Caveolin-1 mediates tumor cell migration and invasion and its regulation by miR-133a in head and neck squamous cell carcinoma

MicroRNAs (miRNAs) are small non-coding RNAs of approximately 22 nucleotides that can function as oncogenes or tumor suppressors in human cancer. Down-regulation of the miRNA miR-133a in many type of cancers, and a reduction of cell proliferation, migration, and invasion upon over-expression, suggests that miR-133a is a tumor suppressor. In this study, genome-wide gene expression analysis of HNSCC cells that over-express miR-133a showed that caveolin-1 (CAV1), a multifunctional scaffolding protein, is down-regulated, a result that was confirmed by real-time PCR and Western blot analysis. A luciferase reporter assay revealed that miR-133a is directly bound to CAV1 mRNA. Cancer cell migration and invasion were significantly inhibited in HNSCC cells transfected with si-CAV1. Therefore, CAV1 functions as an oncogene in HNSCC. The identification of tumor suppressive miRNAs and their target genes could provide new insights into potential mechanism of HNSCC carcinogenesis.     

miR-1 as a tumor suppressive microRNA targeting TAGLN2 in head and neck squamous cell carcinoma

Based on the microRNA (miRNA) expression signatures of hypopharyngeal and esophageal squamous cell carcinoma, we found that miR-1 was significantly down-regulated in cancer cells. In this study, we investigated the functional significance of miR-1 in head and neck squamous cell carcinoma (HNSCC) cells and identified miR-1-regulated novel cancer pathways. Gain-of-function studies using miR-1 revealed significant decreases in HNSCC cell proliferation, invasion, and migration. In addition, the promotion of cell apoptosis and cell cycle arrest was demonstrated following miR-1e transfection of cancer cells. A search for the targets of miR-1 revealed that transgelin 2 (TAGLN2) was directly regulated by miR-1. Silencing of TAGLN2 significantly inhibited cell proliferation and invasion in HNSCC cells. Down-regulation of miR-1 and up-regulation of TAGLN2 were confirmed in HNSCC clinical specimens. Our data indicate that TAGLN2 may have an oncogenic function and may be regulated by miR-1, a tumor suppressive miRNA in HNSCC. The identification of novel miR-1-regulated cancer pathways could provide new insights into potential molecular mechanisms of HNSCC carcinogenesis.     

Replisome genes regulation by antitumor miR‐101‐5p in clear cell renal cell carcinoma

Analysis of microRNA (miRNA) regulatory networks is useful for exploring novel biomarkers and therapeutic targets in cancer cells. The Cancer Genome Atlas dataset shows that low expression of both strands of pre‐miR‐101 (miR‐101‐5p and miR‐101‐3p) significantly predicted poor prognosis in clear cell renal cell carcinoma (ccRCC). The functional significance of miR‐101‐5p in cancer cells is poorly understood. Here, we focused on miR‐101‐5p to investigate the antitumor function and its regulatory networks in ccRCC cells. Ectopic expression of mature miRNAs or siRNAs was investigated in cancer cell lines to characterize cell function, ie, proliferation, apoptosis, migration, and invasion. Genome‐wide gene expression and in silico database analyses were undertaken to predict miRNA regulatory networks. Expression of miR‐101‐5p caused cell cycle arrest and apoptosis in ccRCC cells. Downstream neighbor of son (DONSON) was directly regulated by miR‐101‐5p, and its aberrant expression was significantly associated with shorter survival in propensity score‐matched analysis (P = .0001). Knockdown of DONSON attenuated ccRCC cell aggressiveness. Several replisome genes controlled by DONSON and their expression were closely associated with ccRCC pathogenesis. The antitumor miR‐101‐5p/DONSON axis and its modulated replisome genes might be a novel diagnostic and therapeutic target for ccRCC.     

