Modeling Neoplastic Growth in Renal Cell Carcinoma and Polycystic Kidney Disease

Impaired Glucose Metabolism, Primary Cilium Defects, and Kidney Cystogenesis in Glycogen Storage Disease Type Ia

Key Points

Background

Glycogen storage disease type Ia (GSDIa) is a rare metabolic disorder caused by mutations in the catalytic subunit of glucose-6 phosphatase (G6PC1). This leads to severe hypoglycemia, and most young patients with GSDIa develop CKD. The kidney pathology is characterized by the development of cysts, which typically occur at an advanced stage of CKD.

Methods

To elucidate the molecular mechanisms responsible for cyst formation, we characterized renal metabolism, molecular pathways involved in cell proliferation, and primary cilium integrity using mice in which G6pc1 was specifically deleted in the kidney from an in utero stage.

Results

GSDIa mice exhibited kidney fibrosis, high inflammation, and cyst formation, leading to kidney dysfunction. In addition, the loss of G6PC1 led to the ectopic accumulation of glycogen and lipids in the kidneys and a metabolic shift toward a Warburg-like metabolism. This metabolic adaptation was due to an excess of glucose-6 phosphate, which supports cell proliferation, driven by the mitogen-activated protein kinase/extracellular signal–regulated kinases and protein kinase B/mammalian target of rapamycin pathways. Treatment of GSDIa mice with rapamycin, a target of the mammalian target of rapamycin pathway, reduced cell proliferation and kidney damage. Our results also identified lipocalin 2 as a contributor to renal inflammation and an early biomarker of CKD progression in GSDIa mice. Its inactivation partially prevented kidney lesions in GSDIa. Importantly, primary cilium defects were observed in the kidneys of GSDIa mice.

Conclusions

Metabolic adaptations because of glucose-6 phosphate accumulation in GSDIa renal tubules, toward a Warburg-like metabolism, promoted cell proliferation and cyst formation in a similar manner to that observed in various cystic kidney diseases. This was associated with downregulation of primary cilium gene expression and, consequently, altered cilium morphology.

An oligomeric hyaluronic acid-GX1 molecular target drug with polyvalent targeting to CD44 and VEGF receptors

The off-target toxicity of molecular targeted drug hinders its clinical transformation. Herein, we report a new molecular targeted drug oHA-GX1 constructed by oligomeric hyaluronan (oHA) and peptide GX1 (CGNSNPKSC). The oHA-GX1 can not only suppress the tumor growth by interacting with overexpressed VEGF and CD44 receptors inside tumor tissues, but also reduce the likelihood of off-target toxicity due to the multiple VEGF and CD44 receptors binding sites. The cytotoxicity study shows that the IC₅₀^oHA-GX1 against co-SGC-7901 and co-HUVEC cells fell in the range of common cytotoxic drugs. The animal experiment results reveal that the tumor inhibition rate of oHA-GX1 (100 mg/kg) against SGC-7901 tumor-bearing mice were 78.4 %, which was comparable to that of front-line chemotherapy drugs. Also, the cytotoxicity study on normal cells, hemolysis test, hemagglutination assay and the acute toxicity test demonstrate that oHA-GX1 exhibited excellent biosafety. This molecular targeted drug that utilizes the multiple receptor-binding sites to get rid of the side effects caused by off-target paves a new direction for the discovery of anticancer drugs with high efficacy and low adverse effects.

Inhibition of deubiquitinase USP28 attenuates cyst growth in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease, which is characterized by progressive growth of multiple renal cysts in bilateral kidneys. In the past decades, mechanistic studies have entailed many essential signalling pathways that were regulated through post-translational modifications (PTMs) during cystogenesis. Among the numerous PTMs involved, the effect of ubiquitination and deubiquitination remains largely unknown. Herein, we identified that USP28, a deubiquitinase aberrantly upregulated in patients with ADPKD, selectively removed K48-linked polyubiquitination and reversed protein degradation of signal transducer and activator of transcription 3 (STAT3). We also observed that USP28 could directly interact with and stabilize c-Myc, a transcriptional target of STAT3. Both processes synergistically enhanced renal cystogenesis. Furthermore, pharmacological inhibition of USP28 attenuated the cyst formation both in vivo and in vitro. Collectively, USP28 regulates STAT3 turnover and its transcriptional target c-Myc in ADPKD. USP28 inhibition could be a novel therapeutic strategy against ADPKD.

