Smad4-independent regulation of p21/WAF1 by transforming growth factor-beta.
The transforming growth factor-beta (TGF-beta)-Smad signaling pathway inhibits the growth of human epithelial cells and plays a role in tumor suppression. The Smad4 gene is mutated or deleted in 50% of pancreatic cancers. In this study, the Smad4-null pancreatic cancer cell line BxPC-3 was transfected with either the Smad4 expression vector or the empty vector and incubated in the presence or absence of TGF-beta. The cells were analysed using a cDNA microarray, which included 2280 named genes to screen for target genes regulated by TGF-beta in either a Smad4-dependent or -independent manner. The microarray and subsequent quantitative RT-PCR analysis demonstrated that the Smad4-independent and -dependent signaling pathways driven by TGF-beta upregulated only one of the 2280 genes, respectively, suggesting that Smad4-independent signaling downstream of TGF-beta might be as widespread as Smad4-dependent signaling. In this study, we demonstrated that the cyclin-dependent kinase inhibitor p21/WAF1, which has been considered the major effector of the Smad-dependent growth inhibitory signal of TGF-beta, is upregulated in a Smad4-independent manner. The upregulation occurs through Smad2/3-dependent transcriptional activation of the p21/WAF1 promoter region. These results suggest a novel mechanism of gene regulation, that is, a novel signal mediator other than Smad4.
Ijichi
Hideaki
H
Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. ijichi-2im@h.u-tokyo.ac.jp
Otsuka
Motoyuki
M
Tateishi
Keisuke
K
Ikenoue
Tsuneo
T
Kawakami
Takayuki
T
Kanai
Fumihiko
F
Arakawa
Yoshihiro
Y
Seki
Naohiko
N
Shimizu
Kiyoshi
K
Miyazono
Kohei
K
Kawabe
Takao
T
Omata
Masao
M
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000032:analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D004722:Endoribonucleases; D004790:Enzyme Induction; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000187:drug effects; D016147:Genes, Tumor Suppressor; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010190:Pancreatic Neoplasms / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D004722:Endoribonucleases; C466279:DCP1A protein, human