To the Editor, Monoclonal anti-tumor IgG antibodies are used widely to treat malignancies. Studies in the field of AllergoOncology, focusing on the interactions between IgE, allergy, and cancer, point to biological characteristics of IgE that may engender potent anti-tumor functions.1 These include superior affinity of IgE for cognate Fc receptors and the presence in tumors of effector cell populations (eg, macrophages and mast cells) known to exert anti-tumor activities when activated by IgE.2,3 Following promising preclinical findings,2,4 MOv18 IgE, specific for the tumor-associated antigen folate receptor alpha (FRα), overexpressed in ovarian and basal breast cancers and other solid tumors,5 is the first anti-cancer IgE antibody studied in a first-in-class, first-inhuman clinical trial (ClinicalTrials.gov Identifier: NCT02546921). One of the potential concerns associated with application of IgE as a therapy in the clinic relates to the perceived risk of IgE-mediated anaphylaxis. Safety evaluation of such a novel agent mandated the development of bespoke methods to monitor potential hypersensitivity reactions following intravenous infusion and ideally also to help in predicting such a reaction when selecting patients for treatment. Over the past 15 years, the basophil activation test (BAT) has been developed and widely employed to study and predict type 1 hypersensitivity reactions to food, venom, and drugs in the allergy field.6,7 Thus far, its use in the context of cancer is limited to a small number of studies for the detection of allergic reactions to chemotherapeutic agents.8 Basophil activation in the context of tumor-associated immunomodulation and in often heavily treated patients has not been well-studied. Employing the BAT in whole blood of 42 ovarian cancer patients with diverse treatment histories and tumor histologies, we examined the propensity of human basophils to be activated by anti-cancer IgE ex vivo. We first identified circulating basophils (CCR3highSSClow; gating strategy in Figure S1A) from patients with cancer. Basophils were activated (up-regulation of CD63 expression) ex vivo by IgEand non-IgE-mediated triggers (anti-FcεRI, anti-IgE, and fMLP, Figure 1A, Figure S1B). Consistent with previously reported findings in allergic cohorts,6 levels of basophil activation varied among individuals. We detected no basophil activation following addition of the hapten-specific NIP (4-hydroxy-3-iodo-5-nitrophenylacetic acid) IgE alone or its multivalent antigen (NIP-BSA) alone. However, we detected basophil activation by exogenous stimulation of the hapten-specific NIP IgE in combination with multimeric NIP-BSA (Figure 1A). This suggested that IgE could recognize unoccupied cell surface FcεRI on basophils ex vivo and basophils could be activated by exogenous FcεRI receptor engagement and formation of cross-linking immune complexes. We then examined whether stimulation with the anti-cancer mouse/human chimeric IgE antibody (MOv18) could trigger ex vivo basophil activation (Figure 1B, C). As expected in this cohort (n = 42), stimulation with anti-FcεRI, anti-IgE, and fMLP (positive controls) triggered CD63 up-regulation. In all but one patient sample, no basophil activation was measured following incubation of ovarian cancer patient blood with MOv18 IgE or control non-FRα-reactive IgE in the absence of any additional exogenous cross-linking stimulus (mean fold change in %CD63: 1.4 for MOv18 IgE, 1.3 for control IgE; 7.5 and 10.6, respectively, in the positive responder) (Figure 1D). Activation, or lack thereof, was irrespective of different patient tumor histologies and treatment histories, that is, (a) treatment-naïve patients (n = 7), (b) following primary debulking surgery (n = 8), (c) following surgery and chemotherapy (n = 21), or (d) following treatment with bevacizumab (n = 7) (Figure 1E, F). Neither MOv18 IgE nor control non-FRα-reactive IgE triggered basophil activation in the blood of a patient with already raised serum tryptase, a marker which could indicate mastocytosis (although this clinical information was not available) and may have potentially predisposed this individual to an increased risk of hypersensitivity to IgE stimulation, including to MOv18 IgE (Figure 1G). Since MOv18 IgE recognizes the tumor-associated antigen, FRα, it is possible that FRα shed from cancer cells in tissues and anti-FRα autoantibodies (autoAbs), if present in patient circulation, could form immune complexes with MOv18 IgE. This may result in FcεRI cross-linking and basophil activation (Figure 2A). No CD63 up-regulation on basophils was measured following ex vivo stimulation with either MOv18 IgE or control IgE in any sample from patients with known

中文翻译：

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癌症患者血液中的嗜碱性粒细胞活化测试评估抗肿瘤 IgE 治疗候选药物的潜在超敏性


