Weak promotion of C3H/10T1/2 cell transformation by repeated treatments with formaldehyde.

Abstract

C3H/10T 1/2 cells were treated with N-methyl-N'-nitro-N-nitrosoguanidine and then repeatedly exposed to formaldehyde (0.1 to 2.0 micrograms/ml). Exposure of N-methyl-N'-nitro-N-nitrosoguanidine-initiated cultures to formaldehyde concentrations of 0.5 or 1.0 micrograms/ml in a variety of treatment regimens resulted in focus formation in up to 9% of the treated dishes. Transformed foci were observed in 2% or less of the cultures treated with N-methyl-N'-nitro-N-nitrosoguanidine or formaldehyde alone. Formaldehyde thus appears to be only a weak tumor promoter for C3H/10T 1/2 cell transformation.