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Growth inhibition of ovarian cancer cells induced by antisense IL-6 oligonucleotides
J M Watson1, J S Berek, O Martínez-Maza
1Department of Microbiology & Immunology, UCLA School of Medicine.
Abstract:
In previous work, we saw that interleukin-6 (IL-6), a multifunctional cytokine, is produced by epithelial ovarian cancer cells and that ovarian cancer cells express the IL-6 receptor. Here, we examined the possibility that IL-6 acts as an autocrine growth factor for ovarian cancer cells. Inhibition of IL-6 gene expression by exposure to IL-6 antisense oligonucleotides resulted in greatly decreased cellular proliferation. Exposure of ovarian cancer cell lines (CAOV-3, OVCAR-3, and OC-436), to 1-5 microM of a 15-base single-stranded antisense IL-6 oligodeoxynucleotide, specific for a sequence in the second coding exon of the IL-6 gene, resulted in decreased IL-6 production and a > 80-85% inhibition of cellular proliferation. However, the addition of exogenous IL-6 failed to restore the proliferation of the antisense-treated cells. Antibodies to IL-6 did not consistently inhibit cell growth nor did rIL-6 enhance precursor frequency in a limiting dilution analysis. These results suggest that IL-6 does not directly induce the proliferation of ovarian cancer cells although endogenous IL-6 production is needed for optimal cell growth. As the majority of epithelial ovarian cancers produce IL-6, the direct specific inhibition of IL-6 gene expression is of potential therapeutic value.
Insights
Interleukin-6 (IL-6) is crucial for ovarian cancer cell growth, but doesn't directly drive proliferation. Inhibiting IL-6 gene expression significantly reduces ovarian cancer cell proliferation, suggesting therapeutic potential.
Area of Science:
- Oncology
- Molecular Biology
- Immunology
Background:
- Epithelial ovarian cancer (EOC) cells produce interleukin-6 (IL-6).
- EOC cells express the IL-6 receptor.
- The role of IL-6 as an autocrine growth factor in EOC requires further investigation.
Purpose of the Study:
- To investigate whether IL-6 functions as an autocrine growth factor for ovarian cancer cells.
- To assess the therapeutic potential of inhibiting IL-6 gene expression in EOC.
Main Methods:
- Utilized IL-6 antisense oligonucleotides to inhibit IL-6 gene expression in ovarian cancer cell lines (CAOV-3, OVCAR-3, OC-436).
- Measured cellular proliferation and IL-6 production following antisense treatment.
- Administered exogenous IL-6 and IL-6 antibodies to assess their effects on cell proliferation and precursor frequency.
Main Results:
- Inhibition of IL-6 gene expression led to a >80-85% decrease in ovarian cancer cell proliferation.
- IL-6 antisense treatment reduced endogenous IL-6 production.
- Exogenous IL-6 did not restore proliferation in antisense-treated cells, and IL-6 antibodies did not consistently inhibit growth.
Conclusions:
- Endogenous IL-6 production is necessary for optimal ovarian cancer cell growth, but IL-6 does not directly induce proliferation.
- Targeting IL-6 gene expression represents a potential therapeutic strategy for epithelial ovarian cancers, as most produce IL-6.