Jak1, short for Janus kinase 1, is a cytoplasmic tyrosine kinase. It is a key player in the JAK-STAT signaling pathway, which is involved in the transduction of cytokine-mediated signals. This pathway is crucial for many biological processes such as cell growth, differentiation, and immune response [1,2,3,4,5,6,7].

In inflammatory bowel disease (IBD), the JAK-STAT pathway has been extensively studied. Tofacitinib, a JAK1 inhibitor, is licensed for induction and maintenance of ulcerative colitis, and other JAK1 inhibitors are under investigation [1,4]. In colorectal cancer, METTL3 promotes cancer progression by activating the JAK1/STAT3 signaling pathway. METTL3 increases JAK1 translation and STAT3 transcription, leading to enhanced cancer cell proliferation and metastasis [2]. In renal cell carcinoma, EHBP1L1 binds and stabilizes JAK1, promoting immune evasion through the IFN-γ/JAK1/STAT1/PD-L1 signaling axis. Inhibiting EHBP1L1 can enhance the efficacy of immune checkpoint blockade [3]. JAK1 also promotes HDV replication, and FDA-approved JAK1-specific inhibitors show antiviral effects in vitro [6]. The JAK1/JAK2 inhibitor ruxolitinib can inhibit mediator release from human basophils and mast cells, indicating its potential in treating inflammatory disorders [7].

In conclusion, Jak1 is essential for the proper functioning of the JAK-STAT signaling pathway, influencing various biological processes. Research using models related to Jak1, such as through inhibitor studies, has revealed its significance in diseases like IBD, colorectal cancer, renal cell carcinoma, and HDV-related hepatitis, as well as its potential in treating inflammatory disorders. This understanding of Jak1 provides valuable insights into disease mechanisms and potential therapeutic strategies.