Department of General Surgery, University of Wisconsin Hospitals and Clinics, Madison, Wisconsin, USA.
Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
J Immunother Cancer. 2022 May;10(5). doi: 10.1136/jitc-2022-004834.
Most pediatric cancers are considered immunologically cold with relatively few responding to immune checkpoint inhibition. We recently described an effective combination radio-immunotherapy treatment regimen ( ombination daptive- nnate immunotherapy egimen (CAIR)) targeting adaptive and innate immunity in 9464D-GD2, an immunologically cold model of neuroblastoma. Here, we characterize the mechanism of CAIR and the role of major histocompatibility complex class I (MHC-I) in the treatment response.
Mice bearing GD2-expressing 9464D-GD2 tumors were treated with CAIR (external beam radiotherapy, hu14.18-IL2 immunocytokine, CpG, anti-CD40, and anti-CTLA4) and tumor growth and survival were tracked. Depletion of specific immune cell lineages, as well as testing in immunodeficient R2G2 mice, were used to determine the populations necessary for treatment efficacy. Induction of MHC-I expression in 9464D-GD2 cells in response to interferon-γ (IFN-γ) and CAIR was measured and , respectively, by flow cytometry and quantitative real-time PCR. A cell line with IFN-γ-inducible MHC-I expression (9464D-GD2-I) was generated by transfecting a subclone of the parental cell line capable of expressing MHC-I with GD2 synthase and was used to assess the impact of MHC-I expression on responsiveness to CAIR.
CAIR cures some mice bearing small (50 mm) but not larger (100 mm) 9464D-GD2 tumors and these cured mice develop weak memory responses against tumor rechallenge. Early suppression of 9464D-GD2 tumors by CAIR does not require T or natural killer (NK) cells, but eventual tumor cures are NK cell dependent. Unlike the parental 9464D cell line, 9464D-GD2 cells have uniformly very low MHC-I expression at baseline and fail to upregulate expression in response to IFN-γ. In contrast, 9464D-GD2-I upregulates MHC-I in response to IFN-γ and is less responsive to CAIR.
Treatment with CAIR cures 9464D-GD2 tumors in a NK cell dependent manner and induction of MHC-I by tumors cells was associated with decreased efficacy. These results demonstrate that the early tumor response to this regimen is T and NK cell independent, but that NK cells have a role in generating lasting cures in the absence of MHC-I expression by tumor cells. Further strategies to better inhibit tumor outgrowth in this setting may require further NK activation or the ability to engage alternative immune effector cells.
大多数儿科癌症被认为具有免疫冷性，只有少数对免疫检查点抑制有反应。我们最近描述了一种针对适应性和固有免疫的有效联合放射免疫治疗方案（combination adaptive-innate immunotherapy egimen，CAIR），该方案针对神经母细胞瘤的免疫冷模型 9464D-GD2。在这里，我们描述了 CAIR 的作用机制以及主要组织相容性复合体 I 类（MHC-I）在治疗反应中的作用。
用表达 GD2 的 9464D-GD2 肿瘤的小鼠进行 CAIR（外照射放疗、hu14.18-IL2 免疫细胞因子、CpG、抗 CD40 和抗 CTLA4）治疗，并跟踪肿瘤生长和存活情况。通过特异性免疫细胞谱系的耗竭以及在免疫缺陷 R2G2 小鼠中的测试，确定了治疗效果所必需的群体。通过流式细胞术和定量实时 PCR 分别测量干扰素-γ（IFN-γ）和 CAIR 对 9464D-GD2 细胞中 MHC-I 表达的诱导。通过转染能够表达 GD2 合酶的亲本细胞系的亚克隆，生成了一种 IFN-γ诱导 MHC-I 表达的细胞系（9464D-GD2-I），并用于评估 MHC-I 表达对 CAIR 反应性的影响。
CAIR 治愈了一些携带小（50mm）但不携带大（100mm）9464D-GD2 肿瘤的小鼠，这些治愈的小鼠对肿瘤再挑战产生了微弱的记忆反应。CAIR 早期抑制 9464D-GD2 肿瘤不需要 T 或自然杀伤（NK）细胞，但最终的肿瘤治愈依赖于 NK 细胞。与亲本 9464D 细胞系不同，9464D-GD2 细胞在基线时普遍具有非常低的 MHC-I 表达，并且不能对 IFN-γ做出反应而上调表达。相比之下，9464D-GD2-I 可响应 IFN-γ而上调 MHC-I 表达，并且对 CAIR 的反应性降低。
用 CAIR 治疗可治愈 9464D-GD2 肿瘤，呈 NK 细胞依赖性，肿瘤细胞 MHC-I 的诱导与疗效降低有关。这些结果表明，该方案的早期肿瘤反应与 T 和 NK 细胞无关，但在肿瘤细胞不表达 MHC-I 的情况下，NK 细胞在产生持久治愈方面发挥作用。进一步的策略，以更好地抑制这种情况下的肿瘤生长，可能需要进一步的 NK 激活或能够利用替代的免疫效应细胞。
