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）阳性的，也被表征为管腔型。 BC型;因此，用内分泌疗法（ET）治疗。从ER+管腔细胞向ER阴性细胞的转变 “干细胞样细胞”（SLCs）是ET抵抗的主要机制;然而，潜在的机制仍然存在。 大部分未知。我们发现，Ctr 9是PAFc转录激活因子复合物的一个亚基，是一个决定性的转录因子。 腔细胞身份的标志。使用诱导型和稳定的Ctr 9敲低（KD）BC细胞系， 观察到ER稳定性降低和染色质上抑制性组蛋白标记H3 K27 me 3增加 在Ctr 9耗尽后，表明从管腔BC细胞向SLC的转变。细胞可塑性表现在 通过Ctr 9参与两个下游效应蛋白，Jarid 2和KDM 6A，控制抑制性的水平。 组蛋白标记，H3 K27 me 3。Ctr 9沉默导致PRC 2的亚基Jarid 2减少，并触发PRC 2 亚型从活性较低的PRC2.2转换为具有较高H3 K27 me 3活性的PRC2.1。除了增强 PRC 2 H3 K27 me 3沉积活性，Ctr 9 KD导致KDM 6A的减少，KDM 6A是PRC 2 H3 K27 me 3沉积活性的“擦除”酶。 H3K27me3.此外，Ctr 9缺失产生使BC细胞对EZH 2超敏感的脆弱性 抑制剂（EZHi）。EZH 2在SLC中高度表达，用于干细胞维持和扩增。最近， tazemetostat是一种EZH 2 i，已获得FDA批准用于治疗滤泡性淋巴瘤。我们假设， Ctr 9导致从表达Ctr 9的管腔谱系转变为EZH 2控制的SLC，因此细胞 对EZH 2 i敏感。我们将通过追求三个目标来测试我们的假设：（1）剖析Ctr 9缺失如何影响细胞的生长和发育。 （2）确定Jarid 2和KDM 6A在ER+管腔细胞向SLC转化过程中的作用; （3）确定Ctr 9和H3 K27 me 3是否是预测性的; 研究了体内EZH 2 i敏感性的生物标志物，并研究了Ctr 9水平与H3 K27 me 3的负相关性。 人类标本由于与ER阴性BC相比，ER阴性BC中EZH 2的表达水平更高， ER+ BC，EZH 2抑制已经在ER阴性BC中被广泛研究。这项研究影响很大 因为我们发现Ctr 9在管腔细胞中区分EZH 2活性和H3 K27 me 3水平， 使用EZH 2 i靶向Ctr 9低/H3 K27 me 3高ER+ BC的可能性。成功完成本研究将 证明使用Ctr 9/H3 K27 me 3作为独立生物标志物选择ER+ BC患者进行治疗的临床试验是合理的 在EZH 2 i。