【Abstract】Objective To investigate the expression of PCNA in gastric cancer and its relationship with telomerase activity of peritoneal washings and peritoneal dissemination, and to compare the efficacy of telomerase activity and cytology of peritoneal washings for prediction of peritoneal metastasis of gastric cancer. MethodsTelomeric repeated amplification protocol (TRAP)enzymelinked immunosorbent assay (ELISA) was performed to measure the telomerase activity of peritoneal washings collected from 60 patients with gastric cancer. Exfoliate cytologic analysis of the corresponding samples was used for comparison.Expression of PCNA was measured with immunohistochemical staining.Their relationship with clinicopathologic features were evaluated. ResultsThe positive rate of telomerase activity in peritoneal washing collected from patients with gastric cancer was 41.7%,which well related to serosal invasion, histology types, depth of infiltration and peritoneal metastasis of gastric cancer. The positive rate of telomerase activity increased with the increased depth of infiltration and serosal involvement areas (P＜0.05).The positive rate of exfoliative cytology was 25.0%, which was obviously high in the group with macroscopic peritoneal metastasis (the group of P1-3). The positive rate of exfoliative cytology also increased with the increased depth of infiltration and serosal involvement areas (P＜0.05). Although the positive rate of telomerase activity in peritoneal washing collected from patients with gastric cancer was not significantly higher than that of exfoliative cytology in general, it was significantly higher than that of exfoliative cytology in the group of pT4, P1-3 and undifferentiated type.The PCNA proliferation index (PI) of positive telomerase activity group was significantly higher than that of negative. The PCNA PI was significantly higher in the group of P1-3 and serosal invasion thanthat of P0 and without serosal invasion. ConclusionTo detect telomerase activity in peritoneal washings and to detect tumor cells by cytologic method are useful to predict subclinical metastasis to the peritoneum in patients with gastric cancer,but telomerase activity is more sensitive than the other one.Telomerase activity is well related to proliferating activity of gastric cancer,which was the very important reason of peritoneal metastasis and serosal invasion.