Chemical manipulation of estrogen receptor alpha ligand binding domain structural mobility tunes receptor lifetime and influences breast cancer therapeutic activities. Selective estrogen receptor modulators (SERMs) extend estrogen receptor alpha (ERα) cellular lifetime/accumulation. They are antagonists in the breast but agonists in the uterine epithelium and/or in bone. Selective estrogen receptor degraders/downregulators (SERDs) reduce ERα cellular lifetime/accumulation and are pure antagonists. Activating somatic ESR1 mutations Y537S and D538G enable resistance to first-line endocrine therapies. SERDs have shown significant activities in ESR1 mutant setting while few SERMs have been studied. To understand whether chemical manipulation of ERα cellular lifetime and accumulation influences antagonistic activity, we studied a series of methylpyrollidine lasofoxifene (Laso) derivatives that maintained the drug’s antagonistic activities while uniquely tuning ERα cellular accumulation. These molecules were examined alongside a panel of antiestrogens in live cell assays of ERα cellular accumulation, lifetime, SUMOylation, and transcriptional antagonism. High-resolution x-ray crystal structures of WT and Y537S ERα ligand binding domain in complex with the methylated Laso derivatives or representative SERMs and SERDs show that molecules that favor a highly buried helix 12 antagonist conformation achieve the greatest transcriptional suppression activities in breast cancer cells harboring WT/Y537S ESR1. Together these results show that chemical reduction of ERα cellular lifetime is not necessarily the most crucial parameter for transcriptional antagonism in ESR1 mutated breast cancer cells. Importantly, our studies show how small chemical differences within a scaffold series can provide compounds with similar antagonistic activities, but with greatly different effects of the cellular lifetime of the ERα, which is crucial for achieving desired SERM or SERD profiles.
对雌激素受体α配体结合域结构流动性的化学操纵可调整受体的寿命并影响乳腺癌的治疗活性。选择性雌激素受体调节剂(SERMs)可延长雌激素受体α(ERα)的细胞寿命/蓄积。它们在乳腺中是拮抗剂,但在子宫上皮和/或骨骼中是激动剂。选择性雌激素受体降解剂/下调剂(SERDs)可减少 ERα 细胞的寿命/蓄积,是纯粹的拮抗剂。激活性体细胞 ESR1 突变 Y537S 和 D538G 可使患者对一线内分泌疗法产生抗药性。SERDs 在 ESR1 突变体环境中显示出显著的活性,而对 SERMs 的研究却很少。为了了解对ERα细胞寿命和积累的化学处理是否会影响拮抗活性,我们研究了一系列甲基吡咯烷拉索昔芬(Laso)衍生物,这些衍生物既能保持药物的拮抗活性,又能独特地调整ERα细胞积累。在ERα细胞积累、寿命、SUMOylation和转录拮抗作用的活细胞试验中,这些分子与一系列抗雌激素一起接受了检验。WT 和 Y537S ERα 配体结合结构域与甲基化 Laso 衍生物或代表性 SERM 和 SERD 复合物的高分辨率 X 射线晶体结构显示,在携带 WT/Y537S ESR1 的乳腺癌细胞中,倾向于高度埋藏的螺旋 12 拮抗构象的分子具有最强的转录抑制活性。这些结果共同表明,ERα细胞寿命的化学减少并不一定是ESR1突变乳腺癌细胞转录拮抗作用的最关键参数。重要的是,我们的研究表明,支架系列中微小的化学差异就能提供具有相似拮抗活性的化合物,但对 ERα 细胞寿命的影响却大不相同,而这对实现理想的 SERM 或 SERD 效果至关重要。