Overall, our study reveals that: (1): Higher level of MTA1 accompanies worse prognosis in luminal-b type of breast cancer by analysis of TCGA debase and clinical samples; (2) MTA1 knockdown sensitizes the short-term and withdrawal chemotherapeutic effects of GEM in the MCF-7 cell line in vitro and in vivo. This evidence concerns the gene MTA1 and breast carcinoma.