Dermal oncogenicity studies on two methoxysilanes and two ethoxysilanes in male C3H mice

The dermal oncogenic potential of beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (EEMS), gamma-glycidoxypropyltrimethoxysilane (GPMS), beta-(3,4-epoxycyclohexyl)ethyltriethoxysilane (EEES), and gamma-glycidoxypropyltriethoxysilane (GPES) was assessed by applying 25-microliters aliquots of acetone solutions to the skin of 40 male C3H/HeJ mice. The concentrations applied were 100, 25, 10, and 10% by volume for EEMS, GPMS, EEES, and GPES, respectively. Applications were made thrice weekly until the death of the animals. A negative control group received acetone (solvent) only. No treatment-related skin tumors were observed, nor was there evidence of increased incidence of any internal tumor in the groups that received GPMS, EEES, or GPES. In the group treated with EEMS, four mice were observed with squamous cell carcinomas of the treated skin and two mice had subcutaneous sarcomas outside of the treated area. No skin tumors were observed in the group treated with acetone, but two mice had subcutaneous sarcomas outside of the treated area. The mean survival times were 529, 482, 545, 492, and 502 days for the EEMS, GPMS, EEES, GPES, and acetone control groups, respectively. In no case was the mortality rate significantly different from that of the controls. The results indicate that only EEMS was oncogenic under the conditions of these studies.