title: Transcriptional regulation of STAT3 by SPTBN1 and SMAD3 in HCC through cAMP-response element-binding proteins ATF3 and CREB2.
abstract: The cytoskeletal protein Spectrin, beta, non-erythrocytic 1 (SPTBN1), an adapter protein to SMAD3 in TGF-β signaling, may prevent hepatocellular carcinoma (HCC) development by downregulating the expression of signal transducer and activator of transcription 3 (STAT3). To elucidate the as yet undefined mechanisms that regulate this process, we demonstrate that higher levels of STAT3 transcription are found in livers of heterozygous SPTBN1(+/-) mice as compared to that of wild type mice. We also found increased levels of STAT3 mRNA, STAT3 protein, and p-STAT3 in human HCC cell-lines after knockdown of SPTBN1 or SMAD3, which promoted cell colony formation. Inhibition of STAT3 overrode the increase in cell colony formation due to knockdown of SPTBN1 or SMAD3. We also found that inhibition of SPTBN1 or SMAD3 upregulated STAT3 promoter activity in HCC cell-lines, which is dependent upon the cAMP-response element (CRE) and STAT-binding element (SBE) sites of the STAT3 promoter. Mechanistically, suppression of SPTBN1 and SMAD3 augmented the transcription of STAT3 by upregulating the CRE-binding proteins ATF3 and CREB2 and augmented the binding of those proteins to the regions within or upstream of the CRE site of the STAT3 promoter. Finally, in human HCC tissues, SPTBN1 expression correlated negatively with expression levels of STAT3, ATF3, and CREB2; SMAD3 expression correlated negatively with STAT3 expression; and the level of phosphorylated SMAD3 (p-SMAD3) correlated negatively with ATF3 and CREB2 protein levels. SPTBN1 and SMAD3 collaborate with CRE-binding transcription factors to inhibit STAT3, thereby preventing HCC development.
authors.affiliation: Department of Medicine and Oncology and Innovation Center for Biomedical Informatics, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20007, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Lin
authors.affiliation: Department of Medicine and Oncology and Innovation Center for Biomedical Informatics, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20007, USA.
authors.forename: Zhixing
authors.initials: Z
authors.lastname: Yao
authors.affiliation: Innovation Center for Biomedical Informatics, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20007, USA.
authors.forename: Krithika
authors.initials: K
authors.lastname: Bhuvaneshwar
authors.affiliation: Innovation Center for Biomedical Informatics, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20007, USA.
authors.forename: Yuriy
authors.initials: Y
authors.lastname: Gusev
authors.affiliation: Department of Medicine and Oncology and Innovation Center for Biomedical Informatics, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20007, USA.
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Kallakury
authors.affiliation: Department of Medicine and Oncology and Innovation Center for Biomedical Informatics, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20007, USA.
authors.forename: Shaoxian
authors.initials: S
authors.lastname: Yang
authors.affiliation: Department of Medicine and Oncology and Innovation Center for Biomedical Informatics, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20007, USA.
authors.forename: Kirti
authors.initials: K
authors.lastname: Shetty
authors.affiliation: Department of Medicine and Oncology and Innovation Center for Biomedical Informatics, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20007, USA aiwu.r.he@gunet.georgetown.edu.
authors.forename: Aiwu Ruth
authors.initials: AR
authors.lastname: He
mesh_terms: D051700:Activating Transcription Factor 3 / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D017362:Cyclic AMP Response Element-Binding Protein / Q000096:biosynthesis* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000473:pathology; D051379:Mice; D011401:Promoter Regions, Genetic; D050796:STAT3 Transcription Factor / Q000096:biosynthesis* / Q000235:genetics; D051900:Smad3 Protein / Q000235:genetics*; D013049:Spectrin / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: C490449:ATF3 protein, human; D051700:Activating Transcription Factor 3; D017362:Cyclic AMP Response Element-Binding Protein; C497790:SMAD3 protein, human; C452439:SPTBN1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D051900:Smad3 Protein; D013049:Spectrin