Estrogen receptor α is a novel target of the Von Hippel-Lindau protein and is responsible for the proliferation of VHL-deficient cells under hypoxic conditions

The influence of sex hormones on renal cell carcinoma

Kidney cancer is a common malignancy that constitutes around 5% of all cancer cases. Males are twice as likely to acquire renal cell carcinoma (RCC) compared to females and experience a higher rate of mortality. These disparities indicate that sex hormone (SH)-dependent pathways may have an impact on the aetiology and pathophysiology of RCC. Examination of SH involvement in conventional signalling pathways, as well as genetics and genomics, especially the involvement of ribonucleic acid, reveal further insights into sex-related differences. An understanding of SHs and their influence on kidney cancer is essential to offer patients individualized medicine that would better meet their needs in terms of prevention, diagnosis and treatment. This review presents the understanding of sex-related differences in the clinical manifestation of kidney cancer patients and the underlying biological processes.

Critical role of VHL/BICD2/STAT1 axis in crystal-associated kidney disease

Nephrolithiasis is highly prevalent and associated with the increased risk of kidney cancer. The tumor suppressor von Hippel-Lindau (VHL) is critical for renal cancer development, however, its role in kidney stone disease has not been fully elucidated until now. Here we reported VHL expression was upregulated in renal epithelial cells upon exposure to crystal. Utilizing Vhl+/mu mouse model, depletion of VHL exacerbated kidney inflammatory injury during nephrolithiasis. Conversely, overexpression of VHL limited crystal-induced lipid peroxidation and ferroptosis in a BICD2-depdendent manner. Mechanistically, VHL interacted with the cargo adaptor BICD2 and promoted itsd K48-linked poly-ubiquitination, consequently resulting in the proteasomal degradation of BICD2. Through promoting STAT1 nuclear translocation, BICD2 facilitated IFNγ signaling transduction and enhanced IFNγ-mediated suppression of cystine/glutamate antiporter system Xc-, eventually increasing cell sensitivity to ferroptosis. Moreover, we found that the BRAF inhibitor impaired the association of VHL with BICD2 through triggering BICD2 phosphorylation, ultimately causing severe ferroptosis and nephrotoxicity. Collectively, our results uncover the important role of VHL/BICD2/STAT1 axis in crystal kidney injury and provide a potential therapeutic target for treatment and prevention of renal inflammation and drug-induced nephrotoxicity.

Is hysterectomy associated with kidney cancer risk? A meta-analysis of cohort studies

Introduction

Emerging evidence have suggested a potential relationship between hysterectomy and risk of kidney cancer with inconsistent results. We aimed to investigate the association of hysterectomy with kidney cancer risk based on a meta-analysis of all available cohort studies.

Methods

A comprehensive literature search was performed in the PubMed and Embase database, covering all the papers published by September 2022. The pooled relative risks (RRs) and 95% confidence intervals (CIs) were estimated using a DerSimonian and Laird random effects model.

Results

Overall, our meta-analysis included 10 cohorts from 9 studies with approximately 240 million participants. The pooled RR with its 95% CI showed a significantly positive association between hysterectomy and risk of kidney cancer (RR 1.30, 95% CI 1.19-1.41). No obvious heterogeneity was observed across the studies (P = 0.206 for heterogeneity; I2 = 25.9%).

Conclusion

Findings from this meta-analysis of cohort studies indicated that hysterectomy was positively associated with subsequent kidney cancer risk. Further large prospective studies with long-term follow-up are warranted to verify these findings.

VHL syndrome without clear family history: A rare case report and literature review of Chinese patients

Objective

To analyze the clinical manifestations and imaging features of a hospitalized patient with intermittent headache who was finally diagnosed with von Hippel–Lindau (VHL) syndrome and to perform whole-exon gene detection to improve the understanding of the diagnosis and treatment strategies of the disease.

Methods

A case of suspected VHL syndrome in Shanxi Provincial People's Hospital was analyzed. Proband DNA was also extracted for whole exome sequencing and screened for causative mutation sites, which were validated by Sanger sequencing. The literature about VHL gene mutations in Chinese patients in the past 10 years were also reviewed.

Results

There is a heterozygous mutation site c.499C > G on the VHL gene on the short arm of chromosome 3 of the patient, which is a missense mutation. The mutation results in the substitution of arginine with glycine at amino acid 167 of the encoded protein, which may be primarily responsible for the disease in the patient with VHL syndrome. However, the mutation did not occur in other family members.

Conclusion

Early recognition and treatment of VHL syndrome can be available with genetic testing technology. Strengthening the understanding of this complex genetic disease and improving the diagnostic rate of VHL syndrome are helpful for the precise treatment of patients with this disease, which may help prolong the survival time of patients to a certain extent and improve their quality of life.

