Visual Abstract

Plasmalemma vesicle-associated protein (PLVAP) is the main component of endothelial diaphragms in fenestrae, caveolae, and transendothelial channels. PLVAP is expressed in the adult kidney glomerulus upon injury. Glomerular endothelial injury is associated with progressive loss of kidney function in diabetic kidney disease (DKD). This study aimed to investigate whether PLVAP could serve as a marker for glomerular endothelial damage in DKD. Glomerular PLVAP expression was analyzed in different mouse models of DKD and their respective healthy control animals using automatic digital quantification of histological whole kidney sections. Transgenic mice expressing a dominant-negative GIP receptor (GIPRdn) in pancreatic beta-cells as a model for diabetes mellitus (DM) type 1 and black and tan brachyuric (BTBR) ob/ob mice, as a model for DM type 2, were used. Distinct PLVAP induction was observed in all diabetic models studied. Traces of glomerular PLVAP expression could be identified in the healthy control kidneys using automated quantification. Stainings for other endothelial injury markers such as CD31 or the erythroblast transformation-specific related gene (ERG) displayed no differences between diabetic and healthy groups at the time points when PLVAP was induced. The same was also true for the mesangial cells marker α8Integrin, while the podocyte marker nephrin appeared to be diminished only in BTBR ob/ob mice. Glomerular hypertrophy, which is one of the initial morphological signs of diabetic kidney damage, was observed in both diabetic models. These findings suggest that PLVAP is an early marker of glomerular endothelial injury in diabetes-induced kidney damage in mice.

Introduction: Thymic epithelial tumors (TETs) are very rare. Thymoma A and AB have a better prognosis than more aggressive thymoma B, thymic carcinoma (TC) and neuroendocrine tumors of the thymus (NET). While previous efforts such as TCGA have mainly characterized thymomas (Radovich et al., Cancer Cell 2018), the molecular landscape of TCs and NETs is still elusive. Patients and Methods: Between 03/2014 and 07/2020, we enrolled 44 TET patients (27 TCs, 11 thymomas, 6 NETs) in a prospective observational study (MASTER) conducted by the National Center for Tumor Diseases (NCT) Heidelberg, NCT Dresden and the German Cancer Consortium (DKTK). MASTER applied whole genome/exome sequencing (WGS, n=22; WES, n=22), transcriptome (n=40) and germline analysis to inform therapy recommendations by a dedicated molecular tumor board (MTB). We systematically gathered follow-up data to evaluate outcome and compared progression-free survival (PFS) of the first treatment according to an MTB recommendation (PFS2) to the last prior systemic treatment (PFS1) in each patient (PFS ratio). Results: Tumor mutational burden (TMB) was low (median=0.99 mutations/Mb, range 0.08-3.48) but higher than in TCGA (p<0.05). TMB was higher in TCs than in thymoma (p<0.05). Most frequently mutated genes were TP53 (30%), CYLD (16%), SETD2 (14%) and KIT (14%). Germline analysis revealed (likely) pathogenic germline alterations in 25% of patients (MUTYH, n=3; BRCA1, n=2; BRCA2, BAP1, CHEK2, FANCA, TP53, MEN1, n=1). A comprehensive analysis of candidate biomarkers of homologous recombination repair (HRR) defects revealed a subgroup of TET patients with a rationale for PARP inhibitor therapy. Unsupervised clustering of RNA sequencing data mainly revealed clustering that correlated with WHO classification. Additionally, TCs clustered in two subgroups that we identified as immunologically hot and cold tumors using immunohistochemistry validation. Overall survival of patients with hot tumors was significantly longer (p<0.05). The MTB recommended therapies for 42 patients (95%), which were implemented in 24 cases (57%). Five patients had a PFS2 > 6 months and a PFS ratio > 1.3. The best outcome was achieved using imatinib in a patient with a KIT mutation (p.W557R). After progression, the MTB recommended ponatinib based on a secondary KIT mutation (p.V654A). The patient was still on ponatinib when the observation period ended. Conclusion: We demonstrate that comprehensive molecular analysis provides clinically relevant information in a subgroup of TET patients. Thymoma, TCs, and NETs present with different molecular characteristics. Distinction between immunologically hot and cold TCs may have value for risk stratification and therapeutic strategies. PARP inhibition could be a potential new treatment option in a small subgroup of TETs. Molecular testing of KIT, germline analysis and genetic counseling should be recommended for all patients with advanced TETs. Citation Format: Lino Möhrmann, Lysann Rostock, Małgorzata Oleś, Arne Jahn, Marie Arlt, Nagarajan Paramasivam, Korinna Jöhrens, Luise Rupp, Marc Schmitz, Daniela Richter, Sebastian Uhrig, Martina Fröhlich, Barbara Hutter, Jennifer Hüllein, Elena E. Wolf, Dorothea Hanf, Laura Gieldon, Simon Kreutzfeldt, Christoph E. Heilig, Veronica Teleanu, Daniel B. Lipka, Andreas Mock, Ivan Jelas, Damian T. Rieke, Marcel Wiesweg, Melanie Boerries, Anna L. Illert, Alexander Desuki, Thomas Kindler, Angela M. Krackhardt, C. Benedikt Westphalen, Heidrun Grosch, Leonidas Apostolidis, Albrecht Stenzinger, Irina A. Kerle, Christoph Heining, Daniel Hübschmann, Evelin Schröck, Stefan Fröhling, Hanno Glimm. Genomics-based personalized oncology of advanced thymic epithelial tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 926.