Targeting STAT3 to enhance anti-tumor immunity

摘要 头颈部鳞状细胞癌(HNSCC)是一种常见的致命性癌症，其5年存活率高。 几十年来，利率一直徘徊在大约40%-60%的水平。我们的长期目标是开发有效的、 耐受性良好的药物和策略，以改善HNSCC患者的预后。最近批准的 针对HNSCC的PD-1检查点抑制剂nivolumab和pembrolizumab提示靶向中枢 肿瘤微环境中的免疫抑制介质将导致显著改善 治疗。抑制致癌转录因子STAT3是一种很有前途的新策略 缓解免疫抑制。STAT3在HNSCC中过度激活，促进肿瘤生长， 产生免疫抑制细胞因子，预后差。STAT3在肿瘤中也处于高激活状态 渗入免疫细胞。小鼠造血细胞中STAT3的条件性缺失显示出强大的作用 STAT3在多种免疫细胞群中的免疫抑制作用。因此，对STAT3的选择性靶向 可能产生三方面的抗肿瘤益处：a)直接抑制肿瘤细胞生长，b)抑制细胞- 免疫细胞中的自主免疫抑制，以及c)缓解免疫抑制串扰 肿瘤和免疫细胞。然而，目前可用的STAT3抑制剂要么缺乏效力和特异性，要么 不能有系统地交付。为了克服这一障碍，我们设计了一种15bp的双链寡核苷酸，即 类似于STAT3反应元件的STAT3诱饵选择性地与激活的STAT3结合，诱导 HNSCC凋亡，抑制异种移植瘤生长。一项涉及肿瘤内的0期试验 注射该STAT3诱饵后，发现HNSCC肿瘤中STAT3靶基因表达下调。一个 STAT3诱骗的循环版本表现出更好的稳定性和核酸酶抗性，并抑制肿瘤的生长 全身注射给免疫缺陷小鼠后的异种移植瘤。循环STAT3诱饵的影响 对免疫系统的影响从未被研究过，这限制了进一步临床试验的设计 抗癌剂。我们将利用免疫活性的HNSCC小鼠模型来严格评估 单独及与PD-1抑制剂联合应用对免疫系统的影响。在……里面 此外，我们还将评估循环STAT3诱饵的安全性、免疫效果和潜在功效，在一个独特的 和有价值的宠物猫自然发生HNSCC的动物模型。我们的研究将检验这一假设 通过全身性给予环状STAT3诱饵靶向抑制STAT3将增强抗肿瘤作用 免疫活性HNSCC小鼠模型的免疫及PD-1检查点的增强作用 抑制，同时对患有自然发生的HNSCC的宠物猫表现出最小的毒性。结果来自我们的 研究将确定使用循环STAT3诱骗缓解HNSCC免疫抑制的可能性， 同时为这种高度创新和选择性的STAT3抑制剂的临床进展奠定了基础。

ABSTRACT Head and neck squamous cell carcinoma (HNSCC) is a common and lethal cancer, where 5-year survival rates have lingered at roughly 40-60% for several decades. Our long-term objective is to develop effective, well-tolerated agents and strategies to improve the outcomes of patients with HNSCC. The recent approval of the PD-1 checkpoint inhibitors nivolumab and pembrolizumab for HNSCC suggests that targeting central mediators of immunosuppression in the tumor microenvironment will lead to significant improvements in treatment. Inhibition of the oncogenic transcription factor STAT3 represents a promising new strategy for relieving immunosuppression. STAT3 is hyperactivated in HNSCC, where it contributes to tumor growth, production of immunosuppressive cytokines, and poor prognosis. STAT3 is also hyperactivated in tumor infiltrating immune cells. Conditional deletion of stat3 in murine hematopoietic cells has revealed potent immunosuppressive roles for STAT3 in multiple immune cell populations. Thus, selective targeting of STAT3 may yield a three-fold anti-tumor benefit: a) direct inhibition of tumor cell growth, b) inhibition of cell- autonomous immunosuppression in immune cells, and c) relief of immunosuppressive cross-talk between tumor and immune cells. However, currently available STAT3 inhibitors either lack potency and specificity, or cannot be delivered systemically. To overcome this obstacle we designed a 15-bp duplex oligonucleotide, the STAT3 decoy, which resembles a STAT3 response element, binds selectively to activated STAT3, induces HNSCC apoptosis, and suppresses the growth of xenograft tumors. A Phase 0 trial involving intratumoral injection of this STAT3 decoy demonstrated downmodulation of STAT3 target genes in HNSCC tumors. A cyclic version of STAT3 decoy exhibits improved stability and nuclease resistance, and inhibits the growth of xenograft tumors following systemic delivery to immunodeficient mice. The impact of the cyclic STAT3 decoy on the immune system has never been studied, limiting the design of further clinical trials with this promising anti-cancer agent. We will utilize immunocompetent murine models of HNSCC to rigorously evaluate the effects on the immune system of cyclic STAT3 decoy, alone and in combination with PD-1 inhibition. In addition, we will evaluate safety, immune effects and potential efficacy, of the cyclic STAT3 decoy in a unique and valuable animal model of naturally occurring HNSCC in pet cats. Our studies will test the hypothesis that targeted inhibition of STAT3 via systemic administration of cyclic STAT3 decoy will enhance anti-tumor immunity in immunocompetent mouse models of HNSCC and augment the effects of PD-1 checkpoint inhibition, while exhibiting minimal toxicity in pet cats with naturally occurring HNSCC. Results from our studies will determine the potential for relieving immunosuppression in HNSCC using cyclic STAT3 decoy, while laying the foundation for clinical advancement of this highly innovative and selective STAT3 inhibitor.