Analysis Of MicroRNAs In Peripheral Blood From Patients With Gastric Cancer And Its Clinical Significance

ObjectiveTumor recurrence and metastasis are the leading causes of death in patients with cancer. Hematogeneous spread is one of the important ways of tumor metastasis. Detection of occult cancer cells in peripheral blood has recently received a great deal of attention regarding the monitoring cancer metastasis, and for novel strategies of adjuvant therapy. However, the lack of ideal tumor markers is a major problem for its application. Our previous studies showed that microRNAs (miRNAs) are abnormally expressed in gastric cancer tissues. The significantly upregulated miRNAs include miR-421, miR-106a and miR-17. So, the aims of this study were to explore the tumorigencity of these miRNAs and to investigate whether they can be a marker for detecting circulating tumor cells in patients with gastric cancer.Methods1. To increase the miRNA level in normal gastric epithelial cells or decrese its level in gastric cancer cells, miRNA mimics or inhibitor were transfected with liposome, respectively.2. MTT and flow cytometry were employed to examine the cell growth and cell cycles, respectively.3. To determine the expression effects of miRNA inhibitor on cell cycle-related proteins, Western blot was used.4. To establish nude mouse xenograft model of gastric cancer, MGC-803 cells transfected with miR-106a or miR-421 inhibitor were injected under the skin of nude mice. Then the weight and the sizes of tumors were measured. 5. Peripheral blood samples were collected from 90 gastric cancer patients and 27 healthy volunteers. Real-time RT-PCR was used to detect the level of miR-106a and miR-17. Finally, ROC curves were constructed.Results1. The growth of GES-1 cells was promoted by miR-106a mimic. The miR-106a inhibitor arrested MGC-803 and SGC-7901 at G2/M phase.2. The CDK1 and CDK2 protein levels were both suppressed in gastric cancer cells by miR-106a inhibitor.3. The results of animal experiments showed that the decrease of miR-106a or miR-421 level in cancer cells significantly suppressed tumor growth.4. In preoperative and postoperative patient groups, miR-106a and miR-17 expression levels were significantly higher than those in controls. The AUCs of miR-106a, miR-17 and combinative use of them were 0.684 (P = 0.0066), 0.743 (P = 0.0001), and 0.741 (P = 0.0002), respectively. These results indicate that they had diagnostic value. The result that the differences among three AUCs had no statistical significance meants that miR-106a and miR-17 had the same values in the detecting of circulating gastric cancer cells.ConclusionsThe growth of GES-1 cells was promoted by miRNA mimic and the expressions of oncogenic miRNAs were suppressed by miRNA inhibitor. The in vivo and in vitro mechanism researches explained that miRNAs play an important role in initialization and progression of gastric cancer. The clinical specimen analysis confirmed that the detection of miRNAs in peripheral blood is a useful tool for monitoring circultaing gastric cancer cells in peripheral blood.