VHL substrate transcription factor ZHX2 as an oncogenic driver in clear cell renal cell carcinoma.
ABSTRACT: Inactivation of the von Hippel-Lindau (VHL) E3 ubiquitin ligase protein is a hallmark of clear cell renal cell carcinoma (ccRCC). Identifying how pathways affected by VHL loss contribute to ccRCC remains challenging. We used a genome-wide in vitro expression strategy to identify proteins that bind VHL when hydroxylated. Zinc fingers and homeoboxes 2 (ZHX2) was found as a VHL target, and its hydroxylation allowed VHL to regulate its protein stability. Tumor cells from ccRCC patients with VHL loss-of-function mutations usually had increased abundance and nuclear localization of ZHX2. Functionally, depletion of ZHX2 inhibited VHL-deficient ccRCC cell growth in vitro and in vivo. Mechanistically, integrated chromatin immunoprecipitation sequencing and microarray analysis showed that ZHX2 promoted nuclear factor ?B activation. These studies reveal ZHX2 as a potential therapeutic target for ccRCC.
Project description:Zinc fingers and homeoboxes 2 (ZHX2) was found as a novel VHL substrate target, and acted as an oncogenic driver in ccRCC. However, the detailed mechanism of ZHX2 in ccRCC development remains elusive, and no research has focused on studying ZHX2 in drug resistance yet. A tissue microarray with 358 ccRCC samples was used to determine the expression of ZHX2 in ccRCC patients. VHL-deficient cell line 786-O and VHL-normal cell line CAKI-1 was used for lineage reprogramming by transfecting with lentivirus. The in vitro and in vivo experiments were performed with these new cell lines to determine the mechanism of ZHX2 in ccRCC development and drug resistance. Immunohistochemistry analysis showed that ZHX2 was not highly expressed in ccRCC tumor tissues, only 33.2% (119/358) patients have high ZHX2 expression. However, high ZHX2 was significantly associated with advanced Fuhrman grade (p?=?0.004), and proved to be an independent prognosis factor for progression-free survival (p?=?0.0003), while there is no significant correlation with overall survival. We further discovered that ZHX2 overexpression could increase VEGF secretion and transcriptional activate the MEK/ERK1/2 and promote its downstream targets. We also found ZHX2 overexpression induce Sunitinib resistance though activating autophagy and the combination treatment of Sunitinib and Chloroquine could significantly rescue the phenomenon. In summary, these results indicate that ZHX2 drivers cell growth, migration though increase VEGF expression, and transcriptional activate MEK/ERK1/2 signaling pathway, and could induce Sunitinib resistance by regulating self-protective autophagy, these may provide new insight in advanced ccRCC treatment.
Project description:The von Hippel-Lindau (VHL) is deficient in ?70% of clear-cell renal cell carcinomas (ccRCC), which contributes to the carcinogenesis and drug resistance of ccRCC. Here we show that VHL-deficient ccRCC cells present enhanced cytotoxicity of anthracyclines in a hypoxia-inducible factor-independent manner. By subtractive proteomic analysis coupling with RNAi or overexpression verification, aldehyde dehydrogenase 2 (ALDH2) is found to be transcriptionally regulated by VHL and contributes to enhanced anthracyclines cytotoxicity in ccRCC cells. Furthermore, VHL regulates ALDH2 expression by directly binding the promoter of -130?bp to -160?bp to activate the transcription of hepatocyte nuclear factor 4 alpha (HNF-4?). In addition, a positive correlation is found among the protein expressions of VHL, HNF-4? and ALDH2 in ccRCC samples. These findings will deepen our understanding of VHL function and shed light on precise treatment for ccRCC patients.
Project description:Vascular cell adhesion molecule 1 (VCAM-1) is an adhesion molecule assigned to the activated endothelium mediating immune cells adhesion and extravasation. However, its expression in renal carcinomas inversely correlates with tumor malignancy. Our experiments in clear cell renal cell carcinoma (ccRCC) cell lines demonstrated that von Hippel Lindau (VHL) loss, hypoxia, or PHD (for prolyl hydroxylase domain-containing proteins) inactivation decreased VCAM-1 levels through a transcriptional mechanism that was independent of the hypoxia-inducible factor and dependent on the nuclear factor κB signaling pathway. Conversely, VHL expression leads to high VCAM-1 levels in ccRCC, which in turn leads to better outcomes, possibly by favoring antitumor immunity through VCAM-1 interaction with the α4β1 integrin expressed in immune cells. Remarkably, in ccRCC human samples with VHL nonmissense mutations, we observed a negative correlation between VCAM-1 levels and ccRCC stage, microvascular invasion, and symptom presentation, pointing out the clinical value of VCAM-1 levels as a marker of ccRCC progression.
