Percutaneous microwave ablation on management of hereditary renal cell carcinoma in Von Hippel-Lindau disease.

BACKGROUND: The effect of microwave ablation (MWA) for the renal cell carcinoma (RCC) in Von Hippel-Lindau (VHL) disease is unclear. OBJECTIVE: To assess the safety, Technique efficacy, renal function and oncological outcome of MWA for RCC in VHL patients. METHODS: Consecutive patients with RCCs in VHL disease treated by MWA were retrospectively collected from November 2009 to October 2020. The technical efficacy rate and complications were assessed. The outcomes of pre- and post-ablative eGFR were compared. The local recurrent-free survival (LRFS), renal-cancer-free survival (RCFS), cancer-specific survival (CSS), overall survival (OS) and complications were presented. RESULTS: A total of 10 patients (mean age, 39.0 years ± 10.7 [SD]; 3 women) with 28 RCCs (mean tumor size, 3.0 cm ± 0.34; mean tumor volume, 20.7 mL ± 43.3) treated with MWA were included. Th median follow-up time was 52 months(IQR:27-80). The overall technical efficacy rate was 100% with no major complications occurred. No significant statistical difference between pre-ablative and postablative creatinine level (102.0 µmol/L ± 30.4 vs 112.3 µmol/L ± 38.7, p = 0.06), but the pre-ablative eGFR level was significantly higher than the post-ablative eGFR (78.0 mL/(min*1.73m2) ± 28.6 vs 72 mL/(min*1.73m2) ± 31.4, p = 0.04), with the mean decrease of 5.86 ml/(min*1.73m2). The local recurrent-free survival(LRFS) and renal-cancer-free survival (RCFS) were 100% and 60%, respectively. The cancer specifical survival (CSS) and overall survival (OS) were 95.5% and 100%, respectively. CONCLUSION: Microwave ablation is a safe and feasible method for the treatment of RCC in VHL disease, preserving renal function and yielding satisfactory oncological outcomes.

Discovery of a potent and subtype-selective TYK2 degrader based on an allosteric TYK2 inhibitor.

TYK2, a member of the JAK family of proximal membrane-bound tyrosine kinases, has emerged as an attractive target for the treatment of autoimmune diseases. Herein, we report the discovery of first-in-class potent and subtype-selective TYK2 degraders. By conjugating a TYK2 ligand from a known allosteric TYK2 inhibitor with a VHL ligand as the E3 ligase ligand via alkyl linkers of various lengths, we rapidly identified TYK2 degrader 5 with moderate TYK2 degradation activity. Degrader 5 induced TYK2 degradation without affecting the protein level of subtype kinases (JAK1, JAK2, and JAK3) in Jurkat cellular assays. Furthermore, modifying the TYK2 ligand moiety of degrader 5 yielded the more potent TYK2 degrader 37 with retained selectivity for JAKs. Our subtype-selective TYK2 degraders represent valuable chemical probes for investigating the biology of TYK2 degradation.

A beginner's guide to current synthetic linker strategies towards VHL-recruiting PROTACs.

Over the last two decades, proteolysis targeting chimeras (PROTACs) have been revolutionary in drug development rendering targeted protein degradation (TPD) as an emerging therapeutic modality. These heterobifunctional molecules are comprised of three units: a ligand for the protein of interest (POI), a ligand for an E3 ubiquitin ligase, and a linker that tethers the two motifs together. Von Hippel-Lindau (VHL) is one of the most widely employed E3 ligases in PROTACs development due to its prevalent expression across tissue types and well-characterised ligands. Linker composition and length has proven to play an important role in determining the physicochemical properties and spatial orientation of the POI-PROTAC-E3 ternary complex, thus influencing the bioactivity of degraders. Numerous articles and reports have been published showcasing the medicinal chemistry aspects of the linker design, but few have focused on the chemistry around tethering linkers to E3 ligase ligands. In this review, we focus on the current synthetic linker strategies employed in the assembly of VHL-recruiting PROTACs. We aim to cover a range of fundamental chemistries used to incorporate linkers of varying length, composition and functionality.

