Laminin: an initiating role in retinoblastoma cell attachment and differentiation.

The effect of laminin (LN) on the attachment and differentiation of a human retinoblastoma cell line (Y-79) was investigated. We found that 10 micrograms/ml LN in the serum-free culture medium for 3 to 4 d induces 20 to 30% of the cells to firmly attach to a plastic substratum. This effect seems to be complex because the short-term effect of LN is inhibition of cell attachment. The specificity of LN may be indicated because antilaminin antibody counteracted this effect. The attached cells form small processes immediately after attachment and continue to proliferate, forming small colonies. Treatment of these cells with 4 mM dibutyryl-cyclic AMP (db-cAMP) or 2 mM sodium butyrate starting on the 3rd or 4th d of culture results in extensive differentiation of all the attached cells. Db-cAMP provokes the formation of long ramifying neuritelike processes whereas butyrate induces the appearance of epithelial-like cells with a flat morphology. Thus, laminin seems to act in concert with other agents promoting attachment and potentiating differentiation.