In the absence of miR-155, the number of effector CD8+ T cells was reduced, and miR-155-deficient CD8+ T cells were ineffective at controlling tumor growth by the upregulation of suppressor of cytokine signaling-1, causing defective cytokine signaling through signal transducer and activator of transcription (STAT)-5 in melanoma [79]. The gene discussed is CD8A; the disease is melanoma.