Neuroendocrine neoplasms in the context of inherited tumor syndromes: a reappraisal focused on targeted therapies.

PURPOSE: Neuroendocrine neoplasms can occur as part of inherited disorders, usually in the form of well-differentiated, slow-growing tumors (NET). The main predisposing syndromes include: multiple endocrine neoplasias type 1 (MEN1), associated with a large spectrum of gastroenteropancreatic and thoracic NETs, and type 4 (MEN4), associated with a wide tumour spectrum similar to that of MEN1; von Hippel-Lindau syndrome (VHL), tuberous sclerosis (TSC), and neurofibromatosis 1 (NF-1), associated with pancreatic NETs. In the present review, we propose a reappraisal of the genetic basis and clinical features of gastroenteropancreatic and thoracic NETs in the setting of inherited syndromes with a special focus on molecularly targeted therapies for these lesions. METHODS: Literature search was systematically performed through online databases, including MEDLINE (via PubMed), and Scopus using multiple keywords' combinations up to June 2022. RESULTS: Somatostatin analogues (SSAs) remain the mainstay of systemic treatment for NETs, and radiolabelled SSAs can be used for peptide-receptor radionuclide therapy for somatostatin receptor (SSTR)-positive NETs. Apart of these SSTR-targeted therapies, other targeted agents have been approved for NETs: the mTOR inhibitor everolimus for lung, gastroenteropatic and unknown origin NET, and sunitinib, an antiangiogenic tyrosine kinase inhibitor, for pancreatic NET. Novel targeted therapies with other antiangiogenic agents and immunotherapies have been also under evaluation. CONCLUSIONS: Major advances in the understanding of genetic and epigenetic mechanisms of NET development in the context of inherited endocrine disorders have led to the recognition of molecular targetable alterations, providing a rationale for the implementation of treatments and development of novel targeted therapies.

MicroRNA-155-5p Targets JADE-1, Promoting Proliferation, Migration, and Invasion in Clear Cell Renal Cell Carcinoma Cells.

Clear cell renal cell carcinoma (ccRCC) incidence has been rising in recent years, with strong association between differential microRNA (miRNA) expression and neoplastic progression. Specifically, overexpression of miR-155-5p has been associated with promoting aggressive cancer in ccRCC and other cancers. In this study, we further investigate the role of this miRNA and one of its protein targets, Jade-1, to better understand the mechanism behind aggressive forms of ccRCC. Jade-1, a tumor suppressor, is stabilized by Von-Hippel Lindau (VHL), which is frequently mutated in ccRCC. Experiments featuring downregulation of miR-155-5p in two ccRCC cell lines (786-O and Caki-1) attenuated their oncogenic potential and led to increased levels of Jade-1. Conversely, knockdown experiments with an anti-Jade-1 shRNA in 786-O and Caki-1 cells showed increased metastatic potential through elevated proliferation, migration, and invasion rates. In a mouse xenograft model, downregulation of miR-155 decreased the rate of tumor implantation and proliferation. Direct interaction between miR-155-5p and Jade-1 was confirmed through a 3'UTR luciferase reporter assay. These findings further elucidate the mechanism of action of miR-155-5p in driving an aggressive phenotype in ccRCC through its role in regulating Jade-1.

Multidisciplinary integrated care pathway for von Hippel-Lindau disease.

BACKGROUND: Clinical pathways are care plans established to describe essential steps in the care of patients with a specific clinical problem. They translate (inter)national guidelines into local applicable protocols and clinical practice. The purpose of this article is to establish a multidisciplinary integrated care pathway for specialists and allied health care professionals in caring for individuals with von Hippel-Lindau (VHL) disease. METHODS: Using a modified Delphi consensus-making process, a multidisciplinary panel from 5 Dutch University Medical Centers produced an integrated care pathway relating to the provision of care for patients with VHL by medical specialists, specialized nurses, and associated health care professionals. Patient representatives cocreated the pathway and contributed quality criteria from the patients' perspective. RESULTS: The panel agreed on recommendations for the optimal quality of care for individuals with a VHL gene mutation. These items were the starting point for the development of a patient care pathway. With international medical guidelines addressing the different VHL-related disorders, this article presents a patient care pathway as a flowchart that can be incorporated into VHL expertise clinics or nonacademic treatment clinics. CONCLUSIONS: Medical specialists (internists, urologists, neurosurgeons, ophthalmologists, geneticists, medical oncologists, neurologists, gastroenterologists, pediatricians, and ear-nose-throat specialists) together with specialized nurses play a vital role alongside health care professionals in providing care to people affected by VHL and their families. This article presents a set of consensus recommendations, supported by organ-specific guidelines, for the roles of these practitioners in order to provide optimal VHL care. This care pathway can form the basis for the development of comprehensive, integrated pathways for multiple neoplasia syndromes.

