Department of Biochemistry & Molecular Medicine, School of Medicine & Health Sciences, The George Washington University, Washington, District of Columbia, USA.
Department of Medicine, The Mays Cancer Center, University of Texas Health San Antonio, San Antonio, Texas, USA.
J Immunother Cancer. 2021 Jan;9(1). doi: 10.1136/jitc-2020-001932.
BackgroundThe non-overlapping functions of the two estrogen receptor subtypes, ERα (Estrogen Receptor α)and ERβ (Estrogen Receptor β), in tumor cells have been studied extensively. However, their counterparts in host cells is vastly underinterrogated. Even less is known about how ERα and ERβ activities are regulated in a subtype-specific manner. We previously identified a phosphotyrosine residue (pY36) of human ERβ that is important for tumor ERβ to inhibit growth of breast cancer cells in vitro and in vivo. A role of this ERβ phosphotyrosine switch in regulating host ERβ remains unclear.Conventional gene editing was used to mutate the corresponding tyrosine residue of endogenous mouse ERβ (Y55F) in mouse embryonic stem cells. The derived homozygous mutant mouse strain and its wild-type (WT) counterpart were compared in various transplant tumor models for their ability to support tumor growth. In addition, flow cytometry-based immunophenotyping was carried out to assess antitumor immunity of WT and mutant hosts. Adoptive transfer of bone marrow and purified CD8 T cells were performed to identify the host cell type that harbors ERβ-dependent antitumor function. Furthermore, cell signaling assays were conducted to compare T cell receptor (TCR)-initiated signaling cascade in CD8 T cells of WT and mutant mice. Lastly, the ERβ-selective agonist S-equol was evaluated for its efficacy to boost immune checkpoint blockade (ICB)-based anticancer immunotherapy.Disabling the ERβ-specific phosphotyrosine switch in tumor-bearing hosts exacerbates tumor growth. Further, a cell-autonomous ERβ function was defined in CD8 effector T cells. Mechanistically, TCR activation triggers ERβ phosphorylation, which in turn augments the downstream TCR signaling cascade via a non-genomic action of ERβ. S-equol facilitates TCR activation that stimulates the ERβ phosphotyrosine switch and boosts anti-PD-1 (Programmed cell death protein 1) ICB immunotherapy.Our mouse genetic study clearly demonstrates a role of the ERβ phosphotyrosine switch in regulating ERβ-dependent antitumor immunity in CD8 T cells. Our findings support the development of ERβ agonists including S-equol in combination with ICB immunotherapy for cancer treatment.
雌激素受体亚型 ERα（雌激素受体 α）和 ERβ（雌激素受体 β）在肿瘤细胞中的非重叠功能已被广泛研究。然而，宿主细胞中的对应物则被严重忽视。关于 ERα 和 ERβ 如何以特定于亚型的方式进行调节，人们知之甚少。我们之前确定了人 ERβ 的一个磷酸酪氨酸残基（pY36），对于肿瘤 ERβ 在体外和体内抑制乳腺癌细胞的生长很重要。这种 ERβ 磷酸酪氨酸开关在调节宿主 ERβ 中的作用尚不清楚。
使用常规基因编辑技术突变内源性小鼠 ERβ 的相应酪氨酸残基（Y55F）在小鼠胚胎干细胞中。在各种移植肿瘤模型中比较了由此衍生的纯合突变小鼠品系及其野生型（WT）对照品系在支持肿瘤生长方面的能力。此外，进行基于流式细胞术的免疫表型分析，以评估 WT 和突变宿主的抗肿瘤免疫。进行骨髓和纯化的 CD8 T 细胞的过继转移，以鉴定具有 ERβ 依赖性抗肿瘤功能的宿主细胞类型。此外，进行细胞信号转导测定，以比较 WT 和突变小鼠 CD8 T 细胞中 TCR 起始信号级联。最后，评估 ERβ 选择性激动剂 S--equol 增强免疫检查点阻断（ICB）为基础的抗癌免疫疗法的疗效。
在荷瘤宿主中禁用 ERβ 特异性磷酸酪氨酸开关会加剧肿瘤生长。此外，在 CD8 效应 T 细胞中定义了一个细胞自主的 ERβ 功能。从机制上讲，TCR 激活触发 ERβ 磷酸化，这反过来通过 ERβ 的非基因组作用增强下游 TCR 信号级联。S-Equol 促进 TCR 激活，刺激 ERβ 磷酸酪氨酸开关，并增强抗 PD-1（程序性细胞死亡蛋白 1）ICB 免疫疗法。
我们的小鼠遗传研究清楚地表明，ERβ 磷酸酪氨酸开关在调节 CD8 T 细胞中 ERβ 依赖性抗肿瘤免疫中起作用。我们的研究结果支持包括 S-Equol 在内的 ERβ 激动剂与 ICB 免疫疗法相结合用于癌症治疗的开发。