Hypoxia and ERα Transcriptional Crosstalk Is Associated with Endocrine Resistance in Breast Cancer

Simple Summary

Hormone receptor positive breast cancer patients are treated with anti-hormone molecules as a standard of care. However, resistance frequently occurs, leading to hormone resistant metastatic relapses in foreign organs. Understanding the molecular mechanisms through which breast cancer cells evade therapeutic pressure is of paramount interest. Hypoxia, which refers to oxygen deprivation and is characterized by the activation of hypoxia inducible factors, is a common feature of the solid tumor microenvironment, yet its influence on estrogen receptor alpha activity remains elusive. Here, we investigate the consequence of hypoxia and the signaling of hypoxia inducible factors on hormone responsiveness in breast cancer cells and its clinical implications.

Abstract

Estrogen receptor-alpha (ERα) is the driving transcription factor in 70% of breast cancers and its activity is associated with hormone dependent tumor cell proliferation and survival. Given the recurrence of hormone resistant relapses, understanding the etiological factors fueling resistance is of major clinical interest. Hypoxia, a frequent feature of the solid tumor microenvironment, has been described to promote endocrine resistance by triggering ERα down-regulation in both in vitro and in vivo models. Yet, the consequences of hypoxia on ERα genomic activity remain largely elusive. In the present study, transcriptomic analysis shows that hypoxia regulates a fraction of ERα target genes, underlying an important regulatory overlap between hypoxic and estrogenic signaling. This gene expression reprogramming is associated with a massive reorganization of ERα cistrome, highlighted by a massive loss of ERα binding sites. Profiling of enhancer acetylation revealed a hormone independent enhancer activation at the vicinity of genes harboring hypoxia inducible factor (HIFα) binding sites, the major transcription factors governing hypoxic adaptation. This activation counterbalances the loss of ERα and sustains hormone-independent gene expression. We describe hypoxia in luminal ERα (+) breast cancer as a key factor interfering with endocrine therapies, associated with poor clinical prognosis in breast cancer patients.

The Role of VHL in the Development of von Hippel-Lindau Disease and Erythrocytosis

Von Hippel-Lindau disease (VHL disease or VHL syndrome) is a familial multisystem neoplastic syndrome stemming from germline disease-associated variants of the VHL tumor suppressor gene on chromosome 3. VHL is involved, through the EPO-VHL-HIF signaling axis, in oxygen sensing and adaptive response to hypoxia, as well as in numerous HIF-independent pathways. The diverse roles of VHL confirm its implication in several crucial cellular processes. VHL variations have been associated with the development of VHL disease and erythrocytosis. The association between genotypes and phenotypes still remains ambiguous for the majority of mutations. It appears that there is a distinction between erythrocytosis-causing VHL variations and VHL variations causing VHL disease with tumor development. Understanding the pathogenic effects of VHL variants might better predict the prognosis and optimize management of the patient.

Cardiovascular Risk After SARS-CoV-2 Infection Is Mediated by IL18/IL18R1/HIF-1 Signaling Pathway Axis

Objectives

Currently, cardiovascular risk associated with COVID-19 has been brought to people's attention, but the mechanism is not clear. The aim of this study is to elucidate the mechanisms based on multiple omics data.

Methodology

Weighted gene co-expression network analysis (WGCNA) was used to identify key pathways. Combination analysis with aneurysm and atherosclerosis related pathways, hypoxia induced factor-1 (HIF-1) signaling were identified as key pathways of the increased cardiovascular risk associated with COVID-19. ScMLnet algorithm based on scRNA-seq was used to explore the regulation of HIF-1 pathway by intercellular communication. Proteomic analysis was used to detect the regulatory mechanisms between IL18 and HIF-1 signaling pathway. Pseudo time locus analysis was used to study the regulation of HIF1 signaling pathway in macrophages and vascular smooth muscle cells (VSMC) phenotypic transformation. The Virtual Inference of protein-activity by Enriched Regulon (VIPER) analysis was used to study the activity of regulatory proteins. Epigenetic analysis based on methylation revealed epigenetic changes in PBMC after SARS-CoV-2 infection. Potential therapeutic compounds were explored by using Cmap algorithm.

Results

HIF-1 signaling pathway is a common key pathway for aneurysms, atherosclerosis and SARS-CoV-2 infection. Intercellular communication analysis showed that macrophage-derived interleukin-18 (IL-18) activates the HIF-1 signaling pathway through IL18R1. Proteomic analysis showed that IL18/IL18R1 promote NF-κB entry into the nucleus, and activated the HIF-1 signaling pathway. Macrophage-derived IL18 promoted the M1 polarization of macrophages and the syntactic phenotype transformation of VSMCs. MAP2K1 mediates the functional regulation of HIF-1 signaling pathway in various cell types. Epigenetic changes in PBMC after COVID-19 infection are characterized by activation of the type I interferon pathway. MEK inhibitors are the promising compounds for the treatment of HIF-1 overactivation.

Conclusions

The IL18/IL18R1/HIF1A axis is expected to be an therapeutic target for cardiovascular protection after SARS-CoV-2 infection. MEK inhibitors may be an choice for cardiovascular protection after SARS-COV-2 infection.

