In the TCGA breast cancer dataset, TTP-low tumors are twice as likely to be ER-negative (ER-) or PR-negative (PR-) versus TTP-high tumors, indicating that hormone therapies commonly used to block estrogen activity might be less effective at impairing the growth of breast tumors with low TTP expression (Fig. 4A). This evidence concerns the gene ESR1 and breast neoplasm.