Foetal and cancer patient fibroblasts produce an autocrine migrationstimulating factor not made by normal adult cells

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Abstract
We have previously reported that (1) the migration of foetal and adult fibroblasts into threedimensional collagen matrices is differentially affected by cell density, and (2) skin fibroblasts from cancer patients commonly display a foetal-like mode of migratory behaviour. Data presented here indicate that differences in the migration of these cell types are particularly apparent in cultures plated at high density (i.e. at cell confluence); under these conditions, foetal fibroblasts and the foetal-like fibroblasts of cancer patients migrate into the three-dimensional collagen matrix to a significantly greater extent than do normal adult cells. In this initial study concerned with the biochemical basis of these observations, we report that medium conditioned by either foetal or cancer patient fibroblasts stimulates the migration of confluent adult cells. This stimulation of migration is specific to confluent cells, as the migration of subconfluent adult fibroblasts is unaffected by these conditioned media. Gel filtration chromatography of foetal fibroblast-conditioned medium indicates that migration-stimulating activity is recovered in a single peak with an apparent molecular mass in the range of 50–60 (×103). The active migration stimulating factor (MSF) in both foetal and cancer patient fibroblast-conditioned media appears to be a protein stable at acid pH, but inactivated by heat, alkaline pH and reductive alkylation. MSF produced by foetal and cancer patient fibroblasts is presumably responsible for the characteristically elevated levels of migration displayed by these cells in confluent culture, thereby suggesting an autocrine mode of action for this factor. Stimulation of adult cell migration by MSF requires the presence of either serum or plateletpoor plasma and is not observed in serum-free medium. MSF does not appear to affect either the proliferation or morphology of normal adult cells under any of the culture conditions examined.