Endocrine drugs function by reducing estrogen levels or blocking ER signaling, which including selective estrogen receptor modulators (SERMs), selective estrogen receptor down-regulators (SERDs), and aromatase inhibitors (AIs) etc. Tamoxifen(TAM), as one of the SERMs, is the most frequently used endocrine drug which can competitively block ER to inhibit estrogen signaling and tumor growth [3]. Here, ESR1 is linked to neoplasm.