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Background: Several cancers, including mycosis fungoides (MF), have reported dysregulation of miR‐195‐5p. miR‐195‐5p plays a role in cell cycle regulation in several malignant diseases. Objectives: This study aimed to investigate: (a) the expression level of miR‐195‐5p in lesional MF skin biopsies and (b) the potential regulatory roles of miR‐195‐5p in MF. Methods: Quantitative real‐time polymerase chain reaction (RT‐qPCR) was used to determine miR‐195‐5p expression in MF skin biopsies and cell lines. The effect of miR‐195‐5p and ADP‐ribosylation factor‐like protein 2 (ARL2) on cell cycle and apoptosis was measured by flow cytometry assays. Changes in ARL2 expression were determined by RT‐qPCR and Western blotting (WB). Results: We found lower expression levels of miR‐195‐5p in lesional skin from MF patients compared with non‐lesional MF skin and skin from healthy volunteers. Additionally, miR‐195‐5p showed lower expression levels in the skin from patients with disease progression compared with patients with stable disease. In vitro studies showed that overexpression of miR‐195‐5p induced a cell cycle arrest in G0G1. Using microarray analysis, we identified several genes that were regulated after miR‐195‐5p overexpression. The most downregulated gene after miR‐195‐5p mimic transfection was ARL2. RT‐qPCR and WB analyses confirmed downregulation of ARL2 following transfection with miR‐195‐5p mimic. Lastly, transfection with siRNA against ARL2 also induced a G0G1 arrest. Conclusion: Upregulation of miR‐195‐5p in MF inhibits cycle arrest by downregulation of ARL2. miR‐195‐5p may thus function as a tumor suppressor in MF and low miR‐195‐5p expression in lesional MF skin may promote disease progression. [ABSTRACT FROM AUTHOR]

A prognostic 3-miRNA classifier for early-stage mycosis fungoides has been developed recently, with miR-106b providing the strongest prognostic power. The aim of this study was to investigate the molecular function of miR-106b in mycosis fungoides disease progression. The cellular localization of miR-106b in mycosis fungoides skin biopsies was determined by in situ hybridization. The regulatory role of miR-106b was assessed by transient miR-106b inhibitor/mimic transfection of 2 mycosis fungoides derived cell lines, followed by quantitative real-time PCR (RT-qPCR), western blotting and a proliferation assay. MiR-106b was found to be expressed by dermal T-lymphocytes in mycosis fungoides skin lesions, and miR-106b expression increased with advancing mycosis fungoides stage. Transfection of miR-106b in 2 mycosis fungoides derived cell lines showed that miR-106b represses the tumour suppressors cyclin-dependent kinase inhibitor 1 (p21) and thioredoxin-interacting protein (TXNIP) and promotes mycosis fungoides tumour cell proliferation. In conclusion, these results substantiate that miR-106b has both a functional and prognostic role in progression of mycosis fungoides.