Roles of RACK1 in centrosome regulation and carcinogenesis

Receptor for activated C kinase 1 (RACK1) regulates various cellular functions and signaling pathways by interacting with different proteins. Recently, we showed that RACK1 interacts with breast cancer gene 1 (BRCA1), which regulates centrosome duplication. RACK1 localizes to centrosomes and spindle poles and is involved in the proper centrosomal localization of BRCA1. The interaction between RACK1 and BRCA1 is critical for the regulation of centrosome number. In addition, RACK1 contributes to centriole duplication by regulating polo-like kinase 1 (PLK1) activity in S phase. RACK1 binds directly to PLK1 and Aurora A, promoting the phosphorylation of PLK1 and activating the Aurora A/PLK1 signaling axis. Overexpression of RACK1 causes centrosome amplification, especially in mammary gland epithelial cells, inducing overactivation of PLK1 followed by premature centriole disengagement and centriole re-duplication. Other proteins, including hypoxia-inducible factor α, von Hippel-Lindau protein, heat-shock protein 90, β-catenin, and glycogen synthase kinase-3β, interact with RACK1 and play roles in centrosome regulation. In this review, we focus on the roles and underlying molecular mechanisms of RACK1 in centrosome regulation mediated by its interaction with different proteins and the modulation of their functions.

Sex and Gender Differences in Kidney Cancer: Clinical and Experimental Evidence

Simple Summary

Kidney cancer is a frequent malignant tumor that accounts for approximately 5% of all cancer incidences. It affects both males and females, but males are twice as likely to develop kidney cancer than females. Evidence shows that this discrepancy takes root in individual differences, such as genetics or pathologies that affect the patient. It is then reflected in the clinical characteristics of the tumors, as males have larger and more aggressive tumors. Understanding the sex- and gender-based differences in kidney cancer is essential to be able to offer patients individualized medicine that would better cover their needs in terms of prevention, diagnosis and treatment.

Abstract

Sex and gender disparities have been reported for different types of non-reproductive cancers. Males are two times more likely to develop kidney cancer than females and have a higher death rate. These differences can be explained by looking at genetics and genomics, as well as other risk factors such as hypertension and obesity, lifestyle, and female sex hormones. Examination of the hormonal signaling pathways bring further insights into sex-related differences. Sex and gender-based disparities can be observed at the diagnostic, histological and treatment levels, leading to significant outcome difference. This review summarizes the current knowledge about sex and gender-related differences in the clinical presentation of patients with kidney cancer and the possible biological mechanisms that could explain these observations. Underlying sex-based differences may contribute to the development of sex-specific prognostic and diagnostic tools and the improvement of personalized therapies.

Role of the androgen, estrogen, and progesterone receptors in adherent perinephric fat in robotic partial nephrectomy

To determine whether androgen, estrogen, and/or progesterone signaling play a role in the pathophysiology of adherent perinephric fat (APF). We prospectively recruited patients undergoing robotic assisted partial nephrectomy during 2015-2017. The operating surgeon documented the presence or absence of APF. For those with clear cell renal cell carcinoma (ccRCC), representative sections of tumor and perinephric fat were immunohistochemically stained with monoclonal antibody to estrogen α, progesterone, and androgen receptors. Patient characteristics, operative data, and hormone receptor presence were compared between those with and without APF. Of 51 patients total, 18 (35.3%) and 33 (64.7%) patients did and did not have APF, respectively. APF was associated with history of diabetes mellitus (61.1% vs 24.2%, p = 0.009) and larger tumors (4.0 cm vs 3.0 cm, p = 0.017) but not with age, gender, BMI, Charleston comorbidity index, smoking, or preoperative estimated glomerular filtration rate. APF was not significantly associated with length of operation, positive margins, or 30-day postoperative complications but incurred higher estimated blood loss (236.5 mL vs 209.2 mL, p = 0.049). Thirty-two had ccRCC and completed hormone receptor staining. The majority of tumors and perinephric fat were negative for estrogen and progesterone while positive for androgen receptor expression. There was no difference in hormone receptor expression in either tumor or perinephric fat when classified by presence or absence of APF (p > 0.05). APF is more commonly present in patients with diabetes or larger tumors but was not associated with differential sex hormone receptor expression in ccRCC.

