The principle of promoter-targeted gene delivery was used to direct the expression of reporter genes and inducible caspases to Cox-2-overexpressing cancer cells. The polycation poly(ethylenimine) was used in unmodified form to nonvirally deliver genes into cells, and targeting was achieved at the transcriptional level. Results demonstrated that reporter expression was reduced by an average of 89.8% in normal cells and cell lines not overexpressing Cox-2 when the strong cytomegalovirus promoter was replaced with the human Cox-2 promoter in delivered plasmids. Cocultures of normal and Cox-2-overexpressing cancer cells showed less than 0.5% reporter expression in normal fibroblast cells but over 35% reporter expression in PC3 prostate cancer cells. This targeting method was then used to direct the expression of inducible forms of caspases 3 and 9 to Cox-2-overexpressing cancer cells of the bladder and prostate. Following activation of the resulting caspase pro-forms, cells underwent apoptosis as evidenced by DNA fragmentation and cytoskeletal degradation. This result was also observed in cells resistant to apoptosis in terms of TNF-α initiation. Such directed apoptosis could eventually serve as a treatment for an entire class of Cox-2-overexpressing carcinomas.
- Expression targeting
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