FAQ: Bladder Cancer ceRNA Network and Immune Microenvironment What is the competitive endogenous RNA (ceRNA) hypothesis, and how does it relate to gene expression in bladder cancer? The ceRNA hypothesis proposes that non-coding RNAs (ncRNAs) like circRNAs and lncRNAs can regulate mRNA expression by competing for shared microRNAs (miRNAs). In bladder cancer, this means that circRNAs and lncRNAs can act as "miRNA sponges," preventing miRNAs from binding to and repressing their target mRNAs, thereby influencing gene expression and potentially affecting cancer progression. According to the Heliyon article, "circRNAs or lncRNAs function as miRNA sponges and competitively bind to miRNAs to regulate the expression of target mRNAs, which is called the competitive endogenous RNA (ceRNA) hypothesis." This mechanism can influence the stability and translation of mRNAs involved in cancer development. How was the ceRNA network constructed in the Heliyon study? The ceRNA network was constructed using whole-transcriptome sequencing data from bladder tumor and peritumoral tissues. This data was combined with information from public databases such as ENCORI, circbank, NPInter, TargetScan, mir2disease, miRactDB, miRcode, miRDB, and miRWalk 2.0. A pruning algorithm was then applied to remove redundancy and statistical bias. This algorithm considered regulation similarity (RegSim) and correlation sensitivity (CorPvalue) to identify the most relevant circRNA/lncRNA-miRNA-mRNA interactions. In short, the initial network was built from public data, and a mathematical modeling algorithm was used to prune the network. What is BDNF, and why is it significant in the context of bladder cancer immunity? BDNF (Brain-Derived Neurotrophic Factor) is a neurotrophin that was identified as a key immune-related gene in the Heliyon study. It was found to be downregulated in bladder tumor tissues compared to peritumoral tissues. Further analyses, including WGCNA and ceRNA network construction, highlighted its role in the immune microenvironment of bladder cancer. The Heliyon study states, "We determined BDNF, known as Brain-Derived Neurotrophic Factor, which was the downregulated gene in bladder tumor tissues, as the key immune-related gene and constructed its ceRNA regulatory network." What is the role of hsa-miR-107 in the identified ceRNA network? In the identified ceRNA network, hsa-miR-107 acts as a negative regulator of BDNF expression. Certain circRNAs (e.g., hsa-circ-000211) and lncRNAs (e.g., AC108488.1 and LINC00163) sponge hsa-miR-107, preventing it from binding to BDNF mRNA and reducing its expression. This regulation is key to understanding how ncRNAs can influence BDNF levels and, consequently, the immune response in bladder cancer. The Heliyon article specifies that the constructed network involved "hsa-miR-107 sponged by hsa-circ-000211, AC108488.1, and LINC00163." How do the immune microenvironments of bladder tumors and peritumoral tissues differ? According to the Heliyon study, bladder tumors exhibit lower immune cell infiltration compared to peritumoral tissues. ssGSEA analysis showed that most immune cell types, such as activated B cells, T cells, macrophages, and NK cells, have lower scores in tumor samples. This indicates a less active immune microenvironment within the tumor itself, in contrast to the surrounding tissues. The study says, "the ssGSEA scores of most of the cell types in the tumor samples were significantly lower than those in peritumoral samples," What is WGCNA, and how was it used in the Heliyon study? WGCNA (Weighted Gene Co-expression Network Analysis) is a systems biology method used to identify modules of highly correlated genes within a dataset. In the Heliyon study, WGCNA was applied to immune-related DE-mRNAs to identify co-expression modules specific to tumor or peritumoral tissues. Hub genes within these modules were considered key regulators. As the article describes, "the immune-related DE-mRNAs’ matrix was supplied to WGCNA analysis... to generate the gene correlation matrix." What experimental evidence supports the interaction between hsa-miR-107 and BDNF, aside from computational inference? The Heliyon study provides experimental evidence supporting the interaction between hsa-miR-107 and BDNF through a luciferase reporter assay. Co-transfection of cells with hsa-miR-107 mimics and a BDNF reporter construct resulted in significantly decreased luciferase activity, demonstrating that BDNF is a direct target of hsa-miR-107. A FISH experiment also shows the co-expression of BDNF with hsa-miR-107. In addition, extensive literature exploration has been conducted that supports the interaction between hsa-miR-107 and BDNF, with some literature showing that BDNF is a downstream regulator of hsa-miR-107. What were the key findings of the meta-analysis regarding BDNF and hsa-miR-107 expression and survival in bladder cancer patients? The meta-analysis of public datasets revealed that low expression of BDNF and high expression of hsa-miR-107 were associated with longer overall survival in bladder cancer patients. This suggests that these molecules could serve as prognostic markers, with low BDNF and high hsa-miR-107 levels indicating a more favorable outcome. This was stated as, "low expression of BDNF and high expression of hsa-miR-107 were associated with low risk and good prognosis."