Von Hippel-Lindau tumor suppressor (VHL) stimulates TOR signaling by interacting with phosphoinositide 3-kinase (PI3K).

Cell growth is positively controlled by the phosphoinositide 3-kinase (PI3K)-target of rapamycin (TOR) signaling pathway under conditions of abundant growth factors and nutrients. To discover additional mechanisms that regulate cell growth, here we performed RNAi-based mosaic analyses in the Drosophila fat body, the primary metabolic organ in the fly. Unexpectedly, the knockdown of the Drosophila von Hippel-Lindau (VHL) gene markedly decreased cell size and body size. These cell growth phenotypes induced by VHL loss of function were recovered by activation of TOR signaling in Drosophila Consistent with the genetic interactions between VHL and the signaling components of PI3K-TOR pathway in Drosophila, we observed that VHL loss of function in mammalian cells causes decreased phosphorylation of ribosomal protein S6 kinase and Akt, which represent the main activities of this pathway. We further demonstrate that VHL activates TOR signaling by directly interacting with the p110 catalytic subunit of PI3K. On the basis of the evolutionarily conserved regulation of PI3K-TOR signaling by VHL observed here, we propose that VHL plays an important role in the regulation and maintenance of proper cell growth in metazoans.

Identification of a VHL gene mutation in atypical Von Hippel-Lindau syndrome: genotype-phenotype correlation and gene therapy perspective.

BACKGROUND: Classical von Hippel Lindau (VHL) disease/syndrome includes CNS hemangioblastoma, renal or pancreatic cysts, pheochromocytoma, renal carcinoma and exodermic cystadenoma. The syndrome is caused by mutation of VHL tumor suppressor gene. The most prevalent mutations are present in VHL syndrome. To date, > 500 mutations of gene related to the progression of VHL syndrome have been reported. VHL gene mutation presented in single lung or pancreatic tumor has been reported occasionally, but there is no report of both. METHODS: In this paper, we used CT scan, pathological and genetic examination methods to diagnose a rare atypical VHL syndrome. RESULTS: We reported a rare case of atypical VHL syndrome with authenticated VHL mutation at p.Arg167Gln, that was associated with not only bilateral pheochromocytoma but also lung carcinoid and neuroendocrine tumor of pancreas. Based on literature reviews, the patient was recommended to be further subjected to octreotide-based radionuclide therapy. CONCLUSIONS: Combined with gene detection and clinical diagnosis, we found the inherent relationship between VHL genotype and phenotype, and constructed the standard diagnosis and treatment process of disease with rare VHL mutation from the perspective of gene therapy.

Distinct genome-wide methylation patterns in sporadic and hereditary nonfunctioning pancreatic neuroendocrine tumors.

