Introduction: Interleukin-20 (IL-20) is a pleiotrophic cytokine, which belongs to the IL-10 family. The interaction of this cytokine with its’ specific receptor molecules initiates a broad and varied array of signals that induce cellular antiviral states, modulate inflammatory responses, inhibit or stimulate cell growth, apoptosis, and affect many immune mechanisms. IL-20 has been demonstrated to have a function in skin inflammation (psoriasis) and rheumatoid arthritis. We are examining IL-20, IL-20Rα and IL-20Rβ in lung cancer and their epigenetic regulation by histone deaceytlase inhibitors.
Methods: A panel of lung cell lines: CRL 5820, CRL 5915, Ju 77, One 58 (mesothelioma), H460, H647, H1299 (large cell carcinoma), A549 (adenocarcinoma), SK-MES-1 (squamous cell carcinoma), and HBEC 3, 4 5, BEAS2B (normal cells) were examined for expression of IL-20 and its’ receptors using RT-PCR. Some of these cell lines were used to investigate the effects of Trichostatin A (TSA-250ng/ml) and cyloheximide (10μg/ml) on the expression of the IL-20 family at mRNA and protein level. Matched tumor and normal samples from patients with lung cancer were also examined.
Results: All normal cells expressed low to moderate levels of IL-20. The A549, One- 58 and Ju-77 cells also expressed IL-20 at mRNA level. IL-20Rα was expressed at very low levels in the three large cell carcinomas, while variable expression of IL-20Rβ was detected in all cells. TSA treatment up-regulated IL-20 and both receptors at mRNA and protein level in A549, SK-MES-1 and HBEC 4. IL-20 was also found to be super-induced by cycloheximide treatment in A549 and HBEC 4. Chromatin immuno-precipitation (CHiP) will be used to confirm hyperacetylation of the IL-20 promotor in TSA treated samples. Adenocarcinoma samples displayed a decrease in IL-20Rα relative to matched normal tissue, compared to an increase in IL-20Rβ in 80% of samples tested. IL-20 was down regulated in 40% of normal samples. The numbers in this study is presently being increased. We are currently optimising an IL-20 ELISA, and studying the effects of hypoxia (0.5% oxygen) on the IL-20 family. Furthermore we are examining the effect (if any) of TSA and/or cycloheximide under hypoxic conditions. We are also currently exploring the relationship between the IL-20 family with two pro-inflammatory cytokines, TNFα and IL-1β to assess its’ role in inflammation.
Conclusions: This cytokine may have a significant role in a variety of pathophysiological processes as well as in regulation of the immune system. These findings suggest that IL-20, IL-20Rα and IL-20Rβ expression in normal and lung cancer cell lines is under epigenetic control. The effect of histone deacetylase inhibitors on this expression may provide a potential target for the treatment of lung cancer.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA