ENHANCEMENT OF BALB C 3T3 CELLS TRANSFORMATION BY 1,2-DIBROMOETHANE PROMOTING EFFECT/

Two of the most representative halogenated aliphatic hydrocarbons, 1,2 -dibromoethane and 1,1,2,2-tetrachloroethane, were tested in the two-s tage cell transformation model for analysing the promoting ability. Bo th of these compounds had previously been found to exert genotoxic eff ects, probably acting as moderate initiators, BALB/c 3T3 cells were in itiated with subtransforming doses of N-methyl-N-nitro-N-nitrosoguanid ine or 3-methylcholanthrene and then exposed to a chronic treatment wi th different non-transforming dosages of the two haloalkanes. Tetrachl oroethane did not exert any promoting activity in that system, By cont rast, significant promoting effects by 1,2-dibromoethane were observed both in cells treated with N-methyl-N-nitro-N-nitrosoguanidine and in cells treated with 3-methylcholanthrene, Promotion of the transformat ion process initiated with 3-methylcholanthrene was detectable when co nfluent cells in the chemical-treated plates were replated in the leve l-II amplification test. This experimental procedure allowed cells to perform further rounds of replications and transformed foci to became detectable, Results gave evidence for a promoting role of 1,2-dibromoe thane in multistep carcinogenesis, probably responsible for the higher oncogenic ability of this compound with respect to 1,1,2,2-tetrachlor oethane.