CHEK1 and breast cancer: Considering the above prognostic significance of CHEK1 and miR‐195‐5p for chemotherapy‐treated patients and verified miRNA‐mRNA regulatory interactions, we hypothesized that the downregulation of CHEK1 by miR‐195‐5p could increase the efficacy of anthracycline doxorubicin in luminal BC cell lines.