Tumor suppressive microRNA-375 regulates oncogene AEG-1/MTDH in head and neck squamous cell carcinoma (HNSCC)

Our microRNA (miRNA) expression signatures of hypopharyngeal squamous cell carcinoma, maxillary sinus squamous cell carcinoma and esophageal squamous cell carcinoma revealed that miR-375 was significantly reduced in cancer tissues compared with normal epithelium. In this study, we focused on the functional significance of miR-375 in cancer cells and identification of miR-375-regulated novel cancer networks in head and neck squamous cell carcinoma (HNSCC). Restoration of miR-375 showed significant inhibition of cell proliferation and induction of cell apoptosis in SAS and FaDu cell lines, suggesting that miR-375 functions as a tumor suppressor. We adopted genome-wide gene expression analysis to search for miR-375-regulated molecular targets. Gene expression data and luciferase reporter assays revealed that AEG-1/MTDH was directly regulated by miR-375. Cancer cell proliferation was significantly inhibited in HNSCC cells transfected with si-AEG-1/MTDH. In addition, expression levels of AEG-1/MTDH were significantly upregulated in cancer tissues. Therefore, AEG-1/MTDH may function as an oncogene in HNSCC. The identification of novel tumor suppressive miRNA and its regulated cancer pathways could provide new insights into potential molecular mechanisms of HNSCC oncogenesis.     

The functional significance of microRNA-375 in human squamous cell carcinoma: aberrant expression and effects on cancer pathways

MicroRNAs (miRNAs) are a class of small, non-coding RNA molecules consisting of 19-22 nucleotides that are involved in a variety of biological processes, including development, differentiation, apoptosis and cell proliferation. In cancer research, a growing body of evidence has indicated that miRNAs are aberrantly expressed in many types of human cancers and can function either as tumor suppressors or oncogenes. Bioinformatic predictions suggest that miRNAs regulate more than 30% of protein-coding genes. Aberrant expression of miRNAs in cancer cells causes destruction of miRNA-regulated messenger RNA networks. Therefore, the identification of miRNA-regulated cancer pathways is important for understanding the molecular mechanisms of human cancer. Searching for the aberrant expression of miRNAs in cancer cells is the first step in the functional analysis of miRNAs in cancer cells. Genome-wide miRNA expression signatures can rapidly and precisely reveal aberrant expression of miRNA in cancers. The miRNA expression signatures of human cancers have revealed that miR-375 is significantly downregulated in cancer cells. Our recent data on maxillary sinus, hypopharyngeal and esophageal squamous cell carcinomas have suggested that miR-375 is frequently downregulated and functions as a tumor suppressor that targets several oncogenic genes in cancer cells. In this review, we focus on several types of human squamous cell carcinoma and describe the aberrant expression of miRNAs and the cancer pathways they regulate in these diseases.     

Tumor suppressive microRNA‑138 contributes to cell migration and invasion through its targeting of vimentin in renal cell carcinoma

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 microRNA?138 (miR?138) was significantly reduced in cancer cells. The aim of the present study was to investigate the functional significance of miR?138 and to identify its target genes in RCC cells. Restoration of mature miR?138 in two RCC cell lines (A498 and 786?O) 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 miR?138 functions as a tumor suppressor. Genome-wide gene expression analysis (miR?138 transfectants and RCC clinical specimens) and TargetScan database studies showed that vimentin (VIM) is a promising candidate target gene of miR?138. 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 miR?138 and contributed to cancer cell migration and invasion in RCC cells. Restoration of miR?138 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 miR?138. The existence of a tumor suppressive miR?138-mediated oncogenic pathway provides new insights into the potential mechanisms of RCC oncogenesis and metastasis.     

