Identification of antibody against wingless‑type MMTV integration site family member 7B as a biliary cancer tumor marker

Biliary cancer has a poor prognosis due to a lack of specific biomarkers and difficulty in diagnosis. The present study aimed to identify serum tumor markers for the diagnosis of biliary cancer via serological identification of antigens by recombinant cDNA expression cloning. Wingless‑type MMTV integration site family, member 7 (WNT7B) was identified as a target antigen, suggesting the presence of serum antibodies against this antigen. Deletion mutants were then prepared to evaluate the response to serum antibodies. When serum antibody levels against WNT7B deletion mutants (WNT7B_-92‑2, _-92‑260, _2-260 and _184-260) were examined using amplified luminescence proximity homogeneous assay‑linked immunosorbent assay, the levels of the antibody against WNT7B with amino acids 184‑260 were higher in patients with biliary cancer than in healthy donors. Therefore, the region covering residues 184‑260 of WNT7B was decomposed to generate seven peptides, and the levels of antibodies against these peptides were measured. Among them, the levels of antibodies against WNT7B_234‑253 and WNT7B_244‑260 were higher in patients with biliary cancers than in healthy donors (WNT7B_234‑253, P=0.0009; WNT7B_244‑260, P=0.0005). The levels of the antibody against the former were specifically high in patients with biliary cancer but not in those with esophageal, gastric, colorectal, pancreatic, or breast cancer. Furthermore, analysis by the cutoff value of WNT7B_234‑253 defined by ROC showed a high sensitivity of 70% in patients with biliary cancer. Therefore, the serum levels of the antibody against WNT7B_234‑253 may be useful as a marker for biliary cancer diagnosis.