Exosome-transmitted LINC00960 and LINC02470 promote the epithelial-mesenchymal transition and aggressiveness of bladder cancer cells

Abstract

Background Exosomes are essential for several tumor progression-related processes, including epithelial-mesenchymal transition (EMT). Long noncoding RNAs (lncRNAs) comprise a major group of exosomal components and regulate the neoplastic development of several cancer types; however, the progressive roles of exosomal lncRNAs in bladder cancer have rarely been addressed. In this study, we identified two potential aggressiveness-promoting exosomal lncRNAs, LINC00960 and LINC02470; we found that these lncRNAs potently induced EMT during bladder cancer progression. Methods Low-grade bladder cancer cells (TSGH-8301) were treated with conditioned media or exosomes derived from high-grade bladder cancer cells (T24 or J82), and the aggressiveness-promoting effects were evaluated. Cell viability, cell migratory/invasive activities and clonogenicity were compared to assess the response to these intercellular transmissions. Exosome-transmitted lncRNA candidates were screened with bioinformatic pipelines, and their expression levels were validated in bladder cancer cells and exosomes. Two novel lncRNAs, LINC00960 and LINC02470, were selected, and their roles and regulatory mechanisms in inducing the aggressiveness of bladder cancer cells were investigated. Results 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. Conclusion Our findings indicate that exosome-transmitted LINC00960 and LINC02470 from high-grade bladder cancer cells promotes the malignant behaviors of recipient low-grade bladder cancer cells and induces 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.