Exosomes secreted by prostate cancer cells under hypoxia promote matrix metalloproteinases activity at pre‐metastatic niches

Abstract

Approximately, 30 000 men die from prostate cancer (PCa) every year in the United States, mainly due to the metastasis. Thus, the key events associated with PCa metastasis are under rigorous investigation, with recent studies showing that preparation of pre‐metastatic niches (PMN) in distant organs is an important step. However, the molecular basis for PMN preparation is still unclear. Hypoxia in primary tumors promotes aggressiveness; however, its precise role in metastasis is not clear. We recently reported that exosomes secreted by PCa cells under hypoxia promote stemness and invasiveness in naïve PCa cells; however, whether these extracellular vesicles also influence PMN remains unknown. In the present study, we isolated exosomes from human PCa PC3 cells under normoxic (21% O2, exosomes secreted under normoxic condition [ExoNormoxic]) and hypoxic (1% O2, exosomes secreted under hypoxic condition [ExoHypoxic]) conditions, and characterized their effect (10 µg exosomes, intraperitoneal (IP) treatment every 48 hours for 4 weeks) on key biomarkers associated with PMN in nude mice. Whole animal fluorescence imaging showed that ExoHypoxic treatment promotes matrix metalloproteinases (MMPs) activity in several putative metastatic sites. Histological studies confirmed that ExoHypoxic treatment enhanced the level of MMP2, MMP9, and extracellular matrix proteins (fibronectin and collagen) as well as increased the number of CD11b+ cells at selective PMN sites. Furthermore, proteomic profiling of exosomes by liquid chromatography/mass spectrometry identified cargo proteins in ExoNormoxic and ExoHypoxic as well as distinct canonical pathways targeted by them. These results suggest that exosomes secreted by PCa cells under hypoxia plausibly remodel distant PMN, and thus, could be a potential target to control metastatic PCa.

The Dynamic Relationship of Breast Cancer Cells and Fibroblasts in Fibronectin Accumulation at Primary and Metastatic Tumor Sites

“…Interestingly, although the FN expression was transient, the lung tissue density remained significantly higher in 15, 20, and 25 d mice as compared to wild-type mice (Figure 1). A growing number of proteins have been shown to depend on FN in order to be incorporated into the ECM, including collagens, fibrillins, and tenascin-C. Of particular note, FN and type I collagen have been co-localized in the secretory pathway of fibroblasts, and collagen fibrils do not accumulate in the absence of FN [16,19]. An increase in FN fibrils may act as an initial ECM foundation in the premetastatic niche, which is then replaced with an abundance of collagen I.…”

“…In particular, EVs have been reported as a major cause of FN accumulation in the premetastatic niche. They have also been connected to the recruitment of tumor-supporting stromal cells and the enhanced attachment of disseminated tumor cells [10,19]. We recently demonstrated that conditioning pulmonary fibroblasts with EVs from BC cells could drastically alter the subsequent growth of epithelial BC cells in a FN-dependent manner [14].…”

Effect of Palmitic Acid on Exosome-Mediated Secretion and Invasive Motility in Prostate Cancer Cells

“…Cell motility as such is only one functional component of migration across extracellular matrix barriers, with the most notable other component being digestion and remodeling of the extracellular matrix, which enables motile cells' progress through the meshwork of basement membrane proteins, which is impenetrable to differentiated epithelial cells under normal conditions. The digestion and remodeling in metastatic prostate cancer cells is associated with secreted matrix metalloproteases [16,17,22]. We recently found that in prostate cancer cells, free (unimpeded) migration and invasion across the reconstituted extracellular matrix are controlled differently by isoforms of myosin IC [22].…”

“…The nutritional concerns dovetail with the increasingly evident role of lipids in the biogenesis and activity of prostate cell-derived exosomes. Studies have demonstrated that exosome-mediated cell-cell communication and functions, such as cell invasivity, play an important part in the progression of prostate cancer, while exosome-associated biomarkers gain acceptance in diagnostics [16][17][18][19][20][21]. Our own recent work, in particular, showed that the secretion of matrix metalloprotease-containing exosomes with the participation of a myosin isoform specific to advanced prostate cancer is accompanied by enhanced invasivity of the cells across extracellular matrix barriers [22][23][24].…”

The dynamic behavior of lipid droplets in the pre-metastatic niche

“…In addition, significantly increased lipid levels and LDs were observed in cancer cells under hypoxia 111 . Further research found that exosomes secreted by cancer cells under hypoxic conditions promote matrix metalloproteinase (MMP) activity in several putative metastatic sites 112 . However, a large number of studies have confirmed that BMDCs promote matrix remodeling in the PMN and elevate fibronectin (FN) expression.…”