IL-18 paradox in pancreatic carcinoma: elevated serum levels of free IL-18 are correlated with poor survival.

The role of the proinflammatory interleukin (IL)-18 in cancer progression remains controversial; we thus examined the hypothesis that impaired antitumor immune response in pancreatic carcinoma patients is related to elevated levels of its natural inhibitor IL-18 binding protein (BP) and/or to alteration in the IL-18 receptor complex expression and function. IL-18 and IL-18 binding protein isoform a (BPa) was assessed in pancreatic carcinoma patients at various disease stages, and after surgery/chemotherapy; free bioactive IL-18 concentrations were calculated. IL-18 receptor complex expression in lymphocyte subsets was analyzed and signaling function was assessed versus healthy donors. Carcinoma cells exhibited below normal IL-18BPa expression and above normal IL-18 expression. Circulating IL-18BPa and IL-18 were above controls. Unexpectedly, free unbound IL-18 serum levels were correlated with disease severity and poor survival. IL-18BPa levels were unchanged by surgery but free IL-18 levels were elevated. Gemcitabine with 5-fluorouracil or oxaliplatin, but not alone, increased IL-18 and free IL-18 levels statistically significantly, without affecting IL-18BPa. Spontaneous/induced IL-18 receptor alpha and receptor beta expression in peripheral blood lymphocyte subsets from patients with advanced disease were near-normal, although CD4+ and CD8+ cells were fewer in percentage, and fully functional in inducing interferon-gamma. IL-18 is proposed as novel adjuvant cancer therapy, but free IL-18 levels are increased in the blood of pancreatic carcinoma patients, despite elevated IL-18BP levels, and are associated with poor survival; this highlights recent experimental insights into the prometastatic and proangiogenic effects of IL-18, and suggests that careful preclinical studies are needed to determine the proper application of IL-18 in cancer therapy.

Cytokine expression profile in human pancreatic carcinoma cells and in surgical specimens: implications for survival.

Cytokine shedding by tumor cells into the local microenvironment modulates host immune response, tumor growth, and metastasis. The study aimed to verify the hypothesis that the immunological microenvironment of pancreatic carcinoma exists in a prevalently immunosuppressive state, influencing survival. We analyzed expression profiles of pro-inflammatory (IL-1beta, IL-2, IL-6, IL-8, IL-12 p40, IL-18 and IFN-gamma) and anti-inflammatory (IL-10, IL-11, IL-13 and TGF-beta isoforms) cytokines. The study was performed both in vitro, in five pancreatic carcinoma cell lines (real time RT-PCR), and in specimens from 65 patients, comparing tumoral versus non-tumoral pancreatic tissues (real time RT-PCR and immunohistochemistry). Furthermore, cytokines were measured in supernatants and sera (from patients and controls) by ELISA. All cell lines expressed IL-8, IL-18, TGF-beta1, TGF-beta2 and TGF-beta3, but not IFN-gamma and IL-2 transcripts. Expression of IL-1beta, IL-6, IL-10, IL-11, IL-13 and IL-12 mRNA was variable. All the above cytokines were detected as soluble proteins in supernatants, except IL-13. Tumor tissues overexpressed IL-1beta, IL-6, IL-8, IL-10, IL-11, IL-12 p40, IL-18, IFN-gamma, TGF-beta1, TGF-beta2 and TGF-beta3 at the mRNA level and IL-1beta, IL-18, TGF-beta2 and TGF-beta3 also at the protein level. Conversely, non-tumor tissues had stronger RNA and protein expression of IL-13. Survival was significantly longer in patients with high IL-1beta and IL-11 and moderate IL-12 expression. Serum IL-8, IL-10, IL-12, IL-18, TGF-beta1 and TGF-beta2 were higher in patients than in controls, as opposed to IL-1beta and IL-13. Patients with low circulating levels of IL-6, IL-18 and TGF-beta2 survived longer. Pancreatic cancer is characterized by peculiar cytokine expression patterns, associated with different survival probabilities.

Human pancreatic carcinoma cells secrete bioactive interleukin-18 after treatment with 5-fluorouracil: implications for anti-tumor immune response.

Recently we observed that pancreatic carcinoma cell lines constitutively express Interleukin-18 (IL-18). Bioactive IL-18 induces Interferon (IFN)-gamma production, Fas Ligand (FasL) expression, and inhibits angiogenesis, raising the issue of anti-tumor effects of a tumor-derived cytokine and motivating a more detailed analysis of IL-18 production in pancreatic carcinoma cells. This analysis included the study of effects of chemotherapeutic drugs (5-fluorouracil [5-FU], gemcitabine, cisplatin) commonly used in the treatment of pancreatic cancer patients on IL-18 production and processing. IL-18 expression and post-translational processing were determined using RT-PCR, immunoblot and ELISA in pancreatic carcinoma cell lines and in tumor tissue and serum samples from pancreatic carcinoma patients in the presence and absence of chemotherapeutic drugs. We describe expression of IL-18 in pancreatic carcinoma cells and tissues associated with significantly elevated IL-18 levels in patients sera. Specifically, Capan-2 pancreatic tumor cells produced and secreted precursor IL-18 with no apparent biological activity. However, the chemotherapeutic agent 5-FU, by inducing Caspase-1 and Caspase-3 activation, induced secretion of proteolytically processed mature and degraded IL-18 species, respectively, in Capan-2 cells. Conditioned medium from 5-FU-treated but not control Capan-2 cells induced IFN-gamma production by activated T cells in an IL-18-dependent manner. Furthermore, adjuvant polychemotherapy including 5-FU significantly increased serum levels of mature, bioactive IL-18 in pancreatic carcinoma patients. Treatment of pancreatic cancer cells with 5-FU induced Caspase-dependent processing of pro-IL18 leading to the secretion of biologically active IL-18. These findings delineate a novel mechanism by which chemotherapeutic agents may modulate local anti-tumor cell-mediated immune responses.