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IL6 sensitizes prostate cancer to the antiproliferative effect of IFNα2 through IRF9.

Erb HH, Langlechner RV, Moser PL, Handle F, Casneuf T, Verstraeten K, Schlick B, Schäfer G, Hall B, Sasser K, Culig Z, Santer FR - Endocr. Relat. Cancer (2013)

Bottom Line: Downregulation and overexpression of IRF9 provided evidence for an IFN-independent role of IRF9 in cellular proliferation of different PCa cell lines.Furthermore, expression of IRF9 was essential to mediate the antiproliferative effects of IFNα2.We concluded that IL6 is an inducer of IRF9 expression in PCa and a sensitizer for the antiproliferative effects of IFNα2.

View Article: PubMed Central - PubMed

Affiliation: Division of Experimental Urology, Department of Urology, Innsbruck Medical University, Austria.

ABSTRACT
Development and progression of prostate cancer (PCa) are associated with chronic inflammation. The cytokine interleukin 6 (IL6) can influence progression, differentiation, survival, and angiogenesis of PCa. To identify novel pathways that are triggered by IL6, we performed a gene expression profiling of two PCa cell lines, LNCaP and MDA PCa 2b, treated with 5 ng/ml IL6. Interferon (IFN) regulatory factor 9 (IRF9) was identified as one of the most prevalent IL6-regulated genes in both cell lines. IRF9 is a mediator of type I IFN signaling and acts together with STAT1 and 2 to activate transcription of IFN-responsive genes. The IL6 regulation of IRF9 was confirmed at mRNA and protein levels by quantitative real-time PCR and western blot respectively in both cell lines and could be blocked by the anti-IL6 antibody Siltuximab. Three PCa cell lines, PC3, Du-145, and LNCaP-IL6+, with an autocrine IL6 loop displayed high expression of IRF9. A tissue microarray with 36 PCa tissues showed that IRF9 protein expression is moderately elevated in malignant areas and positively correlates with the tissue expression of IL6. Downregulation and overexpression of IRF9 provided evidence for an IFN-independent role of IRF9 in cellular proliferation of different PCa cell lines. Furthermore, expression of IRF9 was essential to mediate the antiproliferative effects of IFNα2. We concluded that IL6 is an inducer of IRF9 expression in PCa and a sensitizer for the antiproliferative effects of IFNα2.

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IRF9 mediates the antiproliferative effects of IFNα2. Proliferation was measured by [3H]thymidine incorporation assay in LNCaP, LNCaP-IL6+, and PC3 cells after downregulation of IRF9 and additional treatment with 1000 U/ml IFNα2 after 72 h. Data represent mean±s.e.m. from three independent experiments. *P<0.05; **P<0.01; ***P<0.001.
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fig6: IRF9 mediates the antiproliferative effects of IFNα2. Proliferation was measured by [3H]thymidine incorporation assay in LNCaP, LNCaP-IL6+, and PC3 cells after downregulation of IRF9 and additional treatment with 1000 U/ml IFNα2 after 72 h. Data represent mean±s.e.m. from three independent experiments. *P<0.05; **P<0.01; ***P<0.001.

Mentions: Previous studies have shown that IRF9 plays an important role in IFNα2 signaling and mediates the antiproliferative effect of IFNα2 (Caraglia et al. 2005, Tsuno et al. 2009). Furthermore, it has been reported that IFNα2 decreases proliferation of PCa cells and several other tumors in vitro and in vivo and IFNα2 treatment is one of the few FDA-approved cancer immunotherapeutics (Hobeika et al. 1999, Kirkwood 2002, Bracarda et al. 2010). For this reason, we tested whether IRF9 plays a role in the antiproliferative effects of IFNα2. We transfected LNCaP, LNCaP-IL6+, and PC3 cells with IRF9 or control siRNA, treated the cells with 1000 U/ml IFNα2, and measured proliferation after 48 h by [3H]thymidine incorporation. LNCaP transfected with IRF9 or control siRNA showed no change in proliferation after IFNα2 treatment, whereas LNCaP-IL6+ and PC3 cells transfected with control siRNA showed a significant decrease in proliferation after IFNα2 treatment (Fig. 6). However, proliferation of IRF9 siRNA-transfected LNCaP-IL6+ and PC3 cells increased after IFNα2 treatment compared with the untreated IRF9 siRNA-transfected cells. This shows that high expression of IRF9 through IL6 signaling is needed to transmit the antiproliferative effects of IFNα2.


