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Purpose: Abnormal expression of miRNAs is closely related to a variety of human cancers. The purpose of this study is to identify new tumor suppressor miRNA and elucidate its physiological function and mechanism in renal cell carcinoma (RCC). Methods: The expression of miR-145 in 45 RCC and adjacent normal tissues was performed by quantitative RT-PCR. Cell proliferation, migration, invasion, apoptosis and cycle assays were carried out for functional analysis after miR-145 transfection. Two target genes of miR-145 were identified by luciferase reporter assay. The altered expression of 84 epithelial to mesenchymal transition (EMT)-related genes after miR-145 transfection was detected by RT Profiler EMT PCR array. Results: The expression of miR-145 was downregulated in RCC compared to their normal adjacent tissues. Restoring miR-145 expression in RCC cell lines dramatically suppressed cell proliferation, migration and invasion, and induced cell apoptosis and G2-phase arrest. We further validated those miR-145 targets two oncogenes, ANGPT2 and NEDD9 in RCC. In addition, miR-145 was found to regulate numerous genes involved in the EMT. Conclusions: These findings demonstrate that miR-145 functions as tumor suppressor in RCC, suggesting that miR-145 may be a potential therapeutic target for RCC. [ABSTRACT FROM AUTHOR]

Loss-of-function mutations in the KCNQ4 channel cause DFNA2, a subtype of autosomal dominant non-syndromic deafness that is characterized by progressive sensorineural hearing loss. Previous studies have demonstrated that the majority of the pathogenic KCNQ4 mutations lead to trafficking deficiency and loss of KCNQ4 currents. Over the last two decades, various strategies have been developed to rescue trafficking deficiency of pathogenic mutants; the most exciting advances have been made by manipulating activities of molecular chaperones involved in the biogenesis and quality control of the target protein. However, such strategies have not been established for KCNQ4 mutants and little is known about the molecular chaperones governing the KCNQ4 biogenesis. To identify KCNQ4-associated molecular chaperones, a proteomic approach was used in this study. As a result, two major molecular chaperones, HSP70 and HSP90, were identified and then confirmed by reciprocal co-immunoprecipitation assays, suggesting that the HSP90 chaperone pathway might be involved in the KCNQ4 biogenesis. Manipulating chaperone expression further revealed that two different isoforms of HSP90, the inducible HSP90α and the constitutive HSP90β, had opposite effects on the cellular level of the KCNQ4 channel; that HSP40, HSP70, and HOP, three key components of the HSP90 chaperone pathway, were crucial in facilitating KCNQ4 biogenesis. In contrast, CHIP, a major E3 ubiquitin ligase, had an opposite effect. Collectively, our data suggest that HSP90α and HSP90β play key roles in controlling KCNQ4 homeostasis via the HSP40-HSP70-HOP-HSP90 chaperone pathway and the ubiquitin-proteasome pathway. Most importantly, we found that over-expression of HSP90β significantly improved cell surface expression of the trafficking-deficient, pathogenic KCNQ4 mutants L274H and W276S. KCNQ4 surface expression was restored by HSP90β in cells mimicking heterozygous conditions of the DFNA2 patients, even though it was not sufficient to rescue the function of KCNQ4 channels. [ABSTRACT FROM AUTHOR]