Introduction

Molecular targeted therapies have been developed for various cancers, however; which have not advanced beyond conventional chemotherapy for the locally advanced and metastatic bladder cancer (BC). Therefore, establishment of more efficient therapeutic strategy is urgently desired. Recently, extracellular exosomes are paid attention as important mediators of intercellular communication. Tumor-derived exosomes have known to transfer proteins and nucleic acids from the cells of origin to target cells and affect tumor progression and metastatic process. We have been reported that signaling adaptor protein CRK promotes cell growth, invasion, and adhesion in various cancers, however; the relationship between CRK and exosomes has remained unknown. Here, we investigated the effects of CRK-mediated exosomes on tumor progression and metastasis of BC.

Methods

Human BC cell line UM-UC-3 were stably transfected with pCSII-CMV-tdTomato-Luc, and CRK was knocked-down by shRNA technique. The parental and CRK-depleted cells (CRKi) were orthotopically injected into nude mice, and the tumor progression and metastasis were investigated using IVIS Spectrum. In in vitro setting, expression levels of proteins associated with cell growth, survival, and invasion were examined in parental and CRKi UM-UC-3 cells and their exosomes, and the proteins contained in exosomes were identified by LC-TOF/MS. Low grade BC 5637 cells and HUVECs were treated with exosomes from parental UM-UC-3 cells, and the cell proliferation and invasion were analyzed. Furthermore, the metastases in mice pretreated with exosomes from parental and CRKi cells were investigated.

Results

CRKi UM-UC-3 cells inhibited the tumor progression and metastasis in orthotopic xenograft models. We found that CRK and ErbB2 were contained in exosome from the parental UM-UC-3 cells, and the exosomes-incorporated-5637 and -HUVECs significantly promote the cell proliferation and invasion. In contrast, in exosomes from CRKi cells, the expression levels of ErbB2 were reduced, and the exosome-incorporated recipient cells decreased the growth and invasion. Of note, lung metastasis of UM-UC-3 cells was facilitated in mice educated by the parental UM-UC-3-derived exosomes, but not by CRKi cells-derived exosomes.

Conclusions

Here, we provide novel findings that CRK-regulated up-regulation of ErbB2 in the exosomes of BC facilitated the tumor progression and metastasis. Therefore, CRK and ErbB2 might be potent therapeutic targets to prevent the locally advanced and metastasis for BC patients.

Funding

none