Janus kinase 2-Signal transducer and activator of transcription 3 signaling axis (JAK2-STAT3 axis) (JAK2-STAT3 axis)

The Janus kinase 2-Signal transducer and activator of transcription 3 (JAK2-STAT3) signaling axis is a fundamental intracellular pathway that transduces signals from extracellular ligands, such as cytokines (e.g., IL-6) and growth factors, to the nucleus to regulate gene expression [1.2.1, 1.2.2]. Upon ligand binding to cell surface receptors, JAK2 is activated and phosphorylates the receptor's cytoplasmic tail, creating docking sites for STAT3 [1.1.1, 1.3.4]. STAT3 is then phosphorylated by JAK2, leading to its dimerization and translocation into the nucleus, where it acts as a transcription factor for genes involved in cell survival, proliferation, and immune responses [1.2.1, 1.2.3]. Dysregulation or constitutive activation of this axis is a hallmark of various malignancies, particularly solid tumors like triple-negative breast cancer and hematologic disorders, as well as inflammatory and autoimmune conditions [1.3.1, 1.4.1]. Consequently, the JAK2-STAT3 axis is a major therapeutic target, with several JAK inhibitors approved for clinical use and STAT3 inhibitors under active investigation [1.2.1, 1.3.4]. JAK inhibitors like ruxolitinib and tofacitinib work by blocking the kinase activity of JAK2, thereby preventing the downstream activation of STAT3 and the subsequent transcription of pro-inflammatory and pro-survival genes [1.1.2, 1.3.1]. Emerging therapies also include direct STAT3 inhibitors and proteolysis-targeting chimeras (PROTACs) designed to degrade components of the axis [1.3.2, 1.3.3].

Other names

JAK2/STAT3 pathwayJAK2-STAT3 signaling pathwayJAK2-STAT3 cascadeJanus kinase 2/Signal transducer and activator of transcription 3 axis

Drugs targeting this axis primarily function by inhibiting the kinase activity of JAK2, which prevents the phosphorylation of the receptor and the subsequent recruitment and activation of STAT3. This blockade inhibits STAT3 dimerization and nuclear translocation, thereby suppressing the transcription of genes that promote cell survival, proliferation, and inflammation. Alternatively, direct STAT3 inhibitors disrupt the protein's SH2 domain to prevent dimerization or DNA binding.