The effect of HuIFN-beta on the invasive potential of melanoma cells was studied using an in-vitro model system with Transwell chambers equipped with matrigel-coated polycarbonate filters. When (10(2), 10(3) and 10(4) IU/ml) for 3 days and then grown in medium without HuIFN-beta for another 7 days. On day 7, the proliferation of melanoma cells was inhibited by 77 and 87%, respectively, when cells were treated with 10(2) and 10(4) IU/ml of HuIFN-beta. This antiproliferative effect was dose-dependent and more pronounced on day 11. The effect of HuIFN-beta on the invasive potential of melanoma cells was studied using an in-vitro model system with Transwell chambers equipped with Matrigel-coated polycarbonate filters. When cells were treated with HuIFN-beta (10(2), 10(3) and 10(4) IU/ml) for 24 h, the amount of tritiated thymidine incorporated into cells was increased, indicating that cell growth was not inhibited. However, the number of cells that invaded to the filter decreased significantly by 15-40%. HuIFN-beta did not have an inhibitory effect on the haptotactic migration of melanoma cells. These data indicate that the antiproliferative effect of HuIFN-beta occurs after 24 h and that the direct anti-invasive effect is independent of any effect on proliferation.