OBJECTIVES: (1) To study the genetic regulation of cell malignancy by producing hybrids between malignant rodent and nonmalignant human cells as well as between malignant and nonmalignant human cells, the latter with appropriate marker chromosomes, and then determine if a specific chromosome or chromosomes of the nonmalignant partner will suppress the malignant characteristics of the tumor cell. (2) To transfer small amounts of genetic information from donor to recipient cells in order to develop cell systems for clarifying the mechanism by which mammalian cells regulate gene activity. BIBLIOGRAPHIC REFERENCES: Freedman, V.H., Brown, A.L., Klinger, H.P. and Shin, S.I.: Mass production of animal cells in nude mice with retention of cell specific markers. Exp. Cell Res. 98:143-151 (1976). Muller, Hj., and Klinger, H.P.: Chromosome polymorphism in a human newborn population. I. Frequencies of polymorphic chromosome variants. In: Chromosomes Today, P.L. Pearson and K.R. Lewis, Eds., John Wiley and Sons, New York, Vol. V, 249-256 (1976).