ABSTRACT
The microRNA-371-373 (miR-371-373) cluster is specifically expressed in human embryonic stem cells (ESCs) and is thought to be involved in stem cell maintenance. Recently, microRNAs (miRNAs) of this cluster were shown to be frequently upregulated in several human tumors. However, the regulatory mechanism for the involvement of the miR-371-373 cluster in human ESCs or cancer cells remains unclear. In this study, we explored the relationship between this miRNA cluster and the Wnt/ß-catenin-signaling pathway, which has been shown to be involved in both stem cell maintenance and tumorigenesis. We show that miR-371-373 expression is induced by lithium chloride and is positively correlated with Wnt/ß-catenin-signaling activity in several human cancer cell lines. Mechanistically, three TCF/LEF1-binding elements (TBEs) were identified in the promoter region and shown to be required for Wnt-dependent activation of miR-371-373. Interestingly, we also found that miR-372&373, in turn, activate Wnt/ß-catenin signaling. In addition, four protein genes related to the Wnt/ß-catenin-signaling pathway were identified as direct targets of miR-372&373, including Dickkopf-1 (DKK1), a well-known inhibitor of Wnt/ß-catenin signaling. Using a lentiviral system, we showed that overexpression of miR-372 or miR-373 promotes cell growth and the invasive activity of tumor cells as knockdown of DKK1. Taken together, our study demonstrates a novel ß-catenin/LEF1-miR-372&373-DKK1 regulatory feedback loop, which may have a critical role in regulating the activity of Wnt/ß-catenin signaling in human cancer cells.
Subject(s)
Lymphoid Enhancer-Binding Factor 1/metabolism , MicroRNAs/biosynthesis , Wnt Signaling Pathway , beta Catenin/metabolism , Cell Line, Tumor , Cell Proliferation/drug effects , Humans , Intercellular Signaling Peptides and Proteins/metabolism , Lithium Chloride/pharmacology , Lymphoid Enhancer-Binding Factor 1/genetics , Neoplasm Invasiveness , Promoter Regions, Genetic , beta Catenin/geneticsABSTRACT
Hexagonal cadmium selenide (CdSe) nanowires, with diameter around 20 nm, were synthesized using a simple vapor-phase growth. Silicon (Si) powder acts as a source material assisting the synthesis, which is very important to the formation of the CdSe nanowires. We also suggest that self-catalysis at the Cd-terminated (0001) surface, together with the assistance action of Si, leads to the formation of wire-like structures to be formed. Meanwhile, the assistance of Si is responsible for the fineness and uniformity of the CdSe nanowires. The possible growth mechanism of the CdSe nanowires is proposed, and the optical property of the as-grown CdSe nanowires is characterized.
Subject(s)
Cadmium Compounds/chemistry , Nanotechnology , Selenium Compounds/chemistry , Silicon/chemistry , Crystallization , Microscopy, Electron, ScanningABSTRACT
Three kinds of lectins (UEA-I, ConA, PNA) were used to study normal, dysplastic, neoplastic nasopharyngeal epithelium by lectin affinitive histochemical method. UEA-I (ulex europeus agglutinin-I) displayed membrane distribution in normal squamous epithelium, but most of nasopharyngeal carcinoma cells were negative. Notably, severe dysplastic epithelium (precancerous lesion) exhibited a strong membranous and cytoplasmic affinity, which contrasted sharply with the normal epithelium and carcinoma cells. The statistically significant difference in the content and distribution of lectin UEA-I in these three groups suggest that UEA-I is a hopeful marker for diagnosing precancerous lesion of the nasopharynx. However, PNA and ConA are of less diagnostic value.
