406987

MIR204

microRNA 204;MIR204;microRNA 204

hsa-mir-204

9q21.12

ncRNA

BACKGROUND: Our previous studies showed that SIRT1 was over-expressed in gastric cancer specimens and related with lymph node metastasis. However, the mechanism of SIRT1 up-regulation and its association with metastasis in gastric cancer remain unclear. The present study was undertaken to understand the role of microRNA in regulation of SIRT1 in the progression of gastric cancer. METHODS: expression of miR-204 and SIRT1 was assessed in two gastric cancer cell lines and 24 matched cancer specimens. Luciferase reporter assay was carried to verify that miR-204 targeting SIRT1. Cell invasion ability of AGS and BGC was detected by transwell invasion assay. Annexin V/PI assay was used to investigate the cell sensitivity of anoikis. Western blot analysis to assess SIRT1, Vimentin, E-Cadherin, LKB1, and beta-actin expression was performed in gastic cancer cell lines. RESULTS: SIRT1 was defined as the target gene and elucidated the biological functions of miR-204 with a luciferase reporter assay and Western blot analysis. We verified that miR-204 levels were down-regulated and significantly associated with the up-regulation of SIRT1 mRNA levels in gastric cancer specimens. Over-expression of miR-204 reduced cell invasion and anoikis resistance in gastric cancer cells. Up-regulation of miR-204 influenced the levels of the epithelial mesenchymal transition (EMT)-associated genes, increasing E-cadherin levels and decreasing Vimentin levels. We demonstrated that the regulation of EMT by miR-204 involves cooperation with LKB1. Furthermore, silencing of SIRT1 phenocopied the effects of miR-204 in gastric cancer cells. These data demonstrate that miR-204 plays an important role in regulating metastasis of gastric cancer, which is involved in post-transcriptional repression of SIRT1. CONCLUSION: Our results suggest that down-regulation of miR-204 promotes gastric cancer cell invasion by activating the SIRT1-LKB1 pathway. These data demonstrate that miR-204 plays an important role in regulating metastasis of gastric cancer, which is involved in post-transcriptional repression of SIRT1.

BACKGROUND/AIMS: MicroRNAs (miRNAs) play critical roles during carcinogenesis and cancer progression. Down-regulation of miR-204 has been frequently observed in various cancers. In this study, we investigated the roles and mechanisms of miR-204 in human intrahepatic cholangiocarcinoma (ICC). METHODS: The relative expression of miR-204 in ICC tissues and cell lines was monitored by qRT-PCR. Effects of miR-204 were studied in human ICC cell lines HuH28 and HuCCT1, and cells were analyzed for proliferation, migration and invasion. expression levels of miR-204 target gene Slug and EMT markers (E-cadherin and vimentin) in ICC cell lines and tissues were measured by qRT-PCR, western blotting and immunofluorescence. RESULTS: miR-204 was frequently downregulated in human ICC, and the low-level expression of miR-204 was significantly associated with lymph node metastasis. Overexpression of miR-204 dramatically suppressed ICC cell migration and invasion, as well as the epithelial-mesenchymal transition process (EMT). Slug was identified as a direct target of miR-204, and its downregulation by miR-204 in HuH28 cells reversed EMT, as shown by the increased expression of the epithelial marker E-cadherin and decreased expression of the mesenchymal marker vimentin. CONCLUSION: These findings suggest that miR-204 plays negative roles in the invasive and/or metastatic potential of ICC, and that its suppressive effects are mediated by repressing Slug expression.

Increasing evidence suggests that chromosomal regions containing microRNAs are functionally important in cancers. Here, we show that genomic loci encoding miR-204 are frequently lost in multiple cancers, including ovarian cancers, pediatric renal tumors, and breast cancers. MiR-204 shows drastically reduced expression in several cancers and acts as a potent tumor suppressor, inhibiting tumor metastasis in vivo when systemically delivered. We demonstrated that miR-204 exerts its function by targeting genes involved in tumorigenesis including brain-derived neurotrophic factor (BDNF), a neurotrophin family member which is known to promote tumor angiogenesis and invasiveness. Analysis of primary tumors shows that increased expression of BDNF or its receptor tropomyosin-related kinase B (TrkB) parallel a markedly reduced expression of miR-204. Our results reveal that loss of miR-204 results in BDNF overexpression and subsequent activation of the small GTPase Rac1 and actin reorganization through the AKT/mTOR signaling pathway leading to cancer cell migration and invasion. These results suggest that microdeletion of genomic loci containing miR-204 is directly linked with the deregulation of key oncogenic pathways that provide crucial stimulus for tumor growth and metastasis. Our findings provide a strong rationale for manipulating miR-204 levels therapeutically to suppress tumor metastasis.