Anti-α-enolase autoantibodies are down-regulated in advanced cancer patients

Objective: Elevation of serum autoantibodies to a-enolase (ENO1) is often seen in inflammation diseases. However, it is unclear whether the levels of serum ENO1 autoantibodies could be affected during tumor progression. Hence, we attempted to determine the relative serum ENO1 autoantibody levels in healthy individuals and various stages of patients with lung and breast cancers. Methods: Sera were obtained from 99 normal individuals, 21 patients with non-cancerassociated diseases and 178 cancer patients, including Stage I, II and IV non-small cell lung cancer, small cell lung cancer and breast cancer. The ENO1 autoantibody levels were determined by enzyme-linked immunosorbent assay. Results: Compared with the healthy individuals, the levels of ENO1 autoantibodies were significantly decreased in Stage IV non-small cell lung cancer, small cell lung cancer and breast cancer patients. Consistently, this phenomenon was also observed in tumor-grafted mice. Using logistic regression analyses, data show that the titer status of ENO1 autoantibody level is highly associated with the late stage of lung and breast cancers when compared with those of healthy controls. In contrast, there were no statistic differences between healthy controls and early stages of non-small cell lung cancer patients, and total amounts of serum immunoglobulin A, immunoglobulin G and immunoglobulin M levels in Stage IV non-small cell lung cancer patients were not significantly distinct from those of the healthy controls. Thus, the decreased ENO1 autoantibody event in malignant stage of cancer patients is not contributed by reduction in total immunoglobulin. Conclusions: Marked decrease in the basal level of serum ENO1 autoantibodies is a common malignant event of lung and breast cancers, suggesting that ENO1 autoantibody may serve as a prognostic marker to monitor the disease progression of these cancer patients.