Anti-FIRΔexon2 autoantibody as a novel indicator for better overall survival in gastric cancer.

There is no clinically available biomarker for efficiently indicating overall survival or therapy-response of gastric cancer (GC). The autoantibodies (Abs) in the sera of anti- far-upstream element-binding protein-interacting repressor-lacking exon2 (FIRΔexon2), anti-sorting nexin 15 (SNX15), and anti-spermatogenesis and oogenesis-specific basic helix-loop-helix 1 (SOHLH1) were markedly higher in GC patients than those in healthy donors (HDs). These Abs were identified by large-scale serological identification of antigens by recombinant cDNA expression cloning (SEREX) screenings and their expression levels were evaluated by amplified luminescence proximity homogeneous assay (AlphaLISA). Especially, compared with age-matched HDs, the level of anti-FIRΔexon2 Abs in GC patients was significantly higher (P < 0.001). The Spearman's rank correlation analysis between anti-FIRΔexon2 Abs and clinically available tumor markers such as carcinoembryonic antigen (CEA) was statistically insignificant, indicating that FIRΔexon2 Abs is an independent biomarker. We performed the receiver-operating curve (ROC) analysis to evaluate the anti-FIRΔexon2 Ab as a candidate biomarker with CEA and carbohydrate antigen 19-9 (CA19-9). The overall survival (OS) of GC patients with high anti-FIRΔexon2 Abs titer was significantly favorable (P = 0.04) than those not detected anti-FIRΔexon2 Abs. However, clinical stages were not apparently correlated with the levels of anti-FIRΔexon2 Ab, CEA, and CA19-9. Together, anti-FIRΔexon2 Abs detected in GC patients is a potential biomarker for monitoring the better prognosis. Hence, anti-FIRΔexon2 Abs is a promising biomarker for indicating better overall survival of gastric cancer patients.