(n=3); ** indicates P-value <0.01.(C)Overexpression of (3-Carboxypropyl)trimethylammonium chloride miR-133b in MGC-803 cells was confirmed by qRT-PCR.(D)The cell growth of MGC-803 cells at day 0, 1, 2, 3, 4 post transfection which was detected by CCK-8 assay. GC cell lines and in GC tissues compared with adjacent normal tissues. Moreover, lower-level of miR-133b was also associated with venous invasion and a more aggressive tumor phenotype. Re-introduction of miR-133b in GC cells can inhibit cell proliferation, cell migration and invasion. In contrary, knockdown of miR-133b in GES cells can promote cell proliferation and invasion. Further investigation indicated that miR-133b targeted FSCN1 in GC cells and knockdown of FSCN1 can also inhibit GC cell growth and invasion. == Conclusion == Our findings demonstrated that miR-133b was significantly down-regulated in GC tissues and exerted its tumor suppressor role in GC cells. The investigation of the detailed mechanism showed that miR-133b directly targeted FSCN1 which functioned as an oncogenic gene in GC cells. These results suggested that miR-133b can be developed as a new diagnostic marker or therapeutic target for GC. Keywords:Gastric cancer, miR-133b, FSCN1, Tumor suppressor == Background == Gastric cancer (3-Carboxypropyl)trimethylammonium chloride is the second most common cause of cancer-related death in the world. Diverse treatment strategies including surgery, chemotherapy and radiotherapy can relieve the pain and lessen the possibility of systemic metastasis. However, the overall therapeutic activity for advanced disease remains poor [1]. To discover and identify new biomarkers for earlier stages of GC or specific biomarkers for different individuals is urgently required for early detection of cancer and individualized therapies. Recently, the roles of microRNAs (miRNAs) as potential biomarkers and therapy targets have been widely investigated in many kinds of cancers. MiRNAs are endogenous small non-coding RNA molecules, which function in transcriptional and post-transcriptional regulation of gene expression. Accumulating evidence demonstrate that miRNAs play important roles in a variety of biological processes and the deregulation of miRNAs is involved in many diseases [2,3]. Numerous studies have documented that miRNAs acted as oncogenes or tumor suppressors in diverse cancers, such as lung, breast, hepatic, pancreatic cancer and gastric cancer [4-11]. Currently, the aberrant expression of many miRNAs has been observed in GC. For example, miR-21, miR-124, miR-125b, miR-221-222 cluster, miR-106b-25 cluster have been shown to contribute to gastric carcinogenesis by changing the cell cycle, cell apoptosis, cell migration and invasion through targeting the relative genes [12,13]. In addition, a lot of miRNAs, especially circulating miRNAs, have been shown to be associated with tumor stages or patient survival, and might be developed as potential biomarkers for GC diagnosis [14]. Therefore, exploring the aberrant expression pattern of miRNAs and the roles of miRNAs in GC will be benefit to understand the mechanism of GC carcinogenesis and develop new methods for GC diagnosis and therapy. miR-133b, which is initially considered to be a muscle-specific (3-Carboxypropyl)trimethylammonium chloride miRNA [15,16], has been reported to be deregulated in many kinds of cancer [17-22]. The down-regulation of miR-133b in gastric cancer has also been reported by several groups [23,24]. Recently, miR-133b (3-Carboxypropyl)trimethylammonium chloride is found to negatively regulate FGFR1 in gastric cancer and might act as a tumor suppressor in GC [25]. Rabbit Polyclonal to PDXDC1 However, in these studies, the expression of miR-133b was detected only in a small number of GC tissues or just in the GC cell lines. The expression of miR-133b in a large number of clinical samples was not determined. miR-133b has been reported to directly target oncogenic Fascin actin-bundling protein 1 (FSCN1) in esophageal squamous cell carcinoma [26]. In GC, FSCN1 also might act as an oncogene and the high level of FSCN1 was significantly correlated with shorter survival time and several aggressive pathological factors [27]. In addition, FSCN1 mRNA was upregulated in accordance with miR-133b down-regulation in GC patients [24]..