Schema of cell fusion and chromosomal instability. A: Cytosolic cell fusion of two subtype of cells (homotype or heterotype). B and D: Most of cells, at the stage of nuclear cell fusion, revealed no further propagation and subsequently vanished. C: Viable progeny cells propagated again in culture. Giemsa-stained chromosomes of MCF-7 cells were examined. D: Abnormal sets of chromosomes as a consequence of cell fusion and (E) the cells containing giant nuclei (polyploid) were died out and the diverse populations were analogously converged into doxorubicin resistant clones. Table insert, fusion was quantitated by counting the number of cells (%) and nuclei present in a microscope field.