Environmental pro-oxidative stressors and immunosuppression

摘要 黑色素瘤是美国最致命的皮肤癌之一，与大多数其他主要癌症类型不同， 其流行率正在迅速增加。尽管有各种治疗选择，包括放射治疗和 尽管转移性黑色素瘤的化疗、治愈性治疗仍然难以捉摸。免疫疗法显示 有望在一小部分患者中诱导临床反应。然而，总体生存率 转移性黑色素瘤患者的情况令人失望。因此，重要的是要确定限制的因素， 免疫治疗如Ipilimumab的疗效。我们的研究表明，接触促氧化剂 包括紫外线B-照射人类和小鼠皮肤的应激源产生氧化脂质介质， 血小板活化因子（PAF）激动剂活性。这些UVB产生的PAF激动剂通过PAF受体起作用 （PAF-R）并通过环氧化酶2（考克斯-2）介导全身免疫抑制，免疫抑制 细胞因子、白细胞介素10（IL-10）和细胞类型调节性T细胞（T细胞）。重要的是，我们最近发现， UVB/PAF-R激动剂介导的全身性免疫抑制增强小鼠B16 F10的生长， 黑色素瘤肿瘤中的PAF-R依赖的方式。这些作用是通过上调IL-10介导的， 在肿瘤微环境中的作用。值得注意的是，抗氧化剂和针对IL-10和TGFAP的消耗性抗体 （抗CD 25）阻断UVB/PAF-R激动剂介导的增强肿瘤生长，表明参与了 氧化产生的PAF-R激动剂和下游IL-10和Tcl 3在B16 F10肿瘤的免疫逃避中的作用。 因此，促氧化应激物可能在抑制免疫介导的清除中起重要作用。 黑色素瘤，因此可能会损害黑色素瘤免疫疗法的疗效，旨在 抑制免疫逃逸机制值得注意的是，我们现在证明UVB诱导PAF-R 肿瘤中负性共刺激T细胞受体CTLA-4和PD-1的依赖性上调 微环境，已被证明可以抑制针对肿瘤的正常免疫反应 抗原重要的是，我们发现PAF-R激动剂诱导的全身免疫抑制是通过以下途径介导的： 髓源性抑制细胞（MDSC），一种已知抑制宿主抗肿瘤免疫的免疫表型 针对靶抗原。拟议补助金中的研究试图采取主动， 对黑色素瘤的治疗方案有重大影响。下文概述的临床前研究将（1） 潜在地提供了增加抗CTLA-4和/或抗PD-1黑素瘤的功效的新策略 免疫治疗，（2）探索促氧化应激如何抑制宿主抗肿瘤免疫的机制。在 此外，临床研究将允许直接评估治疗剂量的UVB是否可以产生 在接受光疗的患者中维持足够水平的免疫抑制性PAF-R激动剂。这些研究 将有助于确定PAF-R激动剂对患者疾病结局的影响。这些研究将 利用各种转基因和基因敲除小鼠模型作为我们研究的工具。

Abstract Melanoma is one of the deadliest skin cancers in the United States and unlike most other major cancer types, its prevalence is increasing rapidly. Despite having various treatment options including radiation therapy and chemotherapy, curative treatment for metastatic melanoma remains elusive. Immunotherapy has shown promise in inducing clinical responses in a small subset of patients. However, the overall survival rate of patients with metastatic melanoma is disappointing. Thus, it is important to identify factors which limit the efficacy of immunotherapy such as Ipilimumab. Our studies have demonstrated that exposure of pro-oxidative stressors including ultraviolet B-irradiation to human and mouse skin generates oxidized lipid mediators with platelet-activating factor (PAF) agonist activity. These UVB generated PAF agonists act via PAF-receptor (PAF-R) and mediate systemic immunosuppression via cyclooxygenase 2 (COX-2), immunosuppressive cytokine, interleukin 10 (IL-10) and cell type regulatory T cells (Tregs). Importantly, we have recently shown that UVB/PAF-R agonists mediated systemic immunosuppression augments the growth of murine B16F10 melanoma tumors in a PAF-R dependent manner. These effects were mediated via up-regulation of IL-10 and Tregs in the tumor microenvironment. Notably, anti-oxidants and depleting antibodies against IL-10 and Tregs (anti-CD25) blocked UVB/PAF-R agonists-mediated enhanced tumor growth, indicating the involvement of oxidatively generated PAF-R agonists and downstream IL-10 and Tregs in immune evasion of B16F10 tumors. Thus, pro-oxidative stressors may play an important role in inhibiting immune-mediated clearance of melanoma and therefore could potentially compromise the efficacy of melanoma immunotherapy, aimed at suppressing immune escape mechanisms. Notably, we now demonstrate that UVB-induces a PAF-R dependent up-regulation of the negative co-stimulatory T-cell receptors CTLA-4 and PD-1 in the tumor microenvironment, which have been demonstrated to suppress normal immune responses against tumor antigens. Importantly, we show that PAF-R agonists induced systemic immunosuppression is mediated via myeloid derived suppressor cells (MDSCs), an immunophenotype known to suppress host anti-tumor immunity against target antigens. The studies in the proposed grant attempt to take initiative in a direction which could have a major impact on treatment options for melanoma. The preclinical studies outlined below will (1) potentially provide novel strategies to increase the efficacy of anti-CTLA-4 and/or anti-PD-1 melanoma immunotherapy, (2) explore mechanisms of how pro-oxidative stressors can inhibit host anti-tumor immunity. In addition, clinical studies will allow direct assessment of whether therapeutic dose of UVB can generate adequate levels of immunosuppressive PAF-R agonists in patients undergoing phototherapy. These studies will help in determining the impact of PAF-R agonists on the disease outcomes in patients. These studies will take an advantage of various transgenic and knockout mouse models as a tool for our research.