The dual effects of interleukin-18 in tumor progression.

Interleukin-18 (IL-18) was discovered as an interferon-gamma-inducing factor and had a critical role in inflammatory and immune response. It stimulates natural killer (NK) and T cells and enhances Th1 immune response. These activated immune cells eliminate cancer cells and virus-infected cells effectively. However, IL-18 has also been found to promote tumor progression. Higher expression or secretion level of IL-18 is detected in various cancer cells in comparison with normal control, and IL-18 is able to induce angiogenesis, migration/metastasis, proliferation and immune escape. These dual effects and the mechanism of IL-18 need to be investigated further as it relates to cancer.