title: Autophagy is activated by TGF-beta and potentiates TGF-beta-mediated growth inhibition in human hepatocellular carcinoma cells.
abstract: Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that regulates cell growth, differentiation, and apoptosis of various types of cells. Autophagy is emerging as a critical response of normal and cancer cells to environmental changes, but the relationship between TGF-beta signaling and autophagy has been poorly understood. Here, we showed that TGF-beta activates autophagy in human hepatocellular carcinoma cell lines. TGF-beta induced accumulation of autophagosomes and conversion of microtubule-associated protein 1 light chain 3 and enhanced the degradation rate of long-lived proteins. TGF-beta increased the mRNA expression levels of BECLIN1, ATG5, ATG7, and death-associated protein kinase (DAPK). Knockdown of Smad2/3, Smad4, or DAPK, or inhibition of c-Jun NH(2)-terminal kinase, attenuated TGF-beta-induced autophagy, indicating the involvement of both Smad and non-Smad pathway(s). TGF-beta activated autophagy earlier than execution of apoptosis (6-12 versus 48 h), and reduction of autophagy genes by small interfering RNA attenuated TGF-beta-mediated growth inhibition and induction of proapoptotic genes Bim and Bmf, suggesting the contribution of autophagy pathway to the growth-inhibitory effect of TGF-beta. Additionally, TGF-beta also induced autophagy in some mammary carcinoma cells, including MDA-MB-231 cells. These findings show that TGF-beta signaling pathway activates autophagy in certain human cancer cells and that induction of autophagy is a novel aspect of biological functions of TGF-beta.
authors.affiliation: Department of Molecular Pathology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Kiyono
authors.forename: Hiroshi I
authors.initials: HI
authors.lastname: Suzuki
authors.forename: Hironori
authors.initials: H
authors.lastname: Matsuyama
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Morishita
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Komuro
authors.forename: Mitsunobu R
authors.initials: MR
authors.lastname: Kano
authors.forename: Koichi
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Kohei
authors.initials: K
authors.lastname: Miyazono
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D001343:Autophagy / Q000502:physiology*; D000071187:Autophagy-Related Protein 5; D000071193:Autophagy-Related Protein 7; D000072224:Bcl-2-Like Protein 11; D000071186:Beclin-1; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D051785:Smad Proteins / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D044764:Ubiquitin-Activating Enzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics
chemical_list: C502778:ATG5 protein, human; D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D000071187:Autophagy-Related Protein 5; C000606775:BCL2L11 protein, human; C491997:BECN1 protein, human; C486655:BMF protein, human; D000072224:Bcl-2-Like Protein 11; D000071186:Beclin-1; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D011518:Proto-Oncogene Proteins; D018125:Receptors, Transforming Growth Factor beta; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D048031:JNK Mitogen-Activated Protein Kinases; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes