Institute of Medical Bioinformatics and Systems Medicine, Medical Center - University of Freiburg Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Systems Cell-Signaling Laboratory, Department of Biochemistry and Molecular Biology, University of Dhaka, Dhaka, Bangladesh.
Genome Med. 2023 Jul 11;15(1):48. doi: 10.1186/s13073-023-01207-1.
Spatiotemporal heterogeneity originating from genomic and transcriptional variation was found to contribute to subtype switching in isocitrate dehydrogenase-1 wild-type glioblastoma (GBM) prior to and upon recurrence. Fluorescence-guided neurosurgical resection utilizing 5-aminolevulinic acid (5ALA) enables intraoperative visualization of infiltrative tumors outside the magnetic resonance imaging contrast-enhanced regions. The cell population and functional status of tumor responsible for enhancing 5ALA-metabolism to fluorescence-active PpIX remain elusive. The close spatial proximity of 5ALA-metabolizing (5ALA +) cells to residual disease remaining post-surgery renders 5ALA + biology an early a priori proxy of GBM recurrence, which is poorly understood.
We performed spatially resolved bulk RNA profiling (SPRP) analysis of unsorted Core, Rim, Invasive margin tissue, and FACS-isolated 5ALA + /5ALA - cells from the invasive margin across IDH-wt GBM patients (N = 10) coupled with histological, radiographic, and two-photon excitation fluorescence microscopic analyses. Deconvolution of SPRP followed by functional analyses was performed using CIBEROSRTx and UCell enrichment algorithms, respectively. We further investigated the spatial architecture of 5ALA + enriched regions by analyzing spatial transcriptomics from an independent IDH-wt GBM cohort (N = 16). Lastly, we performed survival analysis using Cox Proportinal-Hazards model on large GBM cohorts.
SPRP analysis integrated with single-cell and spatial transcriptomics uncovered that the GBM molecular subtype heterogeneity is likely to manifest regionally in a cell-type-specific manner. Infiltrative 5ALA + cell population(s) harboring transcriptionally concordant GBM and myeloid cells with mesenchymal subtype, -active wound response, and glycolytic metabolic signature, was shown to reside within the invasive margin spatially distinct from the tumor core. The spatial co-localization of the infiltrating MES GBM and myeloid cells within the 5ALA + region indicates PpIX fluorescence can effectively be utilized to resect the immune reactive zone beyond the tumor core. Finally, 5ALA + gene signatures were associated with poor survival and recurrence in GBM, signifying that the transition from primary to recurrent GBM is not discrete but rather a continuum whereby primary infiltrative 5ALA + remnant tumor cells more closely resemble the eventual recurrent GBM.
Elucidating the unique molecular and cellular features of the 5ALA + population within tumor invasive margin opens up unique possibilities to develop more effective treatments to delay or block GBM recurrence, and warrants commencement of such treatments as early as possible post-surgical resection of the primary neoplasm.
在异柠檬酸脱氢酶-1 野生型脑胶质瘤（GBM）复发之前和之后，发现源自基因组和转录组变异的时空异质性导致亚型转换。利用 5-氨基酮戊酸（5ALA）进行荧光引导神经外科切除术，可实现对磁共振成像对比增强区域外浸润性肿瘤的术中可视化。负责将肿瘤中的 5ALA 代谢为荧光活性 PpIX 的细胞群体和功能状态仍不清楚。手术后残留的肿瘤中 5ALA 代谢物（5ALA+）细胞与残留疾病的空间接近度使得 5ALA+生物学成为 GBM 复发的早期先验预测因子，但这一点尚未得到充分理解。
我们对来自 IDH-wt GBM 患者的侵袭性边缘的未分选核心、边缘、浸润边缘组织和 FACS 分离的 5ALA+/5ALA-细胞进行了空间分辨批量 RNA 分析（SPRP），并结合组织学、影像学和双光子激发荧光显微镜分析。使用 CIBEROSRTx 和 UCell 富集算法分别对 SPRP 进行去卷积和功能分析。我们还通过分析来自独立 IDH-wt GBM 队列的空间转录组学数据（N=16）进一步研究了 5ALA+富集区域的空间结构。最后，我们在大型 GBM 队列中使用 Cox 比例风险模型进行了生存分析。
SPRP 分析与单细胞和空间转录组学相结合，揭示了 GBM 分子亚型异质性可能以细胞类型特异性的方式在区域上表现出来。浸润性 5ALA+细胞群体（包含转录上一致的 GBM 和具有间充质亚型、活跃的伤口反应和糖酵解代谢特征的髓样细胞）位于侵袭性边缘，与肿瘤核心在空间上不同。5ALA+区域内浸润性 MES GBM 和髓样细胞的空间共定位表明，PpIX 荧光可有效地切除肿瘤核心以外的免疫反应区。最后，5ALA+基因特征与 GBM 的不良预后和复发相关，表明从原发性到复发性 GBM 的转变不是离散的，而是一个连续的过程，原发性浸润性 5ALA+残余肿瘤细胞更类似于最终的复发性 GBM。
阐明肿瘤侵袭性边缘 5ALA+细胞群体的独特分子和细胞特征为开发更有效的治疗方法以延迟或阻止 GBM 复发提供了独特的可能性，并需要在原发性肿瘤切除后尽早开始此类治疗。
