title: Discovery of JSI-124 (cucurbitacin I), a selective Janus kinase/signal transducer and activator of transcription 3 signaling pathway inhibitor with potent antitumor activity against human and murine cancer cells in mice.
abstract: Constitutively activated, tyrosine-phosphorylated signal transducer and activator of transcription (STAT) 3 plays a pivotal role in human tumor malignancy. To discover disrupters of aberrant STAT3 signaling pathways as novel anticancer drugs, we developed a phosphotyrosine STAT3 cytoblot. Using this high throughput 96-well plate assay, we identified JSI-124 (cucurbitacin I) from the National Cancer Institute Diversity Set. JSI-124 suppressed the levels of phosphotyrosine STAT3 in v-Src-transformed NIH 3T3 cells and human cancer cells potently (IC(50) value of 500 nM in the human lung adenocarcinoma A549) and rapidly (complete inhibition within 1-2 h). The suppression of phosphotyrosine STAT3 levels resulted in the inhibition of STAT3 DNA binding and STAT3-mediated but not serum response element-mediated gene transcription. JSI-124 also decreased the levels of tyrosine-phosphorylated Janus kinase (JAK) but not those of Src. JSI-124 was highly selective for JAK/STAT3 and did not inhibit other oncogenic and tumor survival pathways such as those mediated by Akt, extracellular signal-regulated kinase 1/2, or c-Jun NH(2)-terminal kinase. Finally, JSI-124 (1 mg/kg/day) potently inhibited the growth in nude mice of A549 tumors, v-Src-transformed NIH 3T3 tumors, and the human breast carcinoma MDA-MB-468, all of which express high levels of constitutively activated STAT3, but it did not affect the growth of oncogenic Ras-transformed NIH 3T3 tumors that are STAT3 independent or of the human lung adenocarcinoma Calu-1, which has barely detectable levels of phosphotyrosine STAT3. JSI-124 also inhibited tumor growth and significantly increased survival of immunologically competent mice bearing murine melanoma with constitutively activated STAT3. These results give strong support for pharmacologically targeting the JAK/STAT3 signaling pathway for anticancer drug discovery.
authors.affiliation: Drug Discovery Program, H Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, USA.
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Blaskovich
authors.forename: Jiazhi
authors.initials: J
authors.lastname: Sun
authors.forename: Alan
authors.initials: A
authors.lastname: Cantor
authors.forename: James
authors.initials: J
authors.lastname: Turkson
authors.forename: Richard
authors.initials: R
authors.lastname: Jove
authors.forename: Saïd M
authors.initials: SM
authors.lastname: Sebti
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D053614:Janus Kinase 2; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008546:Melanoma, Experimental / Q000188:drug therapy; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects; D015534:Trans-Activators / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014315:Triterpenes / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D014315:Triterpenes; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C038106:cucurbitacin I