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.

项目概要 大约 70% 的乳腺癌 (BC) 呈雌激素受体 (ER) 阳性，也被称为腔- BC 型；因此，接受内分泌治疗 (ET) 从 ER+ 管腔细胞转变为 ER 阴性。 “干细胞样细胞”（SLC）是 ET 抵抗的主要机制，但其根本机制仍然存在； 我们发现 Ctr9（PAFc 转录激活复合物的一个亚基）是一个决定因素。 使用诱导型和稳定的 Ctr9 敲低 (KD) BC 细胞系，可以显着提高管腔细胞的身份。 观察到 ER 稳定性降低和 H3K27me3（染色质上的抑制性组蛋白标记）增加 Ctr9 耗尽后，表明细胞可塑性从管腔 BC 细胞转变为 SLC。 Ctr9 与两个下游效应蛋白 Jarid2 和 KDM6A 结合，控制抑制水平 组蛋白标记 H3K27me3 沉默会导致 PRC2 的亚基 Jarid2 减少，并触发 PRC2。 亚型从活性较低的 PRC2.2 转换为具有较高 H3K27me3 活性的 PRC2.1。 PRC2 H3K27me3 沉积活性，Ctr9 KD 导致 KDM6A 减少，KDM6A 是 此外，Ctr9 缺失会导致 BC 细胞对 EZH2 过敏。 最近，EZHi 在 SLC 中高表达，用于干细胞的维持和扩增。 tazemetostat 是一种 EZH2i，已获得 FDA 批准用于治疗滤泡性淋巴瘤。 Ctr9 导致从表达 Ctr9 的管腔谱系转变为 EZH2 控制的 SLC，因此细胞 我们将通过追求三个目标来检验我们的假设：（1）剖析 Ctr9 耗尽的方式。 导致从 ER+ 管腔细胞向 SLC 的转变； (2) 确定 Jarid2 和 KDM6A 在此过程中的作用； luminal 到 SLC 的转变以及对 EZH2i 的敏感性； (3) 确定 Ctr9 和 H3K27me3 是否具有预测性 体内 EZH2i 敏感性的生物标志物，并研究 Ctr9 水平与 H3K27me3 的负相关性 因为与人类样本相比，ER 阴性 BC 中 EZH2 的表达水平更高。 ER+ BC、EZH2 抑制主要在 ER 阴性 BC 中进行研究，该研究具有很高的影响力。 因为我们发现 Ctr9 区分了管腔细胞中的 EZH2 活性和 H3K27me3 水平，这开启了令人兴奋的研究 使用 EZH2i 靶向 Ctr9low/H3K27me3high ER+ BC 的可能性将成功完成本研究。 证明使用 Ctr9/H3K27me3 作为独立生物标志物来选择 ER+ BC 患者进行治疗的临床试验的合理性 与 EZH2i。