Pancreatic stellate cells (PSCs) interact with pancreatic cancer cells in the tumor microenvironment. Cell constituents including microRNAