Gastric cancer is the fourth most common malignancy in the world. Although microRNA-200 (miR-200) family members are thought to play roles in tumorigenesis, their functions in carcinogenesis are tumor specific, and the underlying mechanism of action still remains elusive. Few studies to date have addressed the dysregulation and function of miR-200 family members in gastric cancer progression. Here, we report that the miR-200 family members, miR-200c and miR-141, were significantly downregulated in gastric cancer specimens and gastric cancer cell lines. Importantly, on clinical samples, the expression of miR-200c and miR-141 was inversely correlated with TNM stage, tumor invasion depth (T), tumor embolus and disease-free survival. Wound-healing assay results showed that co-transfected miR-200c/141 could inhibit the migration and invasion capability of the gastric cell line SGC-7901. We also found that miR-200c and miR-141 directly targeted zinc finger E-box-binding homeobox 1/2 (ZEB1/2) and upregulated E-cadherin expression. In specimens from gastric cancer patients, reduced expression of miR-200c/141 was associated with increased expression of ZEB1 and/or ZEB2. In addition, the downregulation of miR-200c and miR-141 was found to be due to a highly methylated CpG island located upstream of their genomic sequence and/or upregulated TGF-β signaling. Treatment with the chemotherapeutic agent decitabine, a known DNA methyltransferase inhibitor, increased miR-200c/141 expression and ameliorated decreased expression of miR-200c/141 induced by TGF-β in SGC-7901 cells. Our study revealed that miR-200c/141 was downregulated by CpG island methylation and TGF-β signaling, which decreased ZEB1/2 expression and increased E-cadherin expression to inhibit migration and invasion of gastric cancer cells and provides powerful evidence for the application of decitabine in gastric cancer treatment.

Gastric cancer is the fifth most common malignancy in the world, with Eastern Asia as one of areas with the highest incidence rates. Trastuzumab, a HER2-targeting antibody, combined with chemotherapy has been successfully employed for the gastric cancer patients with HER2 overexpression/amplification. However, trastuzumab resistance is a major problem in clinical practice. Here we observed that the trastuzumab-resistant gastric cancer cell line NCI-N87/TR expressed high levels of epithelial-mesenchymal transition factors and demonstrated increased migration and invasion capability compared with NCI-N87 cells. Downregulated E-cadherin and increased N-cadherin, TGF-β, ZEB1, ZEB2, TWIST1, and Snail were detected in NCI-N87/TR cells. We also found that miR-200c was downregulated in NCI-N87/TR cells compared with parental cells NCI-87 by qRT-PCR. Treatment with TGF-β downregulated the expression of miR-200c and upregulated ZEB2, and significantly decreased the trastuzumab sensitivity of NCI-N87 cells. miR-200c restored trastuzumab sensitivity and inhibited migration and invasion through suppressing ZEB1 and ZEB2. In summary, TGF-β/ZEB2 axis plays an encouraging role in trastuzumab resistance of gastric cancer, while miR-200c overexpression downregulates ZEB1/ZEB2 and resensitizes drugs resistance. Our findings might provide a potential therapeutic strategy for trastuzumab resistance of gastric cancer.

Abstract. Gastric cancer is one of the most common malignant tumors and one of the leading causes of cancer-related mortality. Recent studies have revealed that there is a difference in microRNA (miR/miRNA) profiles between cancerous and normal tissues. To find a potentially useful prognostic predictor and a promising therapeutic tool for gastric cancer, the present study investigated the expression and clinical significance of the miR-200 family in gastric cancer. The miR-200 family has five members: hsa-miR-200a, hsa-miR-200b, hsa-miR-200c, hsa-miR-141 and hsa-miR-429. In 46 clinical samples of gastric cancer and paired non-cancerous tissues, the present study observed that the expression levels of the miR-200 family in the cancer tissues were significantly lower than those in the non-cancerous tissues (P<0.001). Lower levels of the five family members were associated with histological grade and the presence of an intravascular cancer embolus (P<0.05). The results revealed that the miR-200 family is downregulated in gastric cancer, and that there are significant differences in the expression of the miR-200 family between normal and cancer tissues. The miR-200 family may therefore become a potentially useful prognostic predictor of the aggressiveness of gastric cancer and a possible therapeutic tool in affected patients.

Gastric cancer remains a worldwide burden as the second leading cause of cancer-related death. Drug resistance of chemotherapy looms as a major clinical obstacle to successful treatment. Recent evidence indicated that miRNA-200c can restore the sensitivity of NSCLC cells to cisplatin and cetuximab. The expression of miRNA-200c and RhoE were investigated in gastric cancer tissues and cells (SGC7901 and SGC7901/DDP) by qRT-PCR. A luciferase reporter assay was done to understand the potential correlation between miRNA-200c and RhoE. Pre-miR-200c was transfected in SGC7901/DDP cells to confirm whether miRNA-200c could regulate RhoE expression. RhoE was knocked down to explore the role of RhoE on sensitivity of chemotherapy in gastric cancer by MTT. Western blot analysis was performed to further explore the mechanism of RhoE in regulating drug resistance. The results showed that miRNA-200c was significantly lower in cancerous tissues than those in the paired normal tissues, whereas the expression of RhoE was just the opposite. The significant difference of miRNA-200c and RhoE were observed between SGC7901 cells and SGC7901/DDP cells. miRNA-200c has target sites in the 3'-UTR of RhoE mRNA by luciferase reporter assay. Transfection of pre-miR-200c reduces RhoE expression. Meanwhile, the knockdown of RhoE enhanced the sensitivity of SGC7901/DDP cells and changed expression of some genes. These suggested that miRNA-200c regulated the sensitivity of chemotherapy to cisplatin (DDP) in gastric cancer by possibly targeting RhoE.

