Center for Nuclear Receptors & Cell Signaling, Department of Biology & Biochemistry, University of Houston, 3517 Cullen Blvd, SERC Bldg, Rm 3010, Houston, TX, 77204-5056, USA.
Department of Pharmacy Practice and Translational Research, College of Pharmacy, University of Houston, Houston, TX, 77204, USA.
Cell Commun Signal. 2020 Sep 18;18(1):154. doi: 10.1186/s12964-020-00649-z.
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. Video abstract.
激素受体阳性（HR+）乳腺癌（BCa）是最常见的诊断亚型。对常规内分泌治疗（ET）的获得性和内在耐药性通常会导致无法治愈的转移性疾病。因此，ET 耐药（ET-R）HR+BCa 带来了治疗挑战。先前的研究表明，雄激素受体（AR）升高支持 ET 他莫昔芬耐药，并与 HR+BCa 转移相关。然而令人惊讶的是，AR 阻滞剂恩杂鲁胺（Enz）在 ET-R HR+BCa 中的研究结果存在矛盾。我们现在报告说，一种组成型激活的、不同于经典恩杂鲁胺靶向的独特 AR，在内分泌耐药的 HR+BCa 细胞中积累。
使用无细胞修饰试验、内部体内 SUMO 化测定和 PLA 成像来定义获得性和内在 ET-R HR+BCa 中 AR 蛋白谱。使用报告基因测定和有限的转录组分析测试天然 AR 和修饰的 AR 模拟物的基因组活性。使用球体生长和迁移研究来评估 Enz 和联合治疗的抑制作用。
在获得性和内在 ET-R BCa 细胞系中，持续存在更高分子量的 SUMO 修饰的 AR（SUMO-AR）。同时，SUMO 同种型和全局 SUMO 修饰的蛋白质组也在相同的细胞系中积累。我们鉴定出 AR 是 SUMO-E3 连接酶 HSPB1/Hsp27 的新型底物。独立于配体，SUMO-AR 抵抗泛素介导的蛋白酶体降解，在核内富集，易于与染色质结合，具有转录活性。组成性 SUMO-AR 引发有利于上皮-间充质转化的基因表达谱。Enz 与 SUMO 抑制剂联合使用可减弱 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 发生 ET-R 转移。
