Yongquan Shi

miRNA-223 Promotes Gastric Cancer Invasion and Metastasis by Targeting Tumor Suppressor EPB41L3

Traditional research modes aim to find cancer-specific single therapeutic target. Recently, emerging evidence suggested that some micro-RNAs (miRNA) can function as oncogenes or tumor suppressors. miRNAs are single-stranded, small noncoding RNA genes that can regulate hundreds of downstream target genes. In this study, we evaluated the miRNA expression patterns in gastric carcinoma and the specific role of miR-223 in gastric cancer metastasis. miRNA expression signature was first analyzed by real-time PCR on 10 paired gastric carcinomas and confirmed in another 20 paired gastric carcinoma tissues. With the 2-fold expression difference as a cutoff level, we identified 22 differential expressed mature miRNAs. Sixteen miRNAs were upregulated in gastric carcinoma, including miR-223, miR-21, miR-23b, miR-222, miR-25, miR-23a, miR-221, miR-107, miR-103, miR-99a, miR-100, miR-125b, miR-92, miR-146a, miR-214 and miR-191, and six miRNAs were downregulated in gastric carcinoma, including let-7a, miR-126, miR-210, miR-181b, miR-197, and miR-30aa-5p. After examining these miRNAs in several human gastric originated cell lines, we found that miR-223 is overexpressed only in metastatic gastric cancer cells and stimulated nonmetastatic gastric cancer cells migration and invasion. Mechanistically, miR-223, induced by the transcription factor Twist, posttranscriptionally downregulates EPB41L3 expression by directly targeting its 3′-untranslated regions. Significantly, overexpression of miR-223 in primary gastric carcinomas is associated with poor metastasis-free survival. These findings indicate a new regulatory mode, namely, specific miRNA, which is activated by its upstream transcription factor, could suppress its direct targets and lead to tumor invasion and metastasis. Mol Cancer Res; 9(7); 824–33. ©2011 AACR.

Multi-drug resistance in cancer chemotherapeutics: Mechanisms and lab approaches

Multi-drug resistance (MDR) has become the largest obstacle to the success of cancer chemotherapies. The mechanisms of MDR and the approaches to test MDR have been discovered, yet not fully understood. This review covers the in vivo and in vitro approaches for the detection of MDR in the laboratory and the mechanisms of MDR in cancers. This study also envisages the future developments toward the clinical and therapeutic applications of MDR in cancer treatment. Future therapeutics for cancer treatment will likely combine the existing therapies with drugs originated from MDR mechanisms such as anti-cancer stem cell drugs, anti-miRNA drugs or anti-epigenetic drugs. The challenges for the clinical detection of MDR will be to find new biomarkers and to determine new evaluation systems before the drug resistance emerges.

Hypoxia‐inducible factor‐1α contributes to hypoxia‐induced chemoresistance in gastric cancer

Hypoxia induced drug resistance is a major obstacle in the development of effective cancer therapy. Our previous study revealed that hypoxia‐inducible factor‐1 (HIF‐1), the major transcriptional factor significantly activated by hypoxia, was overexpressed in gastric vincristine‐resistant cells SGC7901/vincristine (VCR) under normoxic conditions, which suggested that it was associated with drug resistance in gastric cancer cells. In the present study, a colony‐forming assay revealed that hypoxia and forced HIF‐1α expression increased maximal –8.9‐fold or –14.8‐fold of IC50 toward vincristine in gastric cancer cell lines SGC7901 and SGC7901/VCR, respectively (P < 0.01). Annexin‐V/propidium iodide staining analysis revealed hypoxia or forced HIF‐1α expression reduced apoptosis by 24% or 18% in SGC7901 cells (P < 0.05). Flow cytometry analysis of intracellular adriamycin revealed that hypoxia and forced expression of HIF‐1α increased –1.79‐fold or –2.36‐fold of the adriamycin releasing index, respectively (P < 0.05). However, resistance acquisition subject to hypoxia in vitro and in vivo was suppressed by blocking HIF‐1α expression with siRNA. We further demonstrated that HIF‐1 α overexpression showed a 1.85‐fold increased expression of Bcl‐2 and a 2.16‐fold decreased expression of Bax, and also showed significantly induced expression of p‐gp and MRP1, which indicated that HIF‐1α may confer hypoxia‐induced drug resistance via inhibition of drug‐induced apoptosis and decreases in intracellular drug accumulation. (Cancer Sci 2008; 99: 121–128)

Ectopic expression of MiR-125a inhibits the proliferation and metastasis of hepatocellular carcinoma by targeting MMP11 and VEGF.