Although microRNA-33 (miR-33) family members are known to be involved in the regulation and balancing of cholesterol metabolism, fatty acid oxidation and insulin signaling, their functions in carcinogenesis are controversial and the underlying mechanisms have remained elusive. Gastric cancer is the fourth most common malignancy in the world; however, the dysregulation and function of miR-33 family members in gastric cancer have not been extensively studied. The present study reported that a miR-33 family member, miR-33a, was significantly downregulated in gastric cancer tissues and gastric cancer cell lines. Of note, the expression of miR-33a was inversely correlated with pathological differentiation and metastasis as well as gastric cancer biomarker CA199. A cell-counting kit-8 assay showed that transfection of the SGC-7901 gastric cell line with miR-33a-overexpression plasmid inhibited the capability of the cells to proliferate. Furthermore, overexpression of miR-33a led to cell cycle arrest of SGC-7901 cells in G1 phase. In addition, a luciferase reporter assay showed that miR-33a directly targeted cyclin-dependent kinase 6 (CDK6), cyclin D1 (CCND1) and serine/threonine kinase PIM-1. In gastric cancer specimens, the reduced expression of miR-33a was associated with increased expression of CDK-6, CCND1 and PIM1. However, only PIM1 expression was significantly increased in cancer tissues compared with that in their adjacent tissues. The present study revealed that miR-33a was downregulated in gastric cancer tissues and cell lines, while forced overexpression of miR-33a decreased CDK-6, CCND1 and PIM1 expression to inhibit gastric cancer cell proliferation by causing G1 phase arrest. miR-33a overexpression may therefore resemble an efficient strategy for gastric cancer therapy.

Abstract. The present study was conducted in order to investigate the inhibitory effects of ginsenoside Rg3 combined with chemotherapy on Eca-109 esophageal squamous cell carcinoma (ESCC) in mice. Tumor xenograft models were established in the right forelimb of 20 BALB/c nude mice by subcutaneous injection. The tumor-bearing mice were randomly assigned to 4 treatment groups (n=5 per group) as follows: the control group (saline), the ginsenoside Rg3 alone group (6 mg/kg/day, once a day for 3 weeks), the chemotherapy alone group (paclitaxel 10 mg/kg/day + cisplatin 5 mg/kg/day on days 1, 7, 14 and 21) and the chemotherapy + Rg3 group (combined treatment). The length and width of the tumor were directly measured with calipers at different time points and the tumor volume (cm 3 ) was calculated using the formula 0.52 x length x width 2 every other day. The mice were sacrificed by cervical dislocation following completion of therapy, the tumors were removed and weighed and the expression levels of Ki-67 were determined by immunohistochemistry. The results indicated that the coadministration of ginsenoside Rg3 significantly enhanced the inhibitory effects of chemotherapy on tumor growth. In addition, the expression levels of Ki-67 in the chemotherapy + Rg3 group were significantly lower compared to those in the other 3 groups. The chemotherapy + Rg3 group also exhibited the lowest microvascular density among all four groups. These findings suggested that ginsenoside Rg3 may improve the antitumor efficacy of chemotherapy in Eca-109 ESCC in mice.

The mechanism of extracellular matrix induced tumor progression is poorly understood. Based on the TCGA database and clinical tumor tissues analysis, we observed abundant type I collagen expression in tumor tissues and poor overall survival in gastric patients with high integrin β1 (ITGB1) expression. In vitro , our study found that 3D collagen culture promoted the capability of colony formation and growth in ITGB1 positive gastric cancer, whereas limited colony growth was observed in ITGB1 negative gastric cancer, suggesting the role of ITGB1 in type I collagen associated tumor progression. Mechanistically, we demonstrated that type I collagen was capable of promoting the activation of BCL9L/β-catenin signaling pathway through ITGB1, thereby contributing to the gastric cancer development. Subsequently, β-catenin signals further up-regulated the expression anti-apoptosis protein BCL2, leading to the chemo-resistance in gastric cancer cells. Blockade of β-catenin signals efficiently improved the anticancer effects of chemotherapy, providing an innovative sight for clinical gastric cancer therapy.

Purpose Vascular endothelial growth factor (VEGF) family members contribute greatly to the development and angiogenesis of hypervascular hepatocellular carcinoma (HCC). We have previously shown that Dicer inhibited HCC growth. In this study, we aimed to determine the relationship between Dicer and VEGF in HCC. Methods Gain-of-function studies were performed to determine the effect of different treatments on the proliferation, migration, and invasion of HCC cells. Expression of VEGF-A in xenograft tumor tissues was analysed using Western blotting, and that of CD31 using immunohistochemical analysis. Results We found that Dicer inhibited proliferation, migration and invasion of HCC cells by suppressing VEGF-A expression. Interestingly, VEGF-A165, which is the most prominent VEGF-A isoform, counteracted Dicer-induced inhibition of HCC cells. In addition, a monoclonal anti-VEGF antibody (bevacizumab) enhanced Dicer-induced inhibition of HCC in vitro and in vivo. Further, immunohistochemical analysis of CD31 indicated bevacizumab and Dicer synergized to reduce tumor microvessel density. Conclusion Our data demonstrated that Dicer enhanced bevacizumab-related inhibition of HCC cell via the VEGF pathway; therefore, Dicer in coordination with bevacizumab may provide another potential approach for HCC therapy.