Abstract
BACKGROUND: Chronic inflammation and repeated infection with Opisthorchis viverrini (O. viverrini) induces intrahepatic cholangiocarcinoma (ICC). Inflammatory cytokines such as interleukin (IL) and tumor necrosis factor (TNF) are substances in the immune system that promote inflammation and causes disease to progress. Genes that help express proinflammatory cytokines can affect an individual's susceptibility to disease, especially in cancer-related chronic inflammation. This study aimed to investigate risk factors for ICC with a focus on opisthorchiasis and polymorphisms of proinflammatory cytokines (IL-1β and TNF-α). METHODS: This study was a nested case-control study within a cohort study. 219 subjects who developed a primary ICC were identified and matched with two non-cancer controls from the same cohort based on sex and age at recruitment (±3 years). An O. viverrini-IgG antibody was assessed using enzyme linked immunosorbent assay. IL-1β and TNF-α polymorphisms were analyzed using a polymerase chain reaction with high resolution melting analysis. Associations between variables and ICC were assessed using conditional logistic regression. RESULTS: Subjects with a high infection intensity had higher risk of ICC than those who had a low level (OR = 2.1; 95% CI: 1.2-3.9). Subjects with all genotypes of TNF-α (GG, GA, AA) and high infection intensity were significantly related to an increased risk of ICC (p < 0.05). CONCLUSIONS: Polymorphisms of IL-1β and TNF-α are not a risk of ICC, but an individual with O. viverrini infection has an effect on all genotypes of the TNF-α gene that might promote ICC. Primary prevention of ICC in high-risk areas is based on efforts to reduce O. viverrini infection.