2-Methoxystypandrone inhibits signal transducer and activator of transcription 3 and nuclear factor-κB signaling by inhibiting Janus kinase 2 and IκB kinase.
Bottom Line: The activation of Janus kinase 2 (JAK2) and IκB kinase (IKK) are key events in STAT3 and NF-κB signaling, respectively.We have identified 2-methoxystypandrone (2-MS) from a traditional Chinese medicinal herb Polygonum cuspidatum as a novel dual inhibitor of JAK2 and IKK. 2-MS inhibits both interleukin-6-induced and constitutively-activated STAT3, as well as tumor necrosis factor-α-induced NF-κB activation. 2-MS specifically inhibits JAK and IKKβ kinase activities but has little effect on activities of other kinases tested.We propose that the natural compound 2-MS, as a potent dual inhibitor of STAT3 and NF-κB pathways, is a promising anticancer drug candidate.
Affiliation: Division of Tumor Pharmacology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.Show MeSH
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Mentions: As shown in Fig. 1, 2-MS contains three α,β-unsaturated carbonyl groups which are reactive with thiols. The thiols of cysteines in JAK2 and IKKβ are reported to be important for their kinase activities and several compounds with thiol-reactive groups have been found to covalently bind to Cysteine 179 of IKKβ and inhibit its kinase activity.(23–26) Therefore, we investigated whether the inhibitory effects of 2-MS on JAK2 or IKKβ kinase activity were through interacting with their cysteine thiols. We used two thiol-containing compounds, DTT or GSH, to compete with JAK2 or IKKβ on interacting with 2-MS to test whether the inhibitory effects of 2-MS on the STAT3 or NF-κB pathway could be alleviated by the two thiol-containing compounds. As shown in Figure. 5(a) and (c), after incubation with DTT or GSH, the inhibitory effects of 2-MS on STAT3 and NF-κB pathways were abolished. Therefore, 2-MS may inhibit the STAT3 and NF-κB pathways through interacting with the thiols of JAK2 and IKKβ via its α,β-unsaturated carbonyl groups. To further demonstrate the 2-MS-thiol interaction, 2-MS was mixed with DTT to induce a chemical reaction of Michael addiction. The proposed reaction site of 2-MS is illustrated in Fig. 6(a). The Michael adducts of DTT to 2-MS were then examined using TLC and ESI-MS analysis, which detected one product at m/z 412.97 [2-MS + DTT-H]−, indicating the addition of DTT to 2-MS (Fig. 6b,c). The results strongly support the possibility that 2-MS reacts with the cysteine thiols of JAK2 and IKKβ.
Affiliation: Division of Tumor Pharmacology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.