IDO1 and Immunotolerance in Glioblastoma

摘要 多形性胶质母细胞瘤（GBM）是成人中最常见和最具侵袭性的脑肿瘤。中值 GBM患者的生存期为14.6个月。GBM的一个一致特征是肿瘤内 存在损害患者抗GBM免疫应答的免疫抑制调节性T细胞（Treg）， 与吲哚胺2，3双加氧酶1（IDO 1）的表达一致，IDO 1是一种限速酶， 色氨酸（Trp）至犬尿氨酸（Kyn）。利用原位同基因和免疫活性GL 261-C57 BL 6 在移植模型中，我以前证明了shRNA介导的IDO 1表达抑制在小鼠中， GBM细胞显著降低肿瘤内Treg积累，与溶细胞性T细胞应答一致 导致肿瘤完全消退。这一观察结果促进了对药理学抑制的研究 作为治疗性诱导抗GBM免疫的手段。令人惊讶的是， IDO 1抑制剂对肿瘤内Treg积聚和动物受试者存活均无影响。的假设 为这一悖论提供了一种解释，解决了遗传抑制--而不是药理学抑制-- IDO 1的表达，影响肿瘤内Treg积累和效应T细胞对GBM的应答，形成了肿瘤免疫的基础。 这个提议。最近，我的实验室发现，肿瘤微环境中的细胞，而不是GBM细胞， 负责GL 261-C57 BL 6模型中几乎所有IDO 1介导的Trp至Kyn催化剂。这一观察， 然而，提出了一个关于肿瘤细胞相关IDO 1的作用的问题，IDO 1的遗传抑制 促进针对肿瘤的生产性T细胞应答。这个问题的一个潜在答案出现在 这与我们发现IDO 1定位于GBM细胞的细胞核有关。根据这些观察，我们 本研究拟：1）建立IDO 1在人GBM中的原位表达和催化，2）研究IDO 1 在人GBM细胞中的表达和功能以及3）确定核IDO 1在GBM细胞中的功能。的 拟议的研究旨在调查临床相关的问题和方法，旨在扭转 这是为患者合理设计有效免疫治疗的第一步 患上了无法治愈的脑癌

ABSTRACT Glioblastoma multiforme (GBM) is the most common and aggressive form of brain tumor in adults. Median survival for GBM patients is 14.6 months post-diagnosis. A consistent feature of GBM is the intratumoral presence of immunosuppressive regulatory T cells (Treg) that impair patient anti-GBM immune response, coincident with the expression of indoleamine 2,3 dioxygenase 1 (IDO1), a rate-limiting enzyme that converts tryptophan (Trp) to kynurenine (Kyn). Utilizing the orthotopic syngeneic and immunocompetent GL261-C57BL6 engraftment model, I previously demonstrated that shRNA-mediated suppression of IDO1 expression in murine GBM cells significantly decreases intratumoral Treg accumulation coincident with a cytolytic T cell response leading to complete tumor regression. This observation prompted the investigation into pharmacologic inhibition of IDO1 as a means to therapeutically induce anti-GBM immunity. Surprisingly, however, the administration of IDO1 inhibitor had no effect on intratumoral Treg accumulation nor on animal subject survival. A hypothesis that provides an explanation for this paradox, addressing how genetic suppression-, but not pharmacologic inhibition- of IDO1, affects intratumoral Treg accumulation and effector T cell response against GBM, forms the basis of this proposal. Recently, my lab discovered that cells in the tumor microenvironment, but not GBM cells, are responsible for nearly all IDO1-mediated Trp to Kyn catabolism in the GL261-C57BL6 model. This observation, however, raises a question regarding the role of tumor cell-associated IDO1, whose genetic suppression promotes productive T cell response against tumor. A potential answer to this question has emerged in association with our discovery that IDO1 localizes to the nucleus in GBM cells. Based on these observations we propose to: 1) establish IDO1 cell type expression and catabolism in human GBM in situ, 2) investigate IDO1 expression and function in human GBM cells and to 3) determine the function of nuclear IDO1 in GBM cells. The proposed studies aim to investigate clinically-relevant questions and approaches that aim to reverse immunosuppression in glioma, which is the first step to the rational design of effective immunotherapy for patients with incurable brain cancer.