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Proteomic Profiling of Du145 Cell Line Exosomes Identifies Icam1 as Aputative molecular Mechanism by Which Relb Promotes The proliferation, Migration, and Invasion of Prostate cancer Cells


 Background: Prostate cancer (PC) is a serious health issue in men. Exosome plays essential roles in modulating the oncogenesis and progression of PC. RelB is highly expressed in PC and plays oncogenic parts in DU145 cells. We aim to uncover the protein panel of exosomes derived from RelB-knockdown DU145 cells (siRelB) as compared to control cells (sictrl) and explore a potential mechanism that RelB conferring the more aggressive phenotype to DU145 cells.Methods: Exosomes derived from sictrl and siRelB were subjected to Liquid Chromatography-Mass Spectrometry for proteomics profiling. Label-free quantification strategy iBAQ (intensity-based absolute quantification) was used to quantify and Fold Change (FC) was calculated to identify the differentially expressed proteins (DEPs). The characterization of proteins was conducted by bioinformatics analysis. ICAM1 over-expressing DU145 cells (hICAM1) and control cells (hctrl) were established by transfection using Lipofectamine 2000. The cell growth, migration, and invasion capabilities were measured by the xCelligence real-time monitoring system. Annexin V/PI-staining was adopted to assess apoptosis. CCK-8 assay was applied for proliferation evaluation. Integrin β-1, MMP9, and uPA were detected by Western blot.Results: 1259 exosomal proteins were identified, with 160 and 105 proteins unique to the siRelB and sictrl, respectively, while 994 proteins were present in both. We identified 137 upregulated and 55 downregulated proteins in siRelB. Gene Ontology (GO) analysis revealed that some DEPs had the cell adhesion molecular activity and participated in the cell adhesion process. Kyoto Encyclopedia of Genes and Genomes (KEGG) enriched that intercellular adhesion molecule-1 (ICAM1) was downregulated targeted by the NF-κB signaling. The FC of exosomal ICAM1 was 2.136. The expression of ICAM1 was positively related to RelB in PC by UALCAN. ICAM1 was shown to be co-expressed with RelB by GeneMANIA. The protein abundance of exosomal ICAM1 was lower in siRelB. hICAM1 had enhanced abilities of proliferation, migration, and invasion, with higher expression of Integrin β-1 when compared to hctrl.Conclusions: Our study identified 192 exosomal DEPs downstream of RelB in the DU145 cells. Exosomal ICAM1, conferring a more aggressive phenotype to DU145 cells, is a potential molecular mechanism modulating the tumorigenesis and progression of PC cells.