TET is targeted for proteasomal degradation by the PHD-pVHL pathway to reduce DNA hydroxymethylation

Hypoxia-inducible factors are heterodimeric transcription factors that play a crucial role in a cell's ability to adapt to low oxygen. The von Hippel-Lindau tumor suppressor (pVHL) acts as a master regulator of HIF activity, and its targeting of prolyl hydroxylated HIF-α for proteasomal degradation under normoxia is thought to be a major mechanism for pVHL tumor suppression and cellular response to oxygen. Whether pVHL regulates other targets through a similar mechanism is largely unknown. Here, we identify TET2/3 as novel targets of pVHL. pVHL induces proteasomal degradation of TET2/3, resulting in reduced global 5-hydroxymethylcytosine levels. Conserved proline residues within the LAP/LAP-like motifs of these two proteins are hydroxylated by the prolyl hydroxylase enzymes (PHD2/EGLN1 and PHD3/EGLN3), which is prerequisite for pVHL-mediated degradation. Using zebrafish as a model, we determined that global 5-hydroxymethylcytosine levels are enhanced in vhl-null, egln1a/b-double-null, and egln3-null embryos. Therefore, we reveal a novel function for the PHD-pVHL pathway in regulating TET protein stability and activity. These data extend our understanding of how TET proteins are regulated and provide new insight into the mechanisms of pVHL in tumor suppression.

The effect of oestrogen on mandibular condylar cartilage via hypoxia-inducible factor-2α during osteoarthritis development

Oestrogen and hypoxia inducible factor-2α (HIF2α) are key regulators in the pathogenesis of osteoarthritis (OA). However, the cellular interaction between oestrogen and HIF2α in articular cartilage during OA process remains unknown. Our previous study has revealed that high-physiological level of oestrogen aggravates the degradation of condylar cartilage in the early stage of temporomandibular joint osteoarthritis (TMJ OA). Here, we hypothesize that HIF2α involves the effect of oestrogen on mandibular condylar cartilage in the progression of TMJ OA. Our experiment in vivo found that the degeneration of condylar cartilage caused by unilateral anterior crossbite (UAC) model, characterized by obvious degenerative morphology, loss of cartilage extracellular matrix, up-regulation of TNF-α, HIF2α and its' down-stream OA-related cytokines (MMP-13, VEGF and Col X), could be alleviated by lack of oestrogen while aggravated by high level of oestrogen in rats. Meanwhile, our in vitro study found that 17β-estradiol stimulation resulted in the loss of extracellular matrix, increased expression of TNF-α, IL-1, HIF2α and its' down-stream OA-related cytokines (MMP-13, VEGF and Col X) in primary condylar chondrocytes via oestrogen receptor beta (ERβ), which could be reversed by ER antagonist, selective estrogen receptor modulators (SERMs) and HIF2α translation inhibitor. Our results reveal that high level of oestrogen can aggravate the degenerative changes of mandibular condylar cartilage, while lack of oestrogen can alleviate it via oestrogen-ERβ-HIF2α pathway during TMJ OA progression.

Hypoxia differentially regulates estrogen receptor alpha in 2D and 3D culture formats

Hypoxia is a common feature in solid tumors. Clinical samples show a positive correlation between the expression of the hypoxia-inducible factor HIF-1α and estrogen receptor alpha (ERα) and a negative correlation between HIF-1α and hormone sensitivity. Results from monolayer cultures are in contention with clinical observations, showing that ER (+) cell lines no longer express ERα under hypoxic conditions (1% O2). Here, we compared the impact of hypoxia on the ERα signaling pathway for T47D cells in a 2D and 3D culture format. In the 2D format, the cells were cultured as monolayers. In the 3D format, paper-based scaffolds supported cells suspended in a collagen matrix. Using ELISA, Western blot, and immunofluorescence measurements, we show that hypoxia differentially regulates ERα protein levels in a culture environment-dependent manner. In the 2D format, the protein levels are significantly decreased in hypoxia. In the 3D format, the protein levels are maintained in hypoxia. Hypoxia reduced ERα transcriptional activation in both culture formats. These results highlight the importance of considering tissue dimensionality for in vitro studies. They also show that ERα protein levels in hypoxia are not an accurate indicator of ERα transcriptional activity, and confirm that a positive stain for ERα in a clinical sample may not necessarily indicate hormone sensitivity.

The landscape of miRNA-related ceRNA networks for marking different renal cell carcinoma subtypes

We know that different types of cancers usually have different responses to the same treatment. Therefore, it is important to understand the similarities and differences across subtypes of cancers, so as to provide a basis for the individualized treatments. Until now, no comprehensive investigation on competing endogenous RNAs (ceRNAs) has been reported for the three main subtypes of renal cell carcinoma (RCC), so the regulation characteristics of ceRNAs in three subtypes are not well revealed. This paper firstly describes a comparative analysis of ceRNA-ceRNA interaction networks for all the three subtypes of RCC based on differential microRNAs (miRNAs). We comprehensively summarized all miRNA and messenger RNAdata of RCC from 126 matched tumor-normal tissues in The Cancer Genome Atlas, systematically analyzed a total of more than 80 000 ceRNA interactions and highlighted the common and specific properties among them, aiming to identify critical genes to classify them for providing supplementary help in the precise diagnosis of RCC. From three aspects, including common or specific ceRNAs, upregulated or downregulated and classifications across the three subtypes, we highlighted the common and specific properties for the three subtypes and also explored the classification of RCC by combining the specific ceRNAs with differential regulations. Moreover, for the most major subtype of clear cell renal cell carcinoma (KIRC), three critical genes were screened out from KIRC ceRNA network and further demonstrated to be the potential biomarkers of KIRC by performing biological experiments at the transcriptional level.

