Concern over roles of serum IgG agalactosylation in chronic inflammatory diseases has been mounting for years but less touched in cancers. The present study addressed the underlying role of agalactosylated IgG beyond tumorigenesis. Liquid-chromatography-tandem mass spectrometry was leveraged for the analysis of IgG₁ and IgG₂ N-glycomes. We found that a high percentage of serum fucosyl-agalactosyl IgG₁ (IgG₁-G0F) in patients with cholangiocarcinoma was associated with poor tumor differentiation and tumor metastasis. Results from Kaplan⁻Meier analyses and a stepwise Cox regression analysis showed that patients with serum IgG₁-G0F ≥40% were highly correlated with poor recurrence-free survivals and overall survivals. Interestingly, patients with cholangiocarcinoma whose serum IgG₁-G0F ≥40% had more CD163+ tumor-associated macrophages in cancerous tissues than adjacent non-cancerous counterparts. In vitro assays revealed that agalactosylated IgG upregulated tumor-associated macrophage markers CD163 and CD204 in human U-937 cells and peripheral macrophages. Moreover, a positive and a negative feedback loop of transforming growth factor-β1 and interferon-γ, respectively, on IgG agalactosylation was identified using hybridoma cells and verified in sera of the patients. In conclusion, agalactosylated IgG activates tumor-associated macrophages, thereby promoting tumor metastasis and recurrence of cholangiocarcinoma.
Keywords: IgG; cholangiocarcinoma; glycosylation; tumor-associated macrophage.