IFN-γ has been shown to induce a cell cycle arrest in various tumor cells by multiple cell type-dependent pathways, including via upregulation of cyclin-dependent kinase inhibitors p21WAF1/Cip1 and p27Kip1, the signal transducer and activator of transcription-1 (STAT1) signaling pathway or through the activation of E2F transcription factor proteins via p21WAF1/Cip1 (Schroder et al., 2004). Here, STAT1 is linked to neoplasm.