RelB promotes the migration and invasion of prostate cancer DU145 cells via exosomal ICAM1 in vitro.

RelB confers the aggressiveness to prostate cancer (PC) cells. Exosomes modulate the oncogenesis and progression of PC. We aimed to identify the downstream molecule in the exosomes, by which RelB increases the aggressiveness of DU145. Totally, 137 upregulated and 55 downregulated exosomal proteins were identified from RelB-knockdown DU145 cells by Liquid Chromatography-Mass Spectrometry. UALCAN, GeneMANIA and tissue microarray analysis revealed that intercellular adhesion molecule-1 (ICAM1) was positively related to and co-expressed with RelB in PC. Luciferase reporter assay revealed that RelB bound directly to the promoter of ICAM1. ICAM1 overexpression enhanced the migration and invasion abilities of DU145 cells. Exposure to exosomes derived from ICAM1 overexpressing cells (hICAM1-exo) strengthened the aggressiveness of RelB-knockdown cells, especially the migration and invasion capabilities. Mechanistically, the expression of ICAM1, Integrin β1, MMP9 and uPA were upregulated in RelB-knockdown cells upon hICAM1-exo treatment. Exosomal ICAM1 is the key molecule regulated by RelB, which increased the aggressiveness of DU145. The study suggests that cell-cell communication via exosomal ICAM1 is a novel mechanism by which RelB promotes PC progression.