Histological and molecular characterization of TSPO labeling

TSPO在肿瘤转化组织中经常上调，包括胶质母细胞瘤。这可能用于脑肿瘤的PET成像。与弥漫性浸润的WHO II级和III级星形细胞瘤相比，idh野生型胶质母细胞瘤中TSPO的表达更高。此外，预后不利的间充质胶质母细胞瘤表达亚型显示TSPO表达高于经典亚型或前膜亚型。我们发现，胶质母细胞瘤中TSPO启动子甲基化的缺失可能在机制上驱动了这些肿瘤中观察到的TSPO过表达。然而，由于胶质瘤中作为TSPO-PET信号源的细胞群的异质性，成像生物标志物的解释可能具有挑战性。我们已经证明，除了髓细胞外，神经胶质肿瘤细胞是TSPO信号的主要贡献者。然而，在脑肿瘤疾病的过程中，细胞组成变化，在治疗下引起的反应性和吸收性变化的含量增加。因此，我们计划进行纵向活检研究，收集以TSPO富集为特征的原发性和复发性肿瘤的组织样本。然后，我们将对样品进行组织学和分子解剖，以检测TSPO表达、细胞组成和RNA表达谱。利用体外scRadiotracing的新技术，我们将在各自的组织样本中平行评估TSPO的表达和富集。我们还将在模拟人类胶质母细胞瘤肿瘤微环境的小鼠SB28模型中使用scRadiotracing进行反翻译，以在细胞分辨率上解开TSPO示踪标记。此外，将通过scRadiotracing对移植了人原发性胶质母细胞瘤细胞和SB28的NMRI Foxn1nu/nu小鼠进行研究，比较人和小鼠模型中单细胞TSPO的富集情况。为了更广泛地了解人脑组织中的TSPO标记，我们将对包含肿瘤和非肿瘤疾病状态以及来自不同大脑区域的非病变组织的组织微阵列进行染色。将这些信息与来自各自患者/大脑区域的TSPO- pet结合起来，将生成健康和患病大脑中TSPO表达的图谱，以供临床使用。总之，我们整合组织学、分子和成像数据的方法将为TSPO-PET富集模式提供独特的见解，并将有助于更好地理解和全面描述这种新型成像生物标志物的临床相关性。

TSPO is frequently upregulated in neoplastically transformed tissues, including glioblastomas. This may be of use for PET imaging of brain tumors. TSPO expression is higher in IDH-wildtype glioblastomas compared to diffusely infiltrating WHO grade II and III astrocytomas. Also, the prognostically unfavorable mesenchymal glioblastoma expression subtype shows a higher TSPO expression than the classical or proneural subtype. We found that a loss of TSPO promoter methylation in glioblastoma may mechanistically drive the TSPO overexpression observed in these tumors. However, due to the heterogeneity of cell populations contributing as TSPO-PET signal source in gliomas, the imaging biomarker interpretation may be challenging. We have shown that apart from myeloid cells, glial tumor cells are a major contributor to the TSPO signal. Nevertheless, in the course of the brain tumor disease cell compositions vary, with an increasing content of reactive and resorptive changes induced under therapy. We therefore plan on a longitudinal biopsy study collecting tissue samples from primary and recurrent tumors that have been characterized for TSPO enrichment. We will then histologically and molecularly dissect the samples for TSPO expression, cell composition and RNA expression profiles. Using the novel technique of in vitro scRadiotracing we will assess TSPO expression and enrichment in parallel within the respective tissue samples. We will also perform backtranslation to disentangle TSPO tracer labeling at a cellular resolution by employing scRadiotracing in the murine SB28 model, which mimics the tumor microenvironment of human glioblastoma. Furthermore, NMRI Foxn1nu/nu mice transplanted with human primary glioblastoma cells and SB28 will be investigated by scRadiotracing for comparison of single cell TSPO enrichment in human and murine models. In order to gain a broader overview on TSPO labeling in human brain tissue, we will stain tissue microarrays that contain a spectrum of neoplastic and non-neoplastic disease states as well as non-diseased tissues from different brain regions. Bringing this information together with TSPO-PETs from respective patients/brain regions will generate a map of TSPO expression in healthy and diseased brain for clinical use. Taken together, our approach of integrating histological, molecular and imaging data will provide unique insights into TSPO-PET enrichment patterns and will help to better understand and to comprehensively describe the clinical relevance of this novel imaging biomarker.