Prominent collagen type VI expression in juvenile angiofibromas.
Monika Gramann,Olaf Wendler,Lothar Haeberle,Bernhard Schick
Histochemistry and cell biology
131
2009
Show Abstract
The extracellular matrix component collagen type VI demonstrates potent growth-stimulatory effects and has been associated with aggressive tumour growth. Although, juvenile angiofibromas (JAs) often exhibit an aggressive growth pattern, the collagen type VI expression of this fibrovascular tumour has not been addressed so far. RT-PCR, Western blot analysis and immunohistochemistry were used in this study to analyse collagen type VI, type VI collagen receptor subunits (integrin alpha1, alpha2, alpha10, alpha11 and beta1) and the type VI collagen receptor NG2 in JAs (N = 15) and nasal mucosa (NM, N = 8) samples. The mRNA expression of all three collagen type VI chains was found to be up-regulated significantly (P < 10(-3)-10(-5), adjusted) in JAs compared to NM tissues. The Western blot analysis proved highly prominent collagen-type VI expression in JAs. The ApoTome technique revealed strong collagen-type VI signals in tumour endothelium. NG2 (P < 10(-3), adjusted) and alpha11-integrin (P = 0.04, adjusted) showed a significantly higher mRNA expression levels in JAs than in NM samples. NG2, alpha1-, alpha2- and beta1-intergin were located to tumour vessels, and additional stromal signals were observed for NG2 and alpha1-integrin in JAs. This study demonstrates a prominent collagen-type VI expression in JAs. The collagen-type VI may exert an important growth stimulus in this tumour. | 18797915
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Tumor cell migration and invasion are regulated by expression of variant integrin glycoforms.
Faheem M Shaikh,Eric C Seales,William C Clem,Kristin M Hennessy,Ya Zhuo,Susan L Bellis
Experimental cell research
314
2008
Show Abstract
The ST6Gal-I glycosyltransferase, which adds alpha2-6-linked sialic acids to glycoproteins, is overexpressed in colon adenocarcinoma, and enzyme activity is correlated with tumor cell invasiveness. Previously we reported that forced expression of oncogenic ras in HD3 colonocytes causes upregulation of ST6Gal-I, leading to increased alpha2-6 sialylation of beta1 integrins. To determine whether ras-induced sialylation is involved in promoting the tumor cell phenotype, we used shRNA to downregulate ST6Gal-I in ras-expressors, and then monitored integrin-dependent responses. Here we show that forced ST6Gal-I downregulation, leading to diminished alpha2-6 sialylation of integrins, inhibits cell adhesion to collagen I, a beta1 ligand. Correspondingly, collagen binding is reduced by enzymatic removal of cell surface sialic acids from ras-expressors with high ST6Gal-I levels (i.e., no shRNA). Cells with forced ST6Gal-I downregulation also exhibit decreased migration on collagen I and diminished invasion through Matrigel. Importantly, GD25 cells, which lack beta1 integrins (and ST6Gal-I), do not demonstrate differential invasiveness when forced to express ST6Gal-I, suggesting that the effects of variant sialylation are mediated specifically by beta1 integrins. The observation that cell migration and invasion can be blocked in oncogenic ras-expressing cells by forcing ST6Gal-I downregulation implicates differential sialylation as an important ras effector, and also suggests that ST6Gal-I is a promising therapeutic target. Full Text Article | 18703050
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