Hormone receptor positive (HR+) breast cancer (BCa) is the most frequently diagnosed subtype. Acquired and intrinsic resistance to conventional endocrine therapy (ET) commonly occurs and prompts incurable metastatic disease. Hence, ET-resistant (ET-R) HR+ BCa presents a therapeutic challenge. Previous studies show elevated androgen receptor (AR) that supports resistance to ET tamoxifen and correlates with HR+ BCa metastasis. Yet surprisingly, studies with AR-blocker enzalutamide (Enz) in ET-R HR+ BCa present conflicting results. We now report that a constitutively active, unique from canonical Enz-targeted, AR accumulates in endocrine resistant HR+ BCa cells. AR protein profiles in acquired and intrinsic ET-R HR + -BCa were defined with cell-free modification tests, in-house in-vivo SUMOylation assays, and PLA imaging. Genomic activity of native AR and modified-AR mimetic was tested with reporter assays and limited transcriptome analysis. Spheroid growth and migration studies were used to evaluate inhibitory actions of Enz and combinatorial therapy. Sustained higher molecular weight SUMO-modified AR (SUMO-AR) persists in acquired and intrinsic ET-R BCa cell lines. Concurrently, SUMO isoforms and global SUMO-modified proteome also accumulates in the same cell lines. We identified AR as a novel substrate for the SUMO-E3 ligase HSPB1/Hsp27. Independent of ligand, SUMO-AR is resilient to ubiquitin-mediated proteasomal degradation, enriched in the nucleus, readily chromatin-bound, and transcriptionally active. Constitutive SUMO-AR initiates a gene-expression profile that favors epithelial-mesenchymal transition. Enz combined with a SUMO inhibitor attenuates migration and metastatic phenotype of ET-R HR+ BCa. Targeting both unmodified and SUMO-modified AR prevents the metastatic progression of HR+ BCa with ET-R.

中文翻译：

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组成型活性雄激素受体支持内分泌抗性激素受体阳性乳腺癌的转移表型。

激素受体阳性 (HR+) 乳腺癌 (BCa) 是最常诊断的亚型。对常规内分泌治疗 (ET) 的获得性和内在耐药性通常会发生，并导致无法治愈的转移性疾病。因此，ET 抗性 (ET-R) HR+ BCa 提出了治疗挑战。先前的研究表明，雄激素受体 (AR) 升高，支持对 ET 他莫昔芬的抗性，并与 HR+ BCa 转移相关。然而令人惊讶的是，在 ET-R HR+ BCa 中使用 AR 阻滞剂恩杂鲁胺 (Enz) 进行的研究呈现出相互矛盾的结果。我们现在报告，在内分泌抗性 HR+ BCa 细胞中积累了一种从典型 Enz 靶向中独特的组成型活性 AR。获得性和内在 ET-R HR + -BCa 中的 AR 蛋白谱是通过无细胞修饰测试、内部体内 SUMO 化分析和 PLA 成像来定义的。使用报告基因检测和有限的转录组分析测试了天然 AR 和修饰 AR 模拟物的基因组活性。球体生长和迁移研究用于评估 Enz 和组合疗法的抑制作用。持续的较高分子量 SUMO 修饰 AR (SUMO-AR) 在获得性和内在 ET-R BCa 细胞系中持续存在。同时，SUMO 亚型和全局 SUMO 修饰的蛋白质组也在相同的细胞系中积累。我们将 AR 鉴定为 SUMO-E3 连接酶 HSPB1/Hsp27 的新型底物。SUMO-AR 独立于配体，对泛素介导的蛋白酶体降解具有弹性，在细胞核中富集，易于与染色质结合，并且具有转录活性。组成型 SUMO-AR 启动有利于上皮间质转化的基因表达谱。Enz 与 SUMO 抑制剂结合可减弱 ET-R HR+ BCa 的迁移和转移表型。靶向未修饰和 SUMO 修饰的 AR 可防止 HR+ BCa 与 ET-R 的转移进展。