BACKGROUND: Aberrant methylation is a known cause of cancer initiation and/or progression. There are scant data on the genome-wide methylation pattern of nonfunctioning pancreatic neuroendocrine tumors (NFPanNETs) and sporadic and hereditary NFPanNETs. METHODS: Thirty-three tissue samples were analyzed: they included samples from sporadic (n = 9), von Hippel-Lindau (VHL)-related (n = 10), and multiple endocrine neoplasia type 1 (MEN1)-related NFPanNETs (n = 10) as well as normal islet cells (n = 4) for comparison. Genome-wide CpG methylation profiling was performed with the Infinium MethylationEPIC BeadChip assay and was analyzed with R-based tools. RESULTS: In unsupervised hierarchical clustering, sporadic and MEN1-related NFPanNETs clustered together, and the VHL group was in a separate cluster. MEN1-related NFPanNETs had a higher rate of hypermethylated CpG sites in comparison with sporadic and VHL-related tumor groups. Differentially methylated region analysis confirmed the higher rate of hypermethylation in MEN1-related tumors. Moreover, in an integrated analysis of gene expression data for the same tumor samples, downregulated gene expression was found in most genes that were hypermethylated. In a CpG island methylator phenotype analysis, 3 genes were identified and confirmed to have downregulated gene expression: secreted frizzle-related protein 5 (SFRP5) in sporadic NFPanNETs and cell division cycle-associated 7-like (CDCA7L) and RNA binding motif 47 (RBM47) in MEN1-related NFPanNETs. CONCLUSIONS: MEN1 NFPanNETs have a higher rate of geno me-wide hypermethylation than other NFPanNET subtypes. The similarity between the pathways enriched in a methylation analysis of known genes involved in NFPanNET tumorigenesis suggests a key role for aberrant methylation in the pathogenesis of NFPanNETs.

High speed flow cytometry allows the detection of circulating endothelial cells in hemangioblastoma patients.

Circulating endothelial cells (CECs) detach from the intima monolayer after endothelial damages. Their circulating endothelial progenitors (CEPs) represent less than 0.01% of nucleated blood cells. Increased levels of CECs and CEPs have been detected in patients with several types of cancer, suggesting that they could be a useful blood-based marker for detecting a tumor, or for monitoring its clinical course. However, their routine monitoring is time consuming and technically challenging. Here, we present a flow cytometry method for quantifying such cells in a cohort of patients with hemangioblastoma (HB). HB is a rare benign tumor, responsible for 1-2.5% of primary intracranial tumors and up to 10% of spinal cord tumors, and for which no tools are available to predict the onset or recurrence in patients undergoing surgical removal of tumor mass. This method allowed us to accurately quantifying CEC and CEP before and after surgery. CEPs are present at high levels in HB patients than control before intervention, and decrease after tumor removal, suggesting that their percentage could represent a valid tool to monitor the disease onset and recurrence.

Rootletin prevents Cep68 from VHL-mediated proteasomal degradation to maintain centrosome cohesion.

Centrosome cohesion, mostly regarded as a proteinaceous linker between parental centrioles, ensures the interphase centrosome(s) to function as a single microtubule-organizing center. Maintenance of centrosome cohesion counts on a number of centrosomal linker proteins because depletion of any of those leads to premature centrosome separation in interphase, termed centrosome splitting. However, the underlying mechanisms of the dependence are unknown. Here, we show that absence of Rootletin triggers the von Hippel-Lindau tumour suppressor protein (VHL)-mediated proteasomal degradation of Cep68 and, in turn, results in centrosome splitting. The VHL E3 ligase complex ubiquitinates Cep68 in vitro and in vivo. Co-silencing of Rootletin and VHL reverts Cep68 loss and centrosome splitting. Expression of a stable mutant of Cep68, either diminishing its polyubiquitylation or eliminating binding to ß-domain of VHL, also suppresses centrosome splitting provoked by Rootletin depletion. We propose that the archetypal linker protein Rootletin maintains centrosome cohesion in part through inhibition of VHL-mediated Cep68 degradation.

Renal Cell Carcinoma: Molecular Aspects.

Renal cell carcinoma is the most common form of the kidney cancer accounting for more than 85% of the cases of which clear cell renal cell carcinoma (ccRCC) is the major histological subtype. The central molecular signature for ccRCC pathogenesis is the biallelic inactivation of VHL gene due to the presence of mutations/hyper-methylation/complete gene loss, which results in the downstream HIF activation. These events lead to increased tyrosine kinase receptor signalling pathways (RAS/MEK/ERK pathway, PI3K/AKT/mTOR pathway and NF-κB pathway), which through their downstream effector proteins causes the cell to proliferate and migrate. Recent studies have shown that VHL inactivation alone is not sufficient to induce the tumor. Mutations in numerous other genes that codes for chromatin modifiers (PBRM1, SETD2 and BAP1) and signalling proteins (PTEN and mTOR) have been identified along with activation of alternate signalling pathways like STAT and Sonic Hedgehog (SHH) pathway. It has also been shown that STAT pathway also works cooperatively with HIF to enhance the tumor progression. However, SHH pathway reactivation resulted in tumor regardless of the VHL status, indicating the complex nature of the tumor at the molecular level. Therefore, understanding the complete aetiology of ccRCC is important for future therapeutics.

