VHL suppresses RAPTOR and inhibits mTORC1 signaling in clear cell renal cell carcinoma

Targeting apoptosis in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most prevalent subtype of renal cancer, accounting for approximately 80% of all renal cell cancers. Due to its exceptional inter- and intratumor heterogeneity, it is highly resistant to conventional systemic therapies. Targeting the evasion of cell death, one of cancer's hallmarks, is currently emerging as an alternative strategy for ccRCC. In this article, we review the current state of apoptosis-inducing therapies against ccRCC, including antisense oligonucleotides, BH3 mimetics, histone deacetylase inhibitors, cyclin-kinase inhibitors, inhibitors of apoptosis protein antagonists, and monoclonal antibodies. Although preclinical studies have shown encouraging results, these compounds fail to improve patients' outcomes significantly. Current evidence suggests that inducing apoptosis in ccRCC may promote tumor progression through apoptosis-induced proliferation, anastasis, and apoptosis-induced nuclear expulsion. Therefore, re-evaluating this approach is expected to enable successful preclinical-to-clinical translation.

Von Hippel-Lindau protein signalling in clear cell renal cell carcinoma

The distinct pathological and molecular features of kidney cancer in adaptation to oxygen homeostasis render this malignancy an attractive model for investigating hypoxia signalling and potentially developing potent targeted therapies. Hypoxia signalling has a pivotal role in kidney cancer, particularly within the most prevalent subtype, known as renal cell carcinoma (RCC). Hypoxia promotes various crucial pathological processes, such as hypoxia-inducible factor (HIF) activation, angiogenesis, proliferation, metabolic reprogramming and drug resistance, all of which contribute to kidney cancer development, growth or metastasis formation. A substantial portion of kidney cancers, in particular clear cell RCC (ccRCC), are characterized by a loss of function of Von Hippel-Lindau tumour suppressor (VHL), leading to the accumulation of HIF proteins, especially HIF2α, a crucial driver of ccRCC. Thus, therapeutic strategies targeting pVHL-HIF signalling have been explored in ccRCC, culminating in the successful development of HIF2α-specific antagonists such as belzutifan (PT2977), an FDA-approved drug to treat VHL-associated diseases including advanced-stage ccRCC. An increased understanding of hypoxia signalling in kidney cancer came from the discovery of novel VHL protein (pVHL) targets, and mechanisms of synthetic lethality with VHL mutations. These breakthroughs can pave the way for the development of innovative and potent combination therapies in kidney cancer.

DNA methyltransferase 3A induces the occurrence of oral submucous fibrosis by promoting the methylation of the von Hippel-Lindau

BACKGROUND

Oral submucous fibrosis (OSF) is associated with malignant disorders. DNA methyltransferase 3A (DNMT3A) is a DNA methylesterase reported to be upregulated in multiple organs and shown to inhibit fibrosis. However, the detailed effect of DNMT3A on OSF remains unclear.

METHODS

To mimic OSF in vitro, oral fibroblasts were exposed to arecoline and molecular biological experiments were performed to detect the function of DNMT3A in OSF.

RESULTS

We found that von Hippel-Lindau (VHL) was downregulated and highly methylated in OSF. Arecoline remarkably increased the viability, invasiveness, and migration of oral fibroblasts, but upregulation of VHL partially reversed these effects. DNMT3A induces DNA hypermethylation in the VHL promoter, and VHL markedly inhibits the level of tenascin-C (TNC) by inducing the ubiquitination of TNC. TNC reversed the inhibitory effect of VHL upregulation on the differentiation of oral fibroblasts into myofibroblasts.

CONCLUSION

DNMT3A induces OSF by promoting methylation of the VHL promoter. Hence, our study provides novel insights into the discovery of novel strategies that can be employed against OSF.

Cabozantinib in combination with immune checkpoint inhibitors for renal cell carcinoma: a systematic review and meta-analysis

Context

Cabozantinib combined with immune checkpoint inhibitors (ICIs) has brought a new therapeutic effect for the medical treatment of renal cell carcinoma (RCC).

Objectives

We performed a meta-analysis of randomized controlled trials and single-arm trials to evaluate the efficacy and safety of cabozantinib plus ICIs in RCC.

