Notch1 signaling inhibits growth of human hepatocellular carcinoma through induction of cell cycle arrest and apoptosis.
Notch signaling plays a critical role in maintaining the balance between cell proliferation, differentiation, and apoptosis; hence, perturbed Notch signaling may contribute to tumorigenesis. Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in Africa and Asia. The mechanisms that orchestrate the multiple oncogenic insults required for initiation and progression of HCC are not clear. We constitutively overexpressed active Notch1 in human HCC to explore the effects of Notch1 signaling on HCC cell growth and to investigate the underlying molecular mechanisms. We show here that overexpression of Notch1 was able to inhibit the growth of HCC cells in vitro and in vivo. Biochemical analysis revealed the involvement of cell cycle regulated proteins in Notch1-mediated G(0)/G(1) arrest of HCC cells. Compared with green fluorescent protein (GFP) control, transient transfection of Notch1 ICN decreased expression of cyclin A (3.5-fold), cyclin D1 (2-fold), cyclin E (4.5-fold), CDK2 (2.8-fold), and the phosphorylated form of retinoblastoma protein (3-fold). Up-regulation of p21(waf/cip1) protein expression was observed in SMMC7721-ICN cells stably expressing active Notch1 but not in SMMC7721-GFP cells, which only express GFP. Furthermore, a 12-fold increase in p53 expression and an increase (4.8-fold) in Jun-NH(2)-terminal kinase activation were induced in SMMC7721-ICN cells compared with SMMC7721-GFP cells. In contrast, expression of the antiapoptotic Bcl-2 protein could not be detected in SMMC7721-ICN cells. These findings suggest that Notch1 signaling may participate in the development of HCC cells, affecting multiple pathways that control both cell proliferation and apoptosis.
Qi
Runzi
R
Institute of Immunology, Second Military Medical University, Shanghai, People's Republic of China.
An
Huazhang
H
Yu
Yizhi
Y
Zhang
Minghui
M
Liu
Shuxun
S
Xu
Hongmei
H
Guo
Zhenghong
Z
Cheng
Tao
T
Cao
Xuetao
X
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D042846:CDC2-CDC28 Kinases / Q000096:biosynthesis / Q000235:genetics; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002453:Cell Cycle / Q000502:physiology; D045744:Cell Line, Tumor; D019925:Cyclin A / Q000096:biosynthesis / Q000235:genetics; D056750:Cyclin A1; D019927:Cyclin E / Q000096:biosynthesis / Q000235:genetics; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018014:Gene Transfer Techniques; D006131:Growth Inhibitors / Q000502:physiology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System; D051379:Mice; D008819:Mice, Nude; D020929:Mitogen-Activated Protein Kinase Kinases / Q000096:biosynthesis / Q000235:genetics; D010766:Phosphorylation; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000235:genetics
C503745:CCNA1 protein, human; C493956:CDKN1A protein, human; C503747:Ccna1 protein, mouse; C493957:Cdkn1a protein, mouse; D019925:Cyclin A; D056750:Cyclin A1; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D006131:Growth Inhibitors; C497761:NOTCH1 protein, human; C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases