Abstract: Isolation and Identification of Specific Fluorescent Substances from Gastric Juice of Patientswith Gastric CarcinomaYuening ZHANG1, Xinlian JIN2, Lingmei MENG2, Qiuming GENG3, Jiarou PENG4, Liya ZHOU2, Sanren LIN2Correspondence to: Sanren LIN, E-mail: linsanren@medmail. com.cn1Department of Gastroenterology, The Third Hospital of Peking University, Beijing 100083, China2Central Laboratory, The Third Hospital of Peking University, Beijing 100083, China3Key National Proteomics Laboratory of Beijing University School of Medicine, Beijing 100083, China4Department of Gastroenterology, The Affiliated You-An Hospital of Capital Medical University, Beijing100069, ChinaThis work was supported by the National Natural Science Foundation of China (No.30371603; No.30672395)Abstract Objective: To explore the characteristics of the cancer-specific fluorescent substances found in the gastricjuice of gastric cancer patients and to gain a preliminary understanding of the mechanisms involved in the gastric carcino-ma-specific autofluorescence spectrum. Methods: Clinical and pathological data of patients with different gastric diseasesundergoing gastroscopy in our hospital between August 2006 and March 2008 were collected. Gastric juice was also col-lected. Mono Q ion-exchange combined with C18 reversed-phase high performance liquid chromatography was used toisolate the cancer-specific substances from gastric juice. Substances obtained were analyzed by matrix-assisted laser-de-sorption ionization-flight time mass spectrometry and electrospray ionization mass spectrometry/mass spectrometry to iden-tify their mass-to-charge ratio and peptide sequence. Results: One hundred and eighteen cases were enrolled in this study,of which 56 were gastric carcinoma cases (including 49 with advanced gastric cancer and 7 with early-stage cancer) and62 were controls. Under the conditions of Mono Q ion-exchange high performance liquid chromatography, 4 fluorescentpeaks were shown in the primary gastric juice fluorescence spectrum, in which the first one locating at the retention time of14-21min was significantly stronger in the cancer groups than in the control groups ( P < 0.05 ). The C18 reversed-phasehigh performance liquid chromatography presented a serrated fluorescence peak group in the fluorescent spectrum. The in-tensity of the fluorescent peak locating at the retention time of 30-32min was significantly stronger in the cancer groupsthan in the control groups. Matrix-assisted laser-desorption ionization flight time mass spectrometry revealed that themass-to-charge ratio of these substances from gastric juice after the separation by high performance liquid chromatogra-phy was at a range between 500 and 5300. Sequences of 13 polypeptides currently unknown were obtained through elec-trospray ionization mass spectrometry. Conclusion: Fluorescent polypeptides contribute to the differentiation of the autofluo-rescence spectrum found in gastric juice of patients with gastric cancer from that in those with benign gastric disease .Complicated mechanisms were involved. Further research is warranted to determine the role of fluorescent polypeptides inthe development of malignancy.Keywords Gastric carcinoma; Gastric juice; High performance liquid chromatography; Mass spectrometry; Polypeptide