Among three ER+-breast cancer cell lines, compared with those of MCF-7 cells, the mRNA levels of EIF2AK2 (P<0.05), TGM2 (P<0.0001), DDX58 (P<0.0001), STAT2 (P<0.001), STAT1(P<0.05), S100A8 (P<0.0001), S100A9(P<0.0001) and CCND1(P<0.0001) were significantly lower while those of USP-18 (P<0.0001), PARP9 (P<0.01) and ANXA1(P<0.0001) were significantly higher in BT-474 cells. Here, S100A9 is linked to breast cancer.