Further study of circulating IgG antibodies to CD25‐derived peptide antigens in nonsmall cell lung cancer

A recent study reported that circulating antibodies to CD25‐derived peptide antigens were significantly higher in patients with nonsmall cell lung cancer (NSCLC) than control subjects. The present study was, thus, undertaken to replicate the initial finding with different sample sets. An in‐house ELISA was applied to determine circulating IgG antibodies to linear peptide antigens derived from CD25. A total of 111 patients with NSCLC and 216 control subjects were recruited and divided into the discovery sample (51 vs 108) and the validation sample (60 vs 108) based on the time of sampling. Student's t test showed that circulating anti‐CD25 IgG levels were significantly higher in the patient group than the control group (t = 2.23, P = 0.027) and the validation sample replicated this finding (t = 3.31, P = 0.0012), generating a combined P value of 0.0004 (χ(2) = 20.8, df = 4). Fisher's combining probability revealed that patients with stage IV NSCLC had a significant increase in anti‐CD25 IgG levels compared with control subjects (χ(2) = 22.1, df = 4, P = 0.0002) but those with the other three stages did not. This study suggests that circulating anti‐CD25 IgG antibodies may have prognostic rather than early diagnostic values for lung cancer.