Role of HER2 mutations in breast cancer progression and response to targeted therapies

摘要 ERBB 2（编码HER 2受体酪氨酸激酶（RTK）的基因）的激活突变发生在约3%的 人类肿瘤并与乳腺癌预后不良相关。由于HER 2突变通常发生在 由于缺乏HER 2基因扩增，目前还没有批准用于这种乳腺癌亚型的疗法。 一部分HER 2突变型乳腺癌患者对抗HER 2抗体表现出良好的临床应答 酪氨酸激酶抑制剂（TKI）来那替尼等治疗，表明HER 2突变具有致癌性 司机然而，突变型HER 2促进乳腺癌进展的分子机制是 对最常见的HER 2突变体对多种可用的抗HER 2抗体的反应知之甚少， 治疗方法尚未进行系统研究。最后，对HER 2 TKI的持久临床应答并不 这一规律通常是短暂的，表明耐药机制仍有待发现。 我们的目标是确定突变型HER 2促进乳腺癌发生的机制 并确定对HER 2突变型乳腺癌最有效的治疗方法。我们假设 1）复发性HER 2突变产生功能获得性活性，因此，肿瘤依赖于 异常的HER 2信号传导，可以用靶向疗法抑制; 2）HER 2突变与 在其他ERBB RTK中共发生的突变促进乳腺癌生长;和3）共发生的基因组 在HER 2突变型癌症中，突变将导致对HER 2 TKI的固有或获得性耐药性。 为了验证这些假设，我们提出了以下三个目标：1）确定HER 2 突变促进乳腺癌发生和癌症进展; 2）检查HER 2突变是否 与其他ERBB RTK的改变协同作用;和3）确定HER 2 TKI耐药的机制， HER 2突变型乳腺癌。我们建议将结构、生物化学、分子和体内 实现这些目标的途径。我们将使用计算模型和磷蛋白阵列， 确定HER 2突变发挥其致瘤特性的机制，并将使用抑制剂 在HER 2突变细胞系和患者来源的异种移植物（PDX）中阻断这些效应。我们 将在体外模拟观察到的HER 2/EGFR和HER 2/HER 3共发突变之间的合作， in vivo.我们将采用全基因组遗传筛选来鉴定促进来那替尼耐药的基因± HER 2突变乳腺癌细胞中的抗雌激素。最后，我们将开发获得性耐药模型， 来那替尼使用HER 2突变PDX，并通过下一代DNA和RNA确定耐药机制 测序，这将在来自SUMMIT临床试验的患者样本中得到证实。这些研究将 确定最佳药物组合以抑制突变型HER 2驱动的癌症进展， 将确定克服对HER 2突变抑制剂耐药性的策略。这些研究有可能 快速转化为临床，并显著降低HER 2突变型癌症的死亡率。

ABSTRACT Activating mutations in ERBB2, the gene encoding the HER2 receptor tyrosine kinase (RTK), occur in ~3% of human tumors and correlate with poor prognosis in breast cancer. Since HER2 mutations usually occur in the absence of HER2 gene amplification, there are currently no approved therapies for this breast cancer subtype. A subset of patients with HER2-mutant breast cancers exhibit excellent clinical responses to anti-HER2 therapies such as the tyrosine kinase inhibitor (TKI) neratinib, suggesting that HER2 mutations are oncogenic drivers. However, the molecular mechanisms by which mutant HER2 promotes breast cancer progression are poorly understood and the response of the most common HER2 mutants to the multiple available anti-HER2 therapies has not been systematically investigated. Finally, durable clinical responses to HER2 TKIs are not the rule and are generally transient, suggesting mechanisms of drug resistance that remain to be discovered. Our objectives are to determine the mechanisms by which mutant HER2 promotes breast cancer oncogenesis and to identify the treatments that are most effective against HER2-mutant breast cancers. We hypothesize that 1) recurrent HER2 mutations generate gain-of-function activity and, as such, tumor dependence on aberrant HER2 signaling, which can be inhibited with targeted therapies; 2) HER2 mutations cooperate with co-occurring mutations in other ERBB RTKs to promote breast cancer growth; and 3) co-occurring genomic alterations will lead to intrinsic or acquired resistance to HER2 TKIs in HER2-mutant cancers. To test these hypotheses, we propose the following three aims: 1) To define mechanisms by which HER2 mutants promote breast oncogenesis and cancer progression; 2) To examine whether HER2 mutations cooperate with alterations in other ERBB RTKs; and 3) To identify mechanisms of resistance to HER2 TKIs in HER2-mutant breast cancers. We propose to integrate structural, biochemical, molecular and in vivo approaches to complete these aims. We will use computational modeling and phospho-protein arrays to determine the mechanisms by which HER2 mutations exert their tumorigenic properties, and will use inhibitors of HER2 signaling to block these effects in HER2-mutant cell lines and patient-derived xenografts (PDXs). We will model cooperation between observed co-occurring mutations in HER2/EGFR and HER2/HER3 in vitro and in vivo. We will employ a genome-wide genetic screen to identify genes that promote resistance to neratinib ± antiestrogens in HER2-mutant breast cancer cells. Finally, we will develop models of acquired resistance to neratinib using HER2-mutant PDXs and identify mechanisms of resistance by next-generation DNA and RNA sequencing, which will be confirmed in patient samples from the SUMMIT clinical trial. These studies will determine the best drug combinations to use in order to inhibit mutant HER2-driven cancer progression and will identify strategies to overcome resistance to HER2 mutation inhibitors. These studies have the potential to be rapidly translated to the clinic and significantly reduce mortality from HER2-mutant cancers.