Molecular basis of distinct oestrogen responses in endometrial and breast cancer

Up to 80% of endometrial and breast cancers express oestrogen receptor alpha (ER alpha). Unlike breast cancer, anti-oestrogen therapy has had limited success in endometrial cancer, raising the possibility that oestrogen has different effects in both cancers. We investigated the role of oestrogen in endometrial and breast cancers using data from The Cancer Genome Atlas (TCGA) in conjunction with cell line studies. Using phosphorylation of ER alpha (ER alpha-pSer118) as a marker of transcriptional activation of ER alpha in TCGA datasets, we found that genes associated with ER alpha-pSer118 were predominantly unique between tumour types and have distinct regulators. We present data on the alternative and novel roles played by SMAD3, CREB-pSer133 and particularly XBP1 in oestrogen signalling in endometrial and breast cancer.