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The VHL-dependent regulation of microRNAs in renal cancer.

ABSTRACT: The commonest histological type of renal cancer, clear cell renal cell carcinoma (cc RCC), is associated with genetic and epigenetic changes in the von Hippel-Lindau (VHL) tumour suppressor. VHL inactivation leads to induction of hypoxia-inducible factors (HIFs) and a hypoxic pattern of gene expression. Differential levels of specific microRNAs (miRNAs) are observed in several tumours when compared to normal tissue. Given the central role of VHL in renal cancer formation, we examined the VHL-dependent regulation of miRNAs in renal cancer.VHL-dependent miRNA expression in cc RCC was determined by microarray analysis of renal cell line RCC4 with mutated VHL (RCC4-VHL) and reintroduced wild-type VHL (RCC4 + VHL). Five miRNAs highly upregulated in RCC4 + VHL and five miRNAs highly downregulated in RCC4 + VHL were studied further, in addition to miR-210, which is regulated by the HIF-VHL system. miRNA expression was also measured in 31 cc RCC tumours compared to adjacent normal tissue.A significant increase in miR-210, miR-155 and miR-21 expression was observed in the tumour tissue. miR-210 levels also showed a correlation with a HIF-regulated mRNA, carbonic anhydrase IX (CAIX), and with VHL mutation or promoter methylation. An inverse correlation was observed between miR-210 expression and patient survival, and a putative target of miR-210, iron-sulfur cluster assembly protein (ISCU1/2), shows reciprocal levels of mRNA expression in the tumours.We have identified VHL-regulated miRNAs and found that for some the regulation is HIF-dependent and for others it is HIF-independent. This pattern of regulation was also seen in renal cancer tissue for several of these miRNAs (miR-210, miR-155, let-7i and members of the miR-17-92 cluster) when compared with normal tissue. miR-210 showed marked increases in expression in renal cancer and levels correlated with patient survival. The inverse correlation between miR-210 levels and ISCU1/2 provides support for the hypothesis that ISCU1/2 is a target of miR-210 and that it may contribute to the anaerobic respiration seen in renal (and other) tumours.See Commentary: http://www.biomedcentral.com/1741-7015/8/65.

SUBMITTER: Neal CS

PROVIDER: S-EPMC2978113 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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The VHL-dependent regulation of microRNAs in renal cancer.

Neal Calida S CS Michael Michael Z MZ Rawlings Lesley H LH Van der Hoek Mark B MB Gleadle Jonathan M JM

BMC medicine 20101021

<h4>Background</h4>The commonest histological type of renal cancer, clear cell renal cell carcinoma (cc RCC), is associated with genetic and epigenetic changes in the von Hippel-Lindau (VHL) tumour suppressor. VHL inactivation leads to induction of hypoxia-inducible factors (HIFs) and a hypoxic pattern of gene expression. Differential levels of specific microRNAs (miRNAs) are observed in several tumours when compared to normal tissue. Given the central role of VHL in renal cancer formation, we e ...[more]

PMID: 20964835

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Project description:Renal cell carcinoma (RCC) accounts for around 2-3% of all adult neoplasms and its incidence is increasing. RCC is largely resistant to standard cancer treatment regimens including chemotherapy and radiation therapy, whilst immunotherapy modestly provides benefit to only a small subset of patients. As a result, prognosis for RCC patients with advanced disease is very poor, with a 5-year survival rate of less than 10%. An early event in the development of familial and up to 90% of sporadic RCC is the loss and/or mutation/methylation of the von Hippel-Lindau (VHL) tumour suppressor gene. The tumor suppressor role of VHL relies primarily on its ability to target members of the hypoxia-inducible factors (HIF) for proteosomal degradation, however it has also been implicated in other biological processes linked to oncogenesis, such as the extracellular matrix assembly and the regulation of actin cytoskeleton, that are less clearly defined. Targeting the VHL/HIF pathway may dramatically improve RCC treatment, as demonstrated by an increasing number of novel agents that have shown promising activity in recent clinical trials6. Identification of other possible proteins regulated by VHL that may be involved in tumour suppression will improve our understanding of RCC pathobiology and also provide novel disease biomarkers or potential targets. A number of our studies have identified changes in glycosylation in RCC, at least some of which appear to alter as a result of changes in the VHL gene. Lectin binding immunohistochemistry shows altered reactivity with a number of lectins in the malignant tissue compared with the normal tissue. Comparison of plasma membrane protein enriched fractions from human RCC cells stably transfected with control vector or with wild type VHL led to the identification of VHL-associated changes in the forms of several plasma membrane proteins which we beelive to be due to differential glycosylation. For one of these we have now shown that it is differentially O-glycosylated and this has been confimed in cell lysates and patient tissue by Western blotting. A parallel approach using 2D-PAGE analysis of RCC cell line conditioned medium (CM) has also identified a tumour-specific glycoform of a secretory protein that appears to undergo differential N-glycosylation in RCC and this has been confirmed in analysis of some matched primary tumour/normal pairs. These findings are potentially very interesting, as these proteins could serve as prognostic or diagnostic markers, or even as targets for improving RCC therapy. We are therefore keen to explore the underlying mechanism of differential glycosylation that may be associated to VHL dependent gene expression. As there are an immense number of enzymes involved in the conjugation of N- and particularly O-glycans to proteins, the glyco-microarray is an ideal tool to elucidate this further. For chip analyses we have three cell lines generated from human RCC cells (RCC4, 786-0 and UMRC2) that have been stably transfected with control vector or with wild type VHL i.e. 6 cell lines in total. Whole RNA was extracted from each cell line in 3 replicates per line.

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The VHL-dependent regulation of microRNAs in renal cancer.

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The VHL-dependent regulation of microRNAs in renal cancer.

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