Exosomes secreted by placental stem cells selectively inhibit growth of aggressive prostate cancer cells

The current paradigm in the development of new cancer therapies is the ability to target tumor cells while avoiding harm to noncancerous cells. Furthermore, there is a need to develop novel therapeutic options against drug-resistant cancer cells. Researchers from the Wake Forest School of Medicine characterized the placental-derived stem cell (PLSC) exosomes (PLSCExo) and evaluated their anti-cancer efficacy in prostate cancer (PCa) cell lines. Nanoparticle tracking analyses revealed the size distribution (average size 131.4 ± 0.9 nm) and concentration of exosomes (5.23 × 1010±1.99 × 109 per ml) secreted by PLSC. PLSCExo treatment strongly inhibited the viability of enzalutamide-sensitive and -resistant PCa cell lines (C4-2B, CWR-R1, and LNCaP cells). Interestingly, PLSCExo treatment had no effect on the viability of a non-neoplastic human prostate cell line (PREC-1). Mass spectrometry (MS) analyses showed that PLSCExo are loaded with 241 proteins and mainly with saturated fatty acids. Further, Ingenuity Pathway Analysis analyses of proteins loaded in PLSCExo suggested the role of retinoic acid receptor/liver x receptor pathways in their biological effects. Together, these results suggest the novel selective anti-cancer effects of PLSCExo against aggressive PCa cells.

Characterization of exosomes secreted by PLSCs

exosomes

(A) PLSCExo were analyzed for particle size distribution and concentration by NTA. Representative particle size distribution for exosomes is presented. (B) PLSCExo were analyzed by transmission electron microscopy, and representative image is shown (magnification 98,000×). (C) Proteins loaded in PLSCExo were identified through mass spectroscopy. Subsequently, protein data was analyzed using IPA software, and proteins subcellular (or extracellular) localization is presented in pie diagram.

Peak TC, Praharaj P, Panigrahi GK, Doyle M, Su Y, Schlaepfer IR, Singh R, Vander Griend DJ, Alickson J, Hemal A, Atala A, Deep G. (2018) Exosomes secreted by placental stem cells selectively inhibit growth of aggressive prostate cancer cells. Biochem Biophys Res Commun [Epub ahead of print]. [abstract]

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