Genome-independent hypoxic repression of estrogen receptor alpha in breast cancer cells

BACKGROUND

About 75-80% of breast tumors express the estrogen receptor alpha (ER-α) and are treated with endocrine-target therapeutics, making this the premier therapeutic modality in the breast cancer clinic. However, acquired resistance is common and about 20% of resistant tumors loose ER-α expression via unknown mechanisms. Inhibition of ER-α loss could improve endocrine therapeutic efficacy, benefiting a significant number of patients. Here we test whether tumor hypoxia might commonly produce ER-α loss.

METHODS

Using standard molecular and cellular biological assays and a work station/incubator with controllable oxygen levels, we analyze the effects of hypoxia on ER-α protein, mRNA, and transcriptional activity in a panel of independently-derived ER-α positive cell lines. These lines were chosen to represent the diverse genetic backgrounds and mutations commonly present in ER-α positive tumors. Using shRNA-mediated knockdown and overexpression studies we also elucidate the role of hypoxia-inducible factor 1-alpha (HIF-1α) in the hypoxia-induced decrease in ER-α abundance.

RESULTS

We present the first comprehensive overview of the effects of bona fide low environmental oxygen (hypoxia) and HIF-1α activity on ER-α abundance and transcriptional activity. We find that stabilized HIF-1α induces rapid loss of ER-α protein in all members of our diverse panel of breast cancer cell lines, which involves proteolysis rather than transcriptional repression. Reduced ER-α severely attenuates ER-α directed transcription, and inhibits cell proliferation without overt signs of cell death in the cell lines tested, despite their varying genomic backgrounds.

CONCLUSIONS

These studies reveal a common hypoxia response that produces reduced ER-α expression and cell cycle stalling, and demonstrate a common role for HIF-1α in ER-α loss. We hypothesize that inhibitors of HIF-1α or the proteasome might stabilize ER-α expression in breast tumors in vivo, and work in combination with endocrine therapies to reduce resistance. Our data also suggests that disease re-occurrence in patients with ER-α positive tumors may arise from tumor cells chronically resident in hypoxic environments. We hypothesize that these non-proliferating cells may survive undetected until conditions change to oxygenate the environment, or cells eventually switch to proliferation via other signaling pathways.

Oestrogen receptor negativity in breast cancer: a cause or consequence?

Endocrine resistance, which occurs either by de novo or acquired route, is posing a major challenge in treating hormone-dependent breast cancers by endocrine therapies. The loss of oestrogen receptor α (ERα) expression is the vital cause of establishing endocrine resistance in this subtype. Understanding the mechanisms that determine the causes of this phenomenon are therefore essential to reduce the disease efficacy. But how we negate oestrogen receptor (ER) negativity and endocrine resistance in breast cancer is questionable. To answer that, two important approaches are considered: (1) understanding the cellular origin of heterogeneity and ER negativity in breast cancers and (2) characterization of molecular regulators of endocrine resistance. Breast tumours are heterogeneous in nature, having distinct molecular, cellular, histological and clinical behaviour. Recent advancements in perception of the heterogeneity of breast cancer revealed that the origin of a particular mammary tumour phenotype depends on the interactions between the cell of origin and driver genetic hits. On the other hand, histone deacetylases (HDACs), DNA methyltransferases (DNMTs), miRNAs and ubiquitin ligases emerged as vital molecular regulators of ER negativity in breast cancers. Restoring response to endocrine therapy through re-expression of ERα by modulating the expression of these molecular regulators is therefore considered as a relevant concept that can be implemented in treating ER-negative breast cancers. In this review, we will thoroughly discuss the underlying mechanisms for the loss of ERα expression and provide the future prospects for implementing the strategies to negate ER negativity in breast cancers.

Distinct breast cancer stem/progenitor cell populations require either HIF1α or loss of PHD3 to expand under hypoxic conditions

The heterogeneous nature of breast cancer is a result of intrinsic tumor complexity and also of the tumor microenvironment, which is known to be hypoxic. We found that hypoxia expands different breast stem/progenitor cell populations (cells with increased aldehyde dehydrogenase activity (Aldefluor⁺), high mammosphere formation capacity and CD44⁺CD24^−/low cells) both in primary normal epithelial and tumor cells. The presence of the estrogen receptor (ER) limits hypoxia-dependent CD44⁺CD24^−/low cell expansion. We further show that the hypoxia-driven cancer stem-like cell enrichment results from a dedifferentiation process. The enhanced mammosphere formation and Aldefluor⁺ cell content observed in breast cancer cells relies on hypoxia-inducible factor 1α (HIF1α). In contrast, the CD44⁺CD24^−/low population expansion is HIF1α independent and requires prolyl hydroxylase 3 (PHD3) downregulation, which mimics hypoxic conditions, leading to reduced CD24 expression through activation of NFkB signaling. These studies show that hypoxic conditions expand CSC populations through distinct molecular mechanisms. Thus, potential therapies that combine current treatments for breast cancer with drugs that target CSC should take into account the heterogeneity of the CSC subpopulations.

