Metallothionein (MTs) are a group of small cysteine-rich proteins that bind heavy metals with high affinity. It is widely held that MTs function to protect cells/organisms form heavy metal toxicity because of their binding affinity for heavy metals and because expression of MT genes is induced by heavy metals. In addition to their widely accepted role in preventing heavy metal toxicity, evidence indicates that the MTs may be involved in protection from the carcinogenic action of various chemicals/compounds. For example, transfected cells that overexpress MT show increase resistance to the toxicity of alkylating agents which are known to induce cancer in rodents. In addition, studies with rats suggest that tissues that do not express MT are susceptible to d-induced carcinogenesis. The overall strategy described in this application is designed to directly test the hypothesis that MT protects an organism from the carcinogenic effects of alkylating agents and Cd. The specific aims of the project are: 1) to produce and characterize mice lacking a functional mMT-I gene, mMT-II gene, and mMT-I and mMT-II (mMT-I/mMT-II) genes, 2) to determine if low tissue levels of MT are correlated to an increased incidence of carcinogenesis induced by alkylating agents, 3) to determine if low tissue levels of MT are correlated with an increase incidence of carcinogenesis induced by Cd.