Prostate carcinoma cells LNCaP and glucan cooperate in induction of cytokine synthesis by dendritic cells: Effect on natural killer cells and CD4+ lymphocytes activation

BACKGROUND Glucan is an immunomodulating agent used for cancer therapy. We investigated the effects of glucan on immune cell response to prostate carcinoma. Methods. Dendritic cells (DC) were co-cultured with prostate carcinoma cells LNCaP and/or glucan, and maturation markers expression, cytokine release, and superoxide anion production were evaluated. Conditioned media from glucan-treated or untreated DC and/or LNCaP cultures were used to stimulate T lymphocytes and natural killer (NK) cells. Results. LNCaP promoted partial DC maturation and scarce IL-12 secretion. Glucan induced DC maturation but no IL-12 production by DC. However, glucan increased IL-12 release by DC co-cultured with LNCaP. Moreover, LNCaP enhanced IL-1 beta, IL-23, IL-6, and TNF-alpha secretion, but decreased superoxide anion production in glucan-stimulated DC. The NADPH oxidase inhibitor diphenyliodonium chloride (DPI) and the superoxide anion scavenger superoxide dismutase (SOD) reproduced this effect, but did not affect IL-12 secretion. Conditioned media of glucan-treated DC/LNCaP co-cultures activated IFN-gamma production by NK cells and Th1/Th17 generation by CD4(+) lymphocytes, whereas media from DC/LNCaP co-cultured without glucan produced scarce NK and CD4(+) cells responses. Experiments performed with an IL-12-blocking antibody demonstrated that these effects arise from glucan-dependent regulation of IL-12 production by DC. Conclusions. Glucan and LNCaP cooperate in induction of cytokine synthesis by DC. LNCaP enhance IL-1 beta, IL-23, IL-6, and TNF-alpha secretion by decreasing glucan-dependent NADPH oxidase activity, whereas glucan increases IL-12 production through NADPH oxidase-unrelated mechanisms. This cooperation is essential to elicit a substantial NK cells and CD4(+) lymphocytes activity, pointing out a potential relevance of glucan in prostate cancer therapy. Prostate 72: 566-576, 2012. (C) 2011 Wiley Periodicals, Inc.