JAK inhibition blocks tumor cell–induced reduction of filaggrin and FLG2 in keratinocytes and in ex vivo MF skin. (A) RHE samples were cultured for 24 hours with the malignant MF2059 T-cell line in the presence of either 1 μM JAK inhibitor (tofacitinib) or dimethyl sulfoxide (DMSO) (control). (B) RHE samples were cultured in the presence of supernatants for 48 hours with 1 μM tofacitinib or DMSO. (C) Skin biopsies from MF plaques were cultured with 1 μM tofacitinib or DMSO for 72 hours. mRNA expression was analyzed by qPCR using β-actin as a reference gene in panels A and C. Gene expression was given as relative expression. Protein expression was analyzed by IHC for RHE samples. The RHE samples were stained for H&E, filaggrin, and filaggrin-2. Images are scanned by the Zeiss Axio Scan.Z1 with original magnification ×20. Scale bar; 50 μm. n = 3, ∗P < .05.