Binding of circulating anti-MUC1 antibody and serum MUC1 antigen in stage IV breast cancer.

The present study aimed to investigate the binding of circulating mucin 1 (MUC1) antibody with serum MUC1 antigen in stage IV breast cancer. Serum samples of 61 patients with stage IV breast cancer and 64 patients with early-stage breast cancer were collected. The anti‑MUC1 antibody (IgG) and MUC1 antigen (cancer antigen 15‑3; Ca15‑3) were detected using an indirect enzyme-linked immunosorbent assay (I‑ELISA) and ELISA, respectively. The MUC1 IgG affinity was detected using a urea degradation combining ELISA. Western blot analysis and an inhibition test were performed for verification of the binding of anti‑MUC1 IgG with MUC1 antigen, and their correlation was analyzed. The results showed that there was a negative correlation between anti‑MUC1 IgG and CA15‑3 antigen in stage IV breast cancer when positive CA15‑3 antigen and/or anti‑MUC1 IgG were selected (r=‑0.417; P=0.0044). The positive anti‑MUC1 IgG with positive Ca15‑3 antigen was more common in stage IV breast cancer, compared with early‑stage breast cancer (χ2=4.629; P=0.031), however, Ca15‑3 antigen positivity was higher in stage IV breast cancer, compared with early‑stage breast cancer (χ2=10.58; P=0.001). Anti‑MUC1 IgG was able to bind to the MUC1 antigen in stage IV breast cancer. No differences in the 8R-MUCPT inhibition ratio were found between the two groups (P=0.778), and there were no differences in the affinity of anti‑MUC1 IgG (P=0.873). In stage IV breast cancer, circulating anti‑MUC1 antibody was found to bind serum MUC1 antigen, although their compatibility was low. No significant difference was found in the affinity of the anti‑MUC1 antibody between stage IV breast cancer and early‑stage breast cancer.