Lysosomal-Associated Transmembrane Protein 5 Promotes Proliferation, Migration, and Invasion of Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most aggressive and deadly cancer of the urinary system and is regulated by multiple signaling pathways. However, the specific molecular mechanisms underlying ccRCC have not been fully studied or demonstrated. This study aimed to elucidate the function of lysosomal-associated transmembrane protein 5 (LAPTM5) in ccRCC cell lines and animal models and determine the potential underlying mechanisms. Our results demonstrated that LAPTM5 expression in patients with ccRCC was significantly higher in the tumor group than that in the adjacent nontumor group. Moreover, LAPTM5 promoted proliferation, migration, and invasion of ccRCC cells through the gain and loss of the function of LAPTM5 in 786-0 and Caki-1 cell lines. Similar results regarding LAPTM5 overexpression were obtained in BALB/c nude mice. In addition, LAPTM5 activated the Jun N-terminal kinase (JNK)/p38 signaling cascade by interacting with Ras-related C3 botulinum toxin substrate 1 (RAC1). Treatment with an RAC1 inhibitor eliminated the effects of LAPTM5 in ccRCC. In conclusion, these results indicate that LAPTM5 may be a new therapeutic target for ccRCC via activation of the RAC1-JNK/p38 axis.

Macrophages in Renal Injury, Repair, Fibrosis Following Acute Kidney Injury and Targeted Therapy

Acute kidney injury (AKI) is a renal disease with a high incidence and mortality. Currently, there are no targeted therapeutics for preventing and treating AKI. Macrophages, important players in mammalian immune response, are involved in the multiple pathological processes of AKI. They are dynamically activated and exhibit a diverse spectrum of functional phenotypes in the kidney after AKI. Targeting the mechanisms of macrophage activation significantly improves the outcomes of AKI in preclinical studies. In this review, we summarize the role of macrophages and the underlying mechanisms of macrophage activation during kidney injury, repair, regeneration, and fibrosis and provide strategies for macrophage-targeted therapies.

The international exchange of Drosophila melanogaster strains

Drosophila melanogaster has been a model organism for experimental research for more than a century, and the knowledge and associated genetic technologies accumulated around this species make it extremely important to contemporary biomedical research. A large international community of highly collaborative scientists investigate a remarkable diversity of biological problems using genetically characterised strains of Drosophila, and frequently exchange these strains across borders. Despite its importance to the study of fundamental biological processes and human disease-related cellular mechanisms, and the fact that it presents minimal health, agricultural or environmental risks, Drosophila can be difficult to import. The authors argue that streamlined regulations and practices would benefit biomedical research by lowering costs and increasing efficiencies.

Identification of Hypoxia-Immune-Related Gene Signatures and Construction of a Prognostic Model in Kidney Renal Clear Cell Carcinoma

Introduction: Kidney renal clear cell carcinoma (KIRC), a kind of malignant disease, is a severe threat to public health. Tracking the information of tumor progression and conducting a related dynamic prognosis model are necessary for KIRC. It is crucial to identify hypoxia-immune-related genes and construct a prognostic model due to immune interaction and the influence of hypoxia in the prognosis of patients with KIRC. Methods: The hypoxia and immune status of KIRC patients were identified by utilizing t-SNE and ImmuCellAI for gene expression data. COX and Lasso regression were used to identify some hypoxia-immune-related signature genes and further construct a prognostic risk model based on these genes. Internal and external validations were also conducted to construct a prognostic model. Finally, some potentially effective drugs were screened by the CMap dataset. Results: We found that high-hypoxia and low-immune status tend to induce poor overall survival (OS). Six genes, including PLAUR, UCN, PABPC1L, SLC16A12, NFE2L3, and KCNAB1, were identified and involved in our hypoxia-immune-related prognostic risk model. Internal verification showed that the area under the curve (AUC) for the constructed models for 1-, 3-, 4-, and 5-year OS were 0.768, 0.754, 0.775, and 0.792, respectively. For the external verification, the AUC for 1-, 3-, 4-, and 5-year OS were 0.768, 0.739, 0.763, and 0.643 respectively. Furthermore, the decision curve analysis findings demonstrated excellent clinical effectiveness. Finally, we found that four drugs (including vorinostat, fludroxycortide, oxolinic acid, and flutamide) might be effective and efficient in alleviating or reversing the status of severe hypoxia and poor infiltration of immune cells. Conclusion: Our constructed prognostic model, based on hypoxia-immune-related genes, has excellent effectiveness and clinical application value. Moreover, some small-molecule drugs are screened to alleviate severe hypoxia and poor infiltration of immune cells.

