Project 1 Targeting the PI3K Pathway to Overcome Resistance to Immunotherapy in Melanomas with Loss of PTEN

项目1：项目概要/摘要 皮肤黑色素瘤（CM）具有非常高的体细胞突变率，并确定了致癌驱动因素 在大多数患者中。PTEN，一种调节致癌PI 3 K-AKT信号传导的肿瘤抑制因子 在这些肿瘤中，高达30%的表达完全丧失。我们以前的研究 研究表明，在III期黑色素瘤患者中，PTEN缺失与总生存期缩短相关， IV期疾病患者的靶向治疗结局较差。在这些研究的基础上， 最近，我们研究了PTEN缺失对抗肿瘤免疫应答和免疫治疗的影响。 最初的临床前研究表明，黑色素瘤中PTEN的缺失增加了 免疫抑制性细胞因子，减少关键效应T细胞的肿瘤内浸润，并导致 体外和体内对T细胞介导的免疫疗法的抗性。晚期黑色素瘤队列分析 患者的研究表明，在III期黑色素瘤中，PTEN的缺失与CD 8 + T细胞浸润的减少有关， 在IV期疾病中，对FDA批准的抗PD-1抗体的应答率显著降低。 用GSK 2636771（一种PI 3 K β亚型特异性抑制剂）治疗，AKT活化降低，T细胞增加， 细胞浸润，并增加体内抗PD-1检查点抑制剂治疗的疗效。 PTEN缺失、PD-1抗性黑素瘤的免疫活性模型。值得注意的是，GSK 2636771没有损害 免疫细胞的活力或功能，与具有PTEN的细胞中对PI 3 K β的选择性依赖性一致 损失基于这些研究，我们假设PI 3 K-AKT通路的抑制将克服耐药性。 用于PTEN缺失的黑色素瘤中的抗PD-1免疫疗法。为了验证这一假设， 为了满足PD-1难治性患者的有效治疗需求，我们正在进行一项I/II期临床试验， GSK 2636771联合抗PD-1抗体派姆单抗治疗转移性黑色素瘤患者 对抗PD-1抗体无反应的PTEN缺失患者血液和肿瘤样本将在术前和术后采集。 在治疗过程中以及在进展，以提高我们的理解，这种方案的影响， 审判的结果。在目标1中，我们将确定这种治疗对PI 3 K-AKT活化的影响。 途径，以及途径抑制、GSK 2636771稳态水平和治疗之间的关系 结果。在目的2中，我们将通过评估肿瘤和免疫抑制剂来评估联合治疗的免疫效果。 血液样品中免疫细胞亚群和免疫调节细胞因子的存在和变化， 还将与临床反应性进行比较。在目标3中，我们将使用临床前模型来评估间歇性 给药和与其他亚型选择性PI 3 K抑制剂的组合方法作为进一步 改善GSK 2636771与抗PD-1的疗效。这些研究将增进我们对 PI 3 K-AKT通路在抗肿瘤免疫应答和免疫治疗抵抗中的作用，并帮助识别 为将来在这种和其他具有PTEN缺失的癌症中进行测试提供了额外的合理策略。

Project 1: Project Summary/Abstract Cutaneous melanomas (CM) have a very high rate of somatic mutations, and oncogenic drivers are identified in the majority of patients. PTEN, a tumor suppressor that regulates the oncogenic PI3K-AKT signaling pathway, demonstrates complete loss of expression in up to 30% of these tumors. Our previous studies showed that loss of PTEN is associated with shorter overall survival in stage III melanoma patients, and with inferior outcomes with targeted therapies in patients with stage IV disease. Building upon these studies, recently we investigated the impact of PTEN loss on the anti-tumor immune response and immunotherapy. Initial preclinical studies demonstrated that loss of PTEN in melanomas increases the expression of immunosuppressive cytokines, decreases the intratumoral infiltration of critical effector T cells, and causes resistance to T-cell mediated immunotherapy in vitro and in vivo. Analyses of cohorts of advanced melanoma patients showed that loss of PTEN was associated with decreased CD8+ T cell infiltration in stage III melanoma patients, and significantly decreased response rates to FDA approved anti-PD-1 antibodies in stage IV disease. Treatment with GSK2636771, an isoform-specific inhibitor of PI3Kβ, decreased AKT activation, increased T cell infiltration, and increased the efficacy of anti-PD-1 checkpoint inhibitor therapy in vivo in an immunocompetent model of PTEN-null, PD-1-resistant melanoma. Notably, GSK2636771 did not harm the viability or function of immune cells, consistent with the selective dependence on PI3Kβ in cells with PTEN loss. Based on these studies, we hypothesize that inhibition of the PI3K-AKT pathway will overcome resistance to anti-PD-1 immunotherapy in melanomas with loss of PTEN. To test this hypothesis, and address the unmet need for effective therapies for PD-1-refractory patients, we are conducting a phase I/II clinical trial of GSK2636771 in combination with the anti-PD-1 antibody pembrolizumab in metastatic melanoma patients with PTEN loss that failed to respond to anti-PD-1. Blood and tumor samples will be collected prior to and during treatment as well as at progression to improve our understanding of the effects of this regimen and the results of the trial. In Aim 1 we will determine the effects of this treatment on the activation of the PI3K-AKT pathway, and the relationship between pathway inhibition, GSK2636771 steady-state levels, and treatment outcomes. In Aim 2 we will evaluate the immune effects of the combination treatment by evaluating tumor and blood samples for the presence and changes in immune cell subsets and immunoregulatory cytokines, which will also be compared to clinical responsiveness. In Aim 3 we will use preclinical models to evaluate intermittent dosing and combinatorial approaches with additional isoform-selective PI3K inhibitors as strategies to further improve the efficacy of GSK2636771 with anti-PD-1. These studies will improve our understanding of the role of the PI3K-AKT pathway in the anti-tumor immune response and immunotherapy resistance, and help identify additional rational strategies for future testing in this and other cancers with PTEN loss.