title: Loss of KLF4 and consequential downregulation of Smad7 exacerbate oncogenic TGF-β signaling in and promote progression of hepatocellular carcinoma.
abstract: Hyperactivation of transforming growth factor-β (TGF-β) signaling pathway is a common feature of hepatocellular carcinoma (HCC) progression. However, the driver factors leading to enhanced TGF-β activity are not well characterized. Here, we explore the mechanisms that loss of Krüppel-like factor 4 (KLF4) exacerbates oncogenic TGF-β signaling in human HCC. The expression of KLF4 and TGF-β signaling components in primary HCC and their clinicopathologic relevance and significance was evaluated by using tissue microarray and immunohistochemistry. Cellular and molecular impacts of altered KLF4 expression and TGF-β signaling were determined using immunofluorescence, western blot, reverse-transcriptase PCR, chromatin immunoprecipitation and promoter reporter assays. Loss of KLF4 expression in primary HCC closely correlated with decreased Smad7 expression, increased p-Smad2/3 expression and independently predicts reduced overall and relapse-free survival after surgery. TGF-β signaling components were expressed in most HCC cells, and activation of TGF-β signaling promoted cell migration and invasion. Enforced KLF4 expression blocked TGF-β signal transduction and inhibited cell migration and invasion via activation of Smad7 transcription, whereas deletion of its C-terminal zinc-finger domain diminished this effect. KLF4 protein physically interacts with the Smad7 promoter. Promoter deletion and point mutation analyses revealed that a region between nucleotides -15 bp and -9 bp of the Smad7 promoter was required for the induction of Smad7 promoter activity by KLF4. Our data indicate that KLF4 suppresses oncogenic TGF-β signaling by activation of Smad7 transcription, and that loss of KLF4 expression in primary HCC may contribute to activation of oncogenic TGF-β signaling and subsequent tumor progression.
authors.affiliation: Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.|Department of General Surgery, Shanghai General Hospital, Shanghai, People's Republic of China.
authors.forename: H
authors.initials: H
authors.lastname: Sun
authors.affiliation: Department of General Surgery, Shanghai General Hospital, Shanghai, People's Republic of China.
authors.forename: Z
authors.initials: Z
authors.lastname: Peng
authors.affiliation: Department of Pathology, Shanghai Jiaotong University Affiliated Shanghai General Hospital, Shanghai, People's Republic of China.
authors.forename: H
authors.initials: H
authors.lastname: Tang
authors.affiliation: Department of Oncology and Tumor Institute, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, People's Republic of China.
authors.forename: D
authors.initials: D
authors.lastname: Xie
authors.affiliation: Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Jia
authors.affiliation: Department of General Surgery, Shanghai General Hospital, Shanghai, People's Republic of China.
authors.forename: L
authors.initials: L
authors.lastname: Zhong
authors.affiliation: Department of General Surgery, Shanghai General Hospital, Shanghai, People's Republic of China.
authors.forename: S
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Liver Transplantation Section, Center for Organ Transplantation, Fudan University, Shanghai, People's Republic of China.
authors.forename: Z
authors.initials: Z
authors.lastname: Ma
authors.affiliation: Department of Oncology and Tumor Institute, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, People's Republic of China.
authors.forename: Y
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Tumor Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
authors.forename: L
authors.initials: L
authors.lastname: Zeng
authors.affiliation: Tumor Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
authors.forename: R
authors.initials: R
authors.lastname: Luo
authors.affiliation: Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: K
authors.initials: K
authors.lastname: Xie
mesh_terms: D063646:Carcinogenesis / Q000235:genetics; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D018450:Disease Progression; D015536:Down-Regulation / Q000235:genetics; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000235:genetics* / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D015398:Signal Transduction / Q000235:genetics; D051906:Smad7 Protein / Q000235:genetics* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics* / Q000378:metabolism
chemical_list: C000715467:KLF4 protein, human; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; C497806:SMAD7 protein, human; D051906:Smad7 Protein; D016212:Transforming Growth Factor beta