FIG. 6.

Fibroblasts induce tumor cell aggregation of SW480 on the SISmuc scaffold. HE staining of paraffin sections of the 3D in vitro tumor model shows that Caco2 cells grow as a monolayer (A), while SW480 cells exhibit a less differentiated phenotype with loose cell-to-cell contacts (C). Within both cell lines, former crypt (c) and villi (v) structures remain clearly visible. In contrast to this, fibroblasts remodel the matrix to a flat layer without villi structures (B). PCK/vimentin double immunofluorescence staining demonstrates a strong PCK staining of Caco2 and SW480 cells (D, F), and a high expression of vimentin in fibroblasts (E). Vimentin expression is lost in SW480 in 3D culture conditions compared to 2D conditions (F, inset: 2D staining: PCK/vimentin). HE staining of cocultures indicates a preserved monolayer formation of Caco2 cells even though in some parts, multilayers could also be observed (G). In SW480 cocultures, the morphology of tumor cells changed to tumor tissue-like aggregates inside the matrix (H, arrows). Immunofluorescence double staining of PCK/vimentin shows that in Caco2 cocultures, the fibroblasts stay in the bottom compartment with the tumor cells on top (I), whereas in SW480 cocultures, the tumor cells are enclosed by fibroblasts that grow on top, beneath, and between the tumor nodes (J). HE, hematoxylin and eosin. Color images available online at www.liebertpub.com/tec