New Insights into Protein Hydroxylation and Its Important Role in Human Diseases.

Protein hydroxylation is a post-translational modification catalyzed by 2-oxoglutarate-dependent dioxygenases. The hydroxylation modification can take place on various amino acids, including but not limited to proline, lysine, asparagine, aspartate and histidine. A classical example of this modification is hypoxia inducible factor alpha (HIF-α) prolyl hydroxylation, which affects HIF-α protein stability via the Von-Hippel Lindau (VHL) tumor suppressor pathway, a Cullin 2-based E3 ligase adaptor protein frequently mutated in kidney cancer. In addition to protein stability regulation, protein hydroxylation may influence other post-translational modifications or the kinase activity of the modified protein (such as Akt and DYRK1A/B). In other cases, protein hydroxylation may alter protein-protein interaction and its downstream signaling events in vivo (such as OTUB1, MAPK6 and eEF2K). In this review, we highlight the recently identified protein hydroxylation targets and their pathophysiological roles, especially in cancer settings. Better understanding of protein hydroxylation will help identify novel therapeutic targets and their regulation mechanisms to foster development of more effective treatment strategies for various human cancers.

Von Hippel-Lindau disease: the clinical manifestations and genetic analysis results of two cases from a single family.

von Hippel-Lindau (VHL) disease is an autosomal dominant inherited multi systemic cancer syndrome that is classically associated with neoplasms in multiple organs, and caused by mutations in the VHL gene on chromosome 3p25-p26. Retinal hemangioblastoma (RH) is the most frequent and the earliest clinical sign of the disease, which is seen in 40.0-60.0% of patients. In recent years, studies of patients with VHL tried to put forward the relationship between genotype and phenotype. In this study, two VHL cases in the same family with clinical findings and genetic analysis results are presented. As a consequence of the genetic studies, a heterozygous missense mutation c.202 T>C, p.S68P (Ser68Pro) in exon 1 of the VHL gene that is mapped to chromosome 3p25.3, was found in the patients' DNA sample. The germline mutation of [c.202T>C, p.S68P (Ser68Pro)] that was detected in both cases, has been reported in only two cases in the literature. However, in these reported cases, any systemic involvement except RH, were not reported. Although our cases had the same mutation, we detected renal involve-ment in both cases, and also central nervous system (CNS) involvement in one case, in addition to RH.

Regulation of E2F1 by the von Hippel-Lindau tumour suppressor protein predicts survival in renal cell cancer patients.

Biallelic mutations of the von Hippel-Lindau (VHL) gene are the most common cause of sporadic and inherited renal cell carcinoma (RCC). Loss of VHL has been reported to affect cell proliferation by deregulating cell cycle-associated proteins. We report that the VHL gene product (pVHL) inhibits E2F1 expression at both mRNA and protein level in zebrafish and human RCC cells, while loss of VHL increases E2F1 expression in patient kidney tumour tissue and RCC cells, resulting in a delay of cell cycle progression. RCCs from von Hippel-Lindau patients with known germline VHL mutations express significantly more E2F1 compared to sporadic RCCs with either clear-cell (cc) or non-cc histology. Analysis of 138 primary RCCs reveals that E2F1 expression is significantly higher in tumours with a diameter ≤7 cm and with a favourable American Joint Committee on Cancer (AJCC) stage. The expression of E2F1 in RCC significantly correlates with p27 expression, suggesting that increased expression of E2F1 in RCC induces tumour cell senescence via p27. Cox regression analysis shows significant prediction of E2F1 expression for disease-free survival and overall survival, implying that E2F1 expression in kidney tumour is a novel prognostic factor for patients with RCC.

