Effect of Sodium Arsenite on Mouse Skin Carcinogenesis

Arsenic is carcinogenic in human beings, and environmental exposure to arsenic is a public health issue that affects large populations worldwide. Thus, studies are needed to determine the mode of action of arsenic and prevent harmful effects arising from arsenic intake. The present study assessed the influence of sodium arsenite (As3þ) on potentially carcinogenic processes that are either pre-existing or concomitant with chronic intake of water containing As3þ. Experiments using SENCAR mice were designed to evaluate the effect of chronic administration of As3þ (2, 20, or 200 mg of As3þ/L) in drinking water that overlapped to varying degrees with a 2-stage carcinogenesis protocol carried out over 9 months. The results showed a time-dependent pattern. During early stages of carcinogenesis (6–12 weeks), animals exposed to As3þ and the carcinogenesis protocol showed increased numbers of tumors compared to control animals. During late carcinogenesis (16–30 weeks), the number of tumors stabilized to below con-trol values, but the tumors showed increased malignancy. These findings indicate that the outcomes of the 2-stage skin carcinogenesis protocol are modified by the presence of arsenite in drinking water, which increases the rate of carcinoma development