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Antitumor mechanisms of oligodeoxynucleotides with CpG and polyG motifs in murine prostate cancer cells: decrease of
Weiyin Shen1, Marianella Waldschmidt, Xiuqin Zhao
1Department of Internal Medicine, University of Iowa, Iowa City 52242, USA.
Abstract:
Previous studies have shown that CpG oligodeoxynucleotides (ODNs) have substantial immunostimulatory effects with anticancer applications. The antitumor applications that have been described previously are mediated through the CpG-induced activation of the host immune system, not through direct antitumor effects. Using cytostasis and cell proliferation assays, we demonstrated that specific ODNs inhibit the proliferation of RM-1 cells, a murine prostate cancer cell line. Flow cytometry analysis using propidium iodide (PI) nuclear staining confirmed the direct proapoptotic effect of ODNs on prostate cancer cells. This effect was dose dependent. Further studies using Western blot analysis and electrophoresis mobility shift assay (EMSA) revealed that the treatment of prostate cancer cells with specific ODNs activated the caspase pathway(s) and decreased the binding activities of AP-1 and NF-kappaB in a time-dependent manner. Evaluation of a panel of ODNs containing different DNA motifs demonstrated that the optimal proapoptotic sequences required polyG sequences but that CpG motifs were not essential. Finally, in vivo antitumor studies showed that the proapoptotic polyG motifs significantly inhibited prostate tumor growth. PolyG motifs inhibited tumor growth, and the effects were enhanced by CpG immune activating sequences. ODN containing both polyG and CpG motifs may have enhanced efficacy in tumor therapy through multiple mechanisms of action, including direct antitumor activities and immune activation.
Insights
Specific oligodeoxynucleotides (ODNs) directly inhibit prostate cancer cell proliferation and induce apoptosis. PolyG motifs are key for this effect, with CpG motifs enhancing overall tumor inhibition.
Area of Science:
- Immunology
- Molecular Biology
- Oncology
Background:
- CpG oligodeoxynucleotides (ODNs) are known for immunostimulatory effects in cancer therapy.
- Previous applications focused on immune activation rather than direct tumor cell effects.
Purpose of the Study:
- To investigate the direct anticancer effects of specific ODNs on prostate cancer cells.
- To identify DNA motifs responsible for direct antitumor activity and apoptosis induction.
Main Methods:
- Cytostasis and cell proliferation assays were used to assess ODN effects on RM-1 cells.
- Flow cytometry, Western blot, and electrophoresis mobility shift assay (EMSA) were employed to analyze cellular mechanisms.
- In vivo studies evaluated the antitumor efficacy of ODN motifs in a murine prostate cancer model.
Main Results:
- Specific ODNs demonstrated dose-dependent inhibition of prostate cancer cell proliferation and induced apoptosis.
- ODN treatment activated caspase pathways and modulated AP-1 and NF-kappaB binding activities.
- PolyG sequences were crucial for proapoptotic effects, while CpG motifs were not essential for direct apoptosis but enhanced overall tumor inhibition in vivo.
Conclusions:
- ODNs, particularly those with polyG motifs, possess direct proapoptotic activity against prostate cancer cells.
- Combined polyG and CpG motifs in ODNs may offer enhanced therapeutic efficacy through dual mechanisms: direct cytotoxicity and immune activation.