406929

MIR138-1

MIRN138-1;microRNA 138-1;MIR138-1;microRNA 138-1

hsa-mir-138-1

3p21.32

ncRNA

Metastasis is a critical event in the progression of head and neck squamous cell carcinoma (HNSCC). To identify microRNAs associated with HNSCC metastasis, six 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.

The microRNA miR-138 is dysregulated in several human cancers, but the underlying mechanism remains largely unknown. Here, we report that miR-138 is commonly underexpressed in nasopharyngeal carcinoma (NPC) specimens and NPC cell lines. The ectopic expression of miR-138 dramatically suppressed cell proliferation and colony formation in vitro and inhibited tumorigenesis in vivo. Moreover, we identified the cyclin D1 (CCND1) gene as a novel direct target of miR-138. In consistent with the knocked-down expression of CCND1, overexpression of miR-138 inhibited cell growth and cell cycle progression in NPC cells. Furthermore, CCND1 was widely upregulated in NPC tumors, and its mRNA levels were inversely correlated with miR-138 expression. Taken together, our findings suggest that miR-138 might be a tumor suppressor in NPC, which is exerted partially by inhibiting CCND1 expression. The identification of functional miR-138 in NPC and its direct link to CCND1 might provide good candidates for developing diagnostic markers and therapeutic applications for NPC.

Many studies have recently suggested that microRNAs (miRNAs) contribute to the development of various types of human cancers as well as to their invasive and metastatic capacities. Previously, our miRNA expression signature of renal cell carcinoma (RCC) revealed that microRNA138 (miR138) was significantly reduced in cancer cells. The aim of the present study was to investigate the functional significance of miR138 and to identify its target genes in RCC cells. Restoration of mature miR138 in two RCC cell lines (A498 and 786O) caused changes in the bleb-like cell morphology, characteristics of the epithelial-mesenchymal transition (EMT). Restoration also significantly inhibited migration and invasion in the two RCC cell lines, suggesting that miR138 functions as a tumor suppressor. Genome-wide gene expression analysis (miR138 transfectants and RCC clinical specimens) and TargetScan database studies showed that vimentin (VIM) is a promising candidate target gene of miR138. It is well known that VIM is one of the most widely expressed mammalian intermediate filament proteins. Recent studies showed that VIM functions in cell adhesion, migration, survival and cell signaling processes via dynamic assembly/disassembly in cancer cells. We focused on VIM and investigated whether VIM was regulated by tumor suppressive miR138 and contributed to cancer cell migration and invasion in RCC cells. Restoration of miR138 in RCC cell lines suppressed VIM expression at both the mRNA and protein levels. Silencing studies of VIM in RCC cell lines demonstrated significant inhibition of cell migration and invasion activities in si-VIM transfectants. In clinical specimens of RCC, the expression levels of VIM were significantly upregulated in cancer tissues compared to adjacent non-cancerous tissues. Furthermore, immunohistochemistry showed that VIM expression levels in RCC specimens were significantly higher than those in normal renal tissues. These data suggest that VIM may function as an oncogene and is regulated by tumor suppressive miR138. The existence of a tumor suppressive miR138-mediated oncogenic pathway provides new insights into the potential mechanisms of RCC oncogenesis and metastasis.

The expression of neutrophil gelatinase-associated lipocalin (NGAL) is up-regulated in some cancers; therefore NGAL has potential as a tumor biomarker. Although the regulation mechanism for this is unknown, one study has shown that it is likely to involve a microRNA (miRNA). Here, we investigate the relation between miRNA expression and NGAL expression, and the role of NGAL in tumorigenesis. Using miRNA target-detecting software, we analyze the mRNA sequence of NGAL and identify a target site for microRNA-138 (miR-138) in nucleotides 25-53 of the 3 UTR. We then analyze NGAL and miR-138 expression in three cancer cell lines originating from breast, endometrial and pancreatic carcinomas (the MCF-7, RL95-2 and AsPC-1 cell lines), respectively, using quantitative (real-time) PCR and western blot analysis. Metastasis is a critical event in cancer progression, in which malignant cell proliferation, migration and invasion increase. To determine whether miR-138-regulated NGAL expression is associated with metastasis, the proliferation and migration of the cell line are examined after miR-138 transfection. Using nude mice, we examine both the tumorigenicity of these cell lines and of miR-138-transfected cancer cells in vivo, as well as the effect of treating tumors with an antibody against NGAL. Our results show that these cancer cell lines down-regulate NGAL when miR-138 is highly expressed. Ectopic transfection of miR-138 suppresses NGAL expression and cell migration in RL95-2 and AsPC-1 cells, demonstrating that miR-138-regulated NGAL expression is associated with cell migration. Additionally, injection of the NGAL antibody diminishes NGAL-mediated tumorigenesis in nude mice, and miR-138 transfection of cancer cells reduces tumor formation. As the cell proliferation data showed that the tumor size should be regulated by NGAL-related cell growth. Taken together, our results indicate that NGAL may be a good target for cancer therapy and suggest that miR-138 acts as a tumor suppressor and may prevent metastasis.