Prostate cancer progression is driven by adipocyte-derived extracellular vesicles


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Fabrizio Fontana1, Monica Marzagalli1, Michela Raimondi1, Emanuela Carollo2, Patrizia Sartori1, Patrizia Procacci1, David Carter2, Patrizia Limonta1
1University of Milan, 2Oxford Brookes University

Abstract

Background

It is known that an association exists between obesity and risk of prostate cancer (PCa). A cross-talk between adipocytes and PCa has been demonstrated; however, the study of this dialog has been limited to metabolites and adipokines, although emerging evidence points to a key role of extracellular vesicles (EVs) in the control of tumor progression.

Method

After isolation by SEC, EVs were characterized by NTA, TEM and Western blot analysis (TSG101, Hsc70, Alix, calnexin and cytochrome c). In PC3 and DU145 PCa cells, the effect of 3T3-L1 adipocyte conditioned media and EVs on cell proliferation was evaluated by Trypan blue exclusion assay; AKT phosphorylation was analyzed by Western blot. After adipocyte media/EV conditioning, PC3 and DU145 metastatic potential was assessed by scratch test and Boyden chamber assay, and matrix metalloproteinase and epithelial-to-mesenchymal transition marker levels were analyzed by Western blot, while changes in mitochondrial activity, ATP synthesis, lipid content and glucose consumption were assessed by flow cytometry. The effect of adipocyte conditioned media/EVs on PCa cell resistance to docetaxel was evaluated by Trypan blue exclusion assay and Annexin V/PI assay; Western blot analysis of caspase 3 and PARP levels as well as of CD44 expression was also performed.

Results

We demonstrated that 3T3-L1 adipocyte conditioned media can affect PC3 and DU145 cell features, inducing increased proliferation, associated with AKT phosphorylation, and invasion, correlated with MMP2 and 9 activation, E/N-cadherin switch and Snail upregulation. Moreover, PCa cells were found to accumulate lipid droplets and, more importantly, to undergo a neuroendocrine differentiation, accompanied by CD44 enhanced expression and docetaxel resistance. Notably, these results were confirmed in 3T3-L1 EV-treated PC3 and DU145 cells, where an increase in glucose consumption, mitochondrial activity, ATP production and ROS generation was also observed, suggesting that adipocyte EVs can reprogram PCa metabolism.

Conclusion

These results highlight that an EV-mediated cross-talk exists between adipocytes and PCa, driving tumor aggressiveness. Further studies will be performed to identify the adipocyte EV molecular cargo responsible for the modulation of this dialog.

Impact statement

These findings will clarify the mechanisms underlying the association between obesity and PCa, highlighting the role of EVs as both biomarkers and therapeutic targets.