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Bladder cancer progression and metastasis have become major threats in clinical practice, increasing mortality and therapeutic refractoriness; recently, epigenetic dysregulation of epithelial-to-mesenchymal transition (EMT)-related signaling pathways has been explored. However, research in the fields of long noncoding RNA (lncRNA) and competing endogenous RNA (ceRNA) regulation in bladder cancer progression is just beginning. This study was designed to determine potential EMT-related ceRNA regulation in bladder cancer progression and elucidate the underlying mechanisms that provoke aggressiveness. After screening the intersection of bioinformatic pipelines, LINC02470 was identified as the most upregulated lncRNA during bladder cancer initiation and progression. Both in vitro and in vivo biological effects indicated that LINC02470 promotes bladder cancer cell viability, migration, invasion, and tumorigenicity. On a molecular level, miR-143-3p directly targets and reduces both LINC02470 and SMAD3 RNA expression. Therefore, the LINC02470–miR-143-3p–SMAD3 ceRNA axis rescues SMAD3 translation upon LINC02470 sponging miR-143-3p, and SMAD3 consequently activates the TGF-β-induced EMT process. In conclusion, this is the first study to demonstrate that LINC02470 plays a pivotally regulatory role in the promotion of TGF-β-induced EMT through the miR-143-3p/SMAD3 axis, thereby aggravating bladder cancer progression. Our study warrants further investigation of LINC02470 as an indicatively prognostic marker of bladder cancer.

Gemcitabine (GCB) resistance is a major issue in bladder cancer chemoresistance, but its underlying mechanism has not been determined. Epithelial-mesenchymal transition (EMT) has been shown to be comprehensively involved in GCB resistance in several other cancer types, but the direct connection between EMT and GCB remains unclear. This study was designed to elucidate the mechanism of EMT-related GCB resistance in bladder cancer and identify a potential phytochemical to modulate drug sensitivity. The biological effects of ellagic acid (EA) or its combined effects with GCB were compared in GCB-resistant cells and the GCB-sensitive line in terms of cell viability, apoptosis, motility, and in vivo tumorigenicity. The molecular regulation of EMT-related GCB resistance was evaluated at both the mRNA and protein expression levels. Our results indicated that TGF-β/Smad induced the overactivation of EMT in GCB-resistant cells and reduced the expression of GCB influx transporters (hCNT1 and hENT1). Moreover, ellagic acid (EA) inhibited the TGF-β signaling pathway both in vitro and in vivo by reducing Smad2, Smad3, and Smad4 expression and thereby resensitized GCB sensitivity. In conclusion, our results demonstrate that TGF-β/Smad-induced EMT contributes to GCB resistance in bladder cancer by reducing GCB influx and also elucidate the novel mechanisms of EA-mediated inhibition of TGF-β/Smad-induced EMT to overcome GCB resistance. Our study warrants further investigation of EA as an effective therapeutic adjuvant agent for overcoming GCB resistance in bladder cancer.

Exosomes are essential for several tumor progression-related processes, including the epithelial–mesenchymal transition (EMT). Long non-coding RNAs (lncRNAs) comprise a major group of exosomal components and regulate the neoplastic development of several cancer types; however, the progressive role of exosomal lncRNAs in bladder cancer have rarely been addressed. In this study, we identified two potential aggressiveness-promoting exosomal lncRNAs, LINC00960 and LINC02470. Exosomes derived from high-grade bladder cancer cells enhanced the viability, migration, invasion and clonogenicity of recipient low-grade bladder cancer cells and activated major EMT-upstream signaling pathways, including β-catenin signaling, Notch signaling, and Smad2/3 signaling pathways. Nevertheless, LINC00960 and LINC02470 were expressed at significantly higher levels in T24 and J82 cells and their secreted exosomes than in TSGH-8301 cells. Moreover, exosomes derived from LINC00960 knockdown or LINC02470 knockdown T24 cells significantly attenuated the ability of exosomes to promote cell aggressiveness and activate EMT-related signaling pathways in recipient TSGH-8301 cells. Our findings indicate that exosome-derived LINC00960 and LINC02470 from high-grade bladder cancer cells promote the malignant behaviors of recipient low-grade bladder cancer cells and induce EMT by upregulating β-catenin signaling, Notch signaling, and Smad2/3 signaling. Both lncRNAs may serve as potential liquid biomarkers for the prognostic surveillance of bladder cancer progression.