Abstract 5051: Aberrant endogenous expression of IL-1 promote inflammation and growth in human melanoma

Abstract Chronic inflammation can facilitate the initiation and progression of malignancies through the production of cytokines and reactive oxidative species. The elevation of interleukin 1 (IL-1) signaling pathway has been observed in melanoma and proposed to drive critical aspects of survival, which is tested in this study. Immunohistochemistry staining for IL-1α and β were performed in 168 biopsy samples from melanoma patients, including 35 nevi, 57 primary and 76 metastatic melanomas. Although only 11.4% of melanoma samples are positive for IL-1β, all the nevus samples are negative. The positive IL-1β percentage and intensity are strongly correlated with advanced disease stage (p < 0.0005 and 0.0002). 93.4% of melanomas and 64% of nevi were positive for IL-1α, with tumors showing significantly higher IL-1α intensity scores than nevi (p < 0.007). Melanoma cell lines A375, WM793, WM35, and SB2 highly express IL-1α, IL-1β, and IL-1 receptor I (IL-1RI), but not MeWo and TXM1 confirmed by RT-PCR and western blot. Therefore, the high expression of IL-1α and/or β was significant in some melanoma tissues and cell lines, which may play a crucial role on the melanoma growth. We further investigated the aberrant IL-1 signaling pathway in two mutant B-Raf melanoma cell lines, A375 and WM793. In both cells, the siRNA knockdown of IL-1α, IL-1β, or MyD88 led to dramatic decreases (about 50%) in several important inflammatory markers, including the Cox-2 expression, the levels of total reactive oxygen and nitrogen species, and the levels of phoshorylated SAPK/JNK and IκB. Moreover, the decrease of IL-1α, IL-1β, or MyD88 levels caused significant increase of p21 and p53 levels. Luciferase assay showed that 100 ng/ml IL-1α and β could increase about 30% of iNOS promoter activity in both cells. Our data suggest that aberrant IL-1 signaling pathway can promote inflammation and oxidative stress in melanoma cells. The treatment of 2.5 μg/ml IL-1RI neutralization antibodies could inhibit 20∼30% of cell growth in A375 and WM793 cells in 72 hours, but did not affect the growth of normal melanocytes as comparing with control goat IgG. Consistently, the siRNA knockdown of IL-1α, IL-1β, or MyD88 inhibited cell growth by 40∼60% in A375, WM793, WM35, and SB2 cells with high IL-1α and β levels. For TXM1 and MeWo cells with lower levels of IL-1α and β, siRNA knockdown of IL-1 system genes did not show any significant inhibitory effects on cell growth. Notably, the inhibition of growth by the decrease of IL-1α, IL-1β, or MyD88 levels in A375 and WM793 cells is due to autophagy, which was confirmed by the increases of acidic vesicular organelles in acridine orange staining and the autophagy marker LC3B levels in western blot. Our studies strongly indicate that the interruption of IL-1 signaling pathway can lead to growth suppression in melanoma cells, which can be a promising therapeutic strategy to sub-group melanoma patients with constitutively high expression of IL-1α. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5051. doi:10.1158/1538-7445.AM2011-5051