For patients with head and neck squamous cell carcinoma (HNSCC), survival rates have not improved due to local recurrence and distant metastasis. Current targeted molecular therapies do not substantially benefit HNSCC patients. Therefore, it is necessary to use advanced genomic approaches to elucidate the molecular mechanisms underlying the aggressiveness of HNSCC cells. Analysis of our microRNA (miRNA) expression signature by RNA sequencing showed that the miR‐199 family (miR‐199a‐5p, miR‐199a‐3p, miR‐199b‐5p and miR‐199b‐3p) was significantly reduced in cancer tissues. Ectopic expression of mature miRNA demonstrated that all members of the miR‐199 family inhibited cancer cell migration and invasion by HNSCC cell lines (SAS and HSC3). These findings suggested that both passenger strands and guide strands of miRNA are involved in cancer pathogenesis. In silico database and genome‐wide gene expression analyses revealed that the gene coding for integrin α3 (ITGA3) was regulated by all members of the miR‐199 family in HNSCC cells. Knockdown of ITGA3 significantly inhibited cancer cell migration and invasion by HNSCC cells. Moreover, overexpression of ITGA3 was confirmed in HNSCC specimens, and high expression of ITGA3 predicted poorer survival of the patients (P = 0.0048). Our data revealed that both strands of pre‐miR‐199a (miR‐199a‐5p and miR‐199a‐3p) and pre‐miR‐199b (miR‐199b‐5p and miR‐199b‐3p) acted as anti‐tumor miRNA in HNSCC cells. Importantly, the involvement of passenger strand miRNA in the regulation of cellular processes is a novel concept in RNA research. Novel miRNA‐based approaches for HNSCC can be used to identify potential targets for the development of new therapeutic strategies.

We adopted into RNA-sequencing technologies to construct the microRNA (miRNA) expression signature of head and neck squamous cell carcinoma (HNSCC). Our signature revealed that a total of 160 miRNAs (44 upregulated and 116 downregulated) were aberrantly expressed in cancer tissues. Expression of miR-150-5p (guide strand miRNA) and miR-150-3p (passenger strand miRNA) were significantly silenced in cancer tissues, suggesting both miRNAs act as antitumor miRNAs in HNSCC cells. Ectopic expression of mature miRNAs, miR-150-5p and miR-150-3p inhibited cancer cell aggressiveness. Low expression of miR-150-5p and miR-150-3p predicted significantly shorter overall survival in patients with HNSCC (P = 0.0091 and P = 0.0386) by Kaplan–Meier survival curves analyses. We identified that integrin α3 (ITGA3), integrin α6 (ITGA6), and tenascin C (TNC) were coordinately regulated by these miRNAs in HNSCC cells. Knockdown assays using siRNAs showed that ITGA3, ITGA6 and TNC acted as cancer promoting genes in HNSCC cells. Moreover, ITGA3, ITGA6, and TNC alterations were associated with significantly poorer overall survival (P = 0.0177, P = 0.0237, and P = 0.026, respectively). Dual strands of pre-150 (miR-150-5p and miR-150-3p) functioned as antitumor miRNAs based on the miRNA expression signature of HNSCC. Identification of antitumor miR-150-mediated RNA networks may provide novel insights into pathogenesis of HNSCC.

Background:MicroRNAs (miRNAs) have been shown to play major roles in carcinogenesis in a variety of cancers. The aim of this study was to determine the miRNA expression signature of oral squamous cell carcinoma (OSCC) and to investigate the functional roles of miR-26a and miR-26b in OSCC cells.Methods:An OSCC miRNA signature was constructed by PCR-based array methods. Functional studies of differentially expressed miRNAs were performed to investigate cell proliferation, migration, and invasion in OSCC cells. In silico database and genome-wide gene expression analyses were performed to identify molecular targets and pathways mediated by miR-26a/b.Results:miR-26a and miR-26b were significantly downregulated in OSCC. Restoration of both miR-26a and miR-26b in cancer cell lines revealed that these miRNAs significantly inhibited cancer cell migration and invasion. Our data demonstrated that the novel transmembrane TMEM184B gene was a direct target of miR-26a/b regulation. Silencing of TMEM184B inhibited cancer cell migration and invasion, and regulated the actin cytoskeleton-pathway related genes.Conclusions:Loss of tumour-suppressive miR-26a/b enhanced cancer cell migration and invasion in OSCC through direct regulation of TMEM184B. Our data describing pathways regulated by tumour-suppressive miR-26a/b provide new insights into the potential mechanisms of OSCC oncogenesis and metastasis.

Patients with lung adenocarcinoma may benefit from recently developed molecular targeted therapies. However, analogous advanced treatments are not available for patients with lung squamous cell carcinoma (lung SCC). The survival rate of patients with the advanced stage of lung SCC remains poor. Exploration of novel lung SCC oncogenic pathways might lead to new treatment protocols for the disease. Based on this concept, we have identified microRNA-(miRNA) mediated oncogenic pathways in lung SCC. It is well known that miR-145-5p (the guide strand) functions as a tumor suppressor in several types of cancer. However, the impact of miR-145-3p (the passenger strand) on cancer cells is still ambiguous. Expression levels of miR-145-5p and miR-145-3p were markedly reduced in cancer tissues, and ectopic expression of these miRNAs inhibited cancer cell aggressiveness, suggesting that both miR-145-3p as well as miR-145-5p acted as antitumor miRNAs. We identified seven putative target genes (MTDH, EPN3, TPD52, CYP27B1, LMAN1, STAT1 and TXNDC12) that were coordinately regulated by miR-145-5p and miR-145-3p in lung SCC. Among the seven genes, we found that metadherin (MTDH) was a direct target of these miRNAs. Kaplan-Meier survival curves showed that high expression of MTDH predicted reduced survival of lung SCC patients. We investigated pathways downstream from MTDH by using genome-wide gene expression analysis. Our data showed that several anti-apoptosis and pro-proliferation genes were involved in pathways downstream from MTDH in lung SCC. Taken together, both strands of miR-145, miR-145-5p and miR-145-3p are functional and play pivotal roles as antitumor miRNAs in lung SCC.

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive malignancies. Recently developed molecular targeted therapies are not available for patients with ESCC. After curative surgical resection, patients frequently suffer distant metastasis and recurrence. Exploration of novel ESCC metastatic pathways may lead to the development of new treatment protocols for this disease. Accordingly, we have sequentially identified microRNA (miRNA)-mediated metastatic pathways in several cancers. Our past studies of miRNA expression signatures have shown that microRNA-375 (miR-375) is frequently reduced in several types of cancers, including ESCC. In the present study, we aimed to investigate novel miR-375-mediated metastatic pathways in ESCC cells. The expression of miR-375 was downregulated in ESCC tissues, and ectopic expression of this miRNA markedly inhibited cancer cell migration and invasion, suggesting that miR-375 acted as an antimetastatic miRNA in ESCC cells. Our strategies for miRNA target searching demonstrated that matrix metalloproteinase 13 (MMP13) was directly regulated by miR-375 in ESCC cells. Overexpression of MMP13 was observed in ESCC clinical tissues, and the expression of MMP13 promoted cancer cell aggressiveness. Moreover, oncogenic genes, including CENPF, KIF14 and TOP2A, were shown to be regulated downstream of MMP13. Taken together, these findings demonstrated that the antitumor miR-375/oncogenic MMP13 axis had a pivotal role in ESCC aggressiveness. These results provide novel insights into the potential mechanisms of ESCC pathogenesis.