Project description:Why different species are predisposed to different tumor spectra is not well understood. In particular, whether the physical location of tumor suppressor genes relative to one another influences tumor predisposition is unknown. Renal cancer presents a unique opportunity to explore this question. Renal cell carcinoma (RCC) of clear-cell type (ccRCC), the most common type, begins with an intragenic mutation in the von Hippel-Lindau (VHL) gene and loss of 3p (where VHL is located). Chromosome 3p harbors several additional tumor suppressor genes, including BRCA1-associated protein-1 (BAP1). In the mouse, Vhl is on a different chromosome than Bap1. Thus, whereas loss of 3p in humans simultaneously deletes one copy of BAP1, loss of heterozygosity in the corresponding Vhl region in the mouse would not affect Bap1. To test the role of BAP1 in ccRCC development, we generated mice deficient for either Vhl or Vhl together with one allele of Bap1 in nephron progenitor cells. Six2-Cre;Vhl(F/F);Bap1(F/+) mice developed ccRCC, but Six2-Cre;Vhl(F/F) mice did not. Kidneys from Six2-Cre;Vhl(F/F);Bap1(F/+) mice resembled kidneys from humans with VHL syndrome, containing multiple lesions spanning from benign cysts to cystic and solid RCC. Although the tumors were small, they showed nuclear atypia and exhibited features of human ccRCC. These results provide an explanation for why VHL heterozygous humans, but not mice, develop ccRCC. They also explain why a mouse model of ccRCC has been lacking. More broadly, our data suggest that differences in tumor predisposition across species may be explained, at least in part, by differences in the location of two-hit tumor suppressor genes across the genome.
Project description:The von Hippel-Lindau tumor-suppressor gene (VHL) is lost in most clear cell renal cell carcinomas (ccRCC). Here, using human ccRCC specimens, VHL-deficient cells, and xenograft models, we show that miR-204 is a VHL-regulated tumor suppressor acting by inhibiting macroautophagy, with MAP1LC3B (LC3B) as a direct and functional target. Of note, higher tumor grade of human ccRCC was correlated with a concomitant decrease in miR-204 and increase in LC3B levels, indicating that LC3B-mediated macroautophagy is necessary for RCC progression. VHL, in addition to inducing endogenous miR-204, triggered the expression of LC3C, an HIF-regulated LC3B paralog, that suppressed tumor growth. These data reveal a function of VHL as a tumor-suppressing regulator of autophagic programs.
Project description:Inactivation of the VHL (Von Hippel Lindau) tumour suppressor has long been recognised as necessary for the pathogenesis of clear cell renal cancer (ccRCC); however, the molecular mechanisms underlying transformation and the requirement for additional genetic hits remain unclear. Here, we show that loss of VHL alone results in DNA replication stress and damage accumulation, effects that constrain cellular growth and transformation. By contrast, concomitant loss of the chromatin remodelling factor PBRM1 (mutated in 40% of ccRCC) rescues VHL-induced replication stress, maintaining cellular fitness and allowing proliferation. In line with these data we demonstrate that combined deletion of Vhl and Pbrm1 in the mouse kidney is sufficient for the development of fully-penetrant, multifocal carcinomas, closely mimicking human ccRCC. Our results illustrate how VHL and PBRM1 co-operate to drive renal transformation and uncover replication stress as an underlying vulnerability of all VHL mutated renal cancers that could be therapeutically exploited.
Project description:Inactivation of the von Hippel-Lindau tumor suppressor gene, VHL, is an archetypical tumor-initiating event in clear cell renal carcinoma (ccRCC) that leads to the activation of hypoxia-inducible transcription factors (HIFs). However, VHL mutation status in ccRCC is not correlated with clinical outcome. Here we show that during ccRCC progression, cancer cells exploit diverse epigenetic alterations to empower a branch of the VHL-HIF pathway for metastasis, and the strength of this activation is associated with poor clinical outcome. By analyzing metastatic subpopulations of VHL-deficient ccRCC cells, we discovered an epigenetically altered VHL-HIF response that is specific to metastatic ccRCC. Focusing on the two most prominent pro-metastatic VHL-HIF target genes, we show that loss of Polycomb repressive complex 2 (PRC2)-dependent histone H3 Lys27 trimethylation (H3K27me3) activates HIF-driven chemokine (C-X-C motif) receptor 4 (CXCR4) expression in support of chemotactic cell invasion, whereas loss of DNA methylation enables HIF-driven cytohesin 1 interacting protein (CYTIP) expression to protect cancer cells from death cytokine signals. Thus, metastasis in ccRCC is based on an epigenetically expanded output of the tumor-initiating pathway.
