[Inhibitory effect of a third generation retinoid R8923 and all-trans retinoic acid on two-stage chemical carcinogenesis of BALB/3T3-A31 cells in vitro].

The inhibitory effect of a third generation retinoid R8923 and all-trans retinoic acid (RA) on malignant transformation of Balb/3T3-A31 cells induced by 3-methylcholanthrene (3-MCA) and 12-0-tetradecanoyl phorbol-13-acetate(TPA) was studied in paper. Malignant transformation of Balb/3T3-A31 cells was evaluated by scoring transformation foci and soft agar assay. Actively growing Balb/3T3-A31 cells (1.5 x 10(4) cells per 60-mm-diameter glass dish) were cultured in 5ml of Eagle's Minimum Essential Medium supplemented with 10 percent fetal bovine serum. Twenty-four hours after plating, the cells were treated with 3-MCA (2 micrograms/ml) for 72 hours. TPA was added into the medium at a concentration of 100 ng/ml for 2 weeks. Thirty-six days after cell plating, the transformation foci were counted and the soft agar assay of the cells isolated from each glass dish was performed. Results showed that there were 16.0 +/- 1.58 transformation foci/dish and the colony forming efficiency in soft agar assay was 138.6 +/- 14.47/10(3) cells in 3-MCA and TPA treated dishes (control group). When the cells were exposed to R8923 or RA (at a concentration of 10(-6) M), the transformation foci were 11.2 +/- 0.84 /dish and 9.2 +/- 1.10/dish respectively, and the corresponding colony forming efficiency values were 66.1 +/- 7.68/10(3) cells and 64.8 +/- 4.46/10(3) cells. They were significantly lower than that of the control group. These results demonstrated that R8923 and RA could effectively inhibit 3-MCA and TPA induced malignant transformation of Balb/3T3-A31 cells and suggested that R8923 is a potential drug for cancer chemoprevention.