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Carcinogenicity of Acylating Agents: Chronic Bioassays in Mice and Structure-Activity Relationships (SARC)

A small number of acylating agents are known to be carcinogenic. The structure-activity relationships and carcinogenicity (SARC) of these compounds are reviewed in this report. In addition, the results of chronic bioassays of three previously untested compounds are described. Female ICR/Ha Swiss mice, 30–50 per group, were used in all tests. The test duration was 18–22 months. Diethylcarbamyl chloride (DECC), ethyl chloroformate (ECF), and dichloroacetyl chloride (DCAC) were tested by repeated skin application, in two-stage carcinogenesis with phorbol myristate acetate (PMA) as promoter, and by repeated subcutaneous injection. Dimethylcarbamyl chloride was used as a positive control together with control groups. All three compounds showed marginally significant incidences of papillomas and carcinomas when tested as initiators. ECF and DCAC did not show skin tumorigenicity in the repeated skin application tests. DECC showed weak carcinogenicity compared to DMCC. Subcutaneous injection resulted in the same pattern of tumorigenicity. Thus, the four acylating agents showed the following decreasing order of carcinogenicity: DMCC > DECC > ECF ≅ DCAC. All four compounds hydrolyze rapidly in water, with the following decreasing order of rate of hydrolysis: DCAC > DMCC ECF ≅ DECC. Their mechanisms of hydrolysis are: DMCC, DECC, and DCAC, SN1; ECF, SN2. There is no clear correlation between rate or mechanism of hydrolysis and carcinogenicity of these acylating agents.