Guoguang Ying

Cell-derived microvesicles mediate the delivery of miR-29a/c to suppress angiogenesis in gastric carcinoma

Microvesicles (MVs) secreted from cells have been found to mediate signal transduction between cells. In the tumor microenvironment, VEGF released from cancer cells plays a key role in promoting tumor angiogenesis. In this study, we characterized the inhibitory effect of MV-delivered miR-29a/c on angiogenesis and tumor growth in gastric cancer (GC). We found that the downregulation of miR-29a/c increases VEGF expression and release in GC cells, promoting the growth of vascular cells. By simulating the tumor microenvironment, the MV-delivered miR-29a/c significantly suppresses VEGF expression in GC cells, inhibiting vascular cell growth, metastasis, and tube formation. We also used a tumor implantation mouse model to show that secreted MVs containing overexpressed miR-29a/c significantly reduced the growth rate of the vasculature and tumors in vivo. To conclude, our results contribute to a novel anti-cancer strategy using miRNA-containing MVs to control tumor cell growth by blocking angiogenesis.

Onco-miR-24 regulates cell growth and apoptosis by targeting BCL2L11 in gastric cancer

ABSTRACTGastric cancer is one of the most common malignancies worldwide; however, the molecular mechanism in tumorigenesis still needs exploration. BCL2L11 belongs to the BCL-2 family, and acts as a central regulator of the intrinsic apoptotic cascade and mediates cell apoptosis. Although miRNAs have been reported to be involved in each stage of cancer development, the role of miR-24 in GC has not been reported yet. In the present study, miR-24 was found to be up-regulated while the expression of BCL2L11 was inhibited in tumor tissues of GC. Studies from both in vitro and in vivo shown that miR-24 regulates BCL2L11 expression by directly binding with 3′UTR of mRNA, thus promoting cell growth, migration while inhibiting cell apoptosis. Therefore, miR-24 is a novel onco-miRNA that can be potential drug targets for future clinical use.

Onco-miR-130 promotes cell proliferation and migration by targeting TGFβR2 in gastric cancer

MicroRNAs (miRNAs) have been proved to play crucial roles in tumorigenesis. TGFβ signal pathway abnormality is found in various cancers and correlates with tumor proliferation and metastasis. However, the mechanisms underlying the dys-regulation of TGFβR2 expression in GC have not been investigated yet. In this study, we found that the TGFβR2 protein was clearly repressed in tumor tissues, while miR-130 expression level was dramatically increased in GC tissues. Firefly luciferase activity assay revealed that miR-130 could directly bind to 3′UTR of TGFβR2 mRNA. Meanwhile, miR-130 mimics lead to the decreased TGFβR2 protein levels, while miR-130 inhibitors enhanced TGFβR2 expression in SGC7901 cells. Subsequent functional experiments showed that overexpressed miR-130 could promote proliferation and migration of SGC7901 cells. And siRNA-mediated TGFβR2 down-regulation could simulate the effects of miR-130 mimics on phenotypes of SGC7901 cells. Furthermore, there existed intense relationship between the expression level of miR-130 and epithelial-mesenchymal markers. Our results demonstrated that miR-130 was an oncogene by directly targeting TGFβR2 in GC.

MiR-17-5p regulates cell proliferation and migration by targeting transforming growth factor-β receptor 2 in gastric cancer

TGFBR2 serves as an initial regulator of the TGF-β signaling pathway, and loss or reduction of its expression leads to uncontrolled cell growth and invasion. TGFBR2 plays a crucial role in the carcinogenesis and malignant process of gastric cancer, but the mechanism remains unclear. In this study, we found that TGFBR2 protein levels were consistently upregulated in gastric cancer tissues, whereas TGFBR2 mRNA levels varied among these tissues, indicating that a post-transcriptional mechanism is involved in the regulation of TGFBR2. MiRNAs are known to regulate gene expression at the post-transcriptional level. Therefore, we performed bioinformatics analyses to search for miRNAs potentially targeting TGFBR2. MiR-17-5p was found to bind to the 3′UTR of TGFBR2 mRNA, and further validation of this specific binding was performed through a reporter assay. An inverse correlation between miR-17-5p and TGFBR2 protein was observed in gastric cancer tissues. Cell studies revealed that miR-17-5p negatively regulated TGFBR2 expression by directly binding to the 3′UTR of TGFBR2 mRNA, thereby promoting cell growth and migration. We also validated the role of TGFBR2 using siRNA and an overexpression plasmid. The results of our study suggest a novel regulatory network in gastric cancer mediated by miR-17-5p and TGFBR2 and may indicate that TGFBR2 could serve as a new therapeutic target in gastric cancer.