Project description:In clear-cell renal cell carcinoma (ccRCC), loss of von Hippel-Lindau (VHL) tumour suppressor gene and reduced oxygen tension promote stabilisation of hypoxia-inducible factor (HIF) family of transcription factors, which promote changes in the expression of genes that contribute to oncogenesis. Multiple studies have demonstrated significant perturbations in DNA methylation in ccRCC via largely unclear mechanisms that modify the transcriptional output of tumour cells. Here, we show that the methylation status of the CpG dinucleotide within the consensus hypoxia-responsive element (HRE) markedly influences the binding of HIF and that the loss of VHL results in significant alterations in the DNA methylome. Surprisingly, hypoxia, which likewise promotes HIF stabilisation and activation, has relatively few effects on global DNA methylation. Gene expression analysis of ccRCC patient samples highlighted expression of a group of genes whose transcription correlated with methylation changes, including hypoxic responsive genes such as VEGF and TGF. These results suggest that the loss of VHL alters DNA methylation profile across the genome, commonly associated with and contributing to ccRCC progression.
Project description:Mutations in the von Hippel-Lindau (VHL) gene are pathogenic in VHL disease, congenital polycythaemia and clear cell renal carcinoma (ccRCC). pVHL forms a ternary complex with elongin C and elongin B, critical for pVHL stability and function, which interacts with Cullin-2 and RING-box protein 1 to target hypoxia-inducible factor for polyubiquitination and proteasomal degradation. We describe a comprehensive database of missense VHL mutations linked to experimental and clinical data. We use predictions from in silico tools to link the functional effects of missense VHL mutations to phenotype. The risk of ccRCC in VHL disease is linked to the degree of destabilization resulting from missense mutations. An optimized binary classification system (symphony), which integrates predictions from five in silico methods, can predict the risk of ccRCC associated with VHL missense mutations with high sensitivity and specificity. We use symphony to generate predictions for risk of ccRCC for all possible VHL missense mutations and present these predictions, in association with clinical and experimental data, in a publically available, searchable web server.
Project description:Renal tumor heterogeneity studies have utilized the von Hippel-Lindau VHL gene to classify disease into molecularly defined subtypes to examine associations with etiologic risk factors and prognosis. The aim of this study was to provide a comprehensive analysis of VHL inactivation in clear cell renal tumors (ccRCC) and to evaluate relationships between VHL inactivation subgroups with renal cancer risk factors and VHL germline single nucleotide polymorphisms (SNPs). VHL genetic and epigenetic inactivation was examined among 507 sporadic RCC/470 ccRCC cases using endonuclease scanning and using bisulfite treatment and Sanger sequencing across 11 CpG sites within the VHL promoter. Case-only multivariate analyses were conducted to identify associations between alteration subtypes and risk factors. VHL inactivation, either through sequence alterations or promoter methylation in tumor DNA, was observed among 86.6% of ccRCC cases. Germline VHL SNPs and a haplotype were associated with promoter hypermethylation in tumor tissue (OR?=?6.10; 95% CI: 2.28-16.35, p?=?3.76E-4, p-global?=?8E-5). Risk of having genetic VHL inactivation was inversely associated with smoking due to a higher proportion of wild-type ccRCC tumors [former: OR?=?0.70 (0.20-1.31) and current: OR?=?0.56 (0.32-0.99); P-trend?=?0.04]. Alteration prevalence did not differ by histopathologic characteristics or occupational exposure to trichloroethylene. ccRCC cases with particular VHL germline polymorphisms were more likely to have VHL inactivation through promoter hypermethylation than through sequence alterations in tumor DNA, suggesting that the presence of these SNPs may represent an example of facilitated epigenetic variation (an inherited propensity towards epigenetic variation) in renal tissue. A proportion of tumors from current smokers lacked VHL alterations and may represent a biologically distinct clinical entity from inactivated cases.