Expression of serum let-7c, let-7i, and let-7f microRNA with its target gene, pepsinogen C, in gastric cancer and precancerous disease

This study examined the expression patterns of serum let-7 microRNA (miRNA) and its target gene, pepsinogen C (PGC), in gastric cancer (GC) and precancerous disease patients to evaluate their diagnostic efficiency for GC and its precursor and to investigate any correlation between the two. Serum samples were taken from 638 patients, including 214 GC patients, 222 atrophic gastritis (AG) patients, and 202 controls (CON). The expression of serum let-7 miRNA was detected in control-AG (precancerous disease) through to GC patients using quantitative reverse-transcription polymerase chain reaction. Serum PGC was determined by enzyme-linked immuno-sorbent assay. PGC expression in situ was detected by immunohistochemistry staining. The luciferase reporter gene system was used to verify correlation between let-7 miRNA and its predicted target gene. The results showed that serum let-7c, let-7i, and let-7f demonstrated significant differences in the CON-AG-GC sequence (P = 0.017, P < 0.001, P = 0.003, respectively); let-7c was significantly lower in the AG group, and let-7i and let-7f were significantly higher in the GC group. Significantly different expressions of serum PGC were found among the three diseases, and also between AG vs. CON, and GC vs. CON (P = 0.027, P = 0.001, respectively). Linear-regression analysis suggested that serum let-7c was negatively correlated to the expression of PGC (r = −0.096, P = 0.047), and serum let-7c, let-7i, and let-7f showed no association with PGC expression in tissue. In addition, serum let-7c, let-7f, and let-7i showed significant correlations with environment factors. Serum let-7c, let-7i, and let-7f demonstrated significant differences in the CON-AG-GC disease sequence indicating that let-7 miRNA might have value by serving as potential biomarker in the diagnosis of GC or its precancerous diseases. There were significant negative correlations between serum let-7c and its target gene PGC expression.