3-dimensional in vitro invasion model for oral squamous epithelial carcinomas. Evaluation of tumor and stromal cell properties as well as extracellular matrix [Dreidimensionales In-vitro-Invasionsmodell für orale Plattenepithelkarzinome. Evaluation von Tumor- und Stromazelleigenschaften sowie der extrazellulären Matrix.]

Because tumour cell invasion is a three-dimensional process involving tumour cells as well as stromal cells, tumour invasion models should include equivalents of both compartments in a spatially defined organisation. AIMS: Evaluation of differentiation and invasive potential in relation to basement membrane (BM) formation of new human oral squamous cell carcinoma (OSCC) cell lines under the influence of fibromatosis fibroblasts in a 3D co-culture system (collagen type I/fibroblast-containing matrix). MATERIAL AND METHODS: OSCC cell lines were established and cultured on collagen type I matrix with and without the inclusion of fibro-/myofibroblasts derived from nodular palmar fibromatosis). Evaluation of invasion was done by conventional H & E staining after paraffin embedding; immunohistochemistry was performed for cytokeratins (MNF 116), involucrin (Sy5), vimentin (V9), collagen type IV (CIV22), laminin (alpha 1-chain, 4C7), and Ki-67 (MIB1); and electron microscopy followed. RESULTS: The OSCC cell lines PE/CA-PJ15, PE/CA-PJ34, PE/CA-PJ41 were invasive exclusively on gels containing fibroblasts with stratification of the multilayerd OSCC cell coat and polarised expression of cytokeratin and involucrin. There was no evidence for BM, either by immunohistochemistry or by electron microscopy, although OSCC are immunohistochemically positive for collagen type IV and laminin in the 2D cell culture. There were no differences in proliferative activity of the gels with and without fibroblasts. CONCLUSIONS: Carcinoma cell invasion depends on the presence of fibroblasts in the gel indicating the important role of tumor stromal fibro-/myofibroblasts during carcinomic invasion. The absence of a BM does not, per se, imply an invasive tumour growth. Moreover, stratification and terminal differentiation of epithelial tumour cells occur independently of a structural BM.