致编者，单克隆抗肿瘤 IgG 抗体广泛用于治疗恶性肿瘤。 AllergoOncology 领域的研究重点关注 IgE、过敏和癌症之间的相互作用，指出 IgE 的生物学特性可能产生有效的抗肿瘤功能。1 其中包括 IgE 对同源 Fc 受体的卓越亲和力以及在肿瘤中的存在已知在被 IgE 激活时发挥抗肿瘤活性的效应细胞群（例如巨噬细胞和肥大细胞）的数量。2,3 根据有希望的临床前发现，2,4 MOv18 IgE，对肿瘤相关抗原叶酸受体 α (FRα) 具有特异性），在卵巢癌和基底乳腺癌以及其他实体瘤中过度表达，5 是首个在一流、首次人体临床试验中研究的抗癌 IgE 抗体（ClinicalTrials.gov 标识符：NCT02546921）。与 IgE 作为临床疗法应用相关的潜在问题之一涉及 IgE 介导的过敏反应的感知风险。对这种新型药物的安全性评估要求开发定制方法来监测静脉输注后潜在的过敏反应，并且理想情况下还有助于在选择患者进行治疗时预测此类反应。在过去的 15 年里，嗜碱性粒细胞激活试验 (BAT) 已得到发展并广泛用于研究和预测过敏领域对食物、毒液和药物的 1 型超敏反应。6,7 迄今为止，它的使用情况癌症的研究仅限于检测化疗药物过敏反应的少数研究。8 肿瘤相关免疫调节背景下以及经常接受重治疗的患者中的嗜碱性粒细胞激活尚未得到充分研究。 我们利用 42 名具有不同治疗史和肿瘤组织学的卵巢癌患者的全血中的 BAT，检查了人类嗜碱性粒细胞被抗癌 IgE 离体激活的倾向。我们首先从癌症患者中鉴定出循环嗜碱性粒细胞（CCR3highSSClow；图 S1A 中的门控策略）。嗜碱性粒细胞被 IgE 和非 IgE 介导的触发器（抗 FcεRI、抗 IgE 和 fMLP，图 1A、图 S1B）离体激活（CD63 表达上调）。与之前报道的过敏人群的研究结果一致，6 个体之间的嗜碱性粒细胞活化水平存在差异。单独添加半抗原特异性 NIP（4-羟基-3-碘-5-硝基苯乙酸）IgE 或其多价抗原 (NIP-BSA) 后，我们未检测到嗜碱性粒细胞活化。然而，我们通过外源刺激半抗原特异性 NIP IgE 与多聚体 NIP-BSA 检测到嗜碱性粒细胞活化（图 1A）。这表明 IgE 可以离体识别嗜碱性粒细胞上未占据的细胞表面 FcεRI，并且嗜碱性粒细胞可以通过外源 FcεRI 受体接合和交联免疫复合物的形成而被激活。然后，我们检查了抗癌小鼠/人嵌合 IgE 抗体 (MOv18) 的刺激是否可以触发离体嗜碱性粒细胞激活（图 1B、C）。正如该队列中所预期的那样 (n = 42)，抗 FcεRI、抗 IgE 和 fMLP（阳性对照）的刺激触发了 CD63 上调。在除一名患者样本外的所有患者样本中，在没有任何其他外源交联刺激的情况下，将卵巢癌患者血液与 MOv18 IgE 或对照非 FRα 反应性 IgE 一起孵育后，未测量到嗜碱性粒细胞活化（%CD63 的平均倍数变化：1.4）对于 MOv18 IgE，1.3 对于对照 IgE；7.5 和 10。6，分别在阳性反应者中）（图1D）。激活或缺乏激活与不同患者的肿瘤组织学和治疗史无关，即（a）未接受过治疗的患者（n = 7），（b）初次减瘤手术后（n = 8），（c）手术和化疗 (n = 21)，或 (d) 贝伐单抗治疗后 (n = 7)（图 1E、F）。 MOv18 IgE 和对照非 FRα 反应性 IgE 均不会触发血清类胰蛋白酶已升高的患者血液中的嗜碱性粒细胞活化，这是一种可能表明肥大细胞增多症的标记物（尽管尚无此临床信息），并且可能使该个体易患肥大细胞增多症。对 IgE 刺激（包括 MOv18 IgE）过敏的风险增加（图 1G）。由于 MOv18 IgE 识别肿瘤相关抗原 FRα，因此 FRα 可能从组织中的癌细胞中脱落，而抗 FRα 自身抗体 (autoAbs) 如果存在于患者循环中，可能会与 MOv18 IgE 形成免疫复合物。这可能导致 FcεRI 交联和嗜碱性粒细胞激活（图 2A）。在已知患有已知疾病的患者的任何样本中，用 MOv18 IgE 或对照 IgE 进行离体刺激后，未检测到嗜碱性粒细胞 CD63 上调。