Homo- or heterodimeric compounds that affect dimeric protein function through interaction between monomeric moieties and protein subunits can serve as valuable sources of potent and selective drug candidates. Here, we screened an in-house dimeric natural product collection, and panepocyclinol A (PecA) emerged as a selective and potent STAT3 inhibitor with profound anti-tumor efficacy. Through cross-linking C712/C718 residues in separate STAT3 monomers with two distinct Michael receptors, PecA inhibits STAT3 DNA binding affinity and transcription activity. Molecular dynamics simulation reveals the key conformation changes of STAT3 dimers upon the di-covalent binding with PecA that abolishes its DNA interactions. Furthermore, PecA exhibits high efficacy against anaplastic large T cell lymphoma in vitro and in vivo, especially those with constitutively activated STAT3 or STAT3^Y640F. In summary, our study describes a distinct and effective di-covalent modification for the dimeric compound PecA to disrupt STAT3 function.

Objective To investigate the anti-inflammatory effect and mechanism of sappanone A(SA)on lipopolysaccharide(LPS)-induced RAW264.7 cell model based on JAK2-STAT3 signaling pathway.Methods MTT assay was used to detect the effects of sappanone A,LPS and AG490 on RAW264.7 cell viability.The LPS-induced inflammatory model in RAW264.7 cells was established,and the secretion level of interleukin-6(IL-6)in the supernatant was detected by ELISA.mRNA expressions of IL-6,Janus kinase 2(JAK2)and signal transducer and activator of transcription 3(STAT3)were tested by RT-PCR.The protein expressions of JAK2,phosphorylated JAK2(p-JAK2),STAT3 and phosphorylated STAT3(p-STAT3)were determined by Western Blot.Results Compared with control group,IL-6 secretion level was significantly increased,mRNA expressions of IL-6,JAK2 and STAT3 were up-regulated,and protein expressions of p-JAK2 and p-STAT3 were increased(all P＜0.01)in model group.Compared with model group,high-dosed sappanone A(5 μg·mL-1)was significantly decreased the secretion of IL-6,down-regulated the mRNA expressions of IL-6,JAK2 and STAT3,and inhibited the protein expressions of p-JAK2 and p-STAT3(all P＜0.01).Conclusion Sappanone A may play an anti-inflammatory role by inhibiting the JAK2-STAT3 signaling pathway and hence inhibiting the secretion of IL-6.