Protoplast-mediated gene transfer into human leukemia (K562) cells.

We have examined the usefulness of a protoplast fusion technique as a tool to transfer cloned genes into hematopoietic cells. Protoplasts carrying cloned plasmids, which would express specific markers when successfully transfected into human cells, were prepared and fused with human leukemic cell line K562 cells using polyethylene glycol as a fusogenic factor. As a result, K562 cells fused with protoplasts containing a plasmid pSV2-cat constructed to code for chloramphenicol acetyltransferase (CAT) expressed CAT activity efficiently. K562 cells were also readily transformed to geneticin-(G418) resistant cells following fusion with protoplasts carrying a plasmid pSV2-neo-SV-gpt, which confers the resistance of mammalian cells to G418 and mycophenolic acid. It was also demonstrated that the plasmid genome was stably integrated into the chromosomal DNA of G418-resistant K562 cells. Our results proved that protoplast fusion could be used to study the specific expression and the biologic activities of cloned genes in human hematopoietic cells.