Laminin-1, a major basement membrane glycoprotein, promotes tumor cell malignancy. Incubation of B16-F10 melanoma cells with a peptide containing an active sequence in laminin-1, designated AG-73 (leu-glu-val-glu-leu-ser-ile-arg; LQVQLSIR), enhances in vitro adhesion, migration, invasion and gelatinase production and in vivo lung colonization and metastases to the liver. In the current study, we have tried to define the mechanism of enhancement of liver metastases induced by AG-73 using B16-F10 murine melanoma cells selected for adhesion on AG-73-coated dishes. Cells were sequentially selected for adhesion more than 30 times and then characterized. AG-73 selected cells had much longer cytoplasmic processes and occasionally formed nodular aggregates. AG-73 selected cells attached 1.2- to 1.5-fold better to both AG-73 and laminin-1, were able to invade through the Matrigel-coated filter up to 6-fold more, grew s.c. 1.5-2 times faster, produced twice the number of lung colonies, and showed more liver nodules (12 of 28 vs. 1 of 27) than parental cells. Our data demonstrate that the enhanced malignant phenotype of B16-F10 cells can be observed in the absence of added peptide with the adhesion-selected cells.