Virulizin induces production of IL-17E to enhance antitumor activity by recruitment of eosinophils into tumors

2537 Background: Virulizin (V), has demonstrated strong antitumor activity in a variety of human tumor xenograft models including skin, pancreatic, breast, ovarian and prostate cancer. V is currently undergoing a pivotal Phase III clinical trial for the treatment of advanced pancreatic cancer in combination with Gemcitabine. A significant role of macrophages and NK cells was implicated in the antitumor mechanism of V where expansion as well as increased activity of macrophages and NK cells were observed in mice treated with V. The aim of this study is to evaluate the role of the inflammatory cytokine IL-17E (IL-25) in the antitumor mechanism of V. IL-17E is a proinflammatory cytokine, which can induce a TH2 immune response, associated with eosinophil expansion and infiltration into mucosal tissues. Methods: Antitumor activity of V was assessed on human melanoma C8161 xenograft in CD-1 nude mice. Alteration of IL-17E production in sera from V-treated mice was identified by 2-D gel electrophoresis and MALDI-TOF. The level of IL-17E in the sera was also determined by ELISA. IL-17E mRNA expression was determined by quantitative real-time RT-PCR. Intracellular expression of IL-17E was examined by flow cytometric analysis. The cell surface marker CCR3 on eosinophils was analyzed by flow cytometry. Results: Cytokine IL-17E was increased in sera of V-treated mice bearing human melanoma xenograft, as shown by 2-D gel electrophoresis and ELISA. Treatment of splenocytes in vitro with V resulted in increased IL-17E mRNA expression, which peaked between 24 and 32 hours post-stimulation. Both in vitro and in vivo experiments demonstrated that B lymphocytes produce IL-17E upon V treatment. Furthermore, V treatment in vivo resulted in increased blood eosinophilia. Conclusion: In addition to activating innate immune system, V may manifest its antitumor activity through induction of IL-17E in B cells. This may lead to the recruitment of the proinflammatory cell type, eosinophils, which may function in parallel with macrophages and NK cells in mediating tumor destruction. No significant financial relationships to disclose.