Correlation between negative expression of pepsinogen C and a series of phenotypic markers of gastric cancer in different gastric diseases.

Gastric tumorigenesis is a multistep process initiated by chronic superficial gastritis (SG), followed by atrophic gastritis (AG), then intestinal metaplasia (IM), and finally by dysplasia and adenocarcinoma according to the Correa model. Pepsinogen C (PGC) decreases gradually during progression of cancer, which makes PGC an ideal negative marker for GC. To explore the correlation between PGC and other positive tumor markers in different gastric diseases, we observed the expression of PGC, MG7-Ag, MMP9, NM23, Ki-67, and E-cadherin by immunohistochemistry, quantitative RT-PCR, and immunoblot analysis. Our results showed that in SG, PGC was highly expressed while malignant phenotype markers were rarely expressed. In contrast with SG, malignant phenotype markers were highly expressed while the positive rate of PGC reached only 1.44% in GC. So there was no coexpression of PGC and malignant phenotype markers in SG or GC tissues. Only in the AG group, which is well-known to be gastric precancerous disease, coexpression of PGC and malignant phenotype markers was detected. Our results suggested that the expression of PGC in AG was negatively correlated with that of MG7-Ag and MMP9. Of all AG, those with low expression of PGC and high expression of MG7-Ag and MMP9 may possess a greater potential of malignant transformation. Combined detection of negative marker PGC and positive markers MG7-Ag and MMP9 could be used as a potential follow-up panel for monitoring dynamical progression of AG and improving the detection efficiency of high-risk individuals of gastric cancer, and then taking necessary interventions on the target population.