Up-regulation of transforming growth factor (TGF)-beta receptors by TGF-beta1 in COLO-357 cells.
In the present study we investigated the actions of transforming growth factor (TGF)-beta1 on gene induction and cyclin-dependent kinase inhibitors in relation to TGF-beta receptor modulation in COLO-357 pancreatic cancer cells. TGF-beta1 inhibited the growth of COLO-357 cells in a time- and dose-dependent manner and caused a rapid but transient increase in plasminogen activator inhibitor-I and insulin-like growth factor binding protein-3 mRNA levels. TGF-beta1 caused a delayed but sustained increase in the protein levels of the cyclin-dependent kinase inhibitors p15(Ink4B), p21(Cip1), and p27(Kip1) and a sustained increase in type I and II TGF-beta receptors (TbetaRI and TbetaRII) mRNA and protein levels. The protein synthesis inhibitor cycloheximide (10 microg/ml) completely blocked the TGF-beta1-mediated increase in TbetaRI and TbetaRII expression. Furthermore, a nuclear runoff transcription assay revealed that the increase in receptor mRNA levels was due to newly transcribed RNA. There was a significant increase in TbetaRI and TbetaRII mRNA levels in confluent cells in comparison to subconfluent (</=80% confluent) controls, as well as in serum- starved cells when compared with cells incubated in medium containing 10% fetal bovine serum. COLO-357 cells expressed a normal SMAD4 gene as determined by Northern blot analysis and sequencing. These results indicate that TGF-beta1 modulates a variety of functions in COLO-357 cells and up-regulates TGF-beta receptor expression via a transcriptional mechanism, which has the potential to maximize TGF-beta1-dependent antiproliferative responses.
Kleeff
J
J
Department of Medicine, University of California, Irvine, California 92697, USA.
Korc
M
M
D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis; D002417:Cattle; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000096:biosynthesis; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000096:biosynthesis; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D010190:Pancreatic Neoplasms / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis; D018125:Receptors, Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D015854:Up-Regulation / Q000187:drug effects
C493956:CDKN1A protein, human; C493966:CDKN2B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D018972:Insulin-Like Growth Factor Binding Protein 3; D008869:Microtubule-Associated Proteins; D017395:Plasminogen Activator Inhibitor 1; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27