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Targeting COX-2/PGE(2) pathway in HIPK2 knockdown cancer cells: impact on dendritic cell maturation
Alessia Garufi1, Giuseppa Pistritto, Claudia Ceci
1Department of Experimental Oncology, Molecular Oncogenesis Laboratory, Regina Elena National Cancer Institute, Rome, Italy.
Background:
Homeodomain-interacting protein kinase 2 (HIPK2) is a multifunctional protein that exploits its kinase activity to modulate key molecular pathways in cancer to restrain tumor growth and induce response to therapies. For instance, HIPK2 knockdown induces upregulation of oncogenic hypoxia-inducible factor-1 (HIF-1) activity leading to a constitutive hypoxic and angiogenic phenotype with increased tumor growth in vivo. HIPK2 inhibition, therefore, releases pathways leading to production of pro-inflammatory molecules such as vascular endothelial growth factor (VEGF) or prostaglandin E2 (PGE(2)). Tumor-produced inflammatory mediators other than promote tumour growth and vascular development may permit evasion of anti-tumour immune responses. Thus, dendritic cells (DCs) dysfunction induced by tumor-produced molecules, may allow tumor cells to escape immunosurveillance. Here we evaluated the molecular mechanism of PGE(2) production after HIPK2 depletion and how to modulate it.
Methodology/Principal Findings:
We show that HIPK2 knockdown in colon cancer cells resulted in cyclooxygenase-2 (COX-2) upregulation and COX-2-derived PGE(2) generation. At molecular level, COX-2 upregulation depended on HIF-1 activity. We previously reported that zinc treatment inhibits HIF-1 activity. Here, zinc supplementation to HIPK2 depleted cells inhibited HIF-1-induced COX-2 expression and PGE(2)/VEGF production. At translational level, while conditioned media of both siRNA control and HIPK2 depleted cells inhibited DCs maturation, conditioned media of only zinc-treated HIPK2 depleted cells efficiently restored DCs maturation, seen as the expression of co-stimulatory molecules CD80 and CD86, cytokine IL-10 release, and STAT3 phosphorylation.
Conclusion/Significance:
THESE FINDINGS SHOW THAT: 1) HIPK2 knockdown induced COX-2 upregulation, mostly depending on HIF-1 activity; 2) zinc treatment downregulated HIF-1-induced COX-2 and inhibited PGE(2)/VEGF production; and 3) zinc treatment of HIPK2 depleted cells restored DCs maturation.
Insights
Homeodomain-interacting protein kinase 2 (HIPK2) depletion promotes colon cancer growth by increasing prostaglandin E2 (PGE2) via hypoxia-inducible factor-1 (HIF-1) and cyclooxygenase-2 (COX-2). Zinc treatment reverses this by inhibiting HIF-1, reducing PGE2, and restoring anti-tumor immunity.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Homeodomain-interacting protein kinase 2 (HIPK2) restrains tumor growth by modulating key cancer pathways.
- HIPK2 depletion upregulates hypoxia-inducible factor-1 (HIF-1), promoting tumor growth and inflammation.
- Tumor-produced inflammatory mediators can impair anti-tumor immune responses, such as dendritic cell (DC) dysfunction.
Purpose of the Study:
- To investigate the molecular mechanism of prostaglandin E2 (PGE2) production following HIPK2 depletion.
- To evaluate the potential of modulating PGE2 production and its impact on anti-tumor immunity.
Main Methods:
- HIPK2 knockdown in colon cancer cells.
- Assessment of cyclooxygenase-2 (COX-2) and PGE2 expression.
- Evaluation of HIF-1 activity and the effect of zinc supplementation.
- Analysis of dendritic cell (DC) maturation markers and cytokine release.
Main Results:
- HIPK2 knockdown led to COX-2 upregulation and PGE2 generation, dependent on HIF-1 activity.
- Zinc treatment inhibited HIF-1-induced COX-2 expression and PGE2/VEGF production in HIPK2-depleted cells.
- Conditioned media from zinc-treated HIPK2-depleted cells restored DC maturation, including CD80/CD86 expression and IL-10 release.
Conclusions:
- HIPK2 depletion promotes COX-2 and PGE2 production via HIF-1.
- Zinc supplementation effectively downregulates HIF-1-induced COX-2 and PGE2/VEGF production.
- Zinc treatment restores DC maturation in HIPK2-depleted conditions, suggesting a potential therapeutic strategy.
