The general goal of this study is the development of a predictive assay which may select effective alkylating agents for tumor treatment and detect drug-resistant tumor cells. The development of the assay will be based on o linear relationship between the binding of monoclonal antibody (MAb) F7-26 to cellular DNA and the cytotoxicity of nitrogen mustard derivatives and nitrosoureas in the range of 1-6 log cell killing; and the ability of MAb to distinguish between sensitive and drug-resistant cells. The major question to be answered in this study is whether a quantitative correlation between MAb binding and drug sensitivity or resistance can be observed in different murine and human tumor cells. MAb binding to DNA in individual cells will be measured by flow cytometry. The correlation between MAb F7-26 immunoreactivity with DNA in the cells treated with alkylating agents and cell killing will be studied in two paired cell lines sensitive and resistant to alkylating agents: i) lung carcinoma lines A549 (Mer+ phenotype) and A427 (Mer- phenotype) resistant and sensitive to nitrosoureas, respectively; ii) ovarian carcinoma cell lines A2780 sensitive and resistant to L-PAM. In each pair of lines, relationship between cell survival, initial DNA damage and repair of DNA damage after drug removal will be studied. Mouse solid tumor Lewis lung carcinoma and its sublines resistant to nitrosoureas ans cyclophosphamide will be treated with drugs in vitro and in vivo. The binding of MAb to aneuploid tumor cells will be compared with tumor response to treatment. The relationship between the appearance of cell subsets with low DNA immunoreactivity and the development of drug resistance during repeated drug treatments will be studied. To characterize the type of change in DNA detected with the Mab the antigenic determinant of MAb F7-26 will be studied by direct and competitive ELISA immunoassay. The relative affinity of MAb to different deoxyribohomopolymers and the number of bases in oligonucleotides necessary to bind the MAb will be determined. Flow cytometric study of drug effects on DNA in individual tumor cells proposed herein should make it possible to apply the new methodology in clinical settings.