Background Studies have been shown that miR-125a plays an important role in carcinogenesis, however, the role of miR-125a in hepatocellular carcinoma (HCC) remains elusive. Methodology/Principal Real time-PCR (qRT-PCR) was performed to test the significance of miR-125a in HCC. Ectopic expression of miR-125a was used to test the influences of miR-125a on proliferation and metastasis of HCC cells in vitro and in vivo. Predicted target genes of miR-125a were determined by dual-luciferase reporting, qRT-PCR, and western blot (WB) analyses. Then immunohistochemical staining (IHC) was used to detect the expression of target genes, and the correlations and prognostic values of miR-125a and its target genes were also investigated. Conclusions/Significance Decreased miR-125a was observed in both HCC tissues and cell lines, and associated with patients’ aggressive pathologic features. Up-regulating miR-125a significantly inhibited the malignant phenotypes by repressing the expression of matrix metalloproteinase 11 (MMP11) and vascular endothelial growth factor A (VEGF-A) both in vitro and in vivo. Furthermore, miR-125a expression was inversely correlated with both MMP11 and VEGF-A expression in HCC tissues. Inhibiting miR-125a could increase both MMP11 and VEGF-A expression, and RNA interference targeting MMP11 or VEGF-A mRNA could rescue the loss of miR-125a functions. MiR-125a inhibits the proliferation and metastasis of HCC by targeting MMP11 and VEGF-A. Up-regulation of miR-125a might be a promising approach and a prognostic marker for HCC.

Differentially expressed gene profiles between multidrug resistant gastric adenocarcinoma cells and their parental cells

To better understand the molecular mechanisms of multidrug resistance (MDR) of human cancers, we isolated differentially expressed genes from drug-resistant human gastric adenocarcinoma cell lines using a polymerase chain reaction-based subtractive hybridization technique. Sixty three genes were identified to be differentially expressed in the drug-resistant human gastric adenocarcinoma cell lines. Among the 63 up-regulated genes, 27 were known genes, of which two have been reported to be associated with MDR. The remaining ones were undefined genes or expressed sequenced tags. The results suggest that this strategy is efficient for large-scale cloning of differentially expressed genes in drug-resistant cells. Further characterization of these genes will shed more light on the understanding of molecular mechanisms of MDR of human cancer cells.

MicroRNA-19a/b regulates multidrug resistance in human gastric cancer cells by targeting PTEN.

Multidrug resistance (MDR) is the major cause of failure of gastric cancer chemotherapy. Members of the miR-17-92 cluster, including miR-19a/b, are considered oncomiRs and influence multiple aspects of the malignant phenotype of gastric cancer. However, the role of miR-19a/b in MDR in gastric cancer and its underlying mechanism remain unclear. In this study, we found that miR-19a/b were upregulated in MDR cell lines. Our results also showed that miR-19a/b upregulation decreased the sensitivity of gastric cancer cells to anticancer drugs. We further confirmed that miR-19a/b accelerated the ADR efflux of gastric cancer cells by increasing the levels of mdr1 and P-gp and that miR-19a/b suppressed drug-induced apoptosis by regulating Bcl-2 and Bax. Finally, we verified that PTEN, an inhibitor of AKT phosphorylation, is the functional target of miR-19a/b. Overall, these findings demonstrated that miR-19a/b promote MDR in gastric cancer cells by targeting PTEN.

Cellular prion protein promotes invasion and metastasis of gastric cancer

Cellular prion protein (PrPc) is a glycosylphosphatidylinositol (GPI) ‐anchored membrane protein that is highly conserved in mammalian species. PrPc has the characteristics of adhesive molecules and is thought to play a role in cell adhesion and membrane signaling. Here we investigated the possible role of PrPc in the process of invasiveness and metastasis in gastric cancers. PrPc was found to be highly expressed in metastatic gastric cancers compared to nonmetastatic ones by immunohistochemical staining. PrPc significantly promoted the adhesive, invasive, and in vivo metastatic abilities of gastric cancer cell lines SGC7901 and MKN45. PrPc also increased promoter activity and the expression of MMP11 by activating phosphorylated ErK1/2 in gastric cancer cells. MEK inhibitor PD98059 and MMP11 antibody (Ab) significantly inhibited in vitro invasive and in vivo metastatic abilities induced by PrPc. N‐terminal fragment (amino acid 24–90) was suggested to be an indispensable region for signal transduction and invasion‐promoting function of PrPc. Taken together, the present work revealed a novel function of PrPc that the existence of N‐terminal region of PrPc could promote the invasive and metastatic abilities of gastric cancer cells at least partially through activation of MEK/ERK pathway and consequent transactivation of MMP11.—Pan, Y., Zhao, L., Liang, J., Liu, J., Shi, Y., Liu, N., Zhang, G., Jin, H., Gao, J., Xie, H., Wang, J., Liu, Z., Fan, D. Cellular prion protein promotes invasion and metastasis of gastric cancer. FASEB J. 20, E1205–E1215 (2006)

