Janus kinase 2–Signal transducer and activator of transcription 3 pathway (JAK2–STAT3 pathway)

The Janus kinase 2–Signal transducer and activator of transcription 3 (JAK2–STAT3) pathway is a fundamental signaling axis that transmits extracellular signals from cytokines and growth factors directly to the nucleus to regulate gene expression. This pathway is activated when ligands such as interleukin-6 (IL-6) or erythropoietin bind to their respective receptors, triggering the reciprocal phosphorylation and activation of JAK2, which in turn phosphorylates STAT3 [Source: NIH/NCBI, 2022]. Once activated, STAT3 molecules dimerize and move into the nucleus to act as transcription factors for genes involved in cell survival, proliferation, and the immune response. In many pathological states, particularly myeloproliferative neoplasms (MPNs) and various solid tumors, this pathway is constitutively active due to mutations like JAK2 V617F, leading to uncontrolled cell growth and resistance to programmed cell death [Source: Nature Reviews Cancer, 2021]. Therapeutic intervention typically involves small-molecule JAK inhibitors, such as Ruxolitinib and Fedratinib, which have been successful in reducing spleen size and systemic symptoms in patients with myelofibrosis. Beyond oncology, the JAK2–STAT3 pathway is a key mediator of chronic inflammation and is being investigated as a target for autoimmune and inflammatory disorders [Source: PubMed: 34151234].

Other names

JAK2/STAT3 signaling pathwayJAK2-STAT3 axisJanus kinase 2/Signal transducer and activator of transcription 3 pathway

Drugs targeting this pathway primarily function as ATP-competitive inhibitors of the Janus kinase 2 (JAK2) enzyme. By inhibiting JAK2, these agents prevent the phosphorylation of the Signal transducer and activator of transcription 3 (STAT3) protein. This blockade inhibits STAT3 dimerization and its subsequent translocation into the nucleus, thereby preventing the transcription of downstream target genes that drive cell cycle progression, pro-survival signals, and inflammatory cytokine production [Source: StatPearls, 2023; PubMed: 31533486].