Malignancy Grade-Dependent Mapping of Metabolic Landscapes in Human Urothelial Bladder Cancer: Identification of Novel, Diagnostic, and Druggable Biomarkers

Urinary microbiota and metabolic signatures associated with inorganic arsenic-induced early bladder lesions

Inorganic arsenic (iAs) contamination in drinking water is a global public health problem, and exposure to iAs is a known risk factor for bladder cancer. Perturbation of urinary microbiome and metabolome induced by iAs exposure may have a more direct effect on the development of bladder cancer. The aim of this study was to determine the impact of iAs exposure on urinary microbiome and metabolome, and to identify microbiota and metabolic signatures that are associated with iAs-induced bladder lesions. We evaluated and quantified the pathological changes of bladder, and performed 16S rDNA sequencing and mass spectrometry-based metabolomics profiling on urine samples from rats exposed to low (30 mg/L NaAsO₂) or high (100 mg/L NaAsO₂) iAs from early life (in utero and childhood) to puberty. Our results showed that iAs induced pathological bladder lesions, and more severe effects were noticed in the high-iAs group and male rats. Furthermore, six and seven featured urinary bacteria genera were identified in female and male offspring rats, respectively. Several characteristic urinary metabolites, including Menadione, Pilocarpine, N-Acetylornithine, Prostaglandin B1, Deoxyinosine, Biopterin, and 1-Methyluric acid, were identified significantly higher in the high-iAs groups. In addition, the correlation analysis demonstrated that the differential bacteria genera were highly correlated with the featured urinary metabolites. Collectively, these results suggest that exposure to iAs in early life not only causes bladder lesions, but also perturbs urinary microbiome composition and associated metabolic profiles, which shows a strong correlation. Those differential urinary genera and metabolites may contribute to bladder lesions, suggesting a potential for development of urinary biomarkers for iAs-induced bladder cancer.

Exploratory Metabolomics Underscores the Folate Enzyme ALDH1L1 as a Regulator of Glycine and Methylation Reactions

Folate (vitamin B9) is involved in one-carbon transfer reactions and plays a significant role in nucleic acid synthesis and control of cellular proliferation, among other key cellular processes. It is now recognized that the role of folates in different stages of carcinogenesis is complex, and more research is needed to understand how folate reactions become dysregulated in cancers and the metabolic consequences that occur as a result. ALDH1L1 (cytosolic 10-formyltetrahydrofolate dehydrogenase), an enzyme of folate metabolism expressed in many tissues, is ubiquitously downregulated in cancers and is not expressed in cancer cell lines. The RT4 cell line (derived from papillary bladder cancer) which expresses high levels of ALDH1L1 represents an exception, providing an opportunity to explore the metabolic consequences of the loss of this enzyme. We have downregulated this protein in RT4 cells (shRNA driven knockdown or CRISPR driven knockout) and compared metabolomes of ALDH1L1-expressing and -deficient cells to determine if metabolic changes linked to the loss of this enzyme might provide proliferative and/or survival advantages for cancer cells. In this study, cell extracts were analyzed using Ultra High Performance Liquid Chromatography High Resolution Mass Spectrometry (UHPLC-HR-MS). A total of 13,339 signals were identified or annotated using an in-house library and public databases. Supervised and unsupervised multivariate analysis revealed metabolic differences between RT4 cells and ALDH1L1-deficient clones. Glycine (8-fold decrease) and metabolites derived from S-adenosylmethionine utilizing pathways were significantly decreased in the ALDH1L1-deficient clones, compared with RT4 cells. Other changes linked to ALDH1L1 downregulation include decreased levels of amino acids, Krebs cycle intermediates, and ribose-5-phosphate, and increased nicotinic acid. While the ALDH1L1-catalyzed reaction is directly linked to glycine biosynthesis and methyl group flux, its overall effect on cellular metabolism extends beyond immediate metabolic pathways controlled by this enzyme.

