Gastric cancer is the third most common cause of cancer-related death in worldwide. It is crucial to target the key genes controlling pathogenesis in the early stage of gastric cancer. This study describes an integrated bioinformatics to identify molecular biomarkers for gastric cancer in patients' cancer tissues. We reports differently expression genes in large gastric cancer cohorts from Gene Expression Ominus (GEO). Our findings revealed that 433 genes were significantly different expressed in human gastric cancer. Differently expression gene profile in gastric cancer was further validated by bioinformatic analyses, co-expression network construction. Based on the co-expression network and top-ranked genes, we identified collagen type I alpha 2 (COL1A2) which encodes the pro-alpha2 chain of type I collagen whose triple helix comprises two alpha1 chains and one alpha2 chain, was the key gene in a 37-gene network that modulates cell motility by interacting with the cytoskeleton. Furthermore, the prognostic role of COL1A2 was determined by use of immunohistochemistry on human gastric cancer tissue. COL1A2 was highly expressed in human gastric cancer as compared with normal gastric tissues. Statistical analysis showed COL1A2 expression level was significantly associated with histological type and lymph node status. However, there were no correlations between COL1A2 expression and age, lymph node numbers, tumor size, or clinical stage. In conclusion, the novel bioinformatics used in this study has led to identification of improving diagnostic biomarkers for human gastric cancer and could benefit further analyses of the key alteration during its progression.
Side population (SP) cells are a subset of stem cells that have been isolated from several different gastrointestinal cancer cell lines. Using flow cytometry and the DNA-binding dye Hoechst 33342, we isolated SP cells from SGC-7901 human gastric tumor cell lines and found that they comprise 2.3±0.78% of the tumor cells. Using the Cell Counting Kit-8 (CCK-8) assay, we demonstrated that SP cells have a stronger proliferative activity than non-SP cells. Additionally, we observed tumor mass formation following the cultivation of SP cells in serum-free medium, indicating the capability of these cells for self-renewal. SP cells were observed to undergo non-symmetrical division, which is characteristic of stem cells. A drug resistance assay revealed that SP cells have a high survival rate when exposed to the chemotherapy drug 5-fluorouracil; the results of western blot analysis suggest that this stems from the abundant expression of the chemoresistance-associated proteins ABCG2 and Bcl-2. We also used fluorescence quantitative PCR to reveal that SP cells have relatively high expression levels of the stem cell-related genes Musashi-1 and CD44. In vivo experiments in mice revealed that the subcutaneous injection of 2×103 SP cells resulted in the formation of tumors, while the injection of 2×104 non-SP cells did not. Cumulatively, our results suggest that gastric tumorigenesis associated with SGC-7901 may partly be driven by the activity of SP cells, which exhibit certain biological characteristics of stem cells. Our results also show that the SP cell sorting method is an effective means for isolating and identifying gastric cancer stem cells during early screening.
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