title: Butein suppresses constitutive and inducible signal transducer and activator of transcription (STAT) 3 activation and STAT3-regulated gene products through the induction of a protein tyrosine phosphatase SHP-1.
abstract: The aim of the current study is to determine whether butein (3,4,2',4'-tetrahydroxychalcone) exhibits antiproliferative effects against tumor cells through suppression of the signal transducer and activator of transcription 3 (STAT3) activation pathway. We investigated the effects of butein on constitutive and inducible STAT3 activation, role of tyrosine kinases and phosphatases in STAT3 activation, STAT3-regulated gene products, and growth modulation of tumor cells. We found that this chalcone inhibited both constitutive and interleukin-6-inducible STAT3 activation in multiple myeloma (MM) cells. The suppression was mediated through the inhibition of activation of the upstream kinases c-Src, Janus-like kinase (JAK) 1, and JAK2. Vanadate treatment reversed the butein-induced down-regulation of STAT3 activation, suggesting the involvement of a tyrosine phosphatase. Indeed, we found that butein induced the expression of the tyrosine phosphatase SHP-1 and deletion of SHP-1 gene by small interfering RNA abolished the ability of butein to inhibit STAT3 activation, suggesting the critical role of SHP-1 in the action of this chalcone. Butein down-regulated the expression of STAT3-regulated gene products such as Bcl-xL, Bcl-2, cyclin D1, and Mcl-1, and this led to the suppression of proliferation and induction of apoptosis. Consistent with these results, overexpression of constitutive active STAT3 significantly reduced the butein-induced apoptosis. Moreover, we found that butein significantly potentiated the apoptotic effects of thalidomide and Velcade in MM cells. Overall, these results suggest that butein is a novel blocker of STAT3 activation and thus may have potential in suppression of tumor cell proliferation and reversal of chemoresistance in MM cells.
authors.affiliation: Department of Experimental Therapeutics, Cytokine Research Laboratory, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Manoj K
authors.initials: MK
authors.lastname: Pandey
authors.forename: Bokyung
authors.initials: B
authors.lastname: Sung
authors.forename: Kwang Seok
authors.initials: KS
authors.lastname: Ahn
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Aggarwal
mesh_terms: D043924:Angiogenesis Modulating Agents / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D047188:Chalcones / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects* / Q000502:physiology; D004790:Enzyme Induction / Q000187:drug effects / Q000235:genetics; D006801:Humans; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000096:biosynthesis* / Q000502:physiology; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology
chemical_list: D043924:Angiogenesis Modulating Agents; D000970:Antineoplastic Agents; D047188:Chalcones; D050796:STAT3 Transcription Factor; C040918:butein; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6