Metastasis is a critical event in the progression of head and neck squamous cell carcinoma (HNSCC). To identify microRNAs associated with HNSCC metastasis, 6 paired HNSCC cell lines with different metastatic potential were examined. Using microarrays, a panel of differentially expressed microRNAs was identified, including reduction of miR-138 in highly metastatic cells. Ectopic transfection of miR-138 suppressed cell invasion and led to cell cycle arrest and apoptosis. Knockdown of miR-138 enhanced cell invasion and suppressed apoptosis. Thus, our results suggested miR-138 acts as a tumor suppresser and may serve as a therapeutic target for HNSCC patients at risk of metastasis.

Tumor metastasis is the dominant cause of death in cancer patients, including patients with oral tongue squamous cell carcinoma (TSCC). Previously, we reported that reduced miR-138 level is correlated with enhanced metastatic potential in TSCC cells. Here, we demonstrate that miR-138 suppresses TSCC cell migration and invasion by regulating 2 key genes in the Rho GTPase signaling pathway: RhoC and ROCK2. Direct targeting of miR-138 to specific sequences located in the 3 0 -untranslated regions of both RhoC and ROCK2 mRNAs was confirmed using luciferase reporter gene assays. Ectopic transfection of miR-138 reduced the expression of both RhoC and ROCK2 in TSCC cells. These reduced expressions, in consequence, led to the reorganization of the stress fibers and the subsequent cell morphology change to a round bleb-like shape as well as the suppression of cell migration and invasion. In contrast, knockdown of miR-138 in TSCC cells enhanced the expression of RhoC and ROCK2, which resulted in an altered, elongated cell morphology, enhanced cell stress fiber formation and accelerated cell migration and invasion. Taken together, our results suggest that miR-138 plays an important role in TSCC cell migration and invasion by concurrently targeting RhoC and ROCK2, and miR-138 may serve as a novel therapeutic target for TSCC patients at risk of metastatic disease.Oral cancer, predominately oral squamous cell carcinomas (OSCC), is one of the most devastating diseases. Oral tongue squamous cell carcinomas (TSCC), one of the major subtypes of OSCC, is significantly more aggressive than other forms of OSCCs, with a propensity for rapid local invasion, spread 1 and a high recurrence rate. 2 Despite improvements in surgery, radiotherapy and chemotherapy, the prognosis for TSCC patients has not significantly improved for the past 3 decades. Improvement in patient survival requires better understanding of tumor invasion and metastasis so that aggressive tumors can be detected early in the disease process, and so that targeted therapeutic interventions can be developed. Although attempts have been made to identify genomic alterations that contribute to the aggressive phenotype of TSCC, most of these studies focus on protein-coding genes. Our knowledge of genomic aberrations associated with noncoding genes (e.g., microRNA) and their contributions to cancer initiation and progression is relatively limited.MicroRNAs (miRNAs) are noncoding small RNAs that control the target gene expression at the posttranscriptional level. It is currently estimated that the human genome may have more than 1,000 miRNAs. Although they account for only a minor fraction of the expressed genome, miRNAs are essential regulators of diverse cellular processes including proliferation, differentiation, apoptosis, survival, motility and morphogenesis. Several miRNAs are believed to influence metastasis in various cancer types. These include: miR-23b, which reduces cell migration by targeting urokinase and cmet in hepatocellular carcinoma cells, 3 miR-222, which sup...

miR-7 (microRNA-7) has been characterized as a tumour suppressor in several human cancers. It targets a number of proto-oncogenes that contribute to cell proliferation and survival. However, the mechanism(s) by which miR-7 suppresses tumorigenesis in TSCC (tongue squamous cell carcinoma) is unknown. The present bioinformatics analysis revealed that IGF1R (insulin-like growth factor 1 receptor) mRNA is a potential target for miR-7. Ectopic transfection of miR-7 led to a significant reduction in IGF1R at both the mRNA and protein levels in TSCC cells. Knockdown of miR-7 in TSCC cells enhanced IGF1R expression. Direct targeting of miR-7 to three candidate binding sequences located in the 3′-untranslated region of IGF1R mRNA was confirmed using luciferase-reporter-gene assays. The miR-7-mediated down-regulation of IGF1R expression attenuated the IGF1 (insulin-like growth factor 1)-induced activation of Akt (protein kinase B) in TSCC cell lines, which in turn resulted in a reduction in cell proliferation and cell-cycle arrest, and an enhanced apoptotic rate. Taken together, the present results demonstrated that miR-7 regulates the IGF1R/Akt signalling pathway by post-transcriptional regulation of IGF1R. Our results indicate that miR-7 plays an important role in TSCC and may serve as a novel therapeutic target for TSCC patients.

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