Recently several noninvasive methods have been employed to detect circulating tumor cells (CTCs) in cancer patients. In this study, we have developed a highly sensitive, high-throughput colorimetric membrane-array method that was designed to detect a panel of mRNA markers including human telomerase reverse transcriptase (hTERT), , carcinoembryonic antigen (CEA) and mucin 1 (MUC1) mRNA for the presence of CTCs in the peripheral blood of patients with gastric cancer (GC). Digoxigenin-labeled cDNA targets synthesized following total RNA isolation from peripheral blood samples of 64 GC patients and 80 healthy individuals were subjected to membrane-array hybridization. The results showed that membrane array could positively detect 5 cancer cells/ml of peripheral blood in GC cell-dilution experiments. The sensitivity, specificity and diagnostic accuracy for hTERT, CK-19, CEA and MUC1 mRNA ranged from 78.1% to 82.8%, 76.3% to 85% and 81.3% to 83.3%, respectively. Both CEA and MUC1 mRNA expression was correlated significantly with all malignant biological properties of GC, such as macroscopic type, depth of tumor invasion, lymph-node metastasis, TNM stage and coexisting distant metastasis (all p < 0.05). Using these 4 markers in combination, the sensitivity, specificity and diagnostic accuracy of membrane array were raised to 89.1%, 91.3% and 90.3%, respectively. The expression of all 4 mRNA markers was an independent predictor for postoperative recurrence/metastasis. GC patients with the expression of all the 4 mRNA markers showed a poorer survival rate than those without the expression of any 1 mRNA marker (p 5 0.0223). These findings demonstrated that our membrane-array method could detect CTCs in the circulation of GC patients with considerably high sensitivity and specificity. The identification of CTCs in the peripheral blood may be useful in the auxiliary cancer diagnostics or postoperative surveillance of GC patients for recurrence/metastasis. ' 2006 Wiley-Liss, Inc.Key words: circulating tumor cell; membrane array; gastric cancer; molecular diagnosisThe degrees of tumor penetration in the stomach wall and lymph node metastasis have been used for many decades as the 2 major prognostic determinants for gastric cancer (GC) patients. Unfortunately, despite informative staging of patients with GC, some patients with apparently localized disease at diagnosis will subsequently develop recurrent or metastatic diseases. 1-4 One of the major causes is attributed to the presence of disseminated tumor cells shed from the primary carcinoma into circulation, prior to or during surgery. Even in patients with early GC, blood-born metastasis occurs. 2,5,6 Recent attempts to improve staging include sensitive detection of disseminated tumor cells in the blood or lymph nodes by molecular approaches. Evidence increasingly clarifies that primary cancers begin shedding neoplastic cells into the circulation at an early stage. [7][8][9] It is the dissemination of cancer cells into circulation that is widely accepted as the main cause l...