Induced overexpression of miR-155 in ALK-positive ALCL cell lines resulted in reduced levels of C/EBPβ and SOCS1. In murine engraftment models of ALK− ALCL, anti-miR-155 mimics are able to reduce tumour growth and increase levels of cleaved caspase-3 and SOCS1 resulting in suppression of STAT3 signalling. The gene discussed is SOCS1; the disease is anaplastic large cell lymphoma.