Expression of Von Hippel - Lindau (VHL) gene mutation in diagnosed cases of renal cell carcinoma.

OBJECTIVE: To evaluate the expression of Von Hippel Lindau (VHL) gene in diagnosed cases of renal cell carcinoma. METHODS: This cross sectional study was conducted in department of Pathology, Basic Medical Sciences Institute, JPMC, Karachi, from January 2007 to December 2012. Paraffin embedded blocks of 30 cases of radical nephrectomy specimens diagnosed as renal cell carcinoma including CCRCC 21 (70%) CCPRCC, 3 (10%), PRCC 2 (6.79%), hybrid tumor 4 (13.3%), chromophobe tumor (0%) processed for VHL gene expression on Polymerase Chain Reaction. RESULTS: All the 30 cases previously diagnosed as renal cell carcinoma were processed on PCR, VHL gene mutations were seen in 20 (95.23%) of CCRCC while a single case was negative for VHL mutations. All CCPRCC were negative for VHL mutation. Among the hybrid tumor 03 cases with foci of clear cells show VHL mutation while a single case showing combination of clear cells and chromophobe cells was negative for mutation. Both the cases of PRCC were positive for mutation. Exon 3 mutation at base pair 194 seen in 8 (32%) cases and Exon 2 mutation at base pair 150-159 seen in 17 (68%) cases. None of the cases showed Exon 1 mutation. CONCLUSION: The present study shows that majority of CCRCC showed VHL mutation including the hybrid tumor with clear cell component in our population.

Surgical Outcomes in Patients with Endolymphatic Sac Tumors: A Single-Center Experience of 29 Patients.

OBJECTIVE: To analyze the clinical features and surgical outcomes of patients with endolymphatic sac tumors (ELSTs). STUDY DESIGN: Single institution retrospective cohort study. METHODS: The clinical data of 29 patients with 30 ELSTs who underwent surgery were retrospectively reviewed. Information on patient demographics, tumor size and grade, intraoperative blood loss volume, hearing and facial nerve outcomes, and follow-up data was collected and analyzed. RESULTS: The main symptoms were hearing loss in 26 ELSTs (86.7%) and tinnitus in 17 (56.7%). Twenty-four (80%) ELSTs were in advanced stages (Grade III). The median tumor volume was 6.35 cm3. The median intraoperative blood loss volume was 300 mL. Facial nerve function was well preserved in 21 patients. Among all patients with Grade III tumors, 12 patients underwent tension-free anterior facial nerve rerouting, and 11 patients (91.7%) maintained good facial nerve function postoperatively (HB I and HB II). Only one patient exhibited permanent vocal cord paralysis, and no patients experienced cerebrospinal fluid (CSF) leakage postoperatively. Gross total resection was achieved in 22 patients (73.3%), 5 patients (16.7%) experienced tumor recurrence, and 3 (10%) had residual tumors. CONCLUSIONS: Most ELSTs tend to be diagnosed in the advanced stage. Tension-free anterior facial nerve rerouting could maximally preserve facial nerve function. The intraoperative blood loss volume was associated with tumor size and stage. Tumor recurrence tends to occur at the posterior edge of the petrosal bone, internal auditory canal, and surface of the posterior fossa. Given the relatively high recurrence rate of ELSTs, long-term follow-up is recommended. LEVEL OF EVIDENCE: 4 Laryngoscope, 2024.

The kidney imaging surveillance scoring system (KISSS): using qualitative MRI features to predict growth rate of renal tumors in patients with von-Hippel Lindau (VHL) syndrome.

