The outcome of patients affected by high-risk or metastatic neuroblastoma (NB) remains grim, with ≥ 50% of the children experiencing relapse or progression of the disease despite multimodal, intensive treatment. In order to identify new strategies to improve the overall survival and the quality of life of these children, we recently developed and optimized a third-generation GD2-specific chimeric antigen receptor (CAR) construct, which is currently under evaluation in our Institution in a phase I/II clinical trial (NCT03373097) enrolling patients with relapsed/refractory NB. We observed that our CAR T-cells are able to induce marked tumor reduction and even achieve complete remission with a higher efficiency than that of other CAR T-cells reported in previous studies. However, often responses are not sustained and relapses occur. Here, we demonstrate for the first time a mechanism of resistance to GD2.CAR T-cell treatment, showing how polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) increase in the peripheral blood (PB) of NB patients after GD2.CAR T-cell treatment in case of relapse and loss of response. In vitro, isolated PMN-MDSC demonstrate to inhibit the anti-tumor cytotoxicity of different generations of GD2.CAR T-cells. Gene-expression profiling of GD2.CAR T-cells “conditioned” with PMN-MDSC shows downregulation of genes involved in cell activation, signal transduction, inflammation and cytokine/chemokine secretion. Analysis of NB gene-expression dataset confirms a correlation between expression of these genes and patient outcome. Moreover, in patients treated with GD2.CAR T-cells, the frequency of circulating PMN-MDSC inversely correlates with the levels of GD2.CAR T-cells, resulting more elevated in patients who did not respond or lost response to the treatment. The presence and the frequency of PMN-MDSC in PB of high-risk and metastatic NB represents a useful prognostic marker to predict the response to GD2.CAR T-cells and other adoptive immunotherapy. This study underlines the importance of further optimization of both CAR T-cells and clinical trial in order to target elements of the tumor microenvironment.

中文翻译：

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多形核髓源性抑制细胞损害 GD2.CAR T 细胞在神经母细胞瘤患者中的抗肿瘤功效

受高危或转移性神经母细胞瘤 (NB) 影响的患者的结局仍然严峻，尽管进行了多模式、强化治疗，但仍有 50% 以上的儿童出现疾病复发或进展。为了确定提高这些儿童的总体生存率和生活质量的新策略，我们最近开发和优化了第三代 GD2 特异性嵌合抗原受体 (CAR) 构建体，该构建体目前正在我们的机构中​​进行评估。 I/II 期临床试验 (NCT03373097) 招募患有复发/难治性 NB 的患者。我们观察到，我们的 CAR T 细胞能够诱导显着的肿瘤减少，甚至以比先前研究中报道的其他 CAR T 细胞更高的效率实现完全缓解。然而，通常反应不是持续的并且会发生复发。这里，我们首次证明了对 GD2.CAR T 细胞治疗的耐药机制，显示了 GD2.CAR T 细胞后 NB 患者外周血 (PB) 中多形核髓源性抑制细胞 (PMN-MDSC) 如何增加在复发和失去反应的情况下进行治疗。在体外，分离的 PMN-MDSC 证明可以抑制不同代 GD2.CAR T 细胞的抗肿瘤细胞毒性。用 PMN-MDSC “条件化”的 GD2.CAR T 细胞的基因表达谱显示参与细胞活化、信号转导、炎症和细胞因子/趋化因子分泌的基因下调。NB 基因表达数据集的分析证实了这些基因的表达与患者结果之间的相关性。此外，在接受 GD2.CAR T 细胞治疗的患者中，循环 PMN-MDSC 的频率与 GD2.CAR T 细胞的水平呈负相关，导致对治疗无反应或失去反应的患者升高更多。PMN-MDSC 在高危和转移性 NB 的 PB 中的存在和频率代表了预测对 GD2.CAR T 细胞和其他过继免疫疗法的反应的有用预后标志物。这项研究强调了进一步优化 CAR T 细胞和临床试验以靶向肿瘤微环境元素的重要性。