Breast cancer patients who are treated with tamoxifen are more likely to have higher levels of RUNX1T1 expression, with longer distant metastasis-free survival and relapse-free survival, while those suffering from triple-negative (ER − /PR − /HER2 −) or estrogen receptor α (ERα)-knockdown breast cancer with worse prognosis tend to show lower levels of RUNX1T1 expression [55]. Here, ESR1 is linked to breast cancer.