IL15 and neoplasm: Increased pSTAT5 in tumour-infiltrating T cells is surprising because the cytokines that typically drive STAT5 activation (IL-2, IL-7 and IL-15) are generally scarce in the immunosuppressive TME, and we wondered whether PTPN2/N1 inhibition causes the activation of STAT5 through cytokine-independent tonic JAK1 and JAK3 signalling.