Prognostic nomogram for previously untreated patients with esophageal squamous cell carcinoma after esophagectomy followed by adjuvant chemotherapy

OBJECTIVE The aim of the study was to establish an effective prognostic nomogram for esophageal squamous cell carcinoma after radical esophagectomy followed by adjuvant chemotherapy in those previously untreated patients. METHODS The clinicopathological data from 328 patients who underwent radical esophagectomy followed by adjuvant chemotherapy or not at the Tianjin Medical University Cancer Institute and Hospital between 2006 and 2010 were retrospectively studied. Nomograms which predicted survival of esophageal squamous cell carcinoma were established based on the Cox proportional hazards regression model. To determine its predictive accuracy and discriminatory capacity, the concordance index and calibration curve were calculated after bootstrapping in the internal validation. An external validation of 76 patients in 2011 was prospectively studied at the same institution. To verify the performance of the nomogram, the comparison between the nomogram and Tumor-Node-Metastasis staging system was conducted. RESULTS The 5-year overall survival was 43.1% in the primary cohort. Based on multivariate analyses, five independent prognostic variables including gender, tumor length, T stage, N stage and chemotherapy cycles were selected to build the nomograms to predict disease-free survival and overall survival. The concordance index of the nomogram to predict overall survival was 0.71 (95% confidence interval, 0.63-0.79), which was superior to the predictive power of Tumor-Node-Metastasis staging system (0.64) in the primary cohort. Meanwhile, the calibration curve showed good accuracy between predictive and actual overall survival. In the validation cohort, the concordance index (0.77) and calibration plot displayed favorable performances. The other nomogram to predict disease-free survival also performed well. CONCLUSIONS The prognostic nomogram provided individualized risk estimate of survival in patients after esophagectomy followed by adjuvant chemotherapy.

Cell-derived Exosomes as Promising Carriers for Drug Delivery and Targeted Therapy

Exosomes are small vesicles that are secreted by various types of cells, known to mediate signal transduction between cells. During recent years, novel carriers for the delivery of targeted drugs, chemotherapy drugs and RNAs are under development, which is believed to be beneficial for patients. Considering issues of drug nano-formulations in bloodstream, such as nano-toxicity and rapid clearance by mononuclear phagocyte system, exosomes derived from either patients cells or bodyfluids, seem to be an optimal option. This review presents the current patterns of drug-loaded into exosomes and discusses how exosomes were reconstructed for targeted therapy. Loading either exosomes directly or their donor cells is an alternative, including incubation, electroporation, transfection of exosomes or transfection, incubation, activation of the parent cells. To solve the low efficiency of cargo loading into exosomes, protein loading via optically reversible protein-protein interaction can realize a novel exosomal protein carrier. In addition, targeted therapeutics with exosomes is achieved by three means, via adding targeting peptides into the surface of exosomes, by transferring specific genes within exosomes into tumors to establish a therapeutic target and, lastly, by targeting at exosomes containing tumor associated antigens. Nevertheless, purification and mass production of exosomes need further exploration, as well as more approaches were applied to targeted therapy. Therefore, exosomes could serve as an effective tool for drug delivery and targeted therapy.

MiR-26a/b Inhibit Tumor Growth and Angiogenesis by Targeting the HGF-VEGF Axis in Gastric Carcinoma

Background/Aims: Abnormal expression of HGF is found in various cancers and correlates with tumor proliferation, metastasis and angiogenesis. However, the regulatory mechanism of the HGF-VEGF axis remains unclear. Methods: The expression characteristic of HGF in human gastric cancer tissues was shown by an immunohistochemistry assay, and the expression levels of target protein were detected by Western blot. The relative levels of miR-26a/b and target mRNA were examined by qRT-PCR. We used bioinformatics tools to search for miRNAs that can potentially target HGF. A luciferase assay was used to confirm direct targeting. Furthermore, the functions of miR-26a/b and HGF were evaluated by cell proliferation and migration assays in vitro and by the mouse xenograft tumor model in vivo. Results: We found that the HGF protein was clearly increased while miR-26a/b were dramatically down-regulated in gastric cancer. miR-26a/b directly bind to the 3’-UTR of HGF mRNA at specific targeting sites. We demonstrated that the repression of the HGF-VEGF pathway by miR-26a/b overexpression suppressed gastric cancer cell proliferation and migration. Furthermore, miR-26a/b also showed an anti-tumor effect in the xenograft mouse model by suppressing tumor growth and angiogenesis. Conclusions: miR-26a/b could suppress tumor tumorigenesis and angiogenesis by targeting the HGF-VEGF axis and could serve as a potential treatment modality for targeted therapy in the clinical treatment of gastric cancer.

