ESR1 and breast cancer: For example, the expression of TET1 was shown to negatively correlate with miR-29a and this negative correlation was stronger in estrogen receptor (ER) negative breast cancer samples compared to ER+ ones (35) In another research that studied the role of TET1 in TNBC, TET1 expression was shown to inversely correlate with the expression of EZH2 (25).