Purpose: The objective of the present study was to provide evidence for the hypothesis of fibroblasts and the desmoplastic reaction, respectively, to impact the formation and maturation of the vascular network in human colon tumours via a retrospective in situ study. An in vivo xenograft model was evaluated to verify its potential for fibroblast-related functional studies.
Materials and methods: In situ: Fiftytwo G2/G3 colon tumours were histomorphologically categorised into low (<50%), medium (50-75%) and high (>75%) grade desmoplasia based on hematoxylin/eosin and Elastica van Gieson stained paraffin sections. Low and high grade desmoplastic tumours were identified and stained for endothelial and pericyte markers to morphometrically analyse microvessel count (MVC), vascular surface area (VSA) and vascular maturation status. In vivo: One out of three established subcutaneous xenograft model in NMRI (nu/nu) mice was adapted to monitor the impact of primary human fibroblasts on xenograft formation and morphology.
Results: Vascular structures in human colon tumours are predominantly located in the fibroblastic stromal regions. Highly desmoplastic tumours, however, have significantly lower MVC and VSA values at the invasion front with signs for augmented vascular maturation as compared with low grade desmoplastic colon cancers. Our in vivo approach verified that only high proportions of co-injected normal fibroblasts accelerate xenograft formation of HCT-116 colon cancer cells.
Conclusions: The in situ data clearly support the hypothesis of fibroblasts to contribute to vascular maturation phenomena in colon cancers. The in vivo design of only 500 tumour cells co-injected with normal fibroblast is feasible, results in 100% engraftment and is the basis for further developments.