Expression and clinical significance of plasma methylated Septin9 gene in patients with gastric cancer

Objective To explore the expression and clinical significance of plasma methylated Septin9 gene (mSEPT9) in patients with gastric cancer. Methods From March to October in 2018, 380 patients visited Xijing Hospital of Digestive Diseases were selected. The patients were divided into gastric cancer (GC) group, atrophic gastritis (AG) group and non-atrophic gastritis (NAG) group. The positive expression rate of plasma circulating mSEPT9 of the three groups were detected by polymerase chain reaction (PCR) fluorescence probe method, its correlation with clinicopathological characteristics of gastric cancer were analyzed and also compared with the positive rate of carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9). Chi-square test and continuity correction chi-square test were performed for statistical analysis. Results The actual number of valid samples was 357 including 147 of GC group, 83 of AG group and 127 of NAG group. The positive rate of plasma mSEPT9 of GC group was higher than those of AG group and NAG group (46.9%, 69/147 vs. 4.8%, 4/83 and 3.9%, 5/127), and the differences were statistically significant (χ2=43.438 and 63.912, both P<0.016). The sensitivity and specificity of plasma mSEPT9 in patients with gastric cancers were 46.9%(69/147) and 95.7%(201/210), respectively. The positive rate of mSEPT9 was higher in gastric cancer patients with tumor maximum diameter over 5.0 cm, intestinal-type gastric cancer in Lauren classification, lymphatic metastasis, vascular and neurological invasion, middle-late stage (stage Ⅲ and Ⅳ) in clinical classification, which were 57.6% (38/66) vs. 35.6% (26/73), 52.6%(51/97) vs. 31.0% (13/42), 53.0% (61/115) vs. 25.0% (8/32), 55.6% (65/117) vs. 13.3% (4/30), 50.8% (65/128) vs. 4/19 and 53.5% (61/114) vs. 24.2% (8/33), respectively; and the differences were statistically significant (χ2=6.728, 5.517, 7.905, 17.091, 5.871 and 8.998, all P<0.05). The positive rate of plasma mSEPT9 in gastric cancer patients was higher than those of CEA and CA19-9 (46.9%, 69/147 vs. 32.0%, 47/147 and 17.7%, 26/147, respectively), and the differences were statistically significant (χ2=6.892 and 17.437, both P<0.016). Conclusions The positive expression of plasma mSEPT9 in gastric cancer patients has not only high sensitivity but good specificity as well, and it is also related to the clinical stage. The detection of this gene may have important clinical significance in non-invasive diagnosis and prognosis evaluation in patients with advanced gastric cancer. Key words: Methylation; Stomach neoplasms; SEPT9; Pathological characteristics; Clinical significance