IL-23 promotes growth and proliferation in human squamous cell carcinoma of the oral cavity

Interleukin (IL)-23 is a heterodimeric cytokine, comprising IL-12p40 and the cloned IL-23-specific p19 subunit, was identified as a cancer-associated cytokine in a recent study. Like IL-12, IL-23 is expressed predominantly by activated dendritic cells and phagocytic cells. These cytokines antagonistically regulate local inflammatory responses in the tumor microenvironment and infiltration by intra-epithelial lymphocytes. We have previously demonstrated the expression of IL-23 and its receptors in human oral squamous cell carcinoma (HOSCC) cell lines and tissue. Hence, this study investigated whether IL-23 has a role in the growth and proliferation of oral cancer cells by examining the expression kinetics of IL-23 and NF-kappa B activity, in vitro and in vivo. IL-23, which constitutively expressed in oral cancer, was enhanced by TNF-alpha and IL-23. IL-23 promotes cell proliferation in oral cancer and enhances the transport of nuclear factor-kappa B (NF-kappa B p65, RelA) to the nucleus in HSC-3 cells. Furthermore, luciferase reporter assay showed that IL-23 strongly induces RelA activity, and confirmed this finding by knockdown of IL-23 using RNA interference. Although RelA activity was down-regulated by anti-human IL-23p19 polyclonal antibody, used to neutralize the activity of IL-23, apoptosis was not induced. Immunohistochemistry revealed a weak IL-23 immunoreactivity in the cytoplasm of inflammatory infiltrating cells and in the cancer cells derived from 14 of 40 cases (35%) of oral SCC. In contrast, strong RelA immunoreactivity was observed in 30 of 40 cases of SCC (75%), especially consistent with IL-23 positive cells in SCC tissues. These data suggest that IL-23 up-regulates the growth and cell proliferation of oral cancer by promoting the nuclear transactivation of RelA.