Determination of adhesive properties of variant metastatic melanoma cells to BALB/3T3 cells and their virus-transformed derivatives by a monolayer attachment assay.

The hypothesis that abnormalities in intercellular adhesion are a property of metastatic tumors was examined in vitro with B16 melanoma variants that were selected in vivo for increased metastatic behavior. The adhesive characteristics of low (B16-F1), intermediate (B16-F5), and high (B16-F10) metastatic lines were determined by quantitative adhesion assays that measured the rate and degree of attachment of single cells to confluent monolayers of melanoma, BALB/3T3, or virus-transformed 3T3 cells. Intercellular adhesions were monitored by loss of single cells from suspension and adherence of intraperitoneally grown 125I-5-iodo-2'-deoxyuridine-labeled cells to the monolayers, and were affected by time, temperature, and serum concentration. Although there was little difference in adhesive properties between the untransformed and transformed 3T3 cell lines, the more metastatic melanoma variants exhibited higher relative rates and extents of homotypic and heterotypic monolayer attachment compared with lower metastatic lines (B16-F10 greater than B16-F5 greater than B16-F1). The correlation between in vivo and in vitro tumor cell adhesive properties and metastasis was discussed.