Enabling effective anti-tumor immunity from targeted antibodies through dual innate and adaptive immune checkpoint blockade in non-immunogenic cancers

摘要 在我们之前的研究中，我们已经确定HER2单抗(MAb)具有刺激 抗体依赖的细胞吞噬作用(ADCP)通过先天途径，这是建立 有效的抗肿瘤反应(Tsao等人，JCI-Insight，2019)。在我们正在进行的资助研究(R01 CA238217- 01A1)，我们正在探索是否可以通过先天ICB(靶向)增强HER2特异性ADCP诱导的抗体 CD47)和适应性ICBS(靶向CTLA4/PD1)。这些研究利用了内源性免疫耐受模型。 由致癌的人类亚型HER2，HER2Δ16驱动的HER2+BC(Turpin等人，2016年)。 模型对hER2表位具有免疫耐受性，并在适当的条件下产生hER2Δ16驱动的肿瘤 乳腺微环境，它不能概括HER2+BCS临床上看到的肿瘤异质性，或者 允许开发对HER2单抗疗法的主要耐药机制，这种疗法通常发生在 晚期HER2+BC患者。为了解决这些不足，并加深我们对HER2单抗的理解 HER2+BC的治疗，我们建议利用通过IMAT计划开发的一种新的HER2BOW小鼠 (5R33CA191198；Lubkov等人，NA.细胞生物学，在回顾中)。该模型利用了几个 HER2的不同变异体(HER2-WT、HER2Δ16和HER2-P95)在乳腺内的进化 具有不同病理的异质性HER2+BCS。关键的是，这些不同的病理起源于 这些交替的HER2亚型的表达，这可能解释了观察到的HER2+肿瘤的异质性 从临床上看。此外，该模型含有HER2-P95，它缺乏HER2的胞外结合结构域 单抗发挥抗药性的驱动力作用。然而，HER2特异性单抗能够激发T细胞反应 在临床HER2+BCS的异质性背景下抗HER2细胞内表位，因此其 在异质环境中调解耐药性的重要性尚不清楚。此外，目前尚不清楚IF策略 加强HER2单抗刺激免疫可彻底克服HER2-P95介导的耐药性 增强的HER2免疫交叉引爆。我们假设HER2-P95的表达对 HER2单抗在异种HER2+BCS中的治疗，但双重(先天和适应性)ICB增强 HER2单抗治疗可通过增强HER2表位交叉启动来克服这种耐药性。指导原则 我们的初步数据，这一假设将通过使用可以询问的HER2BOW模型进行验证 我们的具体目标是：1)HER2+CD47单抗和2)HER2/CD47 单抗+CTLA4/PD1 ICB组合。这些研究将确定响应性是否是由于缺乏局部 免疫与肿瘤内的高度异质性有关，或由于快速发展的对 另一种HER2致癌亚型。关键的是，他们还将验证HER2BOW的治疗效用 HER2单抗+ICB联合不同HER2+BCs的模型及治疗潜力 它们对HER2单抗介导的耐药性的发展的影响。

Abstract In our previous studies, we have identified that HER2 monoclonal antibodies (mAb) function to stimulate antibody dependent cellular phagocytosis (ADCP) through innate pathways, which are critical to establish effective anti-tumor responses (Tsao et al., JCI-Insight, 2019). In our ongoing funded studies (R01 CA238217- 01A1), we are exploring if HER2-specific ADCP eliciting antibodies could be enhanced by innate ICB (targeting CD47) and adaptive ICBs (targeting CTLA4/PD1). These studies utilize an endogenous immune-tolerant model of HER2+ BC (Turpin et al., 2016) driven by an oncogenic human isoform of HER2, HER2Δ16. While this model is immune-tolerant to HER2 epitopes and generates HER2Δ16-driven tumors in an appropriate mammary microenvironment, it does not recapitulate the tumor heterogeneity seen clinically in HER2+ BCs, or permit the development of major resistance mechanisms to HER2 mAb therapies, which often occur in advanced HER2+ BC patients. To address these shortcomings and further our understanding of HER2 mAb therapies in HER2+ BC, we propose to utilize a novel HER2BOW mouse developed through the IMAT program (5R33CA191198;Lubkov et al., Nat. Cell Bio., in review). This model utilizes the stochastic activation of several different variants of HER2 (HER2-WT, HER2Δ16, and HER2-p95) within the mammary compartment to evolve heterogeneous HER2+ BCs with disparate pathologies. Critically, these different pathologies stem from the expression of these alternate HER2 isoforms, which may explain HER2+ tumor heterogeneity observed clinically. Moreover, this model contains HER2-p95, which lacks the extracellular binding domain for HER2 mAbs to function as a driver of resistance. However, HER2-specific mAbs are able to prime T cell responses against HER2 intracellular epitopes within the heterogeneous context of clinical HER2+ BCs, thus its importance in mediating resistance in a heterogeneous context is unclear. Moreover, it is unknown if strategies to enhance HER2 mAb stimulated immunity could overcome HER2-p95 mediated resistance thorough enhanced HER2 immune cross-priming. We hypothesize that HER2-p95 expression confers resistance against HER2 mAb therapies within heterogeneous HER2+ BCs, but that dual (innate and adaptive) ICB-enhanced HER2 mAb therapies could overcome this resistance through enhance HER2 epitope cross-priming. Guided by our preliminary data, this hypothesis will be tested by utilizing the HER2BOW model that can be interrogated with the following combinations that comprise our specific aims: 1) HER2+CD47 mAbs and 2) HER2/CD47 mAbs + CTLA4/PD1 ICB combinations. These studies will determine if responsiveness is due to a lack of local immunity related to substantial intratumoral heterogeneity, or due to the rapid development of resistance from alternate HER2 oncogenic isoforms. Critically, they will also validate the therapeutic utility of the HER2BOW model and the therapeutic potential of HER2 mAb+ICB combinations across different HER2+ BCs as well as their impact on the development of HER2 mAb mediated resistance.