Methods

We extracted data from PubMed, Cochrane, Medline and Embase databases, and rated literature quality through Cochrane risk of bias tool and MINORS. RevMan5.3 software was used to analyze the results of randomized controlled trials and single-arm trials.

Results

A total of 7 studies were included. Treatment with cabozantinib plus ICIs improved PFS [HR 0.75, (95%CI: 0.52, 1.08), p = 0.12] and the OS [HR 0.80, (95%CI: 0.60, 1.07), p = 0.13] in randomized controlled trials. Meanwhile, the result of the ORR in randomized controlled trials was [risk ratio (RR) 1.37, (95%CI: 1.21, 1.54), p < 0.00001] and in single-arm trials was [risk difference (RD) 0.49, (95%CI: 0.26, 0.71), p < 0.0001].

Conclusion

Cabozantinib plus ICIs prolonged the PFS and OS, and improved ORR in patients with RCC. Our recommendation is to use cabozantinib plus ICIs to treat advanced RCC, and to continuous monitor and manage the drug-related adverse events.

Systematic Review Registration

identifier CRD42023455878.

Targeting hypoxia-inducible factors: therapeutic opportunities and challenges

Hypoxia-inducible factors (HIFs) are highly conserved transcription factors that are crucial for adaptation of metazoans to limited oxygen availability. Recently, HIF activation and inhibition have emerged as therapeutic targets in various human diseases. Pharmacologically desirable effects of HIF activation include erythropoiesis stimulation, cellular metabolism optimization during hypoxia and adaptive responses during ischaemia and inflammation. By contrast, HIF inhibition has been explored as a therapy for various cancers, retinal neovascularization and pulmonary hypertension. This Review discusses the biochemical mechanisms that control HIF stabilization and the molecular strategies that can be exploited pharmacologically to activate or inhibit HIFs. In addition, we examine medical conditions that benefit from targeting HIFs, the potential side effects of HIF activation or inhibition and future challenges in this field.

Post-translational regulation of the mTORC1 pathway: A switch that regulates metabolism-related gene expression

The mechanistic target of rapamycin complex 1 (mTORC1) is a kinase complex that plays a crucial role in coordinating cell growth in response to various signals, including amino acids, growth factors, oxygen, and ATP. Activation of mTORC1 promotes cell growth and anabolism, while its suppression leads to catabolism and inhibition of cell growth, enabling cells to withstand nutrient scarcity and stress. Dysregulation of mTORC1 activity is associated with numerous diseases, such as cancer, metabolic disorders, and neurodegenerative conditions. This review focuses on how post-translational modifications, particularly phosphorylation and ubiquitination, modulate mTORC1 signaling pathway and their consequential implications for pathogenesis. Understanding the impact of phosphorylation and ubiquitination on the mTORC1 signaling pathway provides valuable insights into the regulation of cellular growth and potential therapeutic targets for related diseases.

New Insights into the Link between SARS-CoV-2 Infection and Renal Cancer

Cancer has been described as a risk factor for greater susceptibility to SARS-CoV-2 infection and severe COVID-19, mainly for patients with metastatic disease. Conversely, to that reported for most solid and hematological malignancies, the few available clinical studies reported that the infection did not increase the risk of death in renal cancer patients. The expression on proximal tubular renal cells of the key players in cellular viral uptake, ACE2, TMPRSS2, and NRP1, seems to be the mechanism for the direct kidney injury seen in patients with COVID-19. Interestingly, data from The Cancer Genome Atlas and experimental analyses on various renal cancer cell lines demonstrated that the above-reported receptors/cofactors are maintained by renal cancer cells. However, whether SARS-CoV-2 infection directly kills renal cancer cells or generates enhanced immunogenicity is a question worth investigating. In addition, some researchers have further addressed the topic by studying the expression and prognostic significance of gene signatures related to SARS-CoV-2 infection in renal cancer patients. The emerging data highlights the importance of better understanding the existence of a link between renal cancer and COVID-19 since it could lead to the identification of new prognostic factors and the development of new therapeutic targets in the management of renal cancer patients.

