To determine the methylation of PAX5, SEPT9 and WIF-1 gene promoters in intracellular free DNA in the plasma of gastric cancer (GC) patients, and their relationship with the characteristics of GC, trying to explore the function of promoter methylation of the three genes in screening detection of primary GC.

The methylation rate of the PAX5, SEPT9, and WIF-1 gene promoters in blood samples from 81 GC patients (GC group) and 39 healthy controls (control group) were measured using the nest methylation-specific PCR technology (MDA-nMSP). The difference of gene methylation rates between the two groups was compared, and the predictive value of plasma methylated PAX5, SEPT9 and WIF-1 gene in GC were evaluated by the receiver operating characteristics (ROC) curve.

The methylation rates of PAX5, SEPT9 and WIF-1 in GC group were 38.3%, 34.6% and 46.9% respectively, while those in the control group were 7.7%, 10.3%, and 5.1% respectively. There were significant differences in methylation rates of the three genes between the two groups (χ²=12.123, 7.956, 20.683; all P<0.01). The occurrence of PAX5 and WIF-1gene promoter methylation were correlated with patients’ age (P<0.05), and the occurrence of SEPT9 gene promoter methylation was correlated with tumor size (P<0.05). As a diagnostic target of GC, the sensitivity, specificity and area under the curve (AUC) of methylated PAX5 were 38.27%, 92.31%, and 0.653 respectively; 34.57%, 89.74% and 0.622 respectively for SEPT9; 46.91%, 94.87%, and 0.709 respectively for WIF-1. The sensitivity and specificity of combined diagnosis for GC were 61.73% (95% CI: 50.3%-72.3%), 84.62% (95% CI: 69.5%-94.1%), and AUC value was 0.732 (95% CI: 0.653-0.810).

The methylation rates of PAX5, SEPT9 and WIF-1 gene promoters in plasma of patients with primary GC are high. When the combination of the three genes for diagnosis of GC, the specificity is similar to that by any single gene, but the sensitivity is greatly improved, which is expected to become a new gene combination for GC detection.