OBJECTIVE: To determine the reliability of an MRI-based qualitative kidney imaging surveillance scoring system (KISSS) and assess which imaging features predict growth rate (GR) of renal tumors in patients with VHL. MATERIALS AND METHODS: We identified 55 patients with VHL with 128 renal tumors who underwent intervention from 2015 to 2020 at the National Cancer Institute. All patients had 2 preoperative MRIs at least 3 months apart. Two fellowship-trained radiologists scored each tumor on location and MR-sequence-specific imaging parameters from the earlier MRI. Weighted kappa was used to determine the degree of agreement between radiologists for each parameter. GR was calculated as the difference in maximum tumor dimension over time (cm/year). Differences in mean growth rate (MGR) within categories of each imaging variable were assessed by ANOVA. RESULTS: Apart from tumor margin and renal sinus, reliability was at least moderate (K > 0.40) for imaging parameters. Median initial tumor size was 2.1 cm, with average follow-up of 1.2 years. Tumor MGR was 0.42 cm/year. T2 hypointense, mixed/predominantly solid, and high restricted diffusion tumors grew faster. When comparing different combinations of these variables, the model with the lowest mean error among both radiologists utilized only solid/cystic and restricted diffusion features. CONCLUSIONS: We demonstrate a novel MR-based scoring system (KISSS) that has good precision with minimal training and can be applied to other qualitative radiology studies. A subset of imaging variables (T2 intensity; restricted diffusion; and solid/cystic) were independently associated with growth rate in VHL renal tumors, with the combination of the latter two most optimal. Additional validation, including in sporadic RCC population, is warranted.

Journey of Von Hippel-Lindau (VHL) E3 ligase in PROTACs design: From VHL ligands to VHL-based degraders.

The scientific community has shown considerable interest in proteolysis-targeting chimeras (PROTACs) in the last decade, indicating their remarkable potential as a means of achieving targeted protein degradation (TPD). Not only are PROTACs seen as valuable tools in molecular biology but their emergence as a modality for drug discovery has also garnered significant attention. PROTACs bind to E3 ligases and target proteins through respective ligands connected via a linker to induce proteasome-mediated protein degradation. The discovery of small molecule ligands for E3 ligases has led to the prevalent use of various E3 ligases in PROTAC design. Furthermore, the incorporation of different types of linkers has proven beneficial in enhancing the efficacy of PROTACs. By far more than 3300 PROTACs have been reported in the literature. Notably, Von Hippel-Lindau (VHL)-based PROTACs have surfaced as a propitious strategy for targeting proteins, even encompassing those that were previously considered non-druggable. VHL is extensively utilized as an E3 ligase in the advancement of PROTACs owing to its widespread expression in various tissues and well-documented binders. Here, we review the discovery of VHL ligands, the types of linkers employed to develop VHL-based PROTACs, and their subsequent modulation to design advanced non-conventional degraders to target various disease-causing proteins. Furthermore, we provide an overview of other E3 ligases recruited in the field of PROTAC technology.

REST-dependent downregulation of von Hippel-Lindau tumor suppressor promotes autophagy in SHH-medulloblastoma.

The RE1 silencing transcription factor (REST) is a driver of sonic hedgehog (SHH) medulloblastoma genesis. Our previous studies showed that REST enhances cell proliferation, metastasis and vascular growth and blocks neuronal differentiation to drive progression of SHH medulloblastoma tumors. Here, we demonstrate that REST promotes autophagy, a pathway that is found to be significantly enriched in human medulloblastoma tumors relative to normal cerebella. In SHH medulloblastoma tumor xenografts, REST elevation is strongly correlated with increased expression of the hypoxia-inducible factor 1-alpha (HIF1α)-a positive regulator of autophagy, and with reduced expression of the von Hippel-Lindau (VHL) tumor suppressor protein - a component of an E3 ligase complex that ubiquitinates HIF1α. Human SHH-medulloblastoma tumors with higher REST expression exhibit nuclear localization of HIF1α, in contrast to its cytoplasmic localization in low-REST tumors. In vitro, REST knockdown promotes an increase in VHL levels and a decrease in cytoplasmic HIF1α protein levels, and autophagy flux. In contrast, REST elevation causes a decline in VHL levels, as well as its interaction with HIF1α, resulting in a reduction in HIF1α ubiquitination and an increase in autophagy flux. These data suggest that REST elevation promotes autophagy in SHH medulloblastoma cells by modulating HIF1α ubiquitination and stability in a VHL-dependent manner. Thus, our study is one of the first to connect VHL to REST-dependent control of autophagy in a subset of medulloblastomas.