Effects on apoptosis and cell cycle arrest contribute to the antitumor responses of interleukin-27 mediated by retrovirus in human pancreatic carcinoma cells

Interleukin (IL)-27, composed of p28 and Epstein-Barr virus-induced gene 3 (EBI3) subunits, has diverse functions in regulating immune systems. Human melanoma cells have been shown to express both IL-27 receptor subunits, and growth inhibition by IL-27 was detected. We investigated whether forced expression of the p28-linked EBI3 gene in human pancreatic carcinoma cells (AsPC1) by retroviral vector would produce IL-27-mediated antitumor effects and the related mechanisms. The data demonstrated that AsPC1 cells expressed both IL-27 receptor subunits, and tumor growth of AsPC1/IL-27 in mice was retarded compared with vector DNA-transduced tumors and survival of the mice was prolonged. Expression of cytokines such as interferon-γ, tumor necrosis factor-α and IL-1β in tumor specimens increased, while the secretion of IFN-γ and TNF-α from spleen cells of mice bearing IL-27-transfected tumors increased. Moreover, cell cycle arrest was induced in AsPC1/IL-27 inoculated mice with upregulated p21 expression and downregulated survivin expression. The appearance of apoptotic cells increased in tumor specimens of mice bearing IL-27-transfected tumors compared with the mice bearing DNA-transfected tumors by confirming the expression of apoptosis-related proteins and activated apoptotic pathways through detection of cleaved PARP. These results suggest that transfection of the IL-27 gene into human pancreatic carcinoma cells could produce antitumor effects in vivo and induction of cell cycle arrest and apoptosis could be the mechanism of IL-27 action in tumor regression.