SP2509, an inhibitor of LSD1, exerts potential antitumor effects by targeting the JAK/STAT3 signaling.

Hyperactivation of Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling promotes tumorigenesis and cancer progression. STAT3 participates in the essential processes of cell proliferation, survival, and differentiation in many types of tumors. In the present study, SP2509 was identified as a potent inhibitor of the JAK/STAT3 signaling pathway by high-throughput drug screening based on a STAT3-driven luciferase expression system. Our results indicated that SP2509 inhibits constitutive STAT3 activation and the expression of STAT3-driven downstream genes. Bcl-xL, c-Myc, and Cyclin D1 were downregulated after treatment with SP2509. In addition, SP2509 specifically inhibits JAK activity, which could cause cell cycle arrest, inhibit cell growth, and induce apoptosis of various cancer cells. These results confirmed that SP2509 inhibits tumor progression by suppressing the expression of JAK/STAT3 signaling and STAT3-related downstream genes. Moreover, we demonstrated that SP2509 inhibits tumor growth in vivo and induces cell death in vitro. SP2509-mediated inhibition of STAT3 phosphorylation is dependent on its original target lysine-specific demethylase 1 in cancer cells. In summary, our results indicate that SP2509 is a novel inhibitor of JAK/STAT3 signaling.