STAT3 activation and infiltration of eosinophil granulocytes in mycosis fungoides.

Eosinophil grunolocvies have been implicated in anticancer immunity but recent data indicate that eosinophils can also promote cancer. Herein, we studied eosinophils in skin lesions from 43 patients with mycosis limgoides (MF). The presence of eosinophils correlated with disease stage: 78% of patients with advanced disease displayed eosinophil infiltration, whereas this was only seen in II% of patients with patches (p<0.01), and in 48% of those with plaque disease. importantly, 72% of patients with positive staining for phospho-signal-transducer-and-activator-oftranscription (pY-STAT3) in malignant T-cells also stained positively for eosinophils, whereas this was only observed in 28% of pY-STAT3-negative patients (p<0.01). Notably, malignant T-cells expressed eosinophilic activation and trafficking factors: High-mobility group BOX-I protein (IIMGB1) and interieukin 5 (1L5). STAT3 siRNA profoundly inhibited 11,5 but not HMGBI expression. In conclusion, these data suggest that malignant T-cells orchestrate accumulation and activation of eosinophils supporting the notion of STAT3 being a putative target for therapy.