STAT1 and leukemia: Interestingly, IFN-γ receptor (IFNGR) is expressed at higher levels than TNF receptors in the leukemia cells, leading to stronger phosphorylation of STAT1 (signal transducer and activator of transcription) relative to NF-κB (nuclear factor kappa-light-chain-enhancer of activated B-cells), which mediates TNF signaling.