Integrated analysis of the miRNA, gene and pathway regulatory network in gastric cancer

Gastric cancer is one of the most common malignant tumors worldwide; however, the efficacy of clinical treatment is limited. MicroRNAs (miRNAs) are a class of small non-coding RNAs that have been reported to play a key role in the development of cancer. They also provide novel candidates for targeted therapy. To date, in-depth studies on the molecular mechanisms of gastric cancer involving miRNAs are still absent. We previously reported that 5 miRNAs were identified as being significantly increased in gastric cancer, and the role of these miRNAs was investigated in the present study. By using bioinformatics tools, we found that more than 4,000 unique genes are potential downstream targets of gastric cancer miRNAs, and these targets belong to the protein class of nucleic acid binding, transcription factor, enzyme modulator, transferase and receptor. Pathway mapping showed that the targets of gastric cancer miRNAs are involved in the MAPK signaling pathway, pathways in cancer, the PI3K-Akt signaling pathway, the HTLV-1 signaling pathway and Ras signaling pathway, thus regulating cell growth, differentiation, apoptosis and metastasis. Analysis of the pathways related to miRNAs may provides potential drug targets for future therapy of gastric cancer.

Exosomes serve as nanoparticles to suppress tumor growth and angiogenesis in gastric cancer by delivering hepatocyte growth factor siRNA

Exosomes derived from cells have been found to mediate signal transduction between cells and to act as efficient carriers to deliver drugs and small RNA. Hepatocyte growth factor (HGF) is known to promote the growth of both cancer cells and vascular cells, and the HGF‐cMET pathway is a potential clinical target. Here, we characterized the inhibitory effect of HGF siRNA on tumor growth and angiogenesis in gastric cancer. In addition, we showed that HGF siRNA packed in exosomes can be transported into cancer cells, where it dramatically downregulates HGF expression. A cell co‐culture model was used to show that exosomes loaded with HGF siRNA suppress proliferation and migration of both cancer cells and vascular cells. Moreover, exosomes were able to transfer HGF siRNA in vivo, decreasing the growth rates of tumors and blood vessels. The results of our study demonstrate that exosomes have potential for use in targeted cancer therapy by delivering siRNA.

MiR-221 and miR-222 synergistically regulate hepatocyte growth factor activator inhibitor type 1 to promote cell proliferation and migration in gastric cancer

Gastric cancer is a common malignancy with limited treatment options and poor prognosis. Introduction of novel pathways of gastric cancer will provide candidates for target therapy. Hepatocyte growth factor activator inhibitor type 1 is an integral-membrane proteinase inhibitor. Hepatocyte growth factor activator inhibitor type 1 abnormality is found in various cancers and correlates with tumor progression and metastasis. However, the mechanisms underlying the dysregulation of hepatocyte growth factor activator inhibitor type 1 expression in gastric cancer remain unclear. Although microRNAs have been reported to be involved in the development of cancer, the roles of miR-221 and miR-222 in gastric cancer have not been reported yet. In this study, we showed that hepatocyte growth factor activator inhibitor type 1 protein was downregulated, while miR-221 and miR-222 were significantly increased in gastric cancer tissues. Bioinformatic predictions and luciferase assay verified that the 3′-untranslated region of the HAI-1 gene is a direct target site for miR-221 and miR-222. Overexpression of miR-221 and miR-222 in MGC-803 cells leads to the inhibition of hepatocyte growth factor activator inhibitor type 1 protein expression, thus promoting cell proliferation and migration; whereas knockdown of miR-221 and miR-222 showed opposite effects. Moreover, we found that the expression level of hepatocyte growth factor activator protein was increased when hepatocyte growth factor activator inhibitor type 1 was knocked down in MGC-803 cells. Thus, gastric cancer is probably an autocrine tumor, and the antitumor mechanism of hepatocyte growth factor activator inhibitor type 1 in vitro might be mediated by regulating the expression of hepatocyte growth factor activator protein. Therefore, our data illustrated a novel pathway comprising miR-221and miR-222 and hepatocyte growth factor activator inhibitor type 1 in gastric cancer, which is a potential target for future clinical use.