| Gastric cancer, which bereaves 160 000 people of their lives in the Chinese population, is the most frequent cancer in our country and accounts for one third of all cancer mortality rate, and the emphasis for prevention and cure of malignant tumors. There is no evident breakthrough for the treatment of patients with middle or terminal stage of gastric cancer, surgery is still the main therapy for it, and 90% cancer patients died of complication related to the recurrence and metastasis which are usually caused by tumor micrometastasis. Tumor micrometastasis, which has not any clinical symptoms and is difficult to be identified using conventional ways such as radiography and pathology, generally means tumor cells spread and survive in blood circulation, lymph nodes, bone marrow and other kinds of tissues or organizations during the development of malignant tumors. Though not all the cancer cells entering blood circulation can survive, while there are many facts confining its growth, its biological characteristics determine its metastatic trend. The existence of tumor cells in peripheral blood is the basis for blood circulation metastasis. Detection of micrometastasis in time is an important problem of clinical significance for a better understanding and control of tumor progression, which will improve patients' survival time. Therefore, it is of the great clinical significance of prevention of metastatic relapse to detect, monitor, and clear minim circulating tumor cells.The amount of tumor cell in blood circulation is too small to be identified. It becomes possible to detect minim tumor cells from amount of blood cells only when these two problems are well solved: one is tumor- specific biologic marker; the other is experimental method with high sensitivity.In the early 1980s, Ugelstad began to use magnetic grain to separate cell, then Dynal Corporation of Norway produced immunomagnetic beads to separate many kinds of cells. Immunomagnetic bead method could be divided into two forms: positive immuno-beadmethod and negative immuno-bead method. The former means immunomagnetic bead wrapped by separated antibody, while the latter means immunomagnetic bead wrapped by other antibodies of separated mixture. Immunomagnetic bead showed its foreground broadly in the area of tumor research and clinical study since then. It could not only enrich tumor cells for the diagnosis, but also eliminate tumor cells in the blood and make it possible for self blood transfusion to the patient with cancer.Reverse transcript-polymerase chain reaction (RT-PCR), with virtues of high sensitivity and strong specificity makes it possible to detect minim tumor cells from peripheral blood. The method with sensitivity of 10-5 using RT-PCR technique, which is evidently superior to that of detecting cancer cells in lymph nodes, has been reported in many national and international magazines.In the present study, to evaluate the methodology and significance of combinative use of negative and positive immunomagnetic beads with quantitative RT-PCR in the detecting peripheral blood micrometastasis in patients with gastric carcinoma, we enriched cancer cells from peripheral blood by using negative and positive immunomagnetic beads successively, analyzed the expression level of carcinoembryonic antigen (CEA) mRNA with fluorescence quantitative RT-PCR (FQ-RT-PCR) assay.Materials and Methods56 blood specimens were obtained from patients in the in-patient Department of theAffiliated Hospital of Ningbo University School of Medicine from August 2002 to August2003, including 41 patients with gastric cancer diagnosed by pathology , 10 patients withbenign gastric ulcer and 5 health blood-donators. Among the gastric cancer patients, there are 26 males and 15 females, varying age from 48 to 93 years old with mean 67. The tumorstages of these cancer patients were stagel ,n=7 ; stagell , n=8; stage III , n=10; and IVn=16 according to the pathology. There are 6 males and 4 females, varying age from 50 to 82 years old with...
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