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Deciphering Tumor Cell Evolution in Cutaneous T-Cell Lymphomas: Distinct Differentiation Trajectories in Mycosis Fungoides and Sézary Syndrome

ABSTRACT: Cutaneous T-cell lymphomas are a heterogeneous group of neoplasms originating in the skin, with mycosis fungoides (MF) and Sézary syndrome (SS) representing the most common variants. The cellular origin of cutaneous lymphomas has remained controversial due to their immense phenotypic heterogeneity that obfuscates lineage reconstruction based on classical surface biomarkers. To overcome this heterogeneity and reconstruct the differentiation trajectory of malignant cells in MF and SS, T-cell receptor sequencing was performed in parallel with targeted transcriptomics at the single-cell resolution among cutaneous samples in MF and SS. Unsupervised lineage reconstruction showed that Sézary cells exist as a population of CD4+ T cells distinct from those in patch, plaque, and tumor MF. Further investigation of malignant cell heterogeneity in SS showed that Sézary cells phenotypically comprised at least three subsets based on differential proliferation potentials and expression of exhaustion markers. A Th1 polarized cell type, intermediate cell type, and exhausted Th2 polarized cell type were identified, with Th1 and Th2 polarized cells displaying divergent proliferation potentials. Collectively, these findings provide evidence to clarify the relationship between MF and SS, and reveal cell subsets in SS that suggest a possible mechanism for therapeutic resistance.

ORGANISM(S): Homo sapiens

PROVIDER: GSE192836 | GEO | 2022/12/31

REPOSITORIES: GEO

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Project description:Epigenetic changes deregulate gene expression to drive oncogenesis. The reversible nature of these changes enables therapeutic targeting, as in cutaneous T-cell lymphoma (MF/SS), Histone deacetylase inhibitors (HDACi), which alter epigenetic modifications, are effective in ~30% of MF/SS patients. However, there are no markers that predict MF/SS progression or therapy resistance. We hypothesized that epigenetic alterations drive MF/SS progression and promote HDACi drug resistance. Therefore, we profiled the epigenomes and transcriptomes of malignant T cell purified from skin biopsies and peripheral blood from MF/SS patients (N=21) before and after treatment with HDACi, as well as in vitro HDACi-treated CD4+ T cells from healthy donors. Here we report for the first time the epigenome-wide map of acetylation changes in MF/SS patients treated with HDACi, and define the significant differences in regulatory element activity and corresponding transcriptional changes in HDACi-sensitive versus resistant tumors. Our studies identified genes not previously associated with MF/SS, nor with disease progression or HDACi resistance, and were enriched in pathways that regulate apoptosis (BIRC5), cell cycle (RRM2), and chromosome cohesion (CENPH). We also identified a striking number of genes whose products are involved in cell adhesion and migration, including CCR6, LAIR2, VCAM1, and EPCAM. The mRNA of LAIR2, which encodes a receptor protein secreted by activated T cells that binds collagen and prevents binding of the inhibitory receptor LAIR1, was significantly upregulated in MF/SS tumors that were resistant to HDACi therapy and manifested in both skin and peripheral blood. We also detected elevated levels of LAIR2 protein in the plasma of MF/SS patients with progressive disease. Taken together, these studies defined the first epigenome-wide acetylation landscape of HDACi responsive and resistant MF/SS tumors, identified significantly altered patterns of epigenetic regulation and corresponding gene expression in HDACi resistant MF/SS tumors, and connected them to novel pathways of disease progression, particularly in cell adhesion and migration. These findings may represent novel predictive markers for MF/SS progression that are also targets for future therapeutic development.

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Deciphering Tumor Cell Evolution in Cutaneous T-Cell Lymphomas: Distinct Differentiation Trajectories in Mycosis Fungoides and Sézary Syndrome

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