Identification and experimental validation of G protein alpha inhibiting activity polypeptide 2 (GNAI2) as a microRNA-138 target in tongue squamous cell carcinoma

Abstract

MicroRNA deregulation is a critical event in tumor initiation and progression. The down-regulation of microRNA-138 has been frequently observed in various cancers, including tongue squamous cell carcinoma (TSCC). Our previous studies suggest that deregulation of miR-138 is associated with the enhanced proliferation and invasion in TSCC cells. Here, we seek to identify the targets of miR-138 in TSCC, and explore their functional relevance in tumorigenesis. Our genome-wide expression profiling experiments identified a panel of 194 unique transcripts that were significantly down-regulated in TSCC cells transfected with miR-138. A comprehensive screening using six different sequence-based microRNA target prediction algorithms revealed that 51 out of these 194 down-regulated transcripts are potential direct targets for miR-138. These targets include: chloride channel, nucleo-tide-sensitive, 1A (CLNS1A), G protein alpha inhibiting activity polypeptide 2 (GNAI2), solute carrier family 20, member 1 (SLC20A1), eukaryotic translation initiation factor 4E binding protein 1 (EIF4EBP1), and Rho-related GTP-binding protein C (RhoC). GNAI2 is a known proto-oncogene that is involved in the initiation and progression of several different types of tumors. Direct targeting of miR-138 to two candidate binding sequences located in the 3′-untranslated region of GNAI2 mRNA was confirmed using luciferase reporter gene assays. Knockdown of miR-138 in TSCC cells enhanced the expression of GNAI2 at both mRNA and protein levels. In contrast, ectopic trans-fection of miR-138 reduced the expression of GNAI2, which, in consequence, led to reduced proliferation, cell cycle arrest and apoptosis. In summary, we identified a number of high-confident miR-138 target genes, including proto-oncogene GNAI2, which may play an important role in TSCC initiation and progression.

Molecular Characterization of the MicroRNA-138-Fos-like Antigen 1 (FOSL1) Regulatory Module in Squamous Cell Carcinoma

“…Our previous study suggested that restoring miR-138 in the HNSCC cell line UM1 led to a significant reduction of FOSL1 mRNA (17). As illustrated in Fig.…”

“…We previously identified 194 genes that were significantly down-regulated by miR-138 (based on microarray analysis on HNSCC cells that were ectopically transfected with miR-138) (17). Bioinformatics analysis identified miR-138 targeting sites in the 3Ј-UTR of 51 out of 194 genes.…”

MicroRNA-138 suppresses proliferation, invasion and glycolysis in malignant melanoma cells by targeting HIF-1α

“…Previously, deregulation of miR-138 was demonstrated to be associated with multiple types of human malignancies, generally acting as a tumor suppressor (23,24). For instance, miR-138 is able to suppress invasion and promote apoptosis in head and neck squamous cell carcinoma cells, via inhibition of the Rho GTPase signaling pathway (25)(26)(27). In addition, miR-138 was found to suppress epithelial-mesenchymal transition in squamous cell carcinoma cell lines, suggesting that it may serve a crucial function in the metastasis of squamous cell carcinoma (28).…”

Downregulation of miR-138 Sustains NF-κB Activation and Promotes Lipid Raft Formation in Esophageal Squamous Cell Carcinoma

“…miR-138 has been found to be downregulated in multiple human cancers, and downregulation of miR-138 contributes to cancer cell proliferation and invasion and inhibits apoptosis via different mechanisms (33)(34)(35)(36)(37)(38)(39)(40). However, the expression of miR-138 has also been shown to be upregulated in tumor-initiating glioma stem cells (GSC) compared with nonneoplastic tissues, and upregulation of miR-138 is associated with tumor recurrence and survival (41).…”