title: Smad4 Decreases the Population of Pancreatic Cancer-Initiating Cells through Transcriptional Repression of ALDH1A1.
abstract: Cancer progression involves a rare population of undifferentiated cancer-initiating cells that have stem cell-like properties for self-renewal capacity and high tumorigenicity. We investigated how maintenance of pancreatic cancer-initiating cells is influenced by Smad4, which is frequently deleted or mutated in pancreatic cancers cells. Smad4 silencing up-regulated the expression of aldehyde dehydrogenase 1A1 (ALDH1A1) mRNA, whereas forced expression of Smad4 in pancreatic cancer cells down-regulated it. Smad4 and ALDH1 expression inversely correlated in some human clinical pancreatic adenocarcinoma tissues, suggesting that ALDH1 in pancreatic cancer cells was associated with decreased Smad4 expression. We then examined whether ALDH1 served as a marker of pancreatic cancer-initiating cells. Pancreatic cancer cells contained ALDH1(hi) cells in 3% to 10% of total cells, with high tumorigenic potential. Because Smad4 is a major mediator of transforming growth factor (TGF)-β family signaling, we investigated the regulatory mechanism of ALDH activity by TGF-β and bone morphogenetic proteins. Treatment with TGF-β attenuated ALDH1(hi) cells in several pancreatic cancer cells, whereas bone morphogenetic protein-4 was not as potent. Biochemical experiments revealed that TGF-β regulated ALDH1A1 mRNA transcription through binding of Smad4 to its regulatory sequence. It appears that TGF-β negatively regulates ALDH1 expression in pancreatic cancer cells in a Smad-dependent manner and in turn impairs the activity of pancreatic cancer-initiating cells.
authors.affiliation: Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Hoshino
authors.affiliation: Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Nishida
authors.affiliation: Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Katsuno
authors.affiliation: Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Daizo
authors.initials: D
authors.lastname: Koinuma
authors.affiliation: Hepato-Biliary-Pancreatic Surgery Division, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Aoki
authors.affiliation: Hepato-Biliary-Pancreatic Surgery Division, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Kokudo
authors.affiliation: Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan. Electronic address: miyazono@m.u-tokyo.ac.jp.
authors.forename: Kohei
authors.initials: K
authors.lastname: Miyazono
authors.affiliation: Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Ehata
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics; D000080924:Aldehyde Dehydrogenase 1 Family; D000818:Animals; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D064593:Heterografts; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000473:pathology*; D010190:Pancreatic Neoplasms / Q000378:metabolism / Q000473:pathology*; D034741:RNA, Small Interfering; D050697:Retinal Dehydrogenase; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051901:Smad4 Protein / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D034741:RNA, Small Interfering; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta; D000080924:Aldehyde Dehydrogenase 1 Family; D000444:Aldehyde Dehydrogenase; C510223:ALDH1A1 protein, human; D050697:Retinal Dehydrogenase