HER-2/neu is rate-limiting for ovarian cancer growth. Conditional depletion of HER-2/neu by ribozyme targeting.
Amplification and overexpression of the HER-2/neu proto-oncogene frequently coincide with an aggressive clinical course of certain human adenocarcinomas. To assess whether HER-2/neu plays a rate-limiting role in ovarian cancer, we used human SK-OV-3 ovarian cancer cells as a model. We applied a conditional mRNA depletion strategy of HER-2/neu with anti-HER-2/neu-targeted hammerhead ribozymes expressed under the control of a tetracycline-regulated promoter system. In these ovarian cancer cells, we reduced HER-2/neu mRNA, protein expression, and tumor growth in nude mice by transfection with HER-2/neu-targeted ribozymes and generated cell lines expressing different levels of HER-2/neu. Expression of the most effective ribozyme (Rz3) quenched HER-2/neu mRNA levels by >90%. Concomitantly, fluorescence-activated cell sorting analysis revealed that expression of the HER-2/neu-encoded surface glycoprotein was almost completely abrogated. In nude mice, tumor growth was dramatically inhibited in the HER-2/neu-depleted Rz3-expressing SK-OV-3 cells. Furthermore, already established tumors started to regress when Rz3 expression was activated midstream by withdrawal of the tetracycline treatment. This study supports the thesis that HER-2/neu can be rate-limiting for the malignant phenotype of ovarian cancer in a gene dose-dependent manner.
Juhl
H
H
Lombardi Cancer Center and Department of Pharmacology, Georgetown University, Washington, D. C. 20007, USA.
Downing
S G
SG
Wellstein
A
A
Czubayko
F
F
D000818:Animals; D015536:Down-Regulation; D005260:Female; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D010051:Ovarian Neoplasms / Q000473:pathology*; D000090063:Proto-Oncogene Mas; D016337:RNA, Catalytic / Q000378:metabolism*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000502:physiology*; D012097:Repressor Proteins / Q000378:metabolism; D013752:Tetracycline / Q000378:metabolism; D015534:Trans-Activators / Q000096:biosynthesis; D014407:Tumor Cells, Cultured
D000090063:Proto-Oncogene Mas; D016337:RNA, Catalytic; D018719:Erb-b2 Receptor Tyrosine Kinases; D012097:Repressor Proteins; D013752:Tetracycline; D015534:Trans-Activators; C000715470:MAS1 protein, human; C034811:tetracycline resistance-encoding transposon repressor protein