We describe the first model system employing human pS2 gene transfer and expression in a non-pS2-expressing cell line, mouse mammary adenocarcinoma 410.4, in order to analyse the potential effect of human trefoil peptide pS2 in glandular epithelium. Two selected clones, AA4 and AD4, were established and shown to have incorporated the pS2 cDNA sequence into the genome, express pS2 containing transcript and produce the pS2 peptide. When grown in 3-D collagen gels both transfectants show striking morphological changes compared to the vector control clone (VA5). VA5 forms large cohesive spherical aggregates with rare coarse spicular outgrowths, accompanied by prominent hyalinised extracellular matrix deposition. pS2 transfectants form poorly cohesive, stellate colonies with very little or no matrix deposition, radiating long cords composed of single elongated cells, an effect previously observed in other cell lines with hepatocyte growth factor. pS2 transfection had no demonstrable effect on proliferation and this is not a morphogenetic phenomenon, as tubulogenesis is not seen. Motility assays suggest that the pS2 'dispersant' effect in collagen gels is due to an increase in cell motility. There were no measurable alterations in either E-cadherin expression or E-cadherin-dependent cell-cell aggregation. pS2 may play a role in maintenance and restitution of mucosal integrity by accelerating migration/dispersion.