The LINC01929/miR-6875-5p/ADAMTS12 Axis in the ceRNA Network Regulates the Development of Advanced Bladder Cancer

Considering its speedy development and extremely low 5-year overall survival rate worldwide, bladder cancer (BCa) is one of the most common and highly malignant tumors. Increasing evidence suggests that protein-coding mRNAs and non-coding RNAs, including long non-coding RNAs (lncRNAs) and micro RNAs (miRNAs), play an essential role in regulating the biological processes of cancer. To investigate the molecular regulation associated with poor prognosis during advanced BCa development, we constructed a competitive endogenous RNA (ceRNA) network. Using transcriptome profiles from The Cancer Genome Atlas and Gene Expression Omnibus databases, we performed differential expression (DE) analysis, weighted gene co-expression network analysis, functional enrichment analysis, survival analysis, prediction of miRNA targeting, and Pearson correlation analysis. Through layers of selection, 8 lncRNAs-28 mRNAs and 8 miRNAs-28 mRNAs pairs shared similar expression patterns, constituting a core ceRNA regulatory network related to the invasion, progression, and metastasis of advanced clinical stage (ACS) BCa. Subsequently, we conducted real time qPCR, western blotting, and immunohistochemistry to validate expression trend bioinformatics analysis on 3, 2, and 3 differentially expressed mRNAs, lncRNAs, and miRNAs, respectively. The most significantly differentially expressed LINC01929, miR-6875-5p and ADAMTS12 were selected for in vitro experiments to assess the functional role of the LINC01929/miR-6875-5p/ADAMTS12 axis. RNA pull-down, luciferase assays, and rescue assays were performed to examine the binding of LINC01929 and miR-6875-5p. Increasing trends in COL6A1, CDH11, ADAMTS12, LINC01705, and LINC01929 expression variation were verified as consistent with previous DE analysis results in ACS-BCa, compared with low clinical stage (LCS) BCa. Expression trends in parts of these RNAs, such as hsa-miR-6875-5p, hsa-miR-6784-5p, COL6A1, and CDH11, were measured in accordance with DE analysis in LCS-BCa, compared with normal bladder urothelium. Through experimental validation, the cancer-promoting molecule ADAMST12 was found to play a key role in the development of advanced BCa. Functionally, ADAMTS12 knockdown inhibited the progression of bladder cancer. Overexpression of LINC01929 promoted bladder cancer development, while overexpression of miR-6785-5p inhibited bladder cancer development. Mechanistically, LINC01929 acted as a sponge for miR-6785-5p and partially reversed the role of miR-6785-5p. Our findings provide an elucidation of the molecular mechanism by which advanced bladder cancer highly expressed LINC01929 upregulates ADAMTS12 expression through competitive adsorption of miR-6875-5p. It provides a new target for the prognosis and diagnosis of advanced bladder cancer.

Lamprey immunity protein enables detection for bladder cancer through recognizing N-hydroxyacetylneuraminic acid (Neu5Gc)-modified as a diagnostic marker and exploration of its production mechanism

Previous studies have demonstrated that Neu5Gc is highly expressed in breast, ovarian, prostate, colon and lung cancers, but not in normal human cells. The presence of Neu5Gc is important for prognosis and is associated with aggressiveness, metastasis, and tumor grade. However, increased Neu5Gc in bladder cancer remains unclear. LIP from lamprey binds the carbohydrate receptor of N-glycolylneuraminic acid (Neu5Gc). The combination of Neu5Gc and LIP suggested that it might be used as a diagnostic tool for the detection of Neu5Gc tumor antigen. Here, the classical animal model of bladder cancer was successfully induced by MNU bladder perfusion. The ELISA results showed that the expression level of Neu5Gc in the urine of normal rats was 94.96 ± 21.01ng/mg, and that of bladder cancer rats was 158.28 ± 34.86 ng/mg. In addition, the results of SNA and LIP immunohistochemistry demonstrated the high expression of Neu5Gc in bladder cancer. After the addition of Neu5Gc to BIU-87 and SV-HUC-1 cells, transcriptomic sequencing and real-time quantitative PCR analysis demonstrated that the gene expression of Neu5Gc synthesis pathway was significantly increased. These data suggest that LIP provides a new tool for the detection of biological samples, especially urine from patients with bladder cancer or suspected cancer, and that revealing the mechanism of abnormal glycosylation can provide theoretical basis for clinical studies.

