MiRNA regulation of T cell exhaustion in cutaneous T cell lymphoma.

Cutaneous T cell lymphoma (CTCL) is characterized by a background of chronic inflammation, where malignant CTCL cells escape immune surveillance. To study how miRNAs (miRs) regulate T cell exhaustion, we performed miRseq analysis, qRT-PCR, and in situ hybridization on 45 primary CTCL samples, 3 healthy skin samples, and CTCL cell lines, identifying miR-155-5p, -130b-3p and -21-3p. Moreover, miR-155-5p, -130b-3p, and -21-3p positively correlated with immune checkpoint gene expression in lesional skin samples and were enriched in the IL6/JAK/STAT signaling pathway by gene set enrichment analysis. Further gene sequencing analysis demonstrated decreased mRNA expression of the major negative regulators of JAK/STAT signaling, SOCS, PIAS and PTPN. Transfection of MyLa and HuT78 cells with anti-miR-155-5p, -21-3p, and -130b revealed a considerable increase in SOCS proteins along with a significant decrease in the levels of activated STAT3 and IC surface protein expression, as well as decreased cell proliferation. Downregulation of miR-155, -130 and -21 in CTCL cell lines decreased CTCL cell growth and facilitated CD8+ T cell-mediated cytotoxic activity, with concordant production of IFNγ and CD107a expression. Our results describe the mechanisms of miR-induced T cell exhaustion, which provide a foundation for developing synthetic anti-miRs to therapeutically target the tumor microenvironment in CTCL.