A Possible Role of FZD10 Delivering Exosomes Derived from Colon Cancers Cell Lines in Inducing Activation of Epithelial-Mesenchymal Transition in Normal Colon Epithelial Cell Line.

Exosomes belong to the family of extracellular vesicles released by every type of cell both in normal and pathological conditions. Growing interest in studies indicates that extracellular vesicles, in particular, the fraction named exosomes containing lipids, proteins and nucleic acid, represent an efficient way to transfer functional cargoes between cells, thus combining all the other cell-cell interaction mechanisms known so far. Only a few decades ago, the involvement of exosomes in the carcinogenesis in different tissues was discovered, and very recently it was also observed how they carry and modulate the presence of Wnt pathway proteins, involved in the carcinogenesis of gastrointestinal tissues, such as Frizzled 10 protein (FZD10), a membrane receptor for Wnt. Here, we report the in vitro study on the capability of tumor-derived exosomes to induce neoplastic features in normal cells. Exosomes derived from two different colon cancer cell lines, namely the non-metastatic CaCo-2 and the metastatic SW620, were found to deliver, in both cases, FZD10, thus demonstrating the ability to reprogram normal colonic epithelial cell line (HCEC-1CT). Indeed, the acquisition of specific mesenchymal characteristics, such as migration capability and expression of FZD10 and markers of mesenchymal cells, was observed. The exosomes derived from the metastatic cell line, characterized by a level of FZD10 higher than the exosomes extracted from the non-metastatic cells, were also more efficient in stimulating EMT activation. The overall results suggest that FZD10, delivered by circulating tumor-derived exosomes, can play a relevant role in promoting the CRC carcinogenesis and propagation.

Lipolysis by downregulating miR-92a activates the Wnt/ß-catenin signaling pathway in hypoxic rats.

The aim of the present study was to investigate the role of miR-92a in lipid metabolism in hypoxic rats. Microarray analysis and reverse transcription-quantitative (RT-q)PCR were used to detect changes in the mRNA expression levels of miR-92a in the epididymal fat of hypoxic and normoxic rats. The downstream target mRNA of miR-92a was predicted using bioinformatics analysis and verified using a dual luciferase reporter assay. Changes in the expression of frizzled (Fzd)10 and c-Myc in the epididymal fat were detected using RT-qPCR and western blotting. Microarray analysis and RT-qPCR results showed that the expression of miR-92a was significantly lower in the fat tissues of the hypoxic rats compared with the normoxic rats. The results of the dual luciferase reporter assay showed that the target gene of miR-92a was Fzd10, which is an acceptor in the Wnt pathway. Fzd10 expression was upregulated in the hypoxic rats. The mRNA expression levels of c-Myc, which is located downstream of the Wnt pathway, was increased significantly. The increase in the mRNA and protein expression levels of Fzd10 and c-Myc may be associated with miR-92a downregulation. Downregulation of miR-92a in-turn may result in lipolysis through the regulation of the Wnt/ß-catenin signaling pathway, and thus weight loss in the rats.

Frizzled-10 and cancer progression: Is it a new prognostic marker?

Frizzled (FZD) proteins, a family of Wnt receptors, are involved in carcinogenesis in different organs. One interesting FZD protein is FZD-10 highly expressed in embryogenesis but completely absent in the membrane or cytosol of healthy proliferated cells. We studied in detail the expression level and the location of Frizzled-10 protein in different cancerous tissues, such as colon, melanoma and gastric cancer and in function of different staging of the tumor and in metastases. We observed a correlation between cancer evolution and FZD-10 expression, and localization of protein during carcinogenesis. In colon, we have an increase of cytoplasmic FZD-10 expression from hyperplastic mucosa to metastatic tissues, while the amount in the nucleus decreases significantly in T3 and T4 staging tumors as well as in metastases. In melanoma and gastric cancer, we observed the opposite trend of FZD-10 protein in the cytosol but both show a decrease in the T3 and T4 stage of the tumor and in metastases. However, the decrease is less prominent in gastric cancer. Our findings indicate an important role of FZD-10 in tumor progression especially in the later stages of tumor. The nuclear expression of FZD-10 or its absence can give a new tool for tumor staging to pathologists. For target therapy, at least for colon cancer, the high presence of FZD-10 in the later stages of tumor progression and the absence in healthy tissue present a promising new approach.

Concentration-dependent effects of WNTLESS on WNT1/3A signaling.

BACKGROUND: WNTLESS (WLS) is a multi-transmembrane protein that transports Wnt ligands from the Golgi to the cell surface. Although WLS loss-of-function experiments in the developing central nervous system reveal phenotypes consistent with defects in WNT1 and WNT3A signaling, data from complementary gain-of-function experiments have not yet been reported. Here, we report the phenotypic consequences of WLS overexpression in cultured cells and in the developing chick spinal cord. RESULTS: Overexpression of small amounts of WLS along with either WNT1 or WNT3A promotes the Wnt/ß-catenin pathway in HEK293T cells, while overexpression of higher levels of WLS inhibits the Wnt/ß-catenin pathway in these cells. Similarly, overexpressed WLS inhibits the Wnt/ß-catenin pathway in the developing spinal cord, as assessed by cell proliferation and specification. These effects appear to be Wnt-specific as overexpression of WLS inhibits the expression of FZD10, a target of ß-catenin-dependent transcription. CONCLUSIONS: Our results show that overexpression of WLS inhibits Wnt/ß-catenin signaling in the spinal cord. As the activation of the Wnt/ß-catenin pathway in the spinal cord requires WNT1 or WNT3A, our results are consistent with a model in which the relative concentration of WLS to Wnt regulates WNT1/3A signaling in the developing spinal cord.