Exosomal LINC00355 derived from cancer-associated fibroblasts promotes bladder cancer cell resistance to cisplatin by regulating miR-34b-5p/ABCB1 axis.

ABSTRACT

Cisplatin resistance is a major challenge for bladder cancer (BC). Evidence indicates that exosome derived from cancer-associated fibroblasts (CAF-Exo) can promote chemotherapy resistance in various human tumors by delivering bioactive molecules. We have previously demonstrated that CAF-derived exosomal LINC00355 promotes BC cell proliferation and invasion. However, the underlying mechanisms are still unclear. In this study, we aimed to investigate the role and mechanisms of CAF-derived exosomal LINC00355 in BC cell resistance to cisplatin. Exosomes were isolated from normal fibroblasts (NFs) and BC tumor-derived CAFs, namely, NF-Exo and CAF-Exo. CAFs were transfected with si-Ctrl or si-LINC00355 and then different exosomes were isolated, namely, CAFsi-Ctrl-Exo and CAFsi-LINC00355-Exo. The human BC cell lines (T24 and 5367) were incubated with NF-Exo, CAF-Exo, CAFsi-Ctrl-Exo, and CAFsi-LINC00355-Exo in the presence of cisplatin. MTT proliferation assay and flow cytometric analysis showed that CAF-Exo promoted BC cell resistance to cisplatin and upregulated ABCB1 expression in BC cells by transferring LINC00355 to BC cells. Luciferase activity assay confirmed the interaction between miR-34b-5p and LINC00355 or ABCB1. qRT-PCR and western blot analysis further showed that LINC00355 sponged miR-34b-5p to upregulate ABCB1 expression. However, the promoting effects of CAF-Exo on BC cell resistance to cisplatin were abolished by miR-34b-5p overexpression and ABCB1 silencing. In conclusion, exosomal LINC00355 derived from CAFs promotes BC cell resistance to cisplatin by regulating the miR-34b-5p/ABCB1 axis.