Objective Previous studies have reported that serum IL-18 levels are increased in some cancers. We investigated whether IL-18 production is increased in sera and cancer cells of patients with non-small cell lung cancer (NSCLC).
Patients or Materials Serum levels of IFN-gamma and IL-18 and thioredoxin 1 (TRX1) were measured in 79 patients ( 51 males, 28 females, median age 67 years) with advanced NSCLC ( 57 adenocarcinoma, 22 squamous cell carcinoma; TNM stages IIIA [n=11], IIIB [n=24], and IV [n=44]) and 75 healthy age-matched controls ( 44 males, 31 females, median age 65 years) by enzyme-linked immunosorbent assay. We examined IL-18 production in the lungs and sites of bone metastasis of adenocarcinoma by immunohistochemistry.
Results Serum IL-18, IFN-gamma, and TRX1 levels in NSCLC patients were significantly (p<0.0001, p=0.0031, and p<0.0001, respectively) higher than in control subjects, while serum IFN-gamma levels in NSCLC were slightly increased. Serum IL-18, but not IFN-gamma or TRX1, levels were significantly (p=0.0102) and negatively associated with overall survival in NSCLC. The serum IL-18 level was identified as an independent prognostic factor for overall survival in multivariate survival analysis. Moreover, serum IL-18 levels were significantly (p=0.049) higher in NSCLC with bone metastasis than in NSCLC without bone metastasis. Based on immunohistochemistry, we observed that cancer cells in the lungs and bone metastases markedly produced IL-18.
Conclusion Our results suggest that elevated serum IL-18 levels may be associated with IL-18 producing cancer cells in advanced NSCLC.