WSB1 promotes tumor metastasis by inducing pVHL degradation

In this study, Kim et al. identified WD repeat and SOCS box-containing protein 1 (WSB1) as a novel regulator of pVHL through WSB1's E3 ligase activity. These findings provide important new insights into the understanding of misregulation of the pVHL–HIF pathway in cancer cell invasion and metastasis.

The von Hippel-Lindau tumor suppressor pVHL is an E3 ligase that targets hypoxia-inducible factors (HIFs). Mutation of VHL results in HIF up-regulation and contributes to processes related to tumor progression such as invasion, metastasis, and angiogenesis. However, very little is known with regard to post-transcriptional regulation of pVHL. Here we show that WD repeat and SOCS box-containing protein 1 (WSB1) is a negative regulator of pVHL through WSB1's E3 ligase activity. Mechanistically, WSB1 promotes pVHL ubiquitination and proteasomal degradation, thereby stabilizing HIF under both normoxic and hypoxic conditions. As a consequence, WSB1 up-regulates the expression of HIF-1α’s target genes and promotes cancer invasion and metastasis through its effect on pVHL. Consistent with this, WSB1 protein level negatively correlates with pVHL level and metastasis-free survival in clinical samples. This work reveals a new mechanism of pVHL's regulation by which cancer acquires invasiveness and metastatic tendency.

Elevated estrogen receptor-α in VHL-deficient condition induces microtubule organizing center amplification via disruption of BRCA1/Rad51 interaction

Since loss of VHL is frequently detected early phase genetic event in human renal cell carcinoma, pVHL is assumed to be indispensable for suppression of tumor initiation step. However, induction of HIF-1α, target of pVHL E3 ligase, is more adequate to angiogenesis step after tumor mass formation. Concerning this, it has been reported that pVHL is involved in centrosome location during metaphase and regulates ER-α signaling. Here, we provide the evidences that pVHL-mediated ER-α suppression is critical for microtubule organizing center (MTOC) maintaining and elevated ER-α promotes MTOC amplification through disruption of BRCA1-Rad51 interaction. In fact, numerous MTOC in VHL- or BRCA1-deficient cells are reduced by Fulvestrant, inhibitor of ER-α expression as well as antagonist. In addition, we reveal that activation of ER signaling can increase γ-tubulin, core factor of TuRC and render the resistance to Taxol. Thus, Fulvestrant but not Tamoxifen, antagonist against ER-α, can restore the Taxol sensitivity in VHL- or BRCA1-deficient cells. Our results suggest that pVHL-mediated ER-α suppression is important for regulation of MTOC as well as drug resistance.

pVHL Negatively Regulates Antiviral Signaling by Targeting MAVS for Proteasomal Degradation

The von Hippel-Lindau (VHL) gene is a well-defined tumor suppressor linked to human heredity cancer syndromes. As a component of the VHL-elongin B/C E3 ligase complex, pVHL performs its tumor function by targeting proteins for proteasomal degradation. It is largely unknown whether pVHL functions in antiviral immunity. In this article, we identify that pVHL negatively regulates innate antiviral immunity, which acts mainly by inducing degradation of mitochondrial antiviral-signaling protein (MAVS, also known as Cardif, IPS-1, or VISA). Overexpression of pVHL abrogated the cellular response to viral infection, whereas knockdown of pVHL exerted the opposite effect. pVHL targeted the K420 residue of MAVS to catalyze the formation of K48-linked polyubiquitin chains, leading to proteasomal degradation of MAVS. After viral infection, Mavs levels remained low in wild type zebrafish embryos but became much higher in vhl-deficient (vhl(-/-)) zebrafish embryos. Higher MAVS levels correlated with a greatly exaggerated antiviral response. In this work, we demonstrate that pVHL exhibits a previously unknown role in innate antiviral immunity.

High ERα36 Expression Level and Membrane Location Predict Poor Prognosis in Renal Cell Carcinoma

Estrogen receptor alpha 36 (ERα36), a truncated variant of ERα, is located in cytoplasm and membrane that is different from other nuclear receptors of ERα family. ERα36 is involved in progression and treatment resistance of a variety of carcinomas. However, the clinical and prognostic significance of ERα36 in renal tumors have not been fully elucidated.Here, renal tumor tissues from 125 patients were collected and immunohistochemical stained with ERα36 antibody. ERα36 expression level and location in these cases were analyzed for their correlations with clinical characteristics. The differential diagnosis value was also assessed for benign and malignant renal tumors, as well as its prognostic value.The results showed that membrane ERα36 expression was rarely detected in benign tumors but predominantly observed in malignant renal tumors. Kaplan-Meier analysis indicated that significant correlations of high ERα36 level and ERα36 membrane expression were correlated with both poor disease-free survival and overall survival. Univariate and multivariate analysis confirmed that both ERα36 high expression and membrane location can serve as unfavorable prognostic indicators for renal cell carcinoma.It is thus concluded that membrane ERα36 expression is valuable for differential diagnosis of malignant renal tumors from benign ones. Both ERα36 high expression and membrane location indicate poor prognosis in renal cell carcinoma.

