Abstract P6-04-13: Gene and microRNA Signatures of the Mesenchymal Epithelial Transition in Pre-Clinical Models of Inflammatory Breast Cancer
Authors: Robertson FM , Player AN , Chu K , Pickei R , Ye Z , Krishnamurthy S , Liu C-G , Liu X , Cristofanilli M , Barsky S. 
Published: April 2011

Inflammatory breast cancer (IBC) is the most aggressive form of locally advanced breast cancer The pathological hallmark of IBC is lymphovasculogenesis resulting in the invasion of tightly adhered cells, defined as tumor emboli, into lymphovascular spaces of the dermis. IBC tumor emboli have been reported to over-express the glycoprotein E-cadherin, which is at odds with the current hypothesis that tumors with a metastatic phenotype lose E-cadherin, and gain expression of specific transcription factors and microRNAs (miRs) that mediate the process of epithelial mesenchymal transition (EMT). Immunohistochemical staining confirms the presence of E-cadherin on tumor emboli in IBC patient tissues as well as in Mary-X tumor xenografts, which is the only model to recapitulate tumor emboli in vivo. Using unbiased global transcriptional profiling, microRNA microarrays, real time PCR, Western blot validation, immunohistochemistry, immunofluorescence and confocal microscopy, we found that IBC cell lines, and Mary-X tumor emboli from xenografts had significantly elevated expression of genes and their corresponding proteins that collectively mediate tight homotypic cell:cell aggregation, including CDH1 which encodes for E-cadherin, DSC2, which encodes for Desmocollin 2 and JUP/CTNNG1, which encodes for junctional plakoglobin/gamma catenin. Regardless of molecular subtype, IBC cell lines and Mary-X tumor spheroids lacked detectable mRNA or protein for zinc finger E-box binding homeobox 1 gene, ZEB1, with very low levels of ZEB2 gene expression. The expression of CDH1, loss of ZEB1 and low gene expression of ZEB2 by IBC cell lines and Mary-X tumor spheroids was associated with increased expression of specific families of microRNAs including the miR 200 family known to be transcriptional regulators of E-cadherin. In contrast to lack of ZEB1 expression, IBC cell lines expressed either one or all of the SNAI1, SNAI2 and TWIST1 genes, which encode for transcription factors that have been associated with the process of EMT. IBC cell lines that contained ZEB1 cDNA lacked expression of CDH1 and did not produce E-cadherin protein, however the IBC/ZEB1 clones exhibited little difference in their ability to invade across an artificial Matrigel membrane compared to either vector control cells or the parental IBC cells. Taken together, the present observations suggest that pre-clinical models of IBC have distinct gene and microRNA signatures characterized by expression of genes and miRs that collectively support the persistence of compact tightly aggregated tumor cells within IBC tumor emboli, while maintaining an invasive and metastatic phenotype, suggesting that IBC tumor emboli display characteristics of the process of mesenchymal-epithelial transition (MET). Supported in part by the American Airlines-Komen For the Cure Foundation Promise Grant KGO81287 (FMR, MC) and The State of Texas Fund for Rare and Aggressive Breast Cancer (FMR, SK).

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-04-13.