicates that members of this hMAPK-miRNA signature are differentially expressed between CAFS and tumor cells, suggesting that different cell types within a solid tumor provide unique contributions to overall miRNA expression. Co-culture of DTs with CAFs resulted in increased MAPK activity in the DTs. Co-culture with CAFs also modulates expression of this hMAPK-miRNA signature in both CAF and tumor cell populations and subsequently alters expression of EMT markers in the tumor cell population.

This work suggests that interactions between tumor cells and other components of the tumor microenvironment contribute to tumor aggressiveness by activating MAPK signaling which establishes a pro-EMT phenotype that is driven in part by miRNA-mediated regulatory events.

Citation Format: Philip C. Miller, Sanket Shah, Stephania Lairet, Alana Steinberg, Alexandra Heyn, Daniel Benito, Dorraya El-Ashry. Co-culture induced EMT in breast tumor cells is mediated through MAPK signaling and microRNA regulation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5325. doi:10.1158/1538-7445.AM2013-5325