Targeting ERα degradation by L-Tetrahydropalmatine provides a novel strategy for breast cancer treatment.

The incidence and mortality of breast cancer (BCa) are the highest among female cancers. There are approximate 70% BCa that are classified as estrogen receptor alpha (ERα) positive. Therefore, targeting ERα is the most significantly therapeutic schedule. However, patients with breast cancer develop resistance to ERα or estrogen (E2) antagonists such as fulvestrant and tamoxifen. In the present study, we found that L-Tetrahydropalmatine (L-THP) significantly suppressed cell proliferation in ERα+ BCa cells via inducing cell cycle arrest rather than apoptosis. Additionally, L-THP enhanced the sensitivity of ERα+ BCa cells to tamoxifen and fulvestrant. Mechanically, the application of L-THP promotes ERα degradation through accumulating ubiquitin chains on ERα. Overexpressing ERα abrogates L-THP induced-antiproliferation in ERα+ BCa cells. Collectively, our work indicates that L-THP may represent a potentially novel therapeutic medicine for ERα+ breast cancer patient.