Modulatory effects of interferon-gamma on the fibronectin receptor function of squamous cell carcinoma cells in vitro

We previously showed that the in vivo invasion of a squamous cell carcinoma induced by the intradermal injection of tumor cells was significantly delayed after the IFN-gamma-producing gene transfer to tumor cells. With respect to the mechanism of the delayed invasion, it was suggested that the IFN-gamma might inhibit the adhesion of the cells to extracellular matrices (ECM) and the subsequent locomotion. Thus, we examined the effect of IFN-gamma on the adhesion of Pam-T cells to ECM. The attachment of Pam-T cells to fibronectin (FN) was significantly higher than that to laminin (LN), collagen type I (COL I) or collagen type IV (COL IV) substrata. The attachment to FN was significantly enhanced specifically by the IFN-gamma-treatment of the cells, although the attachment to LN, COL I or COL IV was not altered by IFN-gamma. Neither IFN-alpha nor IFN-beta had any effect on the attachment of Pam-T cells to FN. When Pam-T cells were treated with IFN-gamma together with a neutralizable anti-IFN-gamma antibody, this enhancement was completely abolished. Moreover, the attachment of IFN-gamma-treated Pam-T cells as well as non-treated cells to FN was blocked by the synthetic peptide Arg-Gly-Asp-Ser (RGDS), but not by the control peptide Arg-Gly-Glu-Ser. Based on these results, we conclude that IFN-gamma specifically enhances the adhesiveness of Pam-T cells to FN substrata by the modulation of integrin activity.