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

项目1：项目摘要/摘要 皮肤黑色素瘤(CM)具有很高的体细胞突变率，致癌因素已被确定 在大多数患者中。PTEN，一种调节致癌PI3K-AKT信号的肿瘤抑制因子 在这些肿瘤中，高达30%的肿瘤完全丧失了表达。我们之前的研究 研究表明，PTEN的缺失与III期黑色素瘤患者的总体生存时间较短有关，并且与 IV期疾病患者靶向治疗的不良结果。以这些研究为基础， 最近，我们研究了PTEN缺失对抗肿瘤免疫反应和免疫治疗的影响。 初步的临床前研究表明，在黑色素瘤中PTEN的缺失增加了 免疫抑制细胞因子，减少关键效应T细胞在肿瘤内的渗透，并导致 体内外对T细胞介导的免疫治疗的抵抗力。晚期黑色素瘤的队列分析 研究表明，在III期黑色素瘤中，PTEN的缺失与CD8+T细胞的减少有关 在IV期疾病中，患者对FDA批准的抗PD-1抗体的应答率显著降低。 用PI3Kβ的异构体特异性抑制剂GSK2636771处理后，AKT活性降低，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有效性 PTEN缺失、PD-1耐药黑色素瘤的免疫活性模型。值得注意的是，GSK2636771不会损害 免疫细胞的活性或功能，与PTEN细胞中对PI3Kβ的选择性依赖一致 损失。基于这些研究，我们假设抑制PI3K-AKT通路将克服耐药性 PTEN缺失的黑色素瘤的抗PD-1免疫治疗。来检验这一假设，并解决未满足的问题 对于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 GSK2636771联合抗PD-1抗体Pembrolizumab治疗转移性黑色素瘤 PTEN缺失，对抗PD-1无效。血液和肿瘤样本将在两年前和 在治疗过程中以及在进展中，以提高我们对这种方案的效果和 试验结果。在目标1中，我们将确定这种治疗对PI3K-AKT激活的影响 途径，以及途径抑制、GSK2636771稳态水平和治疗之间的关系 结果。在目标2，我们将评估联合治疗的免疫效果，通过评估肿瘤和 血液样本中免疫细胞亚群和免疫调节细胞因子的存在和变化， 也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 使用额外的异构体选择性PI3K抑制剂的剂量和组合方法作为进一步 用抗PD-1抗体提高GSK2636771的疗效。这些研究将提高我们对这一角色的理解 研究PI3K-AKT通路在抗肿瘤免疫反应和免疫治疗抵抗中的作用，并有助于识别 为未来PTEN缺失的癌症和其他癌症的测试提供其他合理的策略。

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.