Retinoid-induced adhesion in cultured, transformed mouse fibroblasts

Cultured, spontaneously transformed mouse fibroblasts (Balb/3T12-3 cells) were readily detached from the dish surface in an EDTA-mediated detachment assay. Retinoic acid-treated cells displayed increased adhesion to the culture dish surface. The effect of retinoic acid on the adhesion of Balb/3T12-3 cells was dose-dependent in the range of 0.05-5 μg/ml (0.17-17 μM) in an assay performed on cells cultured for 3 days in the presence of the retinoid. The earliest effect on adhesion was detected at 2 days of culture in the presence of 17 μM retinoic acid. The increase in adhesion displayed by retinoic acid-treated cells was rapidly lost upon removal of the retinoid from the culture medium. Synthetic retinoids were tested for their activity in inducing adhesion of cultured Balb/3T12-3 cells. Retinol, retinoic acid, and their 5,6-epoxy derivatives were the most active, showing activity at 1 μg/ml. 13-cis-Retinoic acid and the dimethylacetylcyclopentenyl and trimethylmethoxyphenyl derivatives were active at 10 μg/ml. However, active derivatives of retinoic acid invariably lost their activity upon chemical esterification or amide formation. Retinoids without biologic activity in other systems were also inactive in inducing adhesion. Among these were the synthetic derivatives of retinol, anhydroretinol and perhydromonoeneretinol, and the phenyl derivative of retinoic acid. β-Ionone, abscisic acid, and juvenile hormone were also inactive. Results showed that this adhesion assay may be used as an additional test for the biologic activity of retinoids containing a free carboxylic or carbinolic function. The phenomenon of induced adhesion may also aid in the study of the metabolic function of vitamin A.