Empowering Melatonin Therapeutics with Drosophila Models

Melatonin functions as a central regulator of cell and organismal function as well as a neurohormone involved in several processes, e.g., the regulation of the circadian rhythm, sleep, aging, oxidative response, and more. As such, it holds immense pharmacological potential. Receptor-mediated melatonin function mainly occurs through MT1 and MT2, conserved amongst mammals. Other melatonin-binding proteins exist. Non-receptor-mediated activities involve regulating the mitochondrial function and antioxidant cascade, which are frequently affected by normal aging as well as disease. Several pathologies display diseased or dysfunctional mitochondria, suggesting melatonin may be used therapeutically. Drosophila models have extensively been employed to study disease pathogenesis and discover new drugs. Here, we review the multiple functions of melatonin through the lens of functional conservation and model organism research to empower potential melatonin therapeutics to treat neurodegenerative and renal diseases.

Identifying Hypoxia Characteristics to Stratify Prognosis and Assess the Tumor Immune Microenvironment in Renal Cell Carcinoma

Background: Renal cell carcinoma (RCC) is a common malignant tumor worldwide, and immune checkpoint inhibitors are a new therapeutic option for metastatic RCC. Infiltrating immune cells in the tumor microenvironment (TME) play a critical part in RCC biology, which is important for tumor therapy and prediction. Hypoxia is a common condition that occurs in the TME and may lead to RCC immunosuppression and immune escape. This study was conducted to analyze the extent of the hypoxia immune microenvironment in the TME of RCC and develop a hypoxia-related risk model for predicting the prognosis of patients with RCC.

Methods: The gene expression profiles of 526 patients with RCC were downloaded from The Cancer Genome Atlas database. Combined with the hallmark-hypoxia gene dataset downloaded from Gene Set Enrichment Analysis, prognosis-related hypoxia genes were selected by survival analysis. A protein–protein interaction network and functional enrichment analysis were performed. A hypoxia-related risk model predicting the prognosis of patients with RCC was established using the least absolute shrinkage and selection operator. Data of 91 cases downloaded from the International Cancer Genome Consortium (ICGC) database were used for validation. CIBERSORT was applied to analyze the fractions of 22 immune cell types in the TME of RCC between low- and high-risk groups. The expression profiles of immunomodulators and immunosuppressive cytokines were also analyzed.

Results: Ninety-three genes were significantly associated with poor overall survival of patients with RCC and were mainly involved in 10 pathways. Using the established hypoxia-related risk model, the receiver operating characteristic curves showed an accuracy of 76.1% (95% CI: 0.719–0.804), and Cox proportional hazards regression analysis revealed that the model was an independent predictor of the prognosis of patients with RCC [hazard ratio (HR) = 2.884; 95% CI: 2.090–3.979] (p < 0.001). Using the ICGC database, we verified that the low-risk score group had a better overall survival outcome than the high-risk group. Additionally, dividing the hypoxia risk score into high-risk and low-risk groups could predict the immune microenvironment of RCC.

Conclusions: We demonstrated that a hypoxia-related risk model can be used to predict the outcomes of patients with RCC and reflect the immune microenvironment of RCC, which may help improve the overall clinical response to immune checkpoint inhibitors.