IL6 sensitizes prostate cancer to the antiproliferative effect of IFNα2 through IRF9.

Erb HH, Langlechner RV, Moser PL, Handle F, Casneuf T, Verstraeten K, Schlick B, Schäfer G, Hall B, Sasser K, Culig Z, Santer FR - Endocr. Relat. Cancer (2013)

IRF9 mediates the antiproliferative effects of IFNα2. Proliferation was measured by [3H]thymidine incorporation assay in LNCaP, LNCaP-IL6+, and PC3 cells after downregulation of IRF9 and additional treatment with 1000 U/ml IFNα2 after 72 h. Data represent mean±s.e.m. from three independent experiments. *P<0.05; **P<0.01; ***P<0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3753051&req=5

fig6: IRF9 mediates the antiproliferative effects of IFNα2. Proliferation was measured by [3H]thymidine incorporation assay in LNCaP, LNCaP-IL6+, and PC3 cells after downregulation of IRF9 and additional treatment with 1000 U/ml IFNα2 after 72 h. Data represent mean±s.e.m. from three independent experiments. *P<0.05; **P<0.01; ***P<0.001.
Mentions: Previous studies have shown that IRF9 plays an important role in IFNα2 signaling and mediates the antiproliferative effect of IFNα2 (Caraglia et al. 2005, Tsuno et al. 2009). Furthermore, it has been reported that IFNα2 decreases proliferation of PCa cells and several other tumors in vitro and in vivo and IFNα2 treatment is one of the few FDA-approved cancer immunotherapeutics (Hobeika et al. 1999, Kirkwood 2002, Bracarda et al. 2010). For this reason, we tested whether IRF9 plays a role in the antiproliferative effects of IFNα2. We transfected LNCaP, LNCaP-IL6+, and PC3 cells with IRF9 or control siRNA, treated the cells with 1000 U/ml IFNα2, and measured proliferation after 48 h by [3H]thymidine incorporation. LNCaP transfected with IRF9 or control siRNA showed no change in proliferation after IFNα2 treatment, whereas LNCaP-IL6+ and PC3 cells transfected with control siRNA showed a significant decrease in proliferation after IFNα2 treatment (Fig. 6). However, proliferation of IRF9 siRNA-transfected LNCaP-IL6+ and PC3 cells increased after IFNα2 treatment compared with the untreated IRF9 siRNA-transfected cells. This shows that high expression of IRF9 through IL6 signaling is needed to transmit the antiproliferative effects of IFNα2.

Bottom Line: Downregulation and overexpression of IRF9 provided evidence for an IFN-independent role of IRF9 in cellular proliferation of different PCa cell lines.Furthermore, expression of IRF9 was essential to mediate the antiproliferative effects of IFNα2.We concluded that IL6 is an inducer of IRF9 expression in PCa and a sensitizer for the antiproliferative effects of IFNα2.

View Article: PubMed Central - PubMed

Affiliation: Division of Experimental Urology, Department of Urology, Innsbruck Medical University, Austria.

ABSTRACT
Development and progression of prostate cancer (PCa) are associated with chronic inflammation. The cytokine interleukin 6 (IL6) can influence progression, differentiation, survival, and angiogenesis of PCa. To identify novel pathways that are triggered by IL6, we performed a gene expression profiling of two PCa cell lines, LNCaP and MDA PCa 2b, treated with 5 ng/ml IL6. Interferon (IFN) regulatory factor 9 (IRF9) was identified as one of the most prevalent IL6-regulated genes in both cell lines. IRF9 is a mediator of type I IFN signaling and acts together with STAT1 and 2 to activate transcription of IFN-responsive genes. The IL6 regulation of IRF9 was confirmed at mRNA and protein levels by quantitative real-time PCR and western blot respectively in both cell lines and could be blocked by the anti-IL6 antibody Siltuximab. Three PCa cell lines, PC3, Du-145, and LNCaP-IL6+, with an autocrine IL6 loop displayed high expression of IRF9. A tissue microarray with 36 PCa tissues showed that IRF9 protein expression is moderately elevated in malignant areas and positively correlates with the tissue expression of IL6. Downregulation and overexpression of IRF9 provided evidence for an IFN-independent role of IRF9 in cellular proliferation of different PCa cell lines. Furthermore, expression of IRF9 was essential to mediate the antiproliferative effects of IFNα2. We concluded that IL6 is an inducer of IRF9 expression in PCa and a sensitizer for the antiproliferative effects of IFNα2.

Show MeSH
Related in: MedlinePlus