Targeting STAT3 to enhance anti-tumor immunity

摘要 头颈部鳞状细胞癌是一种常见的恶性肿瘤， 几十年来，失业率一直徘徊在40-60%左右。我们的长期目标是发展有效的， 耐受性良好的药物和策略，以改善HNSCC患者的结局。最近核准 用于HNSCC的PD-1检查点抑制剂纳武单抗和派姆单抗表明，靶向中枢神经系统 肿瘤微环境中的免疫抑制介质将导致肿瘤微环境的显著改善。 治疗抑制致癌转录因子STAT 3代表了一种有前途的新策略， 缓解免疫抑制。STAT 3在HNSCC中被过度激活，在那里它有助于肿瘤生长， 免疫抑制细胞因子的产生和不良预后。STAT 3在肿瘤中也被过度激活 浸润免疫细胞小鼠造血细胞中stat 3的条件性缺失揭示了有效的 STAT 3在多种免疫细胞群体中的免疫抑制作用。因此，选择性靶向STAT 3 可以产生三倍的抗肿瘤益处：a）直接抑制肿瘤细胞生长，B）抑制细胞增殖， 免疫细胞中的自主免疫抑制，和c）减轻免疫细胞之间的免疫抑制串扰， 肿瘤和免疫细胞。然而，目前可用的STAT 3抑制剂要么缺乏效力和特异性，要么 不能系统地传递。为了克服这个障碍，我们设计了一个15-bp的双链寡核苷酸， 类似于STAT 3应答元件的STAT 3诱饵，选择性结合活化的STAT 3，诱导 HNSCC凋亡，并抑制异种移植肿瘤的生长。一项涉及肿瘤内 注射这种STAT 3诱饵证明了HNSCC肿瘤中STAT 3靶基因的下调。一 环状形式的STAT 3诱饵表现出改善的稳定性和核酸酶抗性，并抑制了细胞的生长。 异种移植肿瘤后全身递送给免疫缺陷小鼠。循环STAT 3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HNSCC的免疫活性小鼠模型来严格评估 单独和与PD-1抑制组合的环状STAT 3诱饵对免疫系统的作用。在 此外，我们将评估安全性，免疫效果和潜在的功效，在一个独特的环STAT 3诱饵， 和有价值的动物模型的自然发生的HNSCC的宠物猫。我们的研究将验证一个假设， 通过全身施用环状STAT 3诱饵靶向抑制STAT 3将增强抗肿瘤作用 HNSCC的免疫活性小鼠模型中的免疫力并增强PD-1检查点的作用 抑制，同时在患有天然存在的HNSCC的宠物猫中表现出最小的毒性。源自我们的 研究将确定使用环状STAT 3诱饵缓解HNSCC中免疫抑制的潜力， 同时为这种高度创新和选择性的STAT 3抑制剂的临床进展奠定基础。

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.