ESR1 and breast carcinoma: In hormone therapy of breast cancer cells, ERRγ is upregulated during the acquisition of TAM resistance in estrogen receptor-positive (ER+) breast cancer cells, thus overexpression of ERRγ is sufficient to induce TAM resistance 18 via cooperation with proline, glutamic acid and leucine rich protein 1 (PELP1) to inhibit TAM-mediated cell death 35.