Differential expression of Caveolin-1 in hepatocellular carcinoma: correlation with differentiation state, motility and invasion.
BACKGROUND
Caveolin-1 is the main component of caveolae membrane structures and has different roles during tumorigenesis in different cancer types with varying expression profiles, indicating that the role of caveolin-1 varies according to tumor type. In this study, we investigated the role and expression of caveolin-1 in hepatocellular carcinogenesis.


METHODS
We analyzed the expression of Caveolin-1 in 96 hepatocellular carcinoma (HCC), 29 cirrhosis, 20 normal liver tissues and 9 HCC cell lines by immunostaining and western blotting, respectively. After caveolin-1 was stably transfected to HepG2 and Huh7 cells, the effects of Caveolin-1 on the cellular motility, matrix invasion and anchorage-independent growth were studied. Also, caveolae structure was disrupted in endogenously caveolin expressing cells, SNU 449 and SNU 475 by addition of methyl-beta-cyclodextrin and analyzed cellular motility and invasion.


RESULTS
In HCC cell lines, Caveolin-1 expression is correlated to differentiation and basal motility status of these cells. The percentage of Caveolin-1 positivity was found extremely low in normal liver tissue (5%) while it was increased in cirrhosis (45%) and in HCC (66%) (p = 0.002 and p = 0.001 respectively). Cav-1 expression in poorly differentiated HCC samples has been found significantly higher than well differentiated ones (p = 0.001). The caveolin-1 expression was found significantly higher in tumor cells than its peritumoral cirrhotic tissues in HCC samples (p < 0.001). Additionally, the patients with positive staining for Caveolin-1 had significantly higher portal vein invasion than those with negative staining (p = 0.02). Caveolin-1 overexpression increased motility and invasion of HepG2 and Huh7 cells. And disruption of caveolae results in a dramatic decline in both motility and invasion abilities in SNU-449 and SNU-475 cells. Furthermore, caveolin-1 overexpression resulted in down-regulation of E-cadherin while up-regulation of Vimentin. Also, it increased secreted MMP-2 and expression levels of MMP-9 and MT1-MMP. There was no significant difference in colony formation in soft agar between stable clones and parental ones.


CONCLUSIONS
In conclusion, stepwise increase in Cav-1 expression in neoplastic stage with respect to pre-neoplastic stage during hepatocellular carcinogenesis and its ability to stimulate HCC cell motility and invasiveness indicate that this protein plays a crucial role in tumor progression.
Cokakli
Murat
M
Dokuz Eylul University, Faculty of Medicine, Department of Medical Biology and Genetics, Inciralti, Izmir, Turkey. murat.cokakli@deu.edu.tr
Erdal
Esra
E
Nart
Deniz
D
Yilmaz
Funda
F
Sagol
Ozgul
O
Kilic
Murat
M
Karademir
Sedat
S
Atabey
Nese
N
D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology; D051242:Caveolin 1 / Q000096:biosynthesis*; D002448:Cell Adhesion / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000378:metabolism / Q000473:pathology; D018450:Disease Progression; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008103:Liver Cirrhosis / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D053511:Matrix Metalloproteinase 14 / Q000096:biosynthesis; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D008648:Mesoderm / Q000378:metabolism / Q000473:pathology; D009361:Neoplasm Invasiveness
D051242:Caveolin 1; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; C507086:MMP14 protein, human; D053511:Matrix Metalloproteinase 14