Mechanism of hepatitis C virus (HCV)-induced osteopontin and its role in epithelial to mesenchymal transition of hepatocytes.
Osteopontin (OPN) is a secreted phosphoprotein, originally characterized in malignant-transformed epithelial cells. OPN is associated with tumor metastasis of several tumors and is overexpressed in hepatocellular carcinoma (HCC) tissue involving HCC invasion and metastasis. Importantly, OPN is significantly up-regulated in liver injury, inflammation, and hepatitis C virus (HCV)-associated HCC. However, the underlying mechanisms of OPN activation and its role in HCV-mediated liver disease pathogenesis are not known. In this study, we investigated the mechanism of OPN activation in HCV-infected cells. We demonstrate that HCV-mediated Ca(2+) signaling, elevation of reactive oxygen species, and activation of cellular kinases such as p38 MAPK, JNK, PI3K, and MEK1/2 are involved in OPN activation. Incubation of HCV-infected cells with the inhibitors of AP-1 and Sp1 and site-directed mutagenesis of AP-1- and Sp1-binding sites on the OPN promoter suggest the critical role of AP-1 and Sp1 in OPN promoter activation. In addition, we show the in vivo interactions of AP-1 and Sp1 with the OPN promoter using chromatin immunoprecipitation assay. We also show the calpain-mediated processing of precursor OPN (∼75 kDa) into ∼55-, ∼42-, and ∼36-kDa forms of OPN in HCV-infected cells. Furthermore, we demonstrate the critical role of HCV-induced OPN in increased phosphorylation of Akt and GSK-3β followed by the activation of β-catenin, which can lead to EMT of hepatocytes. Taken together, these studies provide an insight into the mechanisms of OPN activation that is relevant to the metastasis of HCV-associated HCC.
From the Department of Microbiology and Immunology, H. M. Bligh Cancer Research Laboratories, Rosalind Franklin University of Medicine and Science, Chicago Medical School, North Chicago, Illinois 60064 and.
Jawed
J
Iqbal
Steven
S
McRae
Krishna
K
Banaudha
Thi
T
Mai
Gulam
G
Waris
D020013:Calcium Signaling / Q000235:genetics; D002154:Calpain / Q000235:genetics / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D045744:Cell Line, Tumor; D058750:Epithelial-Mesenchymal Transition; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D016174:Hepacivirus; D006526:Hepatitis C / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D009362:Neoplasm Metastasis; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D018808:Transcription Factor AP-1; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
D016329:Sp1 Transcription Factor; D018808:Transcription Factor AP-1; D051176:beta Catenin; D053495:Osteopontin; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D038362:Glycogen Synthase Kinase 3; D002154:Calpain
Epithelial Mesenchymal Transition; Hepatitis C Virus; Metastasis; Osteopontin; Oxidative Stress