Inhibition of chemically induced morphological transformation and reversion of the transformed phenotype of ascorbic acid in C3H/10T 1/2 cells
Benedict, W.F.; Wheatley, W.L.; Jones, P.A.
Cancer Research 40(8 Pt 1): 2796-2801
1980
ISSN/ISBN: 0008-5472 PMID: 6248214 Document Number: 167033
C3H/10T 1/2 mouse embryo cells were exposed to 3-methylcholanthrene (MCA) for 24 h. Daily addition of ascorbic acid at the noncytotoxic concentration of 1 .mu.g/ml prevented the expression of transformed foci at 42 or 56 days if the ascorbate was added immediately after MCA exposure and daily thereafter for 22 days. Ascorbic acid also could be added as late as 23 days after MCA treatment and still completely inhibit morphological transformation if maintained in the cultures until the dishes were stained. The expression of the transformed phenotype in .apprx. 80% of the cultures containing transformed foci was completely blocked following subculture at 6-8 wk after MCA treatment if the transformed cells from these foci subsequently received ascorbic acid, 1 .mu.g/ml, daily. Only 40% of cultures containing transformed foci returned to a normal morphological phenotype if the cultures were maintained for 10 wk after MCA exposure before passage. The reversion of transformed cells to a normal morphological pattern often appeared to be irreversible since, after 4 subcultures in the presence of ascorbate, the ascorbic acid could subsequently be removed without reexpression of the morphological transformation. Transformed cells became refractory to the effect of ascorbic acid if they were initially subcultured several times without ascorbate and then were exposed to the vitamin. This variation in the response to ascorbic acid between early-and late-passaged transformed cells may indicate a fundamental biological difference between these cells despite a similar morphology. The exact mechanism(s) responsible for inhibition and reversion of the transformed phenotype is presently unknown. However, differential cytotoxicity between transformed and non-transformed cells, the production of an extracellular matrix in ascorbate-treated cultures, adipocyte formation or increases in cyclic AMP were not implicated.