IN-VITRO EXPRESSION OF THE DIPHTHERIA-TOXIN A-CHAIN GENE UNDER THE CONTROL OF HUMAN CHORIONIC-GONADOTROPIN GENE PROMOTERS AS A MEANS OF DIRECTING TOXICITY TO OVARIAN-CANCER CELL-LINES

OBJECTIVE: Our goal was to determine whether toxicity of the diphtheri a toxin A-chain gene regulated by the human chorionic gonadotropin pro moter can be directed to malignant ovarian cell lines. STUDY DESIGN: P lasmids containing diphtheria toxin A-chain gene linked to the regulat ory elements of the metalloergothioneine and human chorionic gonadotro pin promoters were transfected into the cell lines. Expression of diph theria toxin A-chain gene was determined by the inhibition of a cotran sfected luciferase reporter gene. RESULTS: Cytotoxicity of the diphthe ria toxin A-chain gene is shown in a dose-responsive manner. Transfect ion of a plasmid expressing the diphtheria toxin A-chain gene controll ed by a constitutive promoter readily inhibits protein synthesis. Spec ific inhibition of luciferase protein synthesis occurs in ovarian canc er cells transfected with the diphtheria toxin A-chain gene under the control of the human chorionic gonadotropin promoters when compared wi th normal ovarian epithelial cells or fibroblasts. CONCLUSIONS: These data demonstrate the preferential expression of the diphtheria toxin A -chain gene, regulated by the human chorionic gonadotropin promoter, t o ovarian cancer cell lines. This provides an avenue for targeting suc h cells for suicide, toxin, or cytokine genes.