Studies in breast cancer show that many solid tumors harbor mutations and/or display activation of various members of the Wnt/?-catenin pathway. Wnt/?-catenin pathway activation is observed primarily in the basal-like subtype of breast cancer (BBC) that are highly invasive and lack targeted therapy. Thus, elucidation of the role of Wnt/?-catenin pathway in invasion of BBCs is remarkably relevant to be pursued. Our work shows that when Wnt-positive cells are shut down for the Wnt/?-catenin pathway, there is a marked decrease in both in vitro invasion and metastatic spread in vivo. Our RNA-sequencing analysis of Wnt-downregulated cells yielded a list of effector genes involved in invasion/metastasis. In particular, some of the T-box binding proteins, in particular EOMES, had their expression level decreased. EOMES has been shown to be a direct target of the Wnt pathway in T cells. EOMES itself has not been shown to play a role in breast cancer, though studies have shown its importance in driving lymph node metastasis in colorectal cancer. However, other members of its family have been implicated in breast cancer invasion. Preliminary data demonstrate that EOMES plays a pivotal role in the invasive phenotype of Wnt/?-catenin pathway in BBC cells. Downregulating EOMES in Wnt-positive BC cells showed a striking decrease in invasion in vitro and this effect was rescued when EOMES was over-expressed in those cells. When we performed ChEA analysis, approximately one third of the target genes from a Wnt-downregulated BC line overlapped with known target genes of EOMES, whose ontology showed predominately genes involved in cell motility and invasiveness. Taken together, there is strong evidence to propose the role of EOMES in affecting the invasive and metastatic phenotype of Wnt-activated BBC cells in vivo. We expect to find orthotopic transplanted Wnt-downregulated cells less metastatic than their respective control/parental cells. We also anticipate that re-introducing EOMES to the Wnt downregulated BBC cells will likely fully rescue their low-metastatic phenotype back to the full metastatic basal level. Additionally, we also seek to identify whether expression of EOMES is correlated with invasive BBC cells/tumors and whether its expression is distinct to BBCs. Moreover, we will explore our understanding of EOMES in driving metastasis of Wntactivated tumors by performing ChIP- and RNA-sequencing analysis of cells that are downregulated for Wnt pathway and/or EOMES and find the common target effectors that are most modulated. We plan to characterize novel effectors for their ability to affect metastasis. Therefore, by dissectig the metastatic drivers of Wnt-positive tumors, we will be able to identify a signature of genes that drive this phenotype. Finally, we anticipate that our studies on EOMES will have tremendous impact in identifying a novel driver of BBC metastatic spread, deciphering a new putative marker for BBC metastasis, and highlighting the Wnt pathway as an important targetable pathway for improved therapy for BBC patients.
Wnt activation occurs within the basal subtype of breast cancer (BBC). We show that shutting down the Wnt pathway in Wnt+ BBC cells causes a decrease in a novel transcriptional factor, EOMES, and a marked ablation of metastasis. We seek to determine the role of EOMES in affecting the metastatic phenotype of Wnt+ BBC cells, classify the expression of EOMES across subtypes of BCs, identify if its expression lies in metastatic BBCs cells and tumors, and dissect the metastatic drivers of Wnt+ tumors to elucidate a signature of genes that drives this invasive phenotype.
