Enhancing immune therapy in pancreatic cancer by targeting IL-6

胰腺导管腺癌（PDAC）伴有严重的全身性免疫抑制， 使这种疾病对免疫疗法无反应。PDAC的一个标志是致密的基质， 被称为“胰腺星状细胞”（PSC）的活化成纤维细胞围绕每个肿瘤。虽然这些 基质细胞产生许多可能支持肿瘤生长的因子，最近的出版物也表明， 间质在防止转移中的矛盾作用。更令人惊讶的是， 从PDAC的遗传模型中去除PSC导致免疫治疗的功效提高。这些数据 强调了该提案的重要性，以及人们对该提案之间错综复杂的相互作用知之甚少。 基质和免疫细胞存在于肿瘤微环境中。这些结果还表明， PSC抑制针对肿瘤免疫应答，且靶向基质中的关键途径可 增强免疫疗法的疗效。根据这些观察，我们小组最近发表了一份报告， 证明患者来源的PSC分泌可溶性因子以促进骨髓来源的抑制细胞 （MDSC）分化。详细的分析表明，STAT 3信号传导是这一过程所必需的， 原因是PSC分泌大量的白细胞介素-6（IL-6）。这些数据显示了一种新的作用， 间质PSC作为PDAC免疫抑制因子的来源，并激发了我们对 靶向IL-6以增强免疫治疗。我们的初步数据表明，体内施用抗体， (Ab)靶向白细胞介素-6（IL-6）和PD-L1限制了皮下和自体的肿瘤进展， 突变KRAS驱动的PDAC模型。我们还证明了这种治疗组合会增加 T细胞浸润到胰腺肿瘤中，并且这些相同肿瘤内PSC水平降低。我们 假设基质IL-6是PDAC中促进免疫抑制主要屏障， 可以靶向增强对免疫疗法的反应。该提案将涉及三个具体问题 目标。首先，我们将确定IL-6和PD-L1联合阻断抗肿瘤的机制。 在PDAC中的功效，关注T细胞和MDSC的表型和功能特性（目的1）。的相对 肿瘤或宿主组织上PD-L1表达在介导该治疗功效中的重要性将是 研究了接下来，我们将确定基于紫杉烷的化疗是否增强IL-6和PD-L1的疗效。 在本地的，突变的KRas驱动的PDAC模型中的阻断（目的2）。最后，我们将使用一个双 重组酶系统（Flp-FRT和Cre-loxP）来开发具有自发产生的突变型KRas驱动的 PDAC和IL-6缺失的成纤维细胞和原发性患者PSC，以确定基质IL-6在促进成纤维细胞增殖中的作用。 胰腺癌进展和免疫抑制（目的3）。这一建议将增进我们的理解 间质如何影响PDAC中的致癌作用和免疫抑制。这些研究的数据还 具有与靶向IL-6的Ab联合免疫疗法的近期临床影响的潜力。

Pancreatic ductal adenocarcinoma (PDAC) is accompanied by profound systemic immunosuppression that renders this disease non-responsive to immunotherapy. One hallmark of PDAC is the dense stroma consisting of activated fibroblasts termed `pancreatic stellate cells' (PSC) that surround each tumor. Although these stromal cells produce numerous factors that may support tumor growth, recent publications also suggest a contradictory role for the stroma in protecting against metastasis. Even more surprising was the observation that depletion of PSC from genetic models of PDAC led to improved efficacy of immunotherapy. These data highlight the significance of the proposal, and how little is known regarding the intricate interactions between stroma and immune cells present within the tumor microenvironment. These results also suggest that the immune response against tumors is restrained by PSC, and that targeting key pathways in the stroma may augment the efficacy of immunotherapy. In line with these observations, a recent publication from our group demonstrated that patient-derived PSC secrete soluble factors to promote myeloid-derived suppressor cell (MDSC) differentiation. Detailed analyses revealed that STAT3 signaling was required for this process, and was due to copious amounts of interleukin-6 (IL-6) secreted from PSC. These data demonstrated a novel role for stromal PSC as a source of factors that suppress immunity in PDAC, and have fueled our interest in targeting IL-6 to enhance immunotherapy. Our preliminary data show that in vivo administration of antibodies (Ab) targeting interleukin-6 (IL-6) and PD-L1 limit tumor progression in both subcutaneous, and autochthonous, mutant KRas-driven models of PDAC. We also demonstrate this treatment combination results in increased infiltration of T cells into pancreatic tumors, and reduced levels of PSC within these same tumors. We hypothesize that stromal IL-6 is a major barrier promoting immune suppression in PDAC, and that it can be targeted to augment the response to immunotherapy. This proposal will address three Specific Aims. First, we will determine the mechanisms by which combined blockade of IL-6 and PD-L1 elicits antitumor efficacy in PDAC, focusing on phenotypic and functional properties of T cells and MDSC (Aim 1). The relative importance of PD-L1 expression on the tumor or host tissues in mediating efficacy of this treatment will be investigated. Next, we will determine if taxane-based chemotherapy augments the efficacy of IL-6 and PD-L1 blockade in autochthonous, mutant KRas-driven PDAC models (Aim 2). Finally, we will use a dual recombinase system (Flp-FRT and Cre-loxP) to develop mice with spontaneously arising, mutant KRas-driven PDAC and IL-6 deleted fibroblasts, and primary patient PSC to define the role of stromal IL-6 in promoting pancreatic cancer progression and immune suppression (Aim 3). This proposal will enhance our understanding of how the stroma influences carcinogenesis and immune suppression in PDAC. Data from these studies also have potential for near-term clinical impact with Ab targeting IL-6 in combination with immunotherapy.