Type V/type I collagen interactions in vitro and growth-inhibitory effect of hybrid substrates on 8701-BC carcinoma cells.

Different ratios of type V and I collagens were submitted to mixed fibrillogenesis followed by localization of type V collagen within the aggregates by immunoelectron microscopy. At lower concentrations (10-30%), type V collagen segregates into aperiodic filamentous material, peripheral to the cross-banded type I fibrils but making contact in an apparently random manner. Increasing the ratio of type V collagen up to 50% causes the disappearance of collagen fibrils and the formation of a sticky gel composed of weakly immunoreactive long-spacing structures, interspersed with intensely labeled amorphous material. Hybrid type V/type I matrices changed the growth behaviour of 8701-BC carcinoma cells, with inhibition of cell growth being directly related to type V content. This restraining influence on growth was partially reversed when substrates were pre-incubated with low dilutions of anti-type V serum, prior to cell seeding. These findings suggest that the high concentrations of type V collagen, known to exist in vivo in some scirrhous tumors like ductal infiltrating carcinoma of the breast, perturb the normal fibrous architecture of the stroma and concurrently inhibit neoplastic cell growth.