The role that the immune system plays in cancer is now well established, as is the fact that miRNAs act as downstream and upstream modulators that activate important factors such as nuclear factor kappa-B (NF-κB), signal transducers and activators of transcription 3 (STAT3), tumour necrosis factor (TNF), and transforming growth factor β (TGFβ), which tune many immune cell functions [1]. This evidence concerns the gene STAT3 and cancer.