The human promyelocytic cell line HL-60 overexpresses the c-myc protooncogene. Plasmid pDACx carrying antisense human c-myc DNA and neo gene was introduced into HL-60 cells with lipofectin reagent. Upon DNA entering the tar-geted celis and expression of antisense transcripts to c-myc, C-MYC protein level, cell proliferation and colony-forming potentiality were all definitely inhibited.