Targeting Stat3 to Improve Immunotherapy

描述（由申请人提供）：肿瘤微环境严重限制了各种免疫疗法的疗效。对于过继T细胞治疗，需要选择/工程和扩增具有靶向抗原特异性的T细胞，同时仍然保留其效应功能和归巢能力，这带来了额外的挑战。我们和其他人已经证明，Stat3是一个关键的致癌转录因子，在多种癌细胞中组成性激活，对肿瘤细胞存活很重要，也在肿瘤基质免疫细胞中被激活，并具有强大的免疫抑制作用。我们的初步研究表明，骨髓细胞靶向Stat3基因消融导致肿瘤DC活化，肿瘤Treg细胞减少，肿瘤内CD8+ T细胞大量浸润，从而产生有效的抗肿瘤免疫应答。此外，在具有Stat3-/-骨髓腔室的小鼠中，过继转移的CD8+ T细胞增殖良好，并在肿瘤引流淋巴结中高度活化。我们还能够通过多光子共聚焦显微镜捕获转移的Stat3-/- CD8+ T细胞有效浸润肿瘤的实时图像，在那里它们增殖，导致肿瘤抗原特异性免疫反应的激活。我们已经开始了解肿瘤髓细胞和T细胞中Stat3阻碍T细胞介导的抗肿瘤免疫的细胞和分子机制。在这个应用中，我们建议进一步定义这些细胞和分子机制，从而确定额外的靶点来优化Stat3靶向和T细胞治疗。为了促进潜在的未来临床翻译，我们还将测试两种试剂，这两种试剂都显示出对肿瘤免疫环境的积极影响，因为它们有可能改善T细胞治疗。一种是新型toll样受体（TLR）激动剂- sirna偶联物，这是我们最近开发的一种技术平台，能够免疫激活和靶向基因沉默髓细胞和B细胞中所需的免疫检查点，如Stat3。另一个是fda批准的酪氨酸激酶抑制剂舒尼替尼，我们的初步数据表明它可以抑制肿瘤细胞、肿瘤浸润树突状细胞和髓源性抑制细胞中的Stat3。此外，我们将通过在体外用慢病毒sirna沉默T细胞中的Stat3来测试抗肿瘤效果。这些研究可能会导致体内扩增和激活转移T细胞的新策略，从而克服T细胞治疗面临的几个主要障碍，并显着提高其治疗癌症的功效。公共卫生相关性：靶向肿瘤细胞和免疫细胞中的Stat3对肿瘤具有深远的影响，并有可能在体内激活和扩增转移的T细胞。随着fda批准的酪氨酸激酶抑制剂阻断几种类型细胞中的Stat3，一种新的siRNA方法靶向肿瘤骨髓细胞中的Stat3及其关键介质，以及小分子Stat3抑制剂的出现，我们预计拟议的研究将为过继性t细胞转移癌症免疫治疗提供令人兴奋的新可能性。

DESCRIPTION (provided by applicant): The tumor microenvironment severely limits the efficacy of various immunotherapies. For adoptive T cell therapy, the need to select/engineer and expand T cells with targeted antigen specificity while still preserving their effector function and homing capacities poses additional challenges. We and others have demonstrated that Stat3, a key oncogenic transcription factor constitutively activated in diverse cancer cells and important for tumor cell survival, is also activated in tumor stromal immune cells and potently immunosuppressive. Our preliminary studies show that targeted Stat3 gene ablation in myeloid cells results in tumor DC activation, tumor Treg cell reduction and heavy infiltration of CD8+ T cells in tumors, leading to effective antitumor immune responses. Furthermore, in mice with a Stat3-/- myeloid compartment, adoptively transferred CD8+ T cells proliferate well and are highly activated in the tumor draining lymph nodes. We were also able to capture live images by multi-photon confocal microscopy of transferred Stat3-/- CD8+ T cells efficiently infiltrating tumors, where they proliferate, leading to activation of tumor antigen-specific immune responses. We have begun to understand the cellular and molecular mechanisms that allow Stat3 in both tumor myeloid cells and T cells to impede T-cell mediated antitumor immunity. In this application, we propose to further define these cellular and molecular mechanisms and thereby identifying additional targets to optimize Stat3 targeting and T cell therapy. To facilitate potential future clinical translation, we will also test two reagents, both of which have shown positive effects on the tumor immunologic environment, for their potential to improve T cell therapies. One is a novel Toll-like receptor (TLR) agonist-siRNA conjugate, a technology platform we have recently developed, and is capable of immune activation and targeted gene silencing of desired immunologic checkpoints such as Stat3 in myeloid and B cells. The other is an FDA-approved tyrosine kinase inhibitor, sunitinib, as our preliminary data suggested it inhibited Stat3 in tumor cells, tumor-infiltrating dendritic cells and myeloid-derived suppressor cells. Additionally, we will test antitumor efficacy by silencing Stat3 in T cells ex vivo with lentiviral-siRNAs. The proposed studies may lead to new strategies to expand and activate transferred T cells in vivo, thereby overcoming several major hurdles facing T cell therapy, and significantly improve its efficacy for cancer treatment. PUBLIC HEALTH RELEVANCE: Targeting Stat3 in tumor cells and immune cells has profound effects on tumors and the potential to activate and expand transferred T cells in vivo. With an FDA-approved tyrosine kinase inhibitor that blocks Stat3 in several types of cells, a novel siRNA approach that targets Stat3 and its key mediators in myeloid cells in tumor, and emergence of small-molecule Stat3 inhibitors, we anticipate that the proposed studies will provide exciting new possibilities for adoptive T-cell transfer cancer immunotherapy.