Reversal of the Malignant Phenotype of Gastric Cancer Cells by Inhibition of RhoA Expression and Activity

Purpose: The small GTPase RhoA has been implicated in the regulation of cell morphology, motility, and transformation, but the role of RhoA protein in the carcinogenesis of gastric cancer remains unclear. In the present study, we have analyzed the expression status of the RhoA protein in human gastric cancer cells and tissues and investigated the possible involvement of RhoA in regulating the malignant phenotype of gastric cancer cells. Experimental Design: RhoA expression was analyzed by immunohistochemistry and Western blot in gastric cancer tissues and cell lines. The RhoA-specific small interfering RNA (siRNA) vector was designed and constructed. We examined the role of RhoA in the malignant phenotype of gastric cancer cells by using siRNA knockdown and dominant-negative RhoA mutant suppression of endogenous RhoA activity. Results: RhoA was found frequently overexpressed in gastric cancer tissues and cells compared with normal tissues or gastric epithelial cells. RhoA-specific siRNA could specifically and stably reduce RhoA expression up to 90% in AGS cells. Both RhoA-specific siRNA and dominant-negative RhoA expressions could significantly inhibit the proliferation and tumorigenicity of AGS cells and enhance chemosensitivity of the cancer cells to Adriamycin and 5-fluorouracil. Conclusion: RhoA may play a critical role in the carcinogenesis of gastric cancer, and the interference of RhoA expression and/or activity could provide a novel avenue in reversing the malignant phenotype of gastric cancer cells.

Overexpression and significance of prion protein in gastric cancer and multidrug-resistant gastric carcinoma cell line SGC7901/ADR.

In our previous work, cellular prion protein (PrPc) was identified as an upregulated gene in adriamycin‐resistant gastric carcinoma cell line SGC7901/ADR compared to its parental cell line SGC7901. Here we investigate the expression of PrPc in gastric cancer and whether it was involved in multidrug resistance (MDR) of gastric cancer. We demonstrated that PrPc was ubiquitously expressed in gastric cancer cell lines and tissues. PrPc conferred resistance of both P‐glycoprotein (P‐gp)‐related and P‐gp‐nonrelated drugs on SGC7901, which was accompanied by decreased accumulation and increased releasing amount of adriamycin in PrPc‐overexpressing cell line. Inhibition of PrPc expression by antisense or RNAi technology could partially reverse multidrug‐resistant phenotype of SGC7901/ADR. PrPc significantly upregulated the expression of the classical MDR‐related molecule P‐gp but not multidrug resistance associated protein and glutathione S‐transferase pi. The PrPc‐induced MDR could be partially reversed by P‐gp inhibitor verapamil. PrPc could also suppress adriamycin‐induced apoptosis and alter the expression of Bcl‐2 and Bax, which might be another pathway contributing to PrPc‐related MDR. The further study of the biological functions of PrPc may be helpful for understanding the mechanisms of occurrence and development of clinical gastric carcinoma and PrPc‐related MDR and developing possible strategies to treat gastric cancer.

MicroRNA‐107, an oncogene microRNA that regulates tumour invasion and metastasis by targeting DICER1 in gastric cancer

MicroRNAs are small non‐coding RNA molecules that control expression of target genes. Previous studies showed that microRNA‐107 (miR‐107) is overexpressed in gastric cancer tissues compared with the matched normal tissues. However, it remains largely unclear as to how miR‐107 exerts its function and modulates the malignant phenotypes of gastric cancer, because our understanding of miR‐107 signalling pathways is limited. In this study, we demonstrate that miR‐107 is frequently up‐regulated in gastric cancers and its overexpression is significantly associated with gastric cancer metastasis. Furthermore, silencing the expression of miR‐107 could inhibit gastric cancer cell migration and invasion in vitro and in vivo. Subsequent investigation characterized DICER1 as a direct target of miR‐107. Up‐regulation of DICER1 resulted in a dramatic reduction of in vitro migration, invasion, in vivo liver metastasis of nude mice, which is similar to that occurs with the silencing of miR‐107, indicating that DICER1 functions as a metastasis suppressor in gastric cancer. Furthermore, the restoration of DICER1 can inhibit miR‐107‐induced gastric cancer cell invasion and metastasis. In conclusion, our results suggested that miR‐107, an oncogene miRNA promoting gastric cancer metastasis through down‐regulation of DICER1. Inhibition of miR‐107 or restoration of DICER1 may represent a new potential therapeutic target for gastric cancer treatment.