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Exosome-Mediated miR-4792 Transfer Promotes Bladder Cancer Cell Proliferation via Enhanced FOXC1/c-Myc Signaling and Warburg Effect.

ABSTRACT: Bladder cancer is the second-most common malignancy in the urogenital system and the most common in men. However, our understanding of the driving mechanisms of bladder cancer remains incomplete. The forkhead box (FOX) family of transcription factors is implicated in urogenital development and bladder malignancies. Many exosomal microRNAs have been identified as regulators and mediators of the expression of FOX, including the expression of FOXC1. miR-4792 has been known as a tumor miRNA suppressor. However, the function of miR-4792/FOXC1 signaling in bladder cancer development remains unknown. Here, we studied the role of miR-4792/FOXC1 signaling in bladder cancer by using multiple bladder cancer cell lines and bladder cancer mouse models through in vitro and in vivo approaches. We showed that FOXC1 is highly expressed in multiple bladder cancer cell lines and bladder tumor tissues. The knockdown of FOXC1 expression in bladder cancer cell lines decreases c-Myc expression levels, retards cell growth, and reduces aerobic glycolysis (also known as the Warburg effect) and lactic acid content. By contrast, the overexpression of FOXC1 elicits the opposite effects. FOXC1-downregulated bladder cancer cells form significantly smaller tumors in vivo. The inhibition of c-Myc reverses the effects of FOXC1 overexpression and leads to reduced cell proliferation, aerobic glycolysis, and lactic acid content. miR-4792 expression is downregulated in bladder tumor tissues. miR-4792 exposure to bladder cancer cells reduces the expression levels of FOXC1 and c-Myc, slows down cell growth, and decreases aerobic glycolysis and lactic acid content. However, the enhanced miR-4792 expression elicits opposite effects. These findings provided the first evidence that the exosome-mediated delivery of miR-4792 could play an important role in bladder cancer development through the downregulation of FOXC1 and c-Myc, which further inhibited aerobic glycolysis and lactic acid content.

SUBMITTER: Wu JH

PROVIDER: S-EPMC8791735 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:IntroductionExosomes are 30-100 nm membrane vesicles of endocytic origin, mediating diverse biological functions including tumor cell invasion, cell-cell communication and antigen presentation through transfer of proteins, mRNAs and microRNAs. Recent evidence suggests that microRNAs can be released through ceramide-dependent secretory machinery regulated by neutral sphingomyelinase 2 (nSMase2) enzyme encoded by the smpd3 gene that triggers exosome secretion. However, whether exosome-mediated microRNA transfer plays any role in cell invasion remains poorly understood. Thus, the aim of this study was to identify the exosomal microRNAs involved in breast cancer invasion.MethodsThe expression level of endogenous and exosomal miRNAs were examined by real time PCR and the expression level of target proteins were detected by western blot. Scanning electron and confocal microscopy were used to characterize exosomes and to study its uptake and transfer. Luciferase reporter plasmids and its mutant were used to confirm direct targeting. Furthermore, the functional significance of exosomal miR-10b was estimated by invasion assay.ResultsIn this study, we demonstrate that microRNA carrying exosomes can be transferred among different cell lines through direct uptake. miR-10b is highly expressed in metastatic breast cancer MDA-MB-231 cells as compared to non-metastatic breast cancer cells or non-malignant breast cells; it is actively secreted into medium via exosomes. In particular, nSMase2 or ceramide promotes the exosome-mediated miR-10b secretion whereas ceramide inhibitor suppresses this secretion. Moreover, upon uptake, miR-10b can suppress the protein level of its target genes such as HOXD10 and KLF4, indicating its functional significance. Finally, treatment with exosomes derived from MDA-MB-231 cells could induce the invasion ability of non-malignant HMLE cells.ConclusionTogether, our results suggest that a set of specific microRNAs may play an important role in modulating tumor microenvironment through exosomes. Thus, a better understanding of this process may aid in the development of novel therapeutic agents.

Project description:The purpose of our study is to elucidate the expression of lncRNA00518 (lnc00518) in the bladder cancer, and its potential mechanism in regulating the development of bladder cancer. The expression of lnc00518 in bladder cancer tissues and cells was examined by qRT-PCR. Correlation between lnc00518 expression with clinicopathologic characteristics and prognosis of bladder cancer patients was analyzed. In vitro effects of lnc00518 on the cellular behaviors of bladder cancer cells were explored. Moreover, in vivo effect of lnc00518 was evaluated by subcutaneous tumorigenesis in nude mice. The possible miRNA targets of lnc00518 were predicted by bioinformatics and further confirmed by dual-luciferase reporter gene assay, RIP and rescue experiments. Lnc00518 was highly expressed in bladder cancer tissues and cells. Lnc00518 expression was correlated with TNM staging and histological grade of bladder cancer. Besides, the overall survival was lower in bladder cancer patients with high expression of lnc00518 relative to those with low expression. Overexpression of lnc00518 enhanced proliferative, invasive, migratory potentials and clonality, but shortened G0/G1 phase of bladder cancer cells. Lnc00518 knockdown obtained the opposite trends. In vivo experiments revealed that lnc00518 knockdown inhibited subcutaneous tumorigenesis in nude mice. QRT-PCR results indicated that lnc00518 expression was negatively correlated with miRNA-101 expression in bladder cancer cells. Through dual-luciferase reporter gene assay and RIP, we confirmed the binding between lnc00518 and miRNA-101. Furthermore, EZH2 was verified to be the target of miRNA-101. MiRNA-101 knockdown reversed the inhibitory roles of lnc00518 knockdown in proliferative, migratory and invasive potentials of bladder cancer cells. Lnc00518 is highly expressed in bladder cancer and can be served as a predictor of poor prognosis. Lnc00518 promotes the proliferative, invasive and migratory potentials of bladder cancer by upregulating EZH2 via competitively binding to miRNA-101.

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Exosome-Mediated miR-4792 Transfer Promotes Bladder Cancer Cell Proliferation via Enhanced FOXC1/c-Myc Signaling and Warburg Effect.

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