ESR1 and breast cancer: Target genes include well-documented breast cancer genes (MAP3K1 at 5q11.2 [15], ESR1 at 6q25 [16], FGFR2 at 10q26 [21] and CCND1 at 11q13 [23]), TFs (KLF4 at 9q31.2 [18], NRBF2 at 10q21.2 [19] and TBX3 at 12q24 [92]), a putative tumour suppressor gene (IGFBP5 at 2q35 [12, 13, 99]), a methylcytosine dioxygenase (TET2 at 4q24 [14]) and a ribonucleoprotein polymerase that maintains telomere ends (TERT at 5p12 [24]).