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Epigenomics and Single-cell Sequencing Define a Developmental Hierarchy in Langerhans Cell Histiocytosis [ATAC-seq]

ABSTRACT: Langerhans cell histiocytosis (LCH) is a rare neoplasm predominantly affecting children. It occupies a characteristic hybrid position between cancers and inflammatory diseases, which makes it an attractive model for studying cancer development. To explore the molecular mecha-nisms underlying the pathophysiology of LCH and its characteristic clinical heterogeneity, we investi-gated the transcriptomic and epigenomic diversity in primary LCH lesions. Using single-cell RNA se-quencing, we identified multiple recurrent types of LCH cells within these biopsies, including putative LCH progenitor cells and several subsets of differentiated LCH cells. We confirmed the presence of pro-liferative LCH cells in all analysed biopsies using immunohistochemistry, and we defined the epigenomic and gene-regulatory basis of the different LCH cell subsets using chromatin profiling. In summary, our single-cell analysis of LCH uncovered an unexpected degree of cellular, transcriptomic, and epigenomic heterogeneity among LCH cells, reflecting complex developmental hierarchies in LCH lesions.

ORGANISM(S): Homo sapiens

PROVIDER: GSE133785 | GEO | 2019/07/30

REPOSITORIES: GEO

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Project description:Langerhans-cell histiocytosis (LCH) is characterized by heterogeneous lesions containing CD207+ Langerhans cells (LCs) and lymphocytes. In this study, we isolated CD207+ cells and CD3+ T cells from LCH lesions to determine cell-specific gene expression. Compared to control epidermal CD207+ cells, the LCH CD207+ cells yielded 2113 differentially-expressed genes (FDR<0.01). Surprisingly, expression of many genes previously associated with LCH, including cell-cycle regulators, pro-inflammatory cytokines and chemokines were not significantly different from control LCs in our study. However, several novel genes whose products activate and recruit T cells to sites of inflammation, including SPP1 (osteopontin), were highly over-expressed in LCH CD207+ cells. Furthermore, several genes associated with immature myeloid dendritic cells were over-expressed in LCH CD207+ cells. Compared to the peripheral CD3+ cells from LCH patients, the LCH lesion CD3+ cells yielded only 162 differentially-regulated genes (FDR<0.01), and the expression profile of the LCH lesion CD3+ cells was consistent with an activated regulatory T cell phenotype with increased expression of FOXP3, CTLA4 as well as SPP1. Based on these results, we propose a new model of LCH pathogenesis in which lesions do not arise from epidermal Langerhans cells, but from accumulation of bone-marrow derived immature myeloid dendritic cells that recruit activated lymphocytes. Cell-specific gene expression from LCH biopsy specimens was evaluated by comparing hybridization signal from amplified cDNA on Affymetrix gene chips (U133A Plus 2.0) (Table1). Three sets of comparisons were performed: 1) Thirteen LCH CD207+ samples were compared to 12 control skin LCH CD207+ samples. 2) Seven LCH lesion CD3+ samples were compared to 7 peripheral blood CD3+ samples from the same patients. 3) Twelve LCH lesion CD3+ samples were compared to 4 pooled control tonsil CD3+ samples (5 individual tonsil CD3+ samples/pool).

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Epigenomics and Single-cell Sequencing Define a Developmental Hierarchy in Langerhans Cell Histiocytosis [ATAC-seq]

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