Functional Characterization and Clinical Prevalence of ESR1 Fusions in Advanced Endocrine Resistant Breast Cancer

项目摘要 乳腺癌（BrCa）是女性癌症相关死亡的第二大原因， 死亡是由于转移性BrCa疾病。虽然我们对晚期乳腺癌的认识和治疗 癌症有所改善，5年生存率仍保持在令人沮丧的22%。三分之二的BrCa阳性 雌激素受体（ESR 1，ER），其可被靶向抗雌激素治疗剂利用。不幸的是， 25%的ER阳性原发性疾病患者和几乎所有ER阳性转移性BrCa患者将继续 开发这些靶向治疗方案的治疗难治性疾病。ER是癌症的重要组成部分 因此，必须了解晚期ER阳性患者如何产生治疗耐药性。 Lee-Oesterreich实验室最近发现了一种新的ESR 1基因组改变，即框内易位 产生融合基因产物的事件。已经发现了随后的一组ESR 1融合体，这些 估计ESR 1融合在至少1-5%的晚期ER阳性BrCa疾病中普遍存在。 重要的是，这些融合是在对激素治疗产生耐药性的患者中发现的。 这些基因组融合基因的功能作用需要进一步研究。我们将研究ESR 1 融合影响细胞增殖、治疗不敏感性和迁移/侵袭。我们的初步数据 在BrCa细胞系中稳定表达的融合体表现出增强的生长和对激素缺乏应答， 治疗我们还将分析ESR 1融合表达引起的转录和机制变化。 瞬时转染BrCa细胞系的ESR 1融合体的初步数据显示增强的ER激活 与亲本和野生型ER表达细胞相比。融合配偶体的直接诱变将更好地 阐明ESR 1或融合伴侣对整体细胞变化的贡献。最后，我们将研究 融合基因在转移性难治性疾病中的患病率，以确定临床意义。我们将 分析从患者抽血中分离的外泌体RNA，以检测已知和新融合体的存在。 该提案最终将1）在存在的情况下更好地分析ESR 1融合体的转移特性 2）更好地了解ESR 1融合对转录组的影响， 顺式顺式 抗雌激素治疗的临床对照试验成功实现这些目标将有助于 告知临床医生和研究人员ESR 1融合的临床相关性，以及这些基因组变异是否可以 作为生物标志物，用于识别耐药乳腺癌和替代治疗的依据 战略布局

PROJECT SUMMARY Breast cancer (BrCa) is the second leading cause of cancer related deaths in women and the majority of mortality is due to metastatic BrCa disease. Although our understanding and treatment of advanced breast cancer has improved, the 5-year survival rate remains at a dismal 22%. Two-thirds of all BrCa is positive for estrogen receptor (ESR1, ER), which can be exploited by targeted anti-estrogen therapeutics. Unfortunately, 25% of ER-positive primary disease patients and nearly all ER-positive metastatic BrCa patients will go on to develop treatment refractory disease to these targeted regimens. ER is a prominent component of cancer progression; thus, it is imperative to understand how advance ER-positive patients confer treatment resistance. The Lee-Oesterreich lab recently discovered a novel genomic alternation to ESR1, an in-frame translocation event creating a fusion gene product. A subsequent panel of ESR1 fusions have been discovered and these ESR1 fusions are estimated to be prevalent in at least 1-5% of advanced ER-positive BrCa disease. Importantly, these fusions were identified in patients who developed resistance to hormonal therapy. The functional role of these genomic fusion genes requires further investigation. We will investigate how ESR1 fusions influence cellular proliferation, treatment insensitivity and migration/invasion. Our preliminary data of a fusion stably expressed in a BrCa cell line exhibited enhanced growth and lack of response to hormonal treatment. We will also analyze transcriptional and mechanistic changes invoked by ESR1 fusion expression. Preliminary data of ESR1 fusions transiently transfected into a BrCa cell line exhibited enhanced ER activation compared to parental and wildtype ER expressing cells. Direct mutagenesis of the fusion partner will better elucidate the contribution of ESR1 or the fusion partner to global cellular changes. Lastly, we will study the prevalence of the fusion genes in metastatic refractory disease to determine clinical significance. We will analyze exosomal RNA isolated from patient blood draws to detect presence of known and novel fusions. This proposal will ultimately 1) better analyze the metastatic properties of ESR1 fusions both in the presence and absence of treatment, 2) gain a greater appreciation of ESR1 fusion influence on the transcriptome and cistrome and lastly 3) define fusion prevalence in advance BrCa and detection of novel fusions over the course of a controlled clinical trial utilizing anti-estrogen treatment. Successful completion of these Aims will help inform clinicians and researchers the clinical relevance of ESR1 fusions and if these genomic alternations can serve as biomarkers for identifying treatment resistant breast cancer and rationale for alternative treatment strategies.