High-Resolution Spatial Sequencing of Bone Marrow to Dissect T-LGLL Niches
T-cell large granular lymphocytic leukemia (T-LGLL) is characterized by clonal expansion of cytotoxic T-cells within the peripheral blood. Currently, it is not entirely clear which proliferative niche supports T-LGLL expansion before the leukemic T-cells are released into the circulation. The bone marrow (BM) is a compelling candidate for such a niche in T-LGLL, as BM infiltration is present in nearly all T-LGLL patients, and disturbance of normal blood cell production is a common clinical feature.
We set out to characterize the BM of T-LGLL (N=6) by using the 10x Genomics Xenium platform, which enables spatially resolved, in-situ detection of RNA transcripts with a custom panel of 450 genes relevant to T-cell biology, structural cell populations and hematopoiesis. This approach preserves native tissue architecture, allowing us to characterize the cellular identities, transcriptional programs, and spatial relationships of T-LGLL cells and their surrounding microenvironment. The control group (N=5) consisted of individuals who underwent BM biopsy for clinical indications but were confirmed to have normal BM morphology without hematological abnormalities.
Preliminary analysis detected structural cell types (including stromal, endothelial, and adipocytic cells) and immune cell types (such as T cells, B cells, plasma cells, monocytes, macrophages, mast cells, and neutrophils), as well as identifiable trajectories of erythroid and megakaryocytic differentiation. Such resolution is difficult to achieve with single-cell RNA sequencing alone, which often underrepresents fragile or adherent populations due to dissociation bias. As anticipated, T-cell populations were enriched in the BM of T-LGLL patients compared to controls. In contrast, a relative reduction in myeloid cell populations was observed in patient samples, suggesting impaired or suppressed myelopoiesis within the leukemic BM microenvironment.
In our ongoing analysis we are further investigating how spatial interactions within the BM of T-LGLL patients contribute to hematopoietic disruption and the persistence of leukemic T-LGLL cells.