Ubiquitylation of nuclear receptors: new linkages and therapeutic implications

The nuclear receptor (NR) superfamily is a group of transcriptional regulators that control multiple aspects of both physiology and pathology and are broadly recognized as viable therapeutic targets. While receptor-modulating drugs have been successful in many cases, the discovery of new drug targets is still an active area of research, because resistance to NR-targeting therapies remains a significant clinical challenge. Many successful targeted therapies have harnessed the control of receptor activity by targeting events within the NR signaling pathway. In this review, we explore the role of NR ubiquitylation and discuss how the expanding roles of ubiquitin could be leveraged to identify additional entry points to control receptor function for future therapeutic development.

Future perspectives for mTOR inhibitors in renal cell cancer treatment

ABSTRACT 

Everolimus is a mTOR inhibitor that demonstrates antitumor and antiangiogenic activities. In a randomized Phase III trial, patients with metastatic renal cell carcinoma who progressed on sunitinib/sorafenib were treated with everolimus and showed significant improvement in progression-free survival compared with best supportive care. Novel approaches in treatment are expected to ensure less toxic therapies and increase efficacy of everolimus. To provide a new perspective for mTOR inhibitor research and therapy, we discuss renal cell carcinoma cancer stem cells as a potential target for mTOR inhibitors and present new concepts on emerging antiangiogenic therapies. Finally, we point why systems biology approach with reverse molecular engineering may also contribute to the field of drug discovery in renal cell carcinoma.

VHL negatively regulates SARS coronavirus replication by modulating nsp16 ubiquitination and stability

Eukaryotic cellular and most viral RNAs carry a 5′-terminal cap structure, a 5′-5′ triphosphate linkage between the 5′ end of the RNA and a guanosine nucleotide (cap-0). SARS coronavirus (SARS-CoV) nonstructural protein nsp16 functions as a methyltransferase, to methylate mRNA cap-0 structure at the ribose 2′-O position of the first nucleotide to form cap-1 structures. However, whether there is interplay between nsp16 and host proteins was not yet clear. In this report, we identified several potential cellular nsp16-interacting proteins from a human thymus cDNA library by yeast two-hybrid screening. VHL, one of these proteins, was proven to interact with nsp16 both in vitro and in vivo. Further studies showed that VHL can inhibit SARS-CoV replication by regulating nsp16 ubiquitination and promoting its degradation. Our results have revealed the role of cellular VHL in the regulation of SARS-CoV replication.

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Several host proteins were identified to interact with SARS-CoV nsp16 by yeast two-hybrid screening.

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VHL was found to interact with SARS-CoV nsp16 and promotes nsp16 degradation.

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VHL involves in regulating nsp16 ubiquination and stability, and modulating SARS-CoV replication.

Frontiers in clinical and molecular diagnostics and staging of metastatic clear cell renal cell carcinoma

The last few years have brought advances in the understanding of the molecular biology of metastatic clear cell renal cell carcinoma (RCC). Both preclinical research and clinical trials brought together results from the latest advancements in RCC diagnostic and staging. Understanding of the complex molecular alterations involved in the development and progression of RCC enables development of immunohistochemical and genetic diagnostic tools and is also opening the doors for experimental targeted therapies. At the same time, improvements of medical and molecular imaging improves the sensitivity and specificity of metastatic disease diagnosis. Moreover, independent validation of molecular profiles across high-throughput platforms, methods, laboratories and cancer populations has recently been successfully performed in RCC. Generation of informative, clinical diagnostic tools is likely to contribute to development of novel personalized diagnostic and treatment protocols and ensure prolonged survival of RCC patient in the near future.

Autoantibodies to estrogen receptors and their involvement in autoimmune diseases and cancer

The involvement of estrogens, which influence many physiologic processes, has been shown in the development or progression of several diseases including some cancers, most notably breast cancer, and autoimmune disorders. Estrogenic signal is transferred via estrogen receptors (ER) which have dual localization, predominantly intracellular but also in plasma membrane. The discovery of membrane-associated ER (mER) has greatly expanded our understanding of estrogen action; upon ligand binding, mER rapidly activate different signaling pathways inducing downstream transcription factors. Some target genes of the mER pathway may be activated independently of the intracellular ER. Additionally, intracellular ER action can be modulated by mER-initiated signaling. Most notably, the identification of autoantibodies reacting with ER (ERAB) and their possible pathogenic role in autoimmunity and cancer have opened a new path for the research in the estrogen-related receptor activity. In this review, we briefly recapitulate the localization and function of ER and mostly discuss the possible role of ERAB as novel potential prognostic and/or predictive tools in autoimmunity and cancer.

