Involvement of p21(WAF1/Cip1), p27(Kip1), and p18(INK4c) in troglitazone-induced cell-cycle arrest in human hepatoma cell lines.
Peroxisome proliferator-activated receptor gamma (PPARgamma) regulates cell growth and differentiation. Recent evidence has suggested that PPARgamma ligands had anti-tumor effects through inhibiting cell growth and inducing cell differentiation in several types of malignant neoplasm. In the present study, we investigated: 1) the expression of PPARgamma in both human hepatoma cell lines and 5 resected human hepatocellular carcinoma (HCC) tissues; 2) the growth-inhibitory effect of troglitazone, a PPARgamma ligand, on those hepatoma cells; and 3) the molecular mechanisms of troglitazone-induced cell-cycle arrest. Five hepatoma cell lines, HLF, HuH-7, HAK-1A, HAK-1B, and HAK-5, were used. The mRNA expression levels of PPARgamma, p21(WAF1/Cip1), and p27(Kip1) were determined by real-time quantitative reverse transcription-polymerase chain reaction. The expression of cell cycle-regulating proteins, such as p21, p27, p18(INK4c), cyclin E, and pRb, was examined using Western blotting. PPARgamma was constitutively expressed in all the cell lines and the HCC tissues used in this study. A cytostatic effect of troglitazone was found in those cell lines, and this inhibition of cell growth was dosage-dependent. G0/G1 arrest was apparently demonstrated in flow cytometric analysis in HLF, HAK-1A, HAK-1B, and HAK-5, all of which showed an increased expression of p21 protein. However, HuH-7, lacking p21 protein expression, did not demonstrate clear arrest in the cell-cycle analysis. HLF, which was deficient in the protein product of the retinoblastoma tumor-suppressor gene (pRb), responded most profoundly to troglitazone, showing an increased expression in not only p21, but also in p27 and in p18. These findings suggested that p21, p27, and p18 might be involved in troglitazone-induced cell-cycle arrest in human hepatoma cells.
Koga
H
H
Second Department of Medicine, Kurume University School of Medicine, Kurume, Japan. hirokoga@med.kurume-u.ac.jp
Sakisaka
S
S
Harada
M
M
Takagi
T
T
Hanada
S
S
Taniguchi
E
E
Kawaguchi
T
T
Sasatomi
K
K
Kimura
R
R
Hashimoto
O
O
Ueno
T
T
Yano
H
H
Kojiro
M
M
Sata
M
M
D042846:CDC2-CDC28 Kinases; D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000503:physiopathology* / Q000648:ultrastructure; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism; D002839:Chromans / Q000494:pharmacology*; D019927:Cyclin E / Q000235:genetics / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050763:Cyclin-Dependent Kinase Inhibitor p18; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004791:Enzyme Inhibitors; D006801:Humans; D008024:Ligands; D008113:Liver Neoplasms / Q000473:pathology / Q000503:physiopathology* / Q000648:ultrastructure; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology*; D045162:Thiazolidinediones; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism; D000077288:Troglitazone; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
C493956:CDKN1A protein, human; C493971:CDKN2C protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002839:Chromans; D019927:Cyclin E; D050763:Cyclin-Dependent Kinase Inhibitor p18; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D008024:Ligands; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D016160:Retinoblastoma Protein; D013844:Thiazoles; D045162:Thiazolidinediones; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D000077288:Troglitazone