Inhibition of skin carcinogenesis by suppression of NF-kappa B dependent ITGAV and TIMP-1 expression in IL-32 gamma overexpressed condition

Background: Interleukin-32 (IL-32) has been associated with various diseases. Previous studies have shown that IL-32 inhibited the development of several tumors. However, the role of IL-32 gamma, an isotype of IL-32, in skin carcinogenesis remains unknown. Methods: We compared 7,12-Dimethylbenz[a] anthracene/12-O-Tetradecanoylphorbol-13-acetate (DMBA/TPA)-induced skin carcinogenesis in wild type (WT) and IL-32 gamma-overexpressing mice to evaluate the role of IL-32 gamma. We also analyzed cancer stemness and NF-kappa B signaling in skin cancer cell lines with or without IL-32 gamma expression by western blotting, quantitative real-time PCR and immunohistochemistry analysis. Results: Carcinogen-induced tumor incidence in IL-32 gamma mice was significantly reduced in comparison to that in WT mice. Infiltration of inflammatory cells and the expression levels of pro-inflammatory mediators were decreased in the skin tumor tissues of IL-32 gamma mice compared with WT mice. Using a genome-wide association study analysis, we found that IL-32 was associated with integrin aV (ITGAV) and tissue inhibitor of metalloproteinase-1 (TIMP-1), which are critical factor for skin carcinogenesis. Reduced expression of ITGAV and TIMP-1 were identified in DMBA/TPA-induced skin tissues of IL-32 gamma mice compared to that in WT mice. NF-kappa B activity was also reduced in DMBA/TPA-induced skin tissues of IL-32 gamma mice. IL-32 gamma decreased cancer cell sphere formation and expression of stem cell markers, and increased chemotherapy-induced cancer cell death. IL-32 gamma also downregulated expression of ITGAV and TIMP-1, accompanied with the inhibition of NF-kappa B activity. In addition, IL-32 gamma expression with NF-kappa B inhibitor treatment further reduced skin inflammation, epidermal hyperplasia, and cancer cell sphere formation and downregulated expression levels of ITGAV and TIMP-1. Conclusions: These findings indicated that IL-32 gamma suppressed skin carcinogenesis through the inhibition of both stemness and the inflammatory tumor microenvironment by the downregulation of TIMP-1 and ITGAV via inactivation of NF-kappa B signaling.