研究背景

成人胶质瘤约占所有原发性中枢神经系统恶性肿瘤的80%，可依据异柠檬酸脱氢酶（Isocitrate dehydrogenase, IDH）突变与否分为IDH野生型和突变型胶质瘤。IDH野生型胶质母细胞瘤侵袭性强、预后差，而IDH突变型胶质瘤在诊断时多呈低级别病理特征、预后相对较好。然而，约70%的低级别IDH突变型胶质瘤（Low grade gliomas, LGG）患者在接受治疗期间会发生恶性转化（Malignant transformation, MT），进展为高级别胶质瘤（High grade gliomas, HGG），且与患者预后恶化密切相关。肿瘤相关巨噬细胞（Tumor-associated macrophages, TAMs）虽被认为与胶质瘤进展相关，但此前研究多将TAMs简单归结于M1/M2极化分类，对于IDH突变型胶质瘤MT过程中TAMs具体分类和作用机制尚不明确。

研究方法

本研究综合运用多种组学和实验方法展开研究。首先，对临床原发和复发IDH突变型胶质瘤样本进行单细胞转录组学分析，通过“基因分类”算法识别出一类与恶性转化相关的TAMs亚群，差异分析显示该类TAMs高表达表面蛋白PLAUR，定义为PLAUR+TAMs，并且通过体内外实验确定了PLAUR+TAMs的衰老表型，命名为SenTAMs（Senescent TAMs，衰老肿瘤相关巨噬细胞），再利用小鼠模型，从整体动物水平探究SenTAMs在IDH突变型胶质瘤进展中的作用。一方面，设置不同的实验条件，包括野生型对照组、Plaur敲除组（Plaur-knockout, Plaur-ko）、抑制剂干预组（PLAUR抑制剂组、PLAUR抑制剂与IDH抑制剂联用组等），以观察不同处理条件下对肿瘤生长、肿瘤细胞表型、小鼠生存等多方面的影响。另一方面，进行共培养实验，将SenTAMs与T细胞、胶质瘤细胞共培养，通过多种功能学检测手段（如细胞增殖实验、细胞因子测定等）评估SenTAMs对胶质瘤细胞表型转化及T细胞功能的调控作用。

研究结果

1、SenTAMs的识别与鉴定

单细胞转录组学分析结合“基因分类”算法，在IDH突变型胶质瘤中识别出一群具有高PLAUR表达特征的TAM亚群，进一步研究发现这类TAMs具有显著的衰老特征，将其定义为SenTAMs。SenTAMs的丰度在LGG向HGG转化的MT过程中显著上调，提示其可能参与了MT过程。

2、SenTAMs对IDH突变型胶质瘤细胞的影响

增殖干性样肿瘤细胞丰度的升高是恶性转化的特征性标志。SenTAMs可通过PLAUR-ITGAV信号轴，显著促进IDH突变型胶质瘤细胞AKT信号激活，向具有增殖干细胞样表型转变，赋予胶质瘤细胞更强的增殖能力，使其具备更高的恶性程度。从细胞和动物实验两个层面证实，Plaur基因敲除小鼠的肿瘤体积相对减小（中位总荧光值3.65*10^6至3.18*10^6，p=0.0107），相对于Plaur野生型小鼠的生存时间也显著延长（中位生存时间30天延长至52天，log-Rank检验p<0.001），表明PLAUR在IDH突变型胶质瘤MT过程中发挥关键作用。

3、SenTAMs的免疫抑制功能

SenTAMs可显著抑制T细胞的正常功能，降低其特异性抗肿瘤细胞因子的分泌水平（相较于非SenTAMs组，与SenTAMs共培养的T细胞组TNF-α+细胞比例和GZMB+细胞比例显著下调，p=0.0006和p<0.0001），进而诱导肿瘤微环境形成免疫抑制状态，为肿瘤细胞免疫逃逸创造有利条件。

4、肿瘤表观遗传变化与SenTAMs的关联

SenTAMs在IDH突变伴ATRX缺失的胶质瘤中更为富集。IDH突变和ATRX缺失这种常见的基因组合，能够通过旁分泌衰老相关分泌表型（SASP）因子（IL-6水平增加3倍，p<0.05），上调TAMs的STAT3信号通路，诱导TAM向SenTAMs转化。

5、靶向PLAUR和IDH抑制剂的协同效果

IDH抑制剂在治疗IDH突变型胶质瘤过程中，一方面降低肿瘤增殖干性样信号（标准化富集得分Normalized enrichment score，NES=-1.53，p<0.001），产生抗MT作用，另一方面诱导衰老巨噬细胞（NES=1.72, p<0.001)和SASP信号上调（NES=1.82，p<0.001），成为MT的潜在诱因。研究发现PLAUR抑制剂能够增强IDH抑制剂对IDH突变型胶质瘤的治疗效果，二者联用可协同发挥抗肿瘤作用（中位生存时间40天延长至60天，log-Rank检验p<0.05）。

