Table_2_Targeting macrophage Syk enhances responses to immune checkpoint blockade and radiotherapy in high-risk neuroblastoma.xlsx

BackgroundNeuroblastoma (NB) is considered an immunologically cold tumor and is usually less responsive to immune checkpoint blockade (ICB). Tumor-associated macrophages (TAMs) are highly infiltrated in NB tumors and promote immune escape and resistance to ICB. Hence therapeutic strategies targeting immunosuppressive TAMs can improve responses to ICB in NB. We recently discovered that spleen tyrosine kinase (Syk) reprograms TAMs toward an immunostimulatory phenotype and enhances T-cell responses in the lung adenocarcinoma model. Here we investigated if Syk is an immune-oncology target in NB and tested whether a novel immunotherapeutic approach utilizing Syk inhibitor together with radiation and ICB could provide a durable anti-tumor immune response in an MYCN amplified murine model of NB.MethodsMyeloid Syk KO mice and syngeneic MYCN-amplified cell lines were used to elucidate the effect of myeloid Syk on the NB tumor microenvironment (TME). In addition, the effect of Syk inhibitor, R788, on anti-tumor immunity alone or in combination with anti-PDL1 mAb and radiation was also determined in murine NB models. The underlying mechanism of action of this novel therapeutic combination was also investigated.ResultsHerein, we report that Syk is a marker of NB-associated macrophages and plays a crucial role in promoting immunosuppression in the NB TME. We found that the blockade of Syk in NB-bearing mice markedly impairs tumor growth. This effect is facilitated by macrophages that become immunogenic in the absence of Syk, skewing the suppressive TME towards immunostimulation and activating anti-tumor immune responses. Moreover, combining FDA-approved Syk inhibitor, R788 (fostamatinib) along with anti-PDL1 mAb provides a synergistic effect leading to complete tumor regression and durable anti-tumor immunity in mice bearing small tumors (50 mm3) but not larger tumors (250 mm3). However, combining radiation to R788 and anti-PDL1 mAb prolongs the survival of mice bearing large NB9464 tumors.ConclusionCollectively, our findings demonstrate the central role of macrophage Syk in NB progression and demonstrate that Syk blockade can “reeducate” TAMs towards immunostimulatory phenotype, leading to enhanced T cell responses. These findings further support the clinical evaluation of fostamatinib alone or with radiation and ICB, as a novel therapeutic intervention in neuroblastoma.

背景：神经母细胞瘤（NB）被视为一种免疫冷肿瘤，通常对免疫检查点阻断（ICB）的反应性较低。肿瘤相关巨噬细胞（TAMs）在NB肿瘤中高度浸润，并促进免疫逃逸和抗ICB的耐药性。因此，针对免疫抑制性TAMs的治疗策略可以提高NB对ICB的反应。我们最近发现，脾酪氨酸激酶（Syk）将TAMs重新编程为免疫刺激表型，并在肺腺癌模型中增强T细胞反应。在本研究中，我们探讨了Syk是否是NB的免疫肿瘤学靶点，并测试了一种新型免疫治疗方法的可行性，该方法结合Syk抑制剂、放射治疗和ICB，以在MYCN扩增的小鼠NB模型中提供持久的抗肿瘤免疫反应。方法：使用骨髓Syk敲除小鼠和同源MYCN扩增细胞系，阐明骨髓Syk对NB肿瘤微环境（TME）的影响。此外，在小鼠NB模型中，还确定了Syk抑制剂R788单独或与抗PDL1单克隆抗体和放射治疗联合应用对抗肿瘤免疫的影响。还研究了这种新型治疗组合的作用机制。结果：在本研究中，我们报告称Syk是NB相关巨噬细胞的标志物，并在NB TME中促进免疫抑制方面发挥关键作用。我们发现，阻断NB携带小鼠中的Syk显著损害肿瘤生长。这种效应是通过巨噬细胞在没有Syk的情况下变得免疫原性而实现的，将抑制性TME偏向免疫刺激，并激活抗肿瘤免疫反应。此外，将FDA批准的Syk抑制剂R788（ fostamatinib）与抗PDL1单克隆抗体联合使用，在携带小肿瘤（50 mm3）的小鼠中产生协同效应，导致肿瘤完全消退和持久的抗肿瘤免疫，但在携带大肿瘤（250 mm3）的小鼠中则没有。然而，将放射治疗与R788和抗PDL1单克隆抗体结合，可延长携带大NB9464肿瘤的小鼠的生存期。结论：综上所述，我们的研究结果表明巨噬细胞Syk在NB进展中的核心作用，并证明Syk阻断可以将TAMs“重新教育”为免疫刺激表型，从而增强T细胞反应。这些发现进一步支持了fostamatinib单独或与放射治疗和ICB联合使用作为神经母细胞瘤新型治疗干预措施的临床评估。