SCD5 Regulation by VHL Affects Cell Proliferation and Lipid Homeostasis in ccRCC

Clear cell renal cell carcinoma (ccRCC) is the most common histological subtype of renal cancer, and inactivation of the VHL tumor suppressor gene is found in almost all cases of hereditary and sporadic ccRCCs. CcRCC is associated with the reprogramming of fatty acid metabolism, and stearoyl-CoA desaturases (SCDs) are the main enzymes controlling fatty acid composition in cells. In this study, we report that mRNA and protein expression of the stearoyl-CoA desaturase SCD5 is downregulated in VHL-deficient cell lines. Similarly, in C. elegans vhl-1 mutants, FAT-7/SCD5 activity is repressed, supporting an evolutionary conservation. SCD5 regulation by VHL depends on HIF, and loss of SCD5 promotes cell proliferation and a metabolic shift towards ceramide production. In summary, we identify a novel regulatory function of VHL in relation to SCD5 and fatty acid metabolism, and propose a new mechanism of how loss of VHL may contribute to ccRCC tumor formation and progression.

Downstream Targets of VHL/HIF-α Signaling in Renal Clear Cell Carcinoma Progression: Mechanisms and Therapeutic Relevance

The clear cell variant of renal cell carcinoma (ccRCC) is the most common renal epithelial malignancy and responsible for most of the deaths from kidney cancer. Patients carrying inactivating mutations in the Von Hippel-Lindau (VHL) gene have an increased proclivity to develop several types of tumors including ccRCC. Normally, the Hypoxia Inducible Factor alpha (HIF-α) subunits of the HIF heterodimeric transcription factor complex are regulated by oxygen-dependent prolyl-hydroxylation, VHL-mediated ubiquitination and proteasomal degradation. Loss of pVHL function results in elevated levels of HIF-α due to increased stability, leading to RCC progression. While HIF-1α acts as a tumor suppressor, HIF-2α promotes oncogenic potential by driving tumor progression and metastasis through activation of hypoxia-sensitive signaling pathways and overexpression of HIF-2α target genes. One strategy to suppress ccRCC aggressiveness is directed at inhibition of HIF-2α and the associated molecular pathways leading to cell proliferation, angiogenesis, and metastasis. Indeed, clinical and pre-clinical data demonstrated the effectiveness of HIF-2α targeted therapy in attenuating ccRCC progression. This review focuses on the signaling pathways and the involved genes (cyclin D, c-Myc, VEGF-a, EGFR, TGF-α, GLUT-1) that confer oncogenic potential downstream of the VHL-HIF-2α signaling axis in ccRCC. Discussed as well are current treatment options (including receptor tyrosine kinase inhibitors such as sunitinib), the medical challenges (high prevalence of metastasis at the time of diagnosis, refractory nature of advanced disease to current treatment options), scientific challenges and future directions.

RBM3 interacts with Raptor to regulate autophagy and protect cardiomyocytes from ischemia-reperfusion-induced injury

Acute myocardial infarction (AMI) is a common disease with high morbidity and mortality worldwide. However, postinfarction pathogenesis remains unclear, and it is particularly important to identify new therapeutic targets. The RNA-binding motif protein RBM3 (also known as cold-inducible protein) is known to promote translation and is associated with tumor proliferation and neuroprotection. However, little is known about the biological effects of RBM3 on myocardial infarction. In the present study, we found that RBM3 expression was significantly upregulated in ischemia-reperfusion (I/R) condition and downregulation of RBM3 inhibited autophagy and promoted apoptosis in cardiomyocytes. We confirmed that RBM3 interacts with Raptor to regulate the autophagy pathway. Taken together, these findings illustrate the protective effects of RBM3 against I/R-induced myocardial apoptosis through the autophagy pathway.

VHL tumor suppressor as a novel potential candidate biomarker in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common type of endocrine cancer, with an increasing incidence worldwide. The treatment of PTC is currently the subject of clinical controversy, making it critically important to identify molecular markers that would help improve the risk stratification of PTC patients and optimize the therapeutic approach. The VHL tumor suppressor gene has been implicated in tumorigenesis of various types of carcinoma and linked with their aggressive biological behavior. The role of VHL in the origin and development of PTC has only recently begun to be revealed. In this narrative review we attempt to summarize the existing knowledge that implicates VHL in PTC pathogenesis and to outline its potential significance as a candidate molecular biomarker for the grouping of PTC patients into high and low risk groups.

