Several epidemiological investigations indicate that cancer survivors have a lower risk for Alzheimer's disease (AD) and vice versa. However, the associations between plasma amyloid-beta (A beta) levels with cancer remain largely unknown. In this case-control study, 110 cancer patients, 70 AD patients, and 70 age- and gender-matched normal controls were recruited. The cancer types include esophagus cancer, colorectal cancer, hepatic cancer, and lung cancer, all of which were reported to be associated with a lower risk for AD. Plasma levels of A beta 40, A beta 42, common pro-inflammatory cytokines, IL-1 beta, IL-6, TNF-alpha, IFN-gamma, anti-inflammatory IL-4, chemokines, and cytokines MCP-1 were measured with enzyme-linked immunosorbent assay (ELISA) kits. Plasma levels of A beta 40 and A beta 42 in all cancer patients were higher than that in normal controls. More specifically, hepatic cancer patients exhibited significantly higher plasma A beta levels. No significant difference in plasma A beta levels was found between chemotherapy and no chemotherapy subgroups. Plasma A beta levels were not significantly correlated with pro-inflammatory cytokines, anti-inflammatory, chemokines, and cytokines. Peripheral A beta levels increased in cancer patients, especially in patients with hepatic cancer, independent of chemotherapy and inflammation. Further verification is required for the association between plasma A beta and cancer.
