JAK2 and neoplasm: For example, in Pten‐null prostate tumours, activation of the JAK2/STAT3 signalling pathway promotes a senescent phenotype where secretion of pro‐inflammatory cytokines such as CXCL1/CXCL2, IL‐6 and macrophage colony‐stimulating factor (M‐CSF) recruits myeloid‐derived suppressor cells to the tumour site, thereby inhibiting effective cytotoxic T‐cell responses [37].