Ecdysone-inducible foreign gene expression in stably-transformed lepidopteran insect cells

Cultured cell lines that can be stably transformed with inducible gene constructs could prove extremely valuable for the continuous and economical production of recombinant proteins. Toward this goal, we have established 11 clones (designated NISES-BoMo-DK1 to 11) from a previously reported silkworm cell line, NISES-BoMo-DZ. Nine of these clonal lines showed a distinct morphological change. i.e., cell aggregation, in response to treatment with 1 microM 20-hydroxyecdysone (20E). DK10 cells transfected with various reporter assay plasmids under optimal conditions (i.e., 20-30% transfection efficiency) showed inducibility of gene expression by 20E. The 20E treatment of the prototypical DK10 cells resulted in a simultaneous, transient increase of the nuclear ecdysone (E) receptor levels. Further, this inducibility was also observed in a DK10 cell line stably transformed with the reporter plasmid that carries the hygromycin-resistance gene. This offers an opportunity to achieve efficient, continuous production of recombinant proteins. It could also allow high throughput screening for potential E agonists.