Modulation of melanoma cell adhesion to basement membrane components by retinoic acid.

The effect of retinoic acid pretreatment on metastatic B16 melanoma cell adhesion in serum-free medium to tissue culture plastic precoated with fibronectin, laminin/nidogen, type I and type IV collagen was examined. Both control cells grown to subconfluence and cells treated with 10(-6) M-retinoic acid adhered and spread rapidly on fibronectin (greater than 75% following 1 h of incubation) but adhered poorly to type I collagen (less than 15%). Control cells adhered to laminin/nidogen (greater than 35%), type IV collagen (greater than 58%) and type IV collagen plus laminin/nidogen (greater than 80%), while retinoic acid-treated cells showed a reduced ability to attach and spread on these substrata, the number of adherent cells being reduced by 61% on laminin/nidogen, by 19% on type IV collagen, and by 41% on type IV collagen plus laminin/nidogen following 1 h of incubation. The minimum concentration of retinoic acid required to yield an effective reduction in adhesion was 10(-7) M for type IV collagen and 10(-10) M for laminin/nidogen. Melanoma cells harvested at low density showed a reduced adhesion to laminin/nidogen and type IV collagen compared to that of subconfluent control cultures, but also showed a reduced adhesion to fibronectin. The effect of retinoic acid on cell adhesion was not, however, due to reduced cell density, as the cells were seeded so that control and retinoic acid-treated cultures were of a similar density when harvested.