Single-cell lymphocyte heterogeneity inadvanced Cutaneous T-Cell Lymphoma skin tumors

Purpose: The heterogeneity of tumor cells presents a major challenge to cancer diagnosis and therapy. Cutaneous T cell lymphomas (CTCL) are a group of T lymphocyte malignanciesthat primarily affect skin. Lack of highly specific markers for malignant lymphocytes prevents early diagnosis, while only limited treatment options are available for patients with advanced-stage CTCL.Droplet-basedsingle-cell transcriptome analysis of CTCL skin biopsiesopens avenues for dissecting patient-specificT lymphocyte heterogeneity, providing a basis for identifying specific markers for diagnosis and cure of CTCL. Experimental Design: Single-cell RNA-sequencing was performed by Droplet-based sequencing (10X Genomics), focusing on 14,056 CD3+lymphocytes (448 cells from normal and 13,608 cells from CTCL skin samples) from skin biopsies of 5 patients with advanced-stage CTCL and 4 healthy donors.Protein expression of identified genes was validated in advanced-stage CTCL skin tumors byimmunohistochemistry and confocal immunofluorescence microscopy. Results: Our analysis revealed a large inter- and intra-tumor gene expression heterogeneity in the T lymphocyte subset, as well as a common gene expression signature in highly proliferating lymphocytes that was validated in multiple advanced-stage skin tumors. In addition, we established the immunological state of reactive lymphocytes and found heterogeneity in effector and exhaution programs across patient samples. Conclusions: Single-cell analysis of CTCL skin tumor samples reveals patient-specific landscapes of malignant and reactive lymphocytes within the local microenvironment of each tumor, giving anunprecedented view of lymphocyte heterogeneity and identifying tumor-specific molecular signatures, withimportant implications for diagnosis and personalized disease treatment. 5 CTCL samples were analyzed and 4 normal controls were analyzed. ***Raw data will be submitted to dbGaP***