IFN-gamma inhibits human airway smooth muscle cell proliferation by modulating the E2F-1/Rb pathway.
Elucidating the factors that inhibit the increase in airway smooth muscle (ASM) mass may be of therapeutic benefit in asthma. Here, we investigated whether interferon-gamma (IFN-gamma), a potent inducer of growth arrest in various cell types, regulates mitogen-induced ASM cell proliferation. IFN-gamma (1-100 U/ml) was found to markedly decrease both DNA synthesis and ASM cell number induced by the mitogens epidermal growth factor (EGF) and thrombin. Interestingly, IFN-gamma had no effect on mitogen-induced activation of three major mitogenic signaling pathways, phosphatidylinositol 3-kinase, p70(S6k), or mitogen-activated protein kinases. Mitogen-induced expression of cell cycle regulator cyclin D1 was increased by IFN-gamma, whereas no effect was observed on degradation of p27(Kip1). Expression array analysis of 23 cell cycle-related genes showed that IFN-gamma inhibited EGF-induced increases in E2F-1 expression, whereas induction of c-myc, cyclin D2, Egr-1, and mdm2 were unaffected. Induction of E2F-1 protein and Rb hyperphosphorylation after mitogen stimulation was also suppressed by IFN-gamma. In addition, IFN-gamma decreased activation of cdk2 and expression of cyclin E, upstream signaling molecules responsible for Rb hyperphosphorylation in the late G1 phase. IFN-gamma also increased levels of IFI 16 protein, whose mouse homolog p202 has been associated with growth inhibition. Together, our data indicate that IFN-gamma is an effective inhibitor of ASM cell proliferation by blocking transition from G1-to-S phase by acting at two different levels: modulation of cdk2/cyclin E activation and inhibition of E2F-1 gene expression.
Amrani
Yassine
Y
Pulmonary, Allergy, and Critical Care Division, Department of Medicine, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104, USA. amrani@mail.med.upenn.edu
Tliba
Omar
O
Choubey
Divaker
D
Huang
Chien-Da
CD
Krymskaya
Vera P
VP
Eszterhas
Andrew
A
Lazaar
Aili L
AL
Panettieri
Reynold A
RA
D000970:Antineoplastic Agents / Q000494:pharmacology*; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004815:Epidermal Growth Factor / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006490:Hemostatics / Q000494:pharmacology; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008934:Mitogens / Q000494:pharmacology; D032389:Myocytes, Smooth Muscle / Q000166:cytology* / Q000187:drug effects; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013917:Thrombin / Q000494:pharmacology; D014132:Trachea / Q000166:cytology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism
D000970:Antineoplastic Agents; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins; D019938:Cyclin D1; D019927:Cyclin E; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004815:Epidermal Growth Factor; D006490:Hemostatics; D007371:Interferon-gamma; D008934:Mitogens; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D013917:Thrombin; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C493753:E2F1 protein, human; C489664:Ifi16 protein, mouse; C076700:IFI16 protein, human; C495894:CDK2 protein, human