Antineoplastic Agents/chemistry; Carcinogens/chemistry; Cell Transformation, Neoplastic/chemically induced; Immunosuppressive Agents/chemistry; Mutagens/chemistry; Thioguanine/analogs & derivatives; Thioguanine/chemistry; Antineoplastic Agents/metabolism; Antineoplastic Agents/toxicity; Base Sequence; Carcinogens/metabolism; Carcinogens/toxicity; Cell Line; Cell Transformation, Neoplastic/genetics; Cell Transformation, Neoplastic/metabolism; DNA/chemistry; DNA/genetics; Genetic Vectors/chemistry; Genetic Vectors/genetics; Humans; Immunosuppressive Agents/metabolism; Immunosuppressive Agents/toxicity; Molecular Sequence Data; Mutagenesis; Mutagens/metabolism; Mutagens/toxicity; Thioguanine/metabolism; Thioguanine/toxicity