Abstract
Exosomes are 40–100 nm nano-sized extracellular vesicles. They are released from many cell types and move into the extracellular space, thereby transferring their components to recipient cells. Exosomes are receiving increasing attention as novel structures participating in intracellular communication. RAB27B is one of the leading proteins involved in exosome secretion, and oncogenic effects have been reported in several cancers. In recent years, molecularly targeted agents typified by sunitinib are widely used for the treatment of metastatic or recurrent renal cell carcinoma (RCC). However, intrinsic or acquired resistance to sunitinib has become a major issue. The present study aimed to elucidate the role of RAB27B in RCC including sunitinib-resistant and its role in exosomes. Bioinformatic analyses revealed that high expression of RAB27B correlates with progression of RCC. The expression of RAB27B protein in RCC cell lines was significantly enhanced compared with that in normal kidney cell lines. Furthermore, RAB27B protein expression was enhanced in all of the tested sunitinib-resistant RCC cell lines compared to parental cells. Although no specific effect of RAB27B on exosomes was identified in RCC cells, loss-of-function studies demonstrated that knockdown of RAB27B suppressed cell proliferation, migration and invasive activities. Moreover, anti-tumor effects of RAB27B downregulation were also observed in sunitinib-resistant RCC cells. RNA sequence and pathway analysis suggested that the oncogenic effects of RAB27B might be associated with MAPK and VEGF signaling pathways. These results showed that RAB27B is a prognostic marker and a novel therapeutic target in sunitinib-sensitive and -resistant RCCs. Further analyses should improve our understanding of sunitinib resistance in RCC.
Highlights
Renal cell carcinoma (RCC) constitutes approximately 90–95% of all kidney neoplasms [1], making it the seventh most common site for tumours in 2013 [2]
Among the ccRCC cohort of The Cancer Genome Atlas (TCGA), we found that the expression levels of RAB27B were significantly increased in pathological T4 category (Fig 1B, left panel) and pathological high grade G4 cases (Fig 1B, right panel)
RAB27B protein expression levels in RCC cell lines, sunitinib-resistant RCC cell lines and HK2 cells were evaluated by Western blot analyses
Summary
Renal cell carcinoma (RCC) constitutes approximately 90–95% of all kidney neoplasms [1], making it the seventh most common site for tumours in 2013 [2]. Oncogenic effects of RAB27B in sunitinib-sensitive and -resistant RCCs role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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