Ctr9 as a Predictive Biomarker for EZH2 Inhibitor Sensitivity

Ctr9 作为 EZH2 抑制剂敏感性的预测生物标志物

• 批准号: 10608198
• 负责人: Wei Xu
• 金额: $ 39.46万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-04-11 至 2027-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10608198
• 关键词: Adjuvant; Animal Model; Biological Markers; Breast Cancer Cell; Breast Cancer Model; Breast Cancer Patient; Breast Cancer cell line; Catalytic Domain; Cell Fate Control; Cell Line; Cell Maintenance; Cell Proliferation; Cells; Chromatin; Clinical; Clinical Trials; Complex; Data; Deposition; EZH2 gene; Enzymes; Epigenetic Process; Estrogen Receptors; Estrogen Therapy; Estrogen decline; Estrogen receptor negative; Estrogen receptor positive; Estrogens; FDA approved; Follicular Lymphoma; Gene Expression; Genes; Genetic; Genetic Transcription; Histone H3; Histones; Human; MCF7 cell; Measures; Methyltransferase; Molecular; Outcome; Patients; Phenotype; Process; Prognostic Marker; Property; Proteins; Recurrence; Relapse; Resistance; Role; Specimen; Testing; Therapeutic; Transcription Coactivator; Writing; addiction; design; epigenetic drug; genome-wide; histone methylation; hormone therapy; in vivo; inhibitor; knock-down; malignant breast neoplasm; mutant; novel therapeutics; patient derived xenograft model; predictive marker; receptor expression; restoration; single-cell RNA sequencing; stem cells; stem-like cell; transcription factor; triple-negative invasive breast carcinoma; tumor; tumor growth

PROJECT SUMMARY Approximately 70% of breast cancers (BC) are estrogen receptor (ER)-positive, also characterized as luminal- type BC; thus, are treated with endocrine therapy (ET). The transition from ER+ luminal cells to ER-negative ‘stem-like cells’ (SLCs) is a major mechanism of ET resistance; however, the underlying mechanism remains largely unknown. We discovered that Ctr9, a subunit of PAFc transcriptional activator complex, is a determi- nant of luminal cell identity. Using inducible and stable Ctr9 knockdown (KD) BC cell lines, a substantial decrease of ER stability and increase of H3K27me3, a repressive histone mark on chromatin, were observed upon Ctr9 depletion, indicating of a transition from luminal BC cells to SLCs. The cellular plasticity manifested by Ctr9 engages two downstream effector proteins, Jarid2 and KDM6A, that control the levels of repressive histone mark, H3K27me3. Ctr9 silencing leads to decreased Jarid2, a subunit of PRC2, and triggers a PRC2 subtype switch from less active PRC2.2 to PRC2.1 with higher H3K27me3 activity. In addition to enhancing PRC2 H3K27me3 deposition activity, Ctr9 KD results in a decrease of KDM6A, the ‘eraser’ enzyme for H3K27me3. Furthermore, Ctr9 depletion generates vulnerability that renders BC cells hypersensitive to EZH2 inhibitors (EZHi). EZH2 is highly expressed in SLCs for stem cell maintenance and expansion. Recently, tazemetostat, an EZH2i, is FDA-approved for the treatment of follicular lymphoma. We hypothesize that loss of Ctr9 leads to the transition from a Ctr9-expressing luminal lineage to an EZH2-governed SLC, thus the cells become sensitive to EZH2i. We will test our hypothesis by pursuing three aims: (1) Dissect how Ctr9 depletion results in transition from ER+ luminal cells to SLCs; (2) Determine the roles of Jarid2 and KDM6A during luminal to SLC transition and sensitivity to EZH2i; (3) Determine whether Ctr9 and H3K27me3 are predictive biomarkers for EZH2i sensitivity in vivo and study the inverse correlation of Ctr9 levels with H3K27me3 in human specimens. Because of the higher levels of expression of EZH2 in ER-negative BC as compared to ER+ BC, EZH2 inhibition has been extensively investigated in ER-negative BC. The study is of high impact because our findings that Ctr9 demarcates EZH2 activity and H3K27me3 levels in luminal cells opens an excit- ing possibility to target Ctr9low/H3K27me3high ER+ BC using EZH2i. Successful completion of this study will justify a clinical trial to use Ctr9/H3K27me3 as independent biomarker to select ER+ BC patients for treatment with EZH2i.

项目摘要 大约70％的乳腺癌（BC）是雌激素受体（ER）阳性，也被特征在 BC类型；因此，通过内分泌治疗（ET）进行治疗。从ER+腔细胞到ER阴性的过渡 “茎状细胞”（SLC）是ET抗性的主要机制。但是，基本机制仍然存在 在很大程度上未知。我们发现CTR9是PAFC转录激活剂复合物的一个亚基，是一个确定 使用诱导且稳定的CTR9敲低（KD）BC细胞系，这是一种实质性的 观察到H3K27me3的ER稳定性降低和染色质上反射性组蛋白标记的降低 CTR9耗竭后，表明从腔BC细胞向SLCS的过渡。细胞塑性表现出来 由CTR9与两个下游效应蛋白jarid2和kdm6a接合，以控制反射的水平 组蛋白标记，H3K27me3。 CTR9沉默导致PRC2亚基的JARID2下降，并触发PRC2 亚型从较不活跃的PRC2.2转换为具有较高H3K27ME3活性的PRC2.1。除了增强 PRC2 H3K27ME3沉积活性，CTR9 KD导致KDM6A降低，即“橡皮”酶的“橡皮”酶 H3K27me3。此外，CTR9耗竭会产生脆弱性，使BC细胞对EZH2过敏 抑制剂（Ezhi）。 EZH2在SLC中高度表达用于干细胞维护和扩展。最近， tazemetostat是EZH2I，已通过FDA批准用于治疗卵泡淋巴瘤。我们假设损失 CTR9导致从表达CTR9的腔谱系过渡到EZH2获得的SLC，因此细胞 对EZH2I变得敏感。我们将通过追求三个目标来检验我们的假设：（1）剖析CTR9如何部署 导致从ER+腔细胞过渡到SLC； （2）确定JARID2和KDM6A的作用 向SLC转变和对EZH2I的敏感性； （3）确定CTR9和H3K27ME3是否具有预测性 EZH2I在体内敏感性的生物标志物，研究Ctr9水平与H3K27me3的逆相关性 人类标本。由于ER-CH2在ER阴性BC中的表达水平较高，因此 ER+ BC，EZH2抑制已在ER-Congative BC中进行了广泛研究。该研究具有很高的影响 因为我们的发现CTR9在腔细胞中划定EZH2活性和H3K27me3水平，使一个令人兴奋的 使用EZH2I靶向CTR9LOW/H3K27ME3HIGH ER+ BC的可能性。这项研究成功完成将 证明临床试验使用CTR9/H3K27ME3作为独立生物标志物选择ER+ BC患者进行治疗 与ezh2i。