Prostate derived Ets transcription factor and Carcinoembryonic antigen related cell adhesion molecule 6 constitute a highly active oncogenic axis in breast cancer

We previously reported overexpression of Prostate derived Ets transcriptionfactor (PDEF) in breast cancer and its role in breast cancer progression, supportingPDEF as an attractive target in this cancer. The goal of this research was to identifyspecific PDEF induced molecules that, like PDEF, show overexpression in breast tumorsand a role in breast tumor progression. PDEF expression was down regulated byshRNA in MCF-7 human breast tumor cell line, and probes from PDEF down-regulatedand control MCF-7 cells were used to screen the HG-U133A human gene chips. Theseanalyses identified 1318 genes that were induced two-fold or higher by PDEF in MCF-7 cells. Further analysis of three of these genes, namely CEACAM6, S100A7 and B7-H4, in relation to PDEF in primary breast tumors showed that in 82% of ER+, 67%of Her2 overexpressing and 24% of triple-negative breast tumors both PDEF andCEACAM6 expression was elevated 10-fold or higher in comparison to normal breasttissue. Overall, 72% (94 of 131) of the primary breast tumors showed 10-fold orhigher expression of both PDEF and CEACAM6. In contrast, S100A7 and B7-H4 failedto show concordant elevated expression with PDEF in primary tumors. To determinethe significance of elevated PDEF and CEACAM6 expression to tumor phenotype, theirexpression was down regulated by specific siRNAs in human breast tumor cell lines. This resulted in the loss of viability of tumor cells in vitro, supporting an oncogenicrole for both PDEF and CEACAM6 in breast cancer. Together, these findings show thatPDEF-CEACAM6 is a highly active oncogenic axis in breast cancer and suggest thattargeting of these molecules should provide novel treatments for most breast cancerpatients.