The Value of Serum Immunoglobulin G Glycome in the Preoperative Discrimination of Peritoneal Metastasis from Advanced Gastric Cancer

Abstract

Background: Peritoneal metastasis, associated with poor prognosis in gastric cancer, is difficult to discriminate from advanced gastric cancer preoperatively. However, operative diagnosis could bring both mental and physical trauma and economic burden for patients. Consequently, a non-invasive biomarker is necessary to reduce the burden of operative diagnosis and improve survival quality of patients. This study aims to elucidate the correlation between Immunoglobulin G (IgG) N-glycome and peritoneal metastasis and find potential biomarkers in preoperative discrimination of peritoneal metastasis from advanced gastric cancer based on the comprehensive sample set. Methods: A total of 373 gastric cancer patients were enrolled and randomly sorted into training cohort (n=249) and validation cohort (n=124). The IgG N-glycome composition was analyzed by ultra-performance liquid chromatography. Results: Twenty-four glycan peaks were directly detected and 15 traits based on the same structures were evaluated between peritoneal metastasis group and advanced gastric cancer group. Several differences in IgG glycosylation were found: sialylation and fucosylation were increased in peritoneal metastasis, while neutral glycosylation, monogalacosylation and bisecting GlcNAc were decreased. Based on the significant glycomics profile, a glyco-model composed of five glycan peaks (GP6, GP9, GP11, GP21 and GP23) was established with area under the receiver operating characteristic curve (AUC) value of 0.80 (training cohort) and 0.77 (validation cohort), which showed good potential in discriminating peritoneal metastasis from advanced gastric cancer. The diagnostic performance of this model was further validated in a combined cohort (AUC=0.79). Two patients with gastric cancer were selected to perform and demonstrate the usage of the diagnostic workflow. Conclusions: Here we firstly present IgG glycome profiles in a large number of preoperative peritoneal metastasis serums. The IgG glycan was highly associated with peritoneal metastasis. These findings enhance the understanding of peritoneal metastasis. Besides, our results suggested that the newly established glyco-model could be a reliable predictor of the presence of peritoneal metastasis in patients with advanced gastric cancer.

Keywords: Biomarkers; Gastric cancer; Glycosylation; Immunoglobulin G; Peritoneal metastasis.

Figure 1

Representative Ultra Performance Liquid Chromatography (UPLC) chromatogram of serum IgG N-glycan profiles. A total of 24 chromatographic peaks was shown.

Figure 2

The abundance of the nine representative derived traits in patients with PMGC and patients with AGC in the training cohort. The N-glycans were grouped according to their structural features: neutral N-glycans (GPN) (A); total sialylation (GPS) (B); monosialylation (S1) (C); disialylation (S2) (D); monogalactosylation (G1) (E); fucosylation of neutral glycans (FN) (F); fucosylation of sialylated glycans (FS) (G); bisecting N-glycan (B) (H); bisecting N-glycan of neutral glycans (BN) (I).

Figure 3

Efficacy prediction of discriminate glyco-model of the training cohort and the validation cohort. A and C, Plots of ROC results for distinguishing PMGC samples from the AGC samples. Glyco-model shows good diagnostic efficacy in predicting PMGC in training cohort (AUC=0.80, 95%CI: 0.74 to 0.86) (A) and validation cohort (AUC=0.77, 95%CI: 0.68 to 0.86) (C). B and D, the logistic regression predictive score for each patient of the training (B) and validation set (D). Logistic regression predictive score was calculated with the formula, Score=4.49 * GP6 + 5.42 * GP9-50 * GP11 + 30.19 * GP21+ 26.53* GP23+88.33.

Figure 4

Analysis workflow of prediction. Typical base peak of the serum specimen in positive ion mode(A). Identification and quantification of the five IgG glycan of GP6, GP9, GP11, GP21 and GP23 (B). Logistic regression predictive score and outcome prediction of the two samples(C). Typical images of abdominal cavity by staging laparoscopy (D). The circled parts are typical peritoneal metastasis.