研究结论

SenTAMs在IDH突变型胶质瘤的MT进程中占据关键地位。通过PLAUR-ITGAV信号轴推进肿瘤细胞向恶性程度更高的增殖干细胞样表型转变，同时介导免疫抑制微环境，助力肿瘤细胞的MT进程。基于以上发现，本研究提出针对性干预策略，即通过PLAUR抑制剂与IDH抑制剂联合应用，能够更加有效地抑制肿瘤细胞的MT，减缓肿瘤进展，有望提升IDH突变型胶质瘤患者的治疗效果，改善患者预后，为IDH突变型胶质瘤的治疗提供了新的理论基础和潜在的临床治疗方向。

Background​

Adult gliomas account for approximately 80% of all primary central nervous system malignancies and can be classified as IDH wild-type or IDH-mutant gliomas based on isocitrate dehydrogenase (IDH) mutation status. IDH-wild-type glioblastomas are highly invasive and associated with poor prognosis, whereas IDH-mutant gliomas often exhibit low-grade pathological features at diagnosis and relatively favorable outcomes. However, ~70% of patients with low-grade IDH-mutant gliomas (LGG) undergo malignant transformation (MT) into high-grade gliomas (HGG) during treatment, which correlates closely with worsened prognosis. Tumor-associated macrophages (TAMs) are implicated in glioma progression, but prior studies have largely simplified TAMs into M1/M2 polarization classifications. The specific subtypes and mechanisms of TAMs during MT in IDH-mutant gliomas remain unclear.

Methods​

This study employed integrated multi-omics and experimental approaches. First, single-cell transcriptomic analysis of primary and recurrent IDH-mutant glioma samples identified a TAM subset associated with MT using a "gene classification" algorithm. Differential analysis revealed this subset highly expressed the surface protein PLAUR, defining them as PLAUR+ TAMs. In vitro and in vivo experiments confirmed their senescent phenotype, termed SenTAMs (Senescent TAMs). Mouse models were then used to explore SenTAMs' role in IDH-mutant glioma progression. Experimental groups included wild-type controls, Plaur-knockout (Plaur-ko) mice, inhibitor-treated groups (PLAUR inhibitor alone or combined with IDH inhibitor), and co-culture systems of SenTAMs with T cells or glioma cells. Functional assays (e.g., proliferation assays, cytokine measurements) assessed SenTAMs' effects on glioma cell phenotypic transformation and T cell activity.

Results​

​​1, Identification and Characterization of SenTAMs​​

Single-cell transcriptomic analysis identified a PLAUR-high TAM subset in IDH-mutant gliomas. These SenTAMs exhibited prominent senescence features, with elevated abundance during LGG-to-HGG MT, suggesting their involvement in MT.

​​2, SenTAMs Drive Malignant Transformation​​

SenTAMs promoted IDH-mutant glioma cell proliferation and stem-like phenotypes via the PLAUR-ITGAV axis, activating AKT signaling. Plaur knockout reduced tumor volume (median total fluorescence: 3.65×10⁶ vs. 3.18×10⁶, p = 0.0107) and prolonged survival (median survival: 30 vs. 52 days, log-rank p < 0.001).

​​3, SenTAM-Mediated Immunosuppression​​

SenTAMs suppressed T cell function, reducing TNF-α+ and GZMB+ T cell proportions (p = 0.0006 and p < 0.0001), thereby fostering an immunosuppressive microenvironment.

​​4, Genetic and Epigenetic Links​​

SenTAMs were enriched in IDH-mutant/ATRX-deficient gliomas. IDH mutation and ATRX loss upregulated STAT3 signaling via SASP factors (e.g., IL-6 up to 3-fold, p < 0.05), driving SenTAM differentiation.

​​5, Synergistic Effects of PLAUR and IDH Inhibitors​​

While IDH inhibitors reduced proliferative stemness (NES = -1.53, p < 0.001) but induced SenTAM signature and SASP (NES = 1.72 and 1.82, p < 0.001), PLAUR inhibition synergized with IDH inhibitors to enhance antitumor effects (median survival: 40 vs. 60 days, log-rank p < 0.05).

Conclusion​

This study identifies SenTAMs as a pivotal driver of IDH-mutant glioma MT through immune suppression and induction of proliferating stem-like plasticity. The discovery of the PLAUR-ITGAV axis and the paracrine SASP-mediated conversion of TAMs to SenTAMs provides critical insights into the interplay between tumor genetics and immune remodeling. The synergistic efficacy of combining PLAUR and IDH inhibitors highlights a promising therapeutic strategy for patients with IDH-mutant LGGs at risk of MT, offering a new paradigm for precision medicine in IDH-mutant glioma treatment.

Significance​

This research advances the understanding of the immunosuppressive landscape in IDH-mutant gliomas by revealing a novel senescent TAM subpopulation (SenTAMs) that promotes MT through both direct tumor cell proliferating stem-like reprogramming and immune suppression. The identification of the PLAUR-ITGAV axis and the SASP-driven paracrine mechanism establishes a framework for developing combinatorial therapies of targeting the MT modulator (PLAUR) and the IDH inhibitor. These findings have significant implications for improving survival outcomes in patients with IDH-mutant gliomas, particularly those progressing to HGG.