Table_1_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）被认为是一种免疫学冷肿瘤，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ICB的耐药性。因此，针对免疫抑制性TAMs的治疗策略可以改善NB对ICB的反应。我们最近发现，脾酪氨酸激酶（Syk）将TAMs重编程为免疫刺激表型，并在肺腺癌模型中增强T细胞反应。在此，我们研究了Syk是否是NB中的免疫肿瘤学靶点，并测试了利用Syk抑制剂联合放疗和ICB的新型免疫治疗方法是否能在MYCN扩增的小鼠NB模型中提供持久的抗肿瘤免疫反应。方法：使用髓系Syk敲除小鼠和同基因MYCN扩增细胞系，阐明髓系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单克隆抗体和放疗联合使用对抗肿瘤免疫的影响。还研究了这种新型治疗组合的潜在作用机制。结果：本研究报告称，Syk是NB相关巨噬细胞的标志物，在NB TME中促进免疫抑制中起着至关重要的作用。我们发现，在NB携带小鼠中阻断Syk显著损害肿瘤生长。这种效应通过巨噬细胞在没有Syk的情况下变得免疫原性而得到促进，使抑制性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，在小鼠携带小型肿瘤（50 mm3）时产生协同效应，导致肿瘤完全消退和持久的抗肿瘤免疫，但在携带大型肿瘤（250 mm3）的小鼠中则不然。然而，将放疗与R788和抗-PDL1单克隆抗体联合使用可延长携带大型NB9464肿瘤的小鼠的生存期。结论：总之，我们的研究结果证明了巨噬细胞Syk在NB进展中的核心作用，并表明Syk阻断可以将TAMs“再教育”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对 fostamatinib 单独或与放疗和ICB联合使用进行临床评估，作为神经母细胞瘤的一种新型治疗干预措施。