The role of the immune infiltrate in transformation of follicular lymphoma to aggressive lymphoma

• Applicant: Dr. Laura Beckmann
• Subject Area: Hematology, Oncology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549204408

Transformation of follicular lymphoma (FL) into aggressive B cell lymphoma remains the primary cause of disease mortality in FL patients. The tumor microenvironment (TME) plays a crucial role in lymphomagenesis, disease progression and response to therapy in FL, but its role in transformation is poorly understood. Preliminary data acquired by bulk and single cell RNAseq revealed emergence of a dominant malignant B cell clone and shifts of immune cell populations at transformation. We hypothesize that in indolent FL, B cells, T cells and monocytes occupy distinct locations within the organized follicular structure and that these populations are disrupted by the diffuse histology of transformed FL (tFL). Additionally, we hypothesize that different immune evasion pathways in tFL influence the composition of surrounding immune populations and disrupt tertiary follicular structure. In this project, we aim to define the transcriptomic changes and spatial distribution in malignant B cell, T cell and monocyte rich regions in FL compared to tFL (Aim 1) and to analyze the TME interactions altered in transformation leading to disruption of the follicular structure (Aim 2). For our analyses, tissue microarrays (TMA) are assembled of 71 samples including 21 paired FL and tFL FFPE samples. Additionally, we have identified 5 cases, where FL and tFL histology are contained within the same biopsy specimen, allowing analysis of the transitional zone. Spatial transcriptomic analyses will be applied to the TMAs. After selection of regions of interests by cell surface staining, the GeoMx platform will be used allowing sequencing of >18000 gene targets including spatial profiling of gene expression signatures across the sample. Gene expression analysis will be expanded using the LimmaVoom package and by gene set enrichment analysis. Integration of these methods will give us a comprehensive understanding of different spatial composition and transcriptional signatures of the malignant B cell clone and immune cell subsets in tFL compared to FL (Aim 1). Additionally, we will perform spatial proteomic analyses using the CODEX platform employing a 58-antibody panel designed for this project. Computational segmentation approaches will be used to identify individual cells and determine surface marker expression. Colocalization of cells will be calculated with spatial cross correlation index to determine spatial neighborhoods. Specifically, we will analyze the infiltrating T cell subtypes and their functional state, the malignant B cell immune evasion pathways, follicular dendritic cell (FDC) microenvironment signaling interactions, and monocytic cells including inflammatory signaling (Aim 2). In conclusion our large-scale spatial approach allows us to get a comprehensive understanding of FL transformation biology and the mechanisms how the TME influences transformation and mediates re-organization of the follicular structure.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Dr. Erin Parry