肿瘤细胞治疗研究
英文原题：TNF-α and IFN-γ differentially regulate AML cell susceptibility to CD70-antibody-mediated cytotoxicity.
CD70是AML中NK细胞免疫治疗的一个有前景的靶点。然而，AML细胞上HLA分子的IFN-γ依赖性上调导致对ADCC的耐药。这些发现强调了在临床试验中需要合理的联合策略来克服这种可诱导的免疫逃逸机制。
开发急性髓系白血病（AML）免疫疗法面临的挑战包括：由于靶向-非白血病毒性，难以确定合适的靶抗原。CD70在AML bulk和白血病干细胞上表达，而在健康细胞上表达有限，已成为一个有前景的靶点。
本研究评估了CD70作为基于NK细胞免疫治疗靶点的潜力，使用糖工程抗体（PF-08046040，SEA-CD70）进行研究。通过多参数流式细胞术检测了原发AML样本中CD70的表面表达。通过抗体依赖性细胞介导的细胞毒性（ADCC）实验，使用AML细胞系、原发AML样本和严重联合免疫缺陷（SCID）小鼠异种移植模型，分析了SEA-CD70的细胞毒性能力。通过将AML细胞暴露于活化T细胞来源的条件培养基（CM）或重组细胞因子，研究了细胞因子对CD70表达和ADCC的影响。
流式细胞术显示，原代AML细胞中CD70表达在不同遗传亚组间范围为0.2%至89.6%（中位数=7.0%，n=86）；该表达在复发时保持不变（中位数=3.9%，n=14）。SEA-CD70对AML细胞系、原代细胞及SCID小鼠模型表现出强效、剂量依赖性的细胞毒性，且与CD70表达水平相关。值得注意的是，暴露于活化T细胞条件培养基的AML细胞上调了CD70。TNF-α被确定为CD70上调的驱动因素，并转化为对AML细胞增强的ADCC（无TNF-α时细胞毒性=17.9% vs 有TNF-α时=34.3%，n=13-15）。相反，IFN-γ暴露导致ADCC降低（无IFN-γ时细胞毒性=17.9% vs 有IFN-γ时=9.2%，n=15），这归因于NK抑制性受体配体（HLA-ABC、HLA-E）表达增加。阻断相应的抑制性NK受体（KIR/CD158b和NKG2A）可部分逆转此效应。在CD33靶向抗体中也观察到类似发现，表明AML中存在针对基于ADCC的免疫治疗的普遍耐药机制。
BACKGROUND: Challenges to developing immunotherapies for acute myeloid leukemia (AML) include the identification of suitable target antigens due to on-target-off-leukemia toxicity. CD70, expressed on AML bulk and leukemic stem cells with limited expression on healthy cells, has emerged as a promising target. METHODS: This study evaluated CD70 as a target for NK-cell-based immunotherapy using a sugar-engineered antibody (PF-08046040, SEA-CD70). CD70 surface expression was assessed in primary AML samples by multiparameter flow cytometry. The cytotoxic capacity of SEA-CD70 was analyzed through antibody-dependent cellular cytotoxicity (ADCC) assays using AML cell lines, primary AML samples, and a severe combined immunodeficiency (SCID) mouse xenograft model. The effects of cytokines on CD70 expression and ADCC were investigated by exposing AML cells to conditioned medium (CM) derived from activated T cells or recombinant cytokines. RESULTS: Flow cytometry revealed CD70 expression ranging from 0.2% to 89.6% (median=7.0%, n=86) in primary AML cells across genetic subgroups; this expression remained unchanged at relapse (median=3.9%, n=14). SEA-CD70 showed potent, dose-dependent cytotoxicity against AML cell lines, primary cells, and in an SCID mouse model, which correlated with CD70 expression levels. Notably, AML cells exposed to CM from activated T cells upregulated CD70. TNF-α was identified as the driver of CD70 upregulation, translating into enhanced ADCC against AML cells (cytotoxicity w/o TNF-α = 17.9% vs with TNF-α = 34.3%, n=13-15). Conversely, IFN-γ exposure led to reduced ADCC (cytotoxicity w/o IFN-γ = 17.9% vs with IFN-γ = 9.2%, n=15), which is attributed to increased expression of NK inhibitory receptor ligands (HLA-ABC, HLA-E). Blocking of the corresponding inhibitory NK receptors (KIR/CD158b and NKG2A) partially reversed this effect. Similar findings were observed with a CD33-directed antibody, indicating a universal resistance mechanism against ADCC-based immunotherapy in AML. CONCLUSIONS: CD70 is a promising target for NK cell-based immunotherapy in AML. However, IFN-γ-dependent upregulation of HLA molecules on AML cells contributes to resistance to ADCC. These findings underscore the need for rationale combination strategies in clinical trials to overcome this inducible immune escape mechanism.
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