The distribution of collagen types I, III, and IV in normal and malignant colorectal mucosa

Objective: To compare the distribution of interstitial collagens (type I and III) and basement membrane collagen (type IV) in cancerous and normal colon. Design: Retrospective study. Setting: University hospital, Finland. Subjects: 13 patients with colorectal cancer of different stages and grades. Main outcome measures: Indirect immunofluorescence labelling for type I, III, and IV collagens of fresh frozen tissue samples, both normal and cancerous, cut into serial sections 6 mu m thick. Results: In normal mucosa, the epithelial basement membrane showed an intense immunoreaction for type TV collagen. Type I and III collagens were localised to the interstitial stroma underlying it. The membrane in cancer samples was characterised by discontinuities and thinning as estimated by immunolabelling for type IV collagen. Furthermore, immediately adjacent to the membrane type I and III collagen positivity was fragmented. The cancerous stroma showed a strong positive immunosignal for type I and III collagens. Conclusion: Both the epithelial basement membrane and the collagenous matrix immediately beneath it are degraded in malignant tissue. This may suggest the simultaneous activation of several degradative enzymes las type I and II collagens are at least in part degraded by different enzymes from type TV collagen) or alterations in the expression of collagen subtypes in normal compared with malignant tissue.