Pro-tumour activity of interleukin-22 in HPAFII human pancreatic cancer cells.

Interleukin (IL)-22 is a cytokine involved in inflammatory and wound healing processes that is secreted primarily by T helper type 17 (Th17) cells. IL-22 receptor (IL-22R) expression is limited to epithelial cells of the digestive organs, respiratory tract and skin. Most tumours originating in these sites over-express IL-22R. Interestingly, there is an increase in Th17 frequency within the peripheral blood and tumour microenvironment of advanced cancer patients. Subsequently, IL-17 has been shown to display both pro-tumour and anti-tumour functions. Because many tumours lack expression of the IL-17 receptor, the effects of IL-17 on tumour growth are generated by cells that surround the tumour cells. Like IL-17, high levels of IL-22 have been detected in tumour tissues and the peripheral blood of cancer patients; however, the direct effect of IL-22 on tumour cells has remained largely unknown. In this report, we show that IL-22 stimulated production of vascular endothelial growth factor (VEGF) and the anti-apoptotic factor Bcl-X(L) in IL-22R-positive HPAFII human pancreatic cancer cells. Additionally, IL-22 augmented HPAFII cell production of immunosuppressive cytokines. We show further that IL-22 activation of HPAFII cells diminished T cell production of interferon (IFN)-γ through the action of IL-10. Strikingly, we show for the first time that IL-22 can fully protect cancer cells from natural killer (NK) cell-mediated cytotoxicity by stimulating tumour production of IL-10 and transforming growth factor (TGF)-β1. Our data support the idea that IL-22 may act to promote the pathogenesis of cancers rather than function in anti-tumour immunity.