The protein composition of exosomes released by prostate cancer cells is distinctly regulated by androgen receptor-antagonists and -agonist to stimulate growth of target cells

Abstract

Background Prostate cancer (PCa) is a prevalent malignancy in men worldwide, ranking as the second leading cause of cancer-related death in Western countries. Various PCa hormone therapies, such as androgen receptor (AR)-antagonists or supraphysiological androgen level (SAL) reduce cancer cell proliferation. However, treated cells may influence the growth of neighboring cells through secreted exosomes in the tumor microenvironment (TME). Here, the change of protein content of exosomes secreted from PCa cells through treatment with different AR-antagonists or SAL has been analyzed. Methods Isolation of exosomes via ultracentrifugation of treated human PCa LNCaP cells with AR-agonist and various AR-antagonists; analysis of cellular senescence by detection of senescence associated beta galactosidase activity (SA β-Gal); Western blotting and immunofluorescence staining; Mass spectrometry (MS-spec) of exosomes and bioinformatic analyses to identify ligand-specific exosomal proteins. Growth assays to analyze influence of exosomes on non-treated cells. Results MS-spec analysis identified ligand-specific proteins in exosomes. One thousand seventy proteins were up- and 52 proteins downregulated by SAL whereas enzalutamide upregulated 151 proteins and downregulated 42 exosomal proteins. The bioinformatic prediction indicates an up-regulation of pro-proliferative pathways. AR ligands augment hub factors in exosomes that include AKT1, CALM1, PAK2 and CTNND1. Accordingly, functional assays confirmed that the isolated exosomes from AR-ligand treated cells promote growth of untreated PCa cells. Conclusion The data suggest that the cargo of exosomes is controlled by AR-agonist and -antagonists and distinct among the AR-antagonists. Further, exosomes promote growth that might influence the TME. This finding sheds light into the complex interplay between AR signaling and exosome-mediated communication between PCa cells.

Emerging frontiers in androgen receptor research for prostate Cancer: insights from the 2nd international androgen receptor Symposium

“…These exosomes subsequently promoted the growth of LNCaP cells, underscoring their potential tumour-promoting activity within the microenvironment. This study enhances our understanding of AR-regulated exosome secretion by AR-ligands and how their protein content can mediate tumour growth [ 54 ].…”

“…However, the exact mechanism behind SAL’s repressing effects has not yet been described. In his talk, Prof. A. Baniahmad revealed that SAL can induce cellular senescence in CSPC and CRPC in preclinical PCa models to the same extent as antiandrogens [ 54 ]. Data from his research group showed that antiandrogens and SAL induce a tumour suppressive program by the p15/p16 – pRb – E2F1 – Cyclin D1 axis [ 54 , 55 ].…”

“…In his talk, Prof. A. Baniahmad revealed that SAL can induce cellular senescence in CSPC and CRPC in preclinical PCa models to the same extent as antiandrogens [ 54 ]. Data from his research group showed that antiandrogens and SAL induce a tumour suppressive program by the p15/p16 – pRb – E2F1 – Cyclin D1 axis [ 54 , 55 ]. However, he reported a SAL-activated increase in CD9 levels, indicating an enhanced exosome secretion.…”