Changes in three-dimensional structure of cultured S91 mouse melanoma cells associated with growth inhibition and induction of melanogenesis by retinoids.

Abstract

In addition to their established use in the treatment of dermatological disorders, retinoids are potentially useful in oncology. Retinoids inhibit the proliferation of various cultured tumour cells [7], suppress the expression of the transformed phenotype [11] and enhance the differentiation of certain malignant cells [8, 9, 12]. $91 mouse melanoma cells are very sensitive to retinoids, which inhibit both their anchorage-dependent and anchorage-independent growth, and stimulate their melanotic expression [9]. The present paper reports the effects of two retinoids on the growth and melanogenesis of $91 melanoma cells. Using scanning electron microscopy, we found that these effects were associated with marked changes in the threedimensional structure of the cells. Cloudman-S91 mouse melanoma cells (clone M3; Flow Laboratories, UK) were grown on plastic cellculture dishes (Sterilin; 5 cm in diameter). The culture medium was HAM' s F-10 medium supplemented with 15% horse serum, 2% foetal calf serum, 2 mM glutamine and penicilline and streptomycin (50 gg/ml each). The cells were plated at various densities (0.025-0.8 x 106/dish) and allowed to attach overnight; retinoic acid (5 gM) and etretinate (10 gM; Hoffmann-LaRoche Research Laboratories, Basel, Switzerland) were then added as ethanol solutions. The final ethanol concentration was 0.4%. Incubation was performed at 37 ~ C in an atmosphere of 5% CO2/ 95% air. The medium was changed after 3 days of retinoid treatment, and culturing was continued for 3