Development and validation of a nomogram to evaluate the therapeutic effects of second-line axitinib in patients with metastatic renal cell carcinoma

The unpredictable biological behavior and tumor heterogeneity of metastatic renal cell carcinoma (mRCC) cause significant differences in axitinib efficacy. The aim of this study is to establish a predictive model based on clinicopathological features to screen patients with mRCC who can benefit from axitinib treatment. A total of 44 patients with mRCC were enrolled and divided into the training set and validation set. In the training set, variables related with the therapeutic efficacy of second-line treatment with axitinib were screened through univariate Cox proportional hazards regression and least absolute shrinkage and selection operator analyses. A predictive model was subsequently established to assess the therapeutic efficacy of second-line treatment with axitinib. The predictive performance of the model was evaluated by analyzing the concordance index and time-dependent receiver operating characteristic, calibration, and decision curves. The accuracy of the model was similarly verified in the validation set. The International Metastatic RCC Database Consortium (IMDC) grade, albumin, calcium, and adverse reaction grade were identified as the best predictors of the efficacy of second-line axitinib treatment. Adverse reaction grade was an independent prognostic index that correlated with the therapeutic effects of second-line treatment with axitinib. Concordance index value of the model was 0.84. Area under curve values for the prediction of 3-, 6-, and 12-month progression-free survival after axitinib treatment were 0.975, 0.909, and 0.911, respectively. The calibration curve showed a good fit between the predicted and actual probabilities of progression-free survival at 3, 6, and 12 months. The results were verified in the validation set. Decision curve analysis revealed that the nomogram based on a combination of four clinical parameters (IMDC grade, albumin, calcium, and adverse reaction grade) had more net benefit than adverse reaction grade alone. Our predictive model can be useful for clinicians to identify patients with mRCC who can benefit from second-line treatment with axitinib.

Epidemiology of Renal Cell Carcinoma: 2022 Update

CONTEXT

International variations in the rates of kidney cancer (KC) are considerable. An understanding of the risk factors for KC development is necessary to generate opportunities to reduce its incidence through prevention and surveillance.

OBJECTIVE

To retrieve and summarize global incidence and mortality rates of KC and risk factors associated with its development, and to describe known familial syndromes and genetic alterations that represent biologic risk factors.

EVIDENCE ACQUISITION

A systematic review was conducted via Medline (PubMed) and Scopus to include meta-analyses, reviews, and original studies regarding renal cell carcinoma, epidemiology, and risk factors.

EVIDENCE SYNTHESIS

Our narrative review provides a detailed analysis of KC incidence and mortality, with significant variations across time, geography, and sex. In particular, while KC incidence has continued to increase, mortality models have leveled off. Among the many risk factors, hypertension, obesity, and smoking are the most well established. The emergence of new genetic data coupled with observational data allows for integrated management and surveillance strategies for KC care.

CONCLUSIONS

KC incidence and mortality rates vary significantly by geography, sex, and age. Associations of the development of KC with modifiable and fixed risk factors such as obesity, hypertension, smoking, and chronic kidney disease (CKD)/end-stage kidney disease (ESKD) are well described. Recent advances in the genetic characterization of these cancers have led to a better understanding of the germline and somatic mutations that predispose patients to KC development, with potential for identification of therapeutic targets that may improve outcomes for these at-risk patients.

PATIENT SUMMARY

We reviewed evidence on the occurrence of kidney cancer (KC) around the world. Currently, the main avoidable causes are smoking, obesity, and high blood pressure. Although other risk factors also contribute, prevention and treatment of these three factors provide the best opportunities to reduce the risk of developing KC at present.

The Clinical and Molecular Features in the VHL Renal Cancers; Close or Distant Relatives with Sporadic Clear Cell Renal Cell Carcinoma?

