NOS2 Induction by Human Beta Defensin 3 (hBD3) in Macrophages

Objectives: Macrophages are a central player in cancer development and progression, where an M2-like phenotype stimulates chronic inflammatory conditions and perpetuates cancer-promoting processes. hBD3 is an antimicrobial peptide found to play an important role in innate immunity particularly at mucosal surfaces, and has recently been implicated in cancer progression by its ability to chemoattract macrophages to oral carcinoma lesions and to promote an inflammatory cytokine profile in situ. NOS2 (iNOS) is an evolutionarily ancient enzyme that synthesizes nitric oxide, is induced by pro-inflammatory mediators (cytokines, hypoxia, etc.), and is involved in a plethora of physiological processes from vasodilation to direct anti-bacterial effects; aberrant NOS2 expression has been implicated in the pathogenesis of a multitude of inflammatory conditions including asthma, arthritis, colitis, and most recently, cancer. Mounting evidence demonstrates a pro-tumorigenic role of NOS2 in multiple cancers, and this study explores the role of hBD3 in promoting a pro-inflammatory tumor microenvironment through induction of NOS2. Methods: RT-PCR, immunocytochemistry, western blot Results: RNA and protein data show dose-response induction of NOS2 in human THP-1 macrophages by hBD3 treatment (2-10ug). Immunocytochemistry of macrophages treated with hBD3 in combination with intracellular signaling pathway inhibitors suggests that hBD3-mediated induction of NOS2 occurs via the NF-kB (2.5uM inhibitor), but not the JAK/STAT pathway. Conclusion: That hBD3 induces NOS2 expression from human macrophages in vitro suggests an important mechanism by which hBD3 may promote cancer progression. hBD3 has so far been implicated in vivo in oral cancer pathogenesis, but recent data demonstrating hBD3 induction in non-oral cancer lesions suggests that hBD3 may play a role in cancer pathogenesis beyond the oral cavity – this project suggests that hBD3 may do so by establishing a cancer-promoting environment through NOS2 induction.