miR‐155 is involved in tumor progression of mycosis fungoides

Biopsy specimens from 23 early stage and 19 tumor‐stage mycosis fungoides (MF) patients were evaluated for miR‐155 expression by real‐time qualitative PCR and compared with 15 biopsy specimens from patients with T‐cell‐rich inflammatory skin diseases. Significant upregulation of miR‐155 was found in MF tumors compared with both early‐stage MF lesions and controls. There was no difference in miR‐155 expression between early‐stage and inflammatory dermatoses. Using laser capture microdissection, it was found that miR‐155 was significantly higher in the lymphoma cells in tumor stage compared with the intraepidermal lymphocytes in early stage. In contrast, there was no difference in miR‐155 expression between the intraepidermal lymphocytes and the dermal lymphocytes in early‐stage MF. These findings suggest that although miR‐155 expression cannot serve to discriminate early‐stage MF from inflammatory dermatoses; however, it is involved in the switch from the indolent early stage into the aggressive tumor stage of the disease.