ABSTRACT
BACKGROUND: MicroRNAs play important roles in carcinogenesis. A preliminary screening study suggested that down-regulation of miR-370 occurs in oral squamous cell carcinoma (OSCC) tissue. Insulin receptor substratre-1 (IRS-1) is the substrate of insulin-like growth factor receptor (IGFR), which modulates AKT/mTOR activation in malignancies. The relationship between miR-370 and IRS-1, and their functional roles in OSCC pathogenesis are unclear. MATERIALS AND METHODS: Primary OSCC specimens were examined for miR-370 expression. Exogenous expression of miR-370 was established using both stable subclones and transient expression, and these were used to gain insights into miR-370's functions in OSCC cells. Knockdown of miR-370 and IRS-1 was also carried out in OSCC cells using a small interference oligonucleotide approach. RESULTS: Squamous cell carcinoma tissues with perineural invasion had lowered miR-370 expression compared with contrasting OSCC. OSCC cells also exhibited lower miR-370 expression than normal oral keratinocytes, and this can be reversed by treatment with 5-aza-2'-deoxycytidine. Exogenous miR-370 expression decreases the migration and anchorage-independent growth of OSCC cells, which implies a suppressor role for miR-370. The enhancement of anchorage-independent growth of OSCC cells through miR-370 inhibiting can be reduced by knockdown of IRS-1 expression. CONCLUSION: This study concludes that miR-370 is able to target IRS-1 for oral tumorigenesis.
Subject(s)
Carcinoma, Squamous Cell/pathology , Insulin Receptor Substrate Proteins/physiology , MicroRNAs/physiology , Mouth Neoplasms/pathology , Azacitidine/analogs & derivatives , Azacitidine/pharmacology , Carcinogenesis/pathology , Cell Adhesion/genetics , Cell Culture Techniques , Cell Line, Tumor , Cell Movement/genetics , Cells, Cultured , DNA Modification Methylases/antagonists & inhibitors , Decitabine , Down-Regulation , Gene Expression Regulation, Neoplastic/genetics , Gene Knockdown Techniques , Humans , Insulin Receptor Substrate Proteins/genetics , Keratinocytes/drug effects , Keratinocytes/pathology , MicroRNAs/analysis , MicroRNAs/genetics , Neoplasm Invasiveness , Neoplasm Staging , Oncogene Protein v-akt/physiology , RNA, Small Interfering/genetics , TOR Serine-Threonine Kinases/physiologyABSTRACT
MicroRNAs (miRNAs) are endogenous non-coding RNAs that are known to be involved in the pathogenesis of tumors. Gastric carcinoma (GC) is a common malignancy worldwide. The aim of this study was the identification of the expression signature and functional roles of aberrant miRNAs in GC. Initial screening established a profile of aberrantly expressed miRNAs in tumors. miR-370 was confirmed to be overexpressed in GC tissues. Higher expression of miR-370 in GC tissues was associated with more advanced nodal metastasis and a higher clinical stage compared with controls. In addition, significantly higher level of miR-370 was noted in the plasma of GC patients compared with controls. Patients having more invasive or advanced tumors also exhibited a higher plasma level of miR-370. In vitro assays indicated that exogenous miR-370 expression enhanced the oncogenic potential of GC cells. The AGS-GFPM2 cells with exogenous miR-370 expression also exhibited enhanced abdominal metastatic dissemination in nude mice. Reporter assays confirmed that miR-370 targeted predicted sites in 3'UTR of transforming growth factor-ß receptor II (TGFß-RII) gene. The exogenous miR-370 expression decreased TGFß-RII expression and the phosphorylation of Smad3 elicited by TGFß1. The TGFß1-mediated repression in cell migration was reverted by exogenous miR-370 expression. A reverse correlation between miR-370 and TGFß-RII expression was noted in GC tissues. This study concludes that miR-370 is a miRNA that is associated with GC progression by downregulating TGFß-RII. The miRNA expression profile described in this study should contribute to future studies on the role of miRNAs in GC.
