Toxicity of cationic lipid-ribozyme complexes in human prostate tumor cells can mimic ribozyme activity

Stephen J. Freedland, Robert W. Malone, Holger M. Borchers, Zhanna Zadourian, Jill G. Malone, Michael J. Bennett, Michael H. Nantz, Juan Hua Li, Paul H. Gumerlock, Kent L Erickson

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Prostate tumor cell lines have been shown to both produce interleukin- 6 (IL-6) and express the IL-6 receptor, suggesting a potential autocrine growth regulatory role for IL-6. We explored the role of IL-6 in the proliferation of the human prostatic carcinoma cell line, DU145, using ribozymes to inhibit IL-6 expression. Hammerhead-type ribozymes targeted against IL-6 mRNA sequences were prepared, and in vitro analyses were used to demonstrate that these molecules catalyzed the cleavage of IL-6 mRNA polynucleotide fragments. To test in situ activity, these ribozymes were transferred into DU145 cells using cationic transfection lipids, cytofectins. Treatment of cultured cells with ribozyme/cationic lipid complexes resulted in a reduction of IL-6 protein levels in the supernatant and reduced numbers of DU145 cells 48 h after treatment. However, similar results were also seen following treatment with control RNA/lipid complexes. This reduction in IL-6 levels and cell numbers was a function of the RNA/lipid complexes and was not seen with either lipid or RNA alone. Therefore, the reductions in IL-6 levels and cell numbers observed were not due to ribozyme-mediated cleavage of IL-6 mRNA, but rather reflected a dose- dependent, nonspecific toxic effect of the treatment with ribozyme/cytofectin complexes. This effect can resemble functional ribozyme activity, complicating analysis of the activity of synthetic ribozymes after transfection into cultured cells.

Original languageEnglish (US)
Pages (from-to)144-153
Number of pages10
JournalBiochemical and Molecular Medicine
Issue number2
StatePublished - Dec 1996

ASJC Scopus subject areas

  • Biochemistry


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