Overexpression of cancer cell-derived immunoglobulin G correlates with poor prognosis in gastric cancer patients

Background: Various human epithelial origin cancers produce cytoplasmic immunoglobulin (Ig) G. Recent studies have elucidated that it was related with the tumorigenesis. This study was aimed to identify relationship between the cancer cell-derived IgG expression level and clinical parameters in gastric cancer (GC). Methods: Cancer cell-derived IgG expression was assessed using immunohistochemistry analysis in 231 primary GC tissues. The role of cancer cell-derived IgG on cell proliferation, migration and invasion were assessed. Results: Our results indicated that IgG was overexpressed in GC tissues (42.2%, 46/109) than in adjacent tissues (11.0%, 12/109, P<0.0001). Positive IgG expression was more frequently detected in patients with TNM III + IV stages when compared with those with TNM I + II stages in GC (48.6% vs. 37.2%, respectively). Upon univariate analysis, IgG positive group had significantly lower 5-year overall survival than the negative group (P=0.0361). Multivariate analysis showed IgG expression was an independent prognostic indicator for 5-year overall survival of patients with GC (P=0.018). Furthermore, knockdown of IgG by short interfering RNA (siRNA) resulted in reducing proliferation, migration and invasion of GC cell. Conclusions: Our results showed that cancer cell-derived IgG overexpression might be correlated with GC progression, and would be a novel biomarker to predict the prognosis of patients with GC.