The pea3 subfamily ets genes are required for HER2/Neu-mediated mammary oncogenesis

Background: The PEA3 Ets transcription factor is overexpressed in the vast majority of human breast tumors and in nearly all of those of the HER2/Neu- positive subclass. PEA3 is also overexpressed in various transgenic mouse m odels of this disease. Whether PEA3 plays an essential role in HER2/Neu-med iated oncogenesis has heretofore not been addressed. Results: Here, we report that each of the three highly related ets genes of the pea3 subfamily (pea3, er81, and erm) were coordinately overexpressed i n mammary tumors of MMTV-neu transgenic mice. Other ets genes normally expr essed in the mammary gland were not upregulated in these tumors. Expression of a dominant-negative pea3 transgene under the control of the MMTV promot er in mammary epithelial cells of MMTV-neu transgenic mice dramatically del ayed the onset of mammary tumors and reduced the number and size of such tu mors in individual mice. Those tumors that arose in bitransgenic mice expre ssed the MMTV-neu transgene, but not the MMTV-dominant-negative pea3 transg ene, Conclusions: These findings imply that one or more of the PEA3 subfamily Et s proteins or other Ets proteins with related DNA binding specificity play an essential role in Neu-mediated mammary oncogenesis. Hence, agents that i nhibit the expression or activity of the PEA3 subfamily proteins may prove efficacious in the treatment of breast cancer.