Influence of 5-Fluorouracil and Folinic Acid on Interleukin-18 Production in Colorectal Cancer Patients

Clinical and experimental approaches to the pathophysiology of interleukin-18 in cancer progression

Interleukin-18 (IL-18, interferon [IFN]-gamma-inducing factor) is a proinflammatory cytokine converted to a biologically active molecule by interleukin (IL)-1beta converting enzyme (caspase-1). A wide range of normal and cancer cell types can produce and respond to IL-18 through a specific receptor (IL-18R) belonging to the toll-like receptor family. The activity of IL-18 is regulated by IL-18-binding protein (IL-18bp), a secreted protein possessing the ability to neutralize IL-18 and whose blood level is affected by renal function and is induced by IFNgamma. IL-18 plays a central role in inflammation and immune response, contributing to the pathogenesis and pathophysiology of infectious and inflammatory diseases. Because immune-stimulating effects of IL-18 have antineoplastic properties, IL-18 has been proposed as a novel adjuvant therapy against cancer. However, IL-18 increases in the blood of the majority of cancer patients and has been associated with disease progression and, in some cancer types, with metastatic recurrence risk and poor clinical outcome and survival. Under experimental conditions, cancer cells can also escape immune recognition, increase their adherence to the microvascular wall and even induce production of angiogenic and tumor growth-stimulating factors via IL-18-dependent mechanism. This is particularly visible in melanoma cells. Thus, the role of IL-18 in cancer progression and metastasis remains controversial. This review examines the clinical correlations and biological effects of IL-18 during cancer development and highlights recent experimental insights into prometastatic and proangiogenic effects of IL-18 and the use of IL-18bp against cancer progression.

Constitutive expression of interleukin-18 in head and neck squamous carcinoma cells

BACKGROUND

Interleukin (IL)-18 is a potent immunomodulatory cytokine promoting TH-1 and cytotoxic immune responses through interferon (IFN)-gamma induction. The aim of this study was to investigate the production of IL-18 by squamous cell carcinoma of the head and neck (HNSCC).

METHODS

The expression of IL-18 was analyzed by reverse transcriptase-polymerase chain reaction, Western blot, and ELISA in untreated and 5-fluorouracil (5-FU)-treated HNSCC cell lines. Immunohistochemical analysis was performed on tumor specimens from 16 patients with primary invasive HNSCC.

RESULTS

We have demonstrated that HNSCC cell lines express IL-18 at the mRNA, as well as the protein, level. However, the IL-18 protein was expressed intracellularly and predominantly released as an unprocessed inactive 24-kDa form. After exposure to 5-FU, the processed form of IL-18 was detected in the supernatants of both HNSCC cell lines.

CONCLUSIONS

These results indicate that HNSCC cells are a potential source of IL-18 cytokine. The finding that the exposure to 5-FU can elicit its processing suggests a novel target for immunomodulatory intervention in patients with HNSCC.