GSTP1 and breast cancer: As a large numbers of studies confirmed its important role of GSTP1 in chemoresistance of breast cancer, our RNA-seq analysis also demonstrated upregulated the expression of GSTP1 in MCF-7/CLDN6 cells (Additional file 5: Figure S5), therefore we speculated that chemoresistance conferred by CLDN6 may be mediated by GSTP1 in these cells.