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Standardized treatment options are lacking for patients with unresectable or multifocal follicular dendritic cell sarcoma (FDCS) and disease-related mortality is as high as 20%. Applying whole-genome sequencing (WGS) in one case and whole-exome sequencing (WES) in additional twelve cases, this study adds information on the molecular landscape of FDCS, expanding knowledge on pathobiological mechanisms and identifying novel markers of potential theragnostic significance. Massive parallel sequencing showed high frequency of mutations on oncosuppressor genes, particularly in RB1, CARS and BRCA2 and unveiled alterations on homologous recombination DNA damage repair-related genes in 70% (9/13) of cases. This indicates that patients with high-stage FDCS may be eligible for poly ADP ribose polymerase inhibition protocols. Low tumor mutational burden was confirmed in this study despite common PDL1 expression in FDCS arguing on the efficacy of immune checkpoint inhibitors. CDKN2A deletion, detected by WGS and confirmed by fluorescence in situ hybridization in 41% of cases (9/22) indicates that impairment of cell cycle regulation may sustain oncogenesis in FDCS. Absence of mutations in the RAS/RAF/MAPK pathway and lack of clonal hematopoiesis-related mutations in FDCS sanction its differences from dendritic cell-derived neoplasms of hematopoietic derivation. WGS and WES in FDCS provides additional information on the molecular landscape of this rare tumor, proposing novel candidate genes for innovative therapeutical approaches to improve survival of patients with multifocal disease.

Treatment of vascular stenosis with angioplasty results in acute vascular damage, which may lead to restenosis. Owing to the highly complex cellularity of blood vessels, the healing response following this damage is incompletely understood. To gain further insight into this process, scRNA-seq of mouse carotid tissue after wire injury was performed. Stages of acute inflammation, resolution and remodeling were recapitulated in these data. To identify cell types which give rise to neointima, analyses focused on smooth muscle cell and fibroblast populations, and included data integration with scRNA-seq data from myocardial infarction and atherosclerosis datasets. Following carotid injury, a subpopulation of smooth muscle cells which also arises during atherosclerosis and myocardial infarction was identified. So-called stem cell/endothelial cell/monocyte (SEM) cells are candidates for repopulating injured vessels, and were amongst the most proliferative cell clusters following wire-injury of the carotid artery. Importantly, SEM cells exhibit specific transcriptional profiles which could be therapeutically targeted. SEM cell gene expression patterns could also be detected in bulk RNA-sequencing of neointimal tissue isolated from injured carotid vessels by laser capture microdissection. These data indicate that phenotypic plasticity of smooth muscle cells is highly important to the progression of lumen loss following acute carotid injury. Interference with SEM cell formation could be an innovative approach to combat development of restenosis., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Warwick, Buchmann, Pflüger-Müller, Spaeth, Schürmann, Abplanalp, Tombor, John, Weigert, Leo-Hansmann, Dimmeler and Brandes.)

A subset of patients with advanced-stage classical Hodgkin Lymphoma (cHL) relapse or progress following standard treatment. Given their dismal prognosis, identifying this group of patients upfront represents an important medical need. While prior research has identified characteristics of the tumor microenvironment, which are associated with cHL outcomes, biomarkers that are developed and validated in this high-risk group are still missing. Here, we applied whole-slide image analysis (WSI), a quantitative, large-scale assessment of tumor composition that utilizes conventional histopathology slides. We conducted WSI on a study cohort with pre-treatment biopsies of 340 advanced-stage cHL patients enrolled in the HD12 and HD15 trials of the German Hodgkin Study Group (GHSG), and tested our results in in a validation cohort of 147 advanced-stage cHL patients within the GHSG HD18 trial. All patients were treated with BEACOPP-based regimens. By quantifying T cells, B cells, Hodgkin-Reed-Sternberg-cells and macrophages with WSI, 80% of all cells in the tumor tissue were identified. Crucially, low B cell count was associated with significantly reduced progression-free survival (PFS) and overall survival (OS), while T cell-, macrophage- and Hodgkin-Reed-Sternberg-cell content was not associated with the risk of progression or relapse in the study cohort. We further validated low B cell content as a prognostic factor of PFS and OS in the validation cohort and demonstrate good inter-observer agreement of WSI. WSI may represent a key tool for risk stratification of advanced-stage cHL that can easily be added to the standard diagnostic histopathology work-up.

Clinical outcome of mantle cell lymphoma (MCL) is highly heterogeneous. Tumor cell proliferation as assessed by the Ki-67 index has been shown to yield prognostic information on MCL in many studies using heterogeneously treated patient cohorts. The prognostic value of the Ki-67 index in patients treated with anti-CD20 therapy has not been studied so far. We analyzed the Ki-67 index at primary diagnosis in 249 advanced-stage MCL patients treated within randomized trials. Ki-67 showed high prognostic relevance for overall survival (relative risk 1.27 for 10% higher Ki-67, P < .001), also independently from clinical prognostic factors. The 3 groups with different Ki-67 index of less than 10%, 10% to less than 30%, and 30% or more showed significantly different overall survival in patients treated with CHOP (P = .001) as well as in patients treated with CHOP in combination with anti-CD20 therapy (R-CHOP, P = .013). Thus, the Ki-67 index remains an important prognostic marker in the era of anti-CD20 therapy. The Euro-pean MCL study is registered at www.ClinicalTrials.gov as #NCT00016887.