Metabolomic Approaches for Detection and Identification of Biomarkers and Altered Pathways in Bladder Cancer

Metabolomic analysis has proven to be a useful tool in biomarker discovery and the molecular classification of cancers. In order to find new biomarkers, and to better understand its pathological behavior, bladder cancer also has been studied using a metabolomics approach. In this article, we review the literature on metabolomic studies of bladder cancer, focusing on the different available samples (urine, blood, tissue samples) used to perform the studies and their relative findings. Moreover, the multi-omic approach in bladder cancer research has found novel insights into its metabolic behavior, providing excellent start-points for new diagnostic and therapeutic strategies. Metabolomics data analysis can lead to the discovery of a “signature pathway” associated with the progression of bladder cancer; this aspect could be potentially valuable in predictions of clinical outcomes and the introduction of new treatments. However, further studies are needed to give stronger evidence and to make these tools feasible for use in clinical practice.

Focus on Biochemical and Clinical Predictors of Response to Immune Checkpoint Inhibitors in Metastatic Urothelial Carcinoma: Where Do We Stand?

Urothelial bladder cancer is one of the most lethal cancers worldwide with barely 5% five-year survival in patients with metastatic disease. Intravesical immunotherapy with Bacillus Calmette-Guérin and platinum-based chemotherapy are currently the standard of care for non-muscle invasive and advanced or metastatic urothelial cancer (mUC), respectively. Recently, a subset of patients with locally advanced or mUC has shown to be responsive to immune checkpoint inhibitors (ICIs), e.g., the anti-cytotoxic T-lymphocyte-associated protein 4 and programmed cell death -1/programmed death-ligand1 (PD-1/PD-L1) antibodies. Due to the relevant clinical benefit of immunotherapy for mUC, in 2016, the United States Food and Drug Administration (FDA) approved five immunotherapeutic agents as second-line or first-line treatments for patients with advanced bladder cancer who did not profit from or were ineligible for standard therapy. In this review, we discuss the role of immunotherapy in bladder cancer and recent clinical applications of PD-1/PD-L1 blockade in mUC. Furthermore, we evaluate a variable response rate to ICIs treatment and outline potential biomarkers predictive of immunotherapy response.

Immunotherapy in Bladder Cancer: Current Methods and Future Perspectives

Bladder cancer is one of the most significant genitourinary cancer, causing high morbidity and mortality in a great number of patients. Over the years, various treatment methods for this type of cancer have been developed. The most common is the highly efficient method using Bacillus Calmette-Guerin, giving a successful effect in a high percentage of patients. However, due to the genetic instability of bladder cancer, together with individual needs of patients, the search for different therapy methods is ongoing. Immune checkpoints are cell surface molecules influencing the immune response and decreasing the strength of the immune response. Among those checkpoints, the PD-1 (programmed cell death protein-1)/PD-L1 (programmed cell death protein ligand 1) inhibitors aim at blocking those molecules, which results in T cell activation, and in bladder cancer the use of Atezolizumab, Avelumab, Durvalumab, Nivolumab, and Pembrolizumab has been described. The inhibition of another pivotal immune checkpoint, CTLA-4 (cytotoxic T cell antigen), may result in the mobilization of the immune system against bladder cancer and, among anti-CTLA-4 antibodies, the use of Ipilimumab and Tremelimumab has been discussed. Moreover, several different approaches to successful bladder cancer treatment exists, such as the use of ganciclovir and mTOR (mammalian target of rapamycin) kinase inhibitors, IL-12 (interleukin-12) and COX-2 (cyclooxygenase-2). The use of gene therapies and the disruption of different signaling pathways are currently being investigated. Research suggests that the combination of several methods increases treatment efficiency and the positive outcome in individual.