Von Hippel-Lindau (VHL) disease is an autosomal dominant inherited cancer syndrome caused by germline mutations in the VHL tumor suppressor gene, characterized by the susceptibility to a wide array of benign and malign neoplasms, including clear-cell renal cell carcinoma. Moreover, VHL somatic inactivation is a crucial molecular event also in sporadic ccRCCs tumorigenesis. While systemic biomarkers in the VHL syndrome do not currently play a role in clinical practice, a new promising class of predictive biomarkers, microRNAs, has been increasingly studied. Lots of pan-genomic studies have deeply investigated the possible biological role of microRNAs in the development and progression of sporadic ccRCC; however, few studies have investigated the miRNA profile in VHL patients. Our review summarize all the new insights related to clinical and molecular features in VHL renal cancers, with a particular focus on the overlap with sporadic ccRCC.

New Therapeutic Interventions for Kidney Carcinoma: Looking to the Future

Simple Summary

Renal cell carcinoma (RCC) in metastatic form is a lethal pathology difficult to treat; therefore, the research of new therapeutic options for the treatment of metastatic patients is crucial to improve quality of life and overall survival. Recently, new signaling pathways and biological processes involved in cancer development and progression by scientific research community have been identified. These components including factors affecting angiogenesis, cell migration and invasion, autophagy and ferroptosis that are dysregulated in kidney cancer represent novel possible target molecules. In this work, we discuss current and new therapies for kidney cancer treatment; in particular, agents targeting new molecules involved in renal carcinogenesis that in future might become more powerful drugs for the cure of metastatic RCC.

Abstract

Patients suffering from metastatic renal cell carcinoma (mRCC) show an overall survival rate of lower than 10% after 5 years from diagnosis. Currently, the first-line treatment for mRCC patients is based on antiangiogenic drugs that are able to inhibit tyrosine kinase receptors (TKI) in combination with immuno-oncology (IO) therapy or IO-IO treatments. Second-line therapy involves the use of other TKIs, immunotherapeutic drugs, and mTOR inhibitors. Nevertheless, many patients treated with mTOR and TK inhibitors acquire drug resistance, making the therapy ineffective. Therefore, the research of new therapeutic targets is crucial for improving the overall survival and quality of life of mRCC patients. The investigation of the molecular basis of RCC, especially in clear cell renal cell carcinoma (ccRCC), has led to the identification of different signaling pathways that are involved in renal carcinogenesis. Most of ccRCCs are associated with mutation in VHL gene, which mediates the degradation of hypoxia-inducible factors (HIFs), that, in turn, regulate the pathways related to tumorigenesis, including angiogenesis and invasion. Renal tumorigenesis is also associated with the activation of tyrosine kinases that modulate the PI3K-Akt-mTOR pathway, promoting cell proliferation and survival. In ccRCC, the abnormal activity of mTOR activates the MDM2 protein, which leads to the degradation of tumor suppressor p53 via proteasome machinery. In addition, p53 may be degraded by autophagy in a mechanism involving the enzyme transglutaminase 2 (TG2). Suppression of wild-type p53 promotes cell growth, invasion, and drug resistance. Finally, the activation of ferroptosis appears to inhibit cancer progression in RCC. In conclusion, these pathways might represent new therapeutic targets for mRCC.

Loss of Von Hippel-Lindau (VHL) Tumor Suppressor Gene Function: VHL-HIF Pathway and Advances in Treatments for Metastatic Renal Cell Carcinoma (RCC)

Renal cell carcinoma (RCC) is a malignancy of the kidney originating from the tubular epithelium. Inactivation of the von Hippel–Lindau tumor-suppressor gene (VHL) is found in most clear cell renal cell carcinomas (ccRCCs). The VHL–HIF–VEGF/VEGFR pathway, which involves the von Hippel–Lindau tumor suppressor protein (VHL), hypoxia-inducible factor (HIF), vascular endothelial growth factor (VEGF), and its receptor (VEGFR), is a well-studied therapeutic target for metastatic ccRCC. Therefore, over the past decade, anti-angiogenic agents targeting VEGFR have served as the standard treatment for metastatic RCC. Recently, based on the immunomodulatory effect of anti-VEGFR therapy, anti-angiogenic agents and immune checkpoint inhibitor combination strategies have also emerged as therapeutic strategies. These advances were made possible by the improved understanding of the VHL–HIF pathway. In this review, we summarize the historical evolution of ccRCC treatments, with a focus on the involvement of the VHL–HIF pathway.