KRAS and DAXX/ATRX gene mutations are correlated with the clinicopathological features, advanced diseases, and poor prognosis in Chinese patients with pancreatic neuroendocrine tumors

Background and Aim: Pancreatic neuroendocrine tumor (pNET) is a clinically rare and heterogeneous group of tumors; its pharmacogenetic characteristics are not fully understood. This study was designed to examine the relationship between key gene variations and disease development and prognosis among Chinese patients with pNET.

Methods: Various pNET associated genes such as DAXX/ATRX, KRAS, MEN1, PTEN, TSC2, SMAD4/DPC, TP53 and VHL were analyzed in high-throughput sequencing. The links between the gene mutations and the clinicopathological features and prognosis of the patients were determined.

Results: The somatic mutation frequencies of the DAXX/ATRX, KRAS, MEN1, mTOR pathway genes (PTEN and TSC2), SMAD4/DPC, TP53, and VHL in Chinese pNET patients were 54.05%, 10.81%, 35.14%, 54.05%, 2.70%, 13.51%, and 40.54%, respectively, while the same figures in Caucasians pNET patients were 43%, 0%, 44%, 15%, 0%, 3%, and 0%, respectively. The numbers of mutated genes were from 0 to 6; 4 patients with more than 3 mutated genes had higher proliferation (Ki-67) index or nerve vascular invasion or organ involvement, but only 9 of 27 patients with 3 or few mutated genes had such features. Mutations in KRAS and DAXX/ATRX, but not other genes analyzed, were associated with a shortened survival.

Conclusion: The mutation rates of these genes in Chinese pNET patients are different from those in Caucasians. A higher number of gene mutations and the DAXX/ATRX and KRAS gene mutations are correlated with a poor prognosis of patients with pNET.

Loss of VHL promotes progerin expression, leading to impaired p14/ARF function and suppression of p53 activity

Renal cell carcinomas (RCCs) are frequently occurring genitourinary malignancies in the aged population. A morphological characteristic of RCCs is an irregular nuclear shape, which is used to index cancer grades. Other features of RCCs include the genetic inactivation of the von Hippel-Lindau gene, VHL, and p53 genetic-independent inactivation. An aberrant nuclear shape or p53 suppression has not yet been demonstrated. We examined the effect of progerin (an altered splicing product of the LMNA gene linked to Hutchinson Gilford progeria syndrome; HGPS) on the nuclear deformation of RCCs in comparison to that of HGPS cells. In this study, we showed that progerin was suppressed by pVHL and was responsible for nuclear irregularities as well as p53 inactivation. Thus, progerin suppression can ameliorate nuclear abnormalities and reactivate p53 in response to genotoxic addition. Furthermore, we found that progerin was a target of pVHL E3 ligase and suppressed p53 activity by p14/ARF inhibition. Our findings indicate that the elevated expression of progerin in RCCs results from the loss of pVHL and leads to p53 inactivation through p14/ARF suppression. Interestingly, we showed that progerin was expressed in human leukemia and primary cell lines, raising the possibility that the expression of this LMNA variant may be a common event in age-related cancer progression.

The von hippel-lindau protein suppresses androgen receptor activity

The androgen receptor (AR) plays a pivotal role in prostate homeostasis and prostate cancer development. To understand the mechanism underlying the regulation of the AR holds a promise for developing novel therapeutic approaches for prostate cancer. Here, we show that the Von Hippel-Lindau gene product, pVHL, physically interacts with AR and inhibits AR transcription activity but does not induce AR turnover. Moreover, pVHL also suppresses androgen-induced cell proliferation, implicating a physiological role of pVHL in androgen-induced signaling pathway. In addition, we provide evidence to show that pVHL actually enhanced AR de-ubiquitination instead of inducing AR ubiquitination, uncovering a noncanonical role of pVHL in the ubiquitin proteasome pathway. Our data reveal a novel function of pVHL in the regulation of AR transcription activity, which may expand the scope of pVHL in tumor suppression and provide mechanistic insight into prostate cancer initiation and progression.

Regulation of the transcriptional activation of the androgen receptor by the UXT-binding protein VHL

Loss and/or inactivation of the VHL (von Hippel-Lindau) tumour suppressor causes various tumours. Using a yeast two-hybrid system, we have identified the AR (androgen receptor) co-activator UXT (ubiquitously expressed transcript), as a VHL-interacting protein. GST pull-down and co-immunoprecipitation assays show that UXT interacts with VHL. In addition, UXT recruits VHL to the nucleus. VHL associates with the DBD (DNA-binding domain) and hinge domains of the AR and induces AR ubiquitination. Moreover, VHL interaction with the AR activates AR transactivation upon DHT (dihydrotestosterone) treatment. VHL knockdown inhibits AR ubiquitination and decreases transcriptional activation of the AR. Our data suggest that the VHL-UXT interaction and VHL-induced ubiquitination of AR regulate transcriptional activation of the AR.