Potentiating the Efficacy of Immune Checkpoint Blockade by Targeting Epithelial-Mesenchymal Transition (EMT)-induced Immunosuppression in Breast Carcinomas

项目总结/摘要 上皮-间充质转化（EMT）是一种细胞生物学过程，其驱动转移性肿瘤的发生。 扩散的肿瘤细胞，并导致侵袭性，获得肿瘤引发的性质， 对治疗方案的抵抗力增强。使用新的上皮和间充质的体内模型 乳腺癌，我已经证明，上皮肿瘤是严重浸润的生物 活性CD 8+细胞毒性T细胞，并含有低水平的免疫抑制性T细胞。而反观 更多的间质肿瘤排除耗尽的CD 8+细胞毒性T细胞，并招募免疫抑制性T细胞。 肿瘤和促肿瘤，M2样巨噬细胞代替。最重要的是，上皮肿瘤在很大程度上 对抗CTLA 4免疫疗法敏感，而间叶肿瘤具有抗性。这些 研究结果表明间叶性乳腺癌是一种免疫抑制肿瘤， 微环境（TME）和对免疫检查点阻断（ICB）的难治性应答。 然而，这种情况发生的确切机制尚不清楚。间叶细胞癌是否 细胞表达细胞内在的免疫抑制因子，直接调节免疫应答的难治性反应。 间充质肿瘤与ICB的关系尚不清楚。因此，本提案的一个目标是确定 间叶细胞癌细胞内因子在免疫抑制中作用 和对ICB的难治性反应。虽然我的数据表明，只有肿瘤产生于 间充质细胞系而不是上皮细胞系富含免疫抑制细胞， 这些不同子集的重要性是未知的。因此，本提案的另一个目标是确定 免疫浸润本身是否参与诱导和/或维持免疫浸润， 间叶肿瘤中的免疫抑制性TME。除了上述结果外，我 一小部分（约10%）的间充质细胞可以在很大程度上保护一个 大多数（90%）混合的上皮癌细胞被抗CTLA 4消除。这样不仅 是间充质癌细胞免疫抑制，但他们也保护他们的上皮邻居， 免疫攻击。然而，无论它们是否通过在全身免疫系统中施加免疫抑制力来达到这一目的， （内分泌）方式或局部（旁分泌）方式尚不清楚。因此，本提案的最终目标是 探索间充质癌细胞如何保护同一肿瘤内的上皮细胞， 免疫攻击这项提案中提出的工作可能会揭示分子参与者， 参与诱导EMT介导的免疫抑制的细胞亚群。这项研究预计将 通过识别新的乳腺癌诊断和预后标志物， 也可以用于免疫干预的癌症。

Project Summary/Abstract The Epithelial-to-Mesenchymal Transition (EMT) is a cell-biological process that drives the metastatic dissemination of tumor cells and results in invasiveness, acquisition of tumor-initiating properties and elevated resistance to treatment regimes. Using novel in vivo models of epithelial and mesenchymal breast carcinomas, I have demonstrated that epithelial tumors are heavily infiltrated with biologically active CD8+ cytotoxic T-cells, and contain low levels of immunosuppressive Tregs. In contrast, the more mesenchymal tumors exclude exhausted, CD8+ cytotoxic T-cells and recruit immunosuppressive Tregs and pro-tumor, M2-like macrophages instead. Most importantly, epithelial tumors are largely sensitive to anti-CTLA4 immunotherapy, whereas the mesenchymal tumors are resistant. These findings suggest that mesenchymal breast carcinomas assemble an immunosuppressive tumor microenvironment (TME) and mount refractory responses to immune checkpoint blockade (ICB). However, the precise mechanism(s) by which this occurs is unclear. Whether mesenchymal carcinoma cells express cell-intrinsic immunosuppressive factors that directly regulate the refractory responses of mesenchymal tumors to ICB is not known. For this reason, one goal of this proposal is to determine the identity and function of mesenchymal carcinoma cell-intrinsic factors in regulating immunosuppression and refractory responses to ICB. While my data demonstrate that only the tumors arising from mesenchymal, but not epithelial cell lines are enriched in immunosuppressive cells, the functional significance of these distinct subsets is unknown. Thus, another goal of this proposal is to determine whether immune infiltrates themselves are involved in the induction and/or maintenance of an immunosuppressive TME in the mesenchymal tumors. In addition to the aforementioned results, I made the striking observation that a small minority (~10%) of more mesenchymal cells could largely protect a majority (90%) of commingled epithelial carcinoma cells from elimination by anti-CTLA4. Thus, not only are mesenchymal carcinoma cells immunosuppressive, but they also protect their epithelial neighbors from immune attack. However, whether they do so by exerting immunosuppressive forces in a systemic (endocrine) fashion or localized (paracrine) fashion is unclear. Hence the final goal of this proposal is to explore how mesenchymal carcinoma cells protect epithelial cells residing within the same tumor from immune attack. The work proposed in this proposal is likely to uncover the molecular players and cellular subsets involved in inducing EMT-mediated immunosuppression. This study is expected to have an important positive impact through identifying novel diagnostic and prognostic markers of breast carcinomas that could potentially be used for immunotherapeutic intervention as well.