Prominent collagen type VI expression in juvenile angiofibromas

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.