Expression of interleukin-22 in murine carcinoma cells did not influence tumour growth in vivo but did improve survival of the inoculated hosts.

Interleukin (IL)-22, a novel cytokine belonging to the IL-10 family, is secreted from activated T and natural killer cells and is possibly involved in inflammatory responses. We examined whether expression of the IL-22 gene in murine colon carcinoma Colon 26 cells (Colon 26/IL-22) could produce any antitumour effects in the inoculated mice. Although growth of Colon 26/IL-22 tumours in syngeneic mice was not different from that of parent tumours, survival of the mice that were subcutaneously or intraperitoneally inoculated with Colon 26/IL-22 tumours was significantly prolonged compared with the mice inoculated with parent tumours. Metastasis was not influenced by IL-22 expressed in tumours. Expression of the IL-22 receptor-specific gene, IL-22R, was not induced in spleen cells stimulated with concanavalin A, anti-CD3 or anti-CD40 antibody, despite constitutive expression of the IL-10R2 gene, which encodes another component of the heterodimeric IL-22 receptor complex. IL-22 thereby does not directly act on immunocompetent cells, and IL-22 expressed in tumours can favour apothanasia of inoculated hosts.