Genetic and Tumorigenic Characteristics of Cell Hybrids Formed In Vivo Between Injected Tumor Cells and Host Cells

Abstract

Highly tumorigenfc A9HT cells derived from the mouse L-cell were Injected into irradiated, syngeneic newborn C3H mice. Tumors were explanted and cell cultures were established. Two morphogically distinct cell types appeared in the culture: Type I cells resembled the A9HT, and type II cells were large and polygonal. Chromosome and biochemical analysis demonstrated that type I cells were derived from the injected A9HT cells and that type II cells were hybrids resulting from in vivo fusions between the Injected A9HT cells and the normal mouse cells of the host. Similar findings were obtained after two other mouse L-cells, A9 and 882, were injected into irradiated syngeneic mice. Tumorigenicity tests showed that the type II cells and their clonal cultures were 200-fold less tumorigenic than were the A9HT cells. Chromosome analysis was also done on cells of the tumors that developed in animals given injections of cells from type II clones. All had lower total chromosome numbers than did the cells injected. These findings agreed with conclusions about chromosome constitution and malignancy of in vitro hybrids studied in other laboratories.