Increased tumor metastasis after in vitro alteration of the cell surface.

A strain-specific transplantable melanoma (S-91) growing progressively in DBA/1 mice and metastasizing selectively to the lungs was maintained for 16 days in organ culture before being grafted to syngeneic (DBA/1) and allogeneic (BALB/c and C57BL/6) recipients. The cultured S-91 grew progressively in the syngeneic mice and to a moderate degree in the allogeneic strains; it showed an increased tendency to metastasize in both the DBA/1 and C57BL/6 recipients. Heterophilic cytoagglutination assays of cultured S-91 were less apt to aggregate in the presence of concanavalin A than were their noncultured counterparts, which suggested alteration of the plasma membrane. Organ culture explantation appeared to alter phenotypically the cell-surface membrane and thus increase the cell's ability to metastasize while possibly reducing the immunogenicity of the cultured tumor cells.