Tumor suppressive microRNA-375 regulates lactate dehydrogenase B in maxillary sinus squamous cell carcinoma

The expression of microRNA-375 (miR-375) is significantly reduced in cancer tissues of maxillary sinus squamous cell carcinoma (MSSCC). The aim of this study was to investigate the functional significance of miR-375 and a possible regulatory role in the MSSCC networks. Restoration of miR-375 significantly inhibited cancer cell proliferation and invasion in IMC-3 cells, suggesting that miR-375 functions as a tumor suppressor in MSSCC. Genome-wide gene expression data and luciferase reporter assays indicated that lactate dehydro-genase?B (LDHB) was directly regulated by miR-375. Cancer cell proliferation and invasion were significantly inhibited by transfection of si-LDHB into IMC-3 cells, suggesting that LDHB may play a role in MSSCC oncogenic function. In clinical MSSCC specimens, LDHB mRNA levels were up-regulated in cancer tissues, which were inversely correlated with the expression of miR-375. In addition, Kaplan-Meier curves and log-rank tests revealed that the high mRNA expression levels of LDHB had a significant adverse effect on survival rate. The identification of a cancer network regulated by the miR-375 tumor suppressor could provide new insights into the molecular mechanisms of MSSCC oncogenesis.     

Actin-related protein 2/3 complex subunit 5 (ARPC5) contributes to cell migration and invasion and is directly regulated by tumor-suppressive microRNA-133a in head and neck squamous cell carcinoma

Our expression signatures of human cancers including head and neck squamous cell carcinoma (HNSCC) demonstrated that downregulation of microRNA-133a (miR-133a) were frequently observed in cancer cells. The restoration of miR-133a in cancer cells revealed that it functions as a tumor suppressor. In this study, we investigated the novel molecular targets of miR-133a in HNSCC cancer cells and its oncogenic function, especially as it contributes to cancer cell migration and invasion. The genome-wide gene expression analysis and bioinformatics study showed that actin-related protein 2/3 complex subunit 5 (ARPC5) is a candidate target of miR-133a. Furthermore, luciferase reporter assay demonstrated that ARPC5 is directly regulated by miR-133a. Silencing of ARPC5 revealed significant inhibition of cell migration and invasion in HNSCC cell lines, SAS, HSC3 and IMC-3. In HSC3 cells, restoration of miR-133a or silencing ARPC5 led to a reorganization of the actin cytoskeleton and a subsequent change in cell morphology to a round, bleb-like shape. The expression levels of ARPC5 were significantly higher in HNSCC tissues than in non-cancer tissues. Immunohistochemistry showed that the levels of ARPC5 expression were significantly higher in invasive cancer cells. ARPC5 contributed to cancer cell migration and invasion in HNSCC and this gene was directly regulated by miR-133a. Our analysis of novel tumor-suppressive miR?133a-mediated cancer pathways provides new insights into the potential mechanisms of HNSCC oncogenesis.     

Identification of novel molecular targets regulated by tumor suppressive miR-1/miR-133a in maxillary sinus squamous cell carcinoma

Based on our microRNA (miRNA) expression signature analysis of maxillary sinus squamous cell carcinoma (MSSCC), we found that miR-1 and miR-133a were significantly reduced in tumor tissues. Quantitative real-time RT-PCR revealed that the expression levels of miR-1 and miR-133a were significantly downregulated in clinical MSSCC tumor tissues compared with normal tissues. We focused on the functional significance of miR-1 and miR-133a in cancer cells and identification of the novel cancer networks regulated by these miRNAs in MSSCC. Restoration of downregulated miRNAs (miR-1 or miR-133a) in cancer cells revealed that both miRNAs significantly inhibited cancer cell proliferation and induced cell apoptosis. Molecular target identification of these miRNAs showed that transgelin 2 (TAGLN2) and purine nucleoside phosphorylase (PNP) were regulated by miR-1 and miR-133a. Both TAGLN2 and PNP mRNA expression levels were significantly upregulated in clinical MSSCC tumor tissues. Silencing studies of target genes demonstrated that both genes inhibited cancer cell proliferation. The identification of novel miR-1/miR-133a-regulated cancer pathways could provide new insights into potential molecular mechanisms of MSSCC oncogenesis.