Previous studies confirmed that WBP2 is a co-activator of ERα and WBP2 is conducive to the transcriptional activity of ERα through binding to ERα.24 Moreover, a previous report verified that ERα directly activated MDR1 transcription in PTX-induced resistance of ERα-positive breast cancer cells.15 Thus, we hypothesised that ERα was the key determinant that affected the expression pattern between WBP2 and MDR1 in breast cancer. This evidence concerns the gene WBP2 and breast carcinoma.