Study of circulating IgG antibodies to BIRC5 and MYC in non-small cell lung cancer.

An in-house enzyme-linked immunosorbent assay (ELISA) was developed in this study to detect circulating IgG antibodies to peptide antigens derived from baculoviral IAP repeat-containing protein 5 isoform 2 (BIRC5) and myc proto-oncogene protein (MYC) in non-small cell lung cancer (NSCLC). Student's t-test revealed that circulating anti-MYC IgG levels were significantly increased in patients with NSCLC compared with control subjects in the discovery sample (t = 3.96, P = 0.0001) but not in the validation sample (t = 1.24, P = 0.217), generating a combined P-value of 0.0003. Neither the discovery sample nor the validation sample showed a significant change in anti-BIRC5 IgG levels in NSCLC. Further analysis was performed to investigate whether circulating IgG antibodies to these two tumor-associated antigens (TAAs) significantly changed with early (stages I + II) and late (stages III + IV) NSCLC stages. The results showed that neither anti-MYC IgG nor anti-BIRC5 IgG levels significantly changed in patients with early stage NSCLC, while patients with late stage NSCLC had higher levels of circulating anti-MYC IgG than control subjects in the discovery sample (t = 4.74, P < 0.0001) but not in the validation sample (t = 0.80, P = 0.423), generating a combined P-value of 0.00003 (X (2) = 26.13, df = 4). In conclusion, circulating IgG antibodies to MYC and BIRC5 do not appear to serve as biomarkers for early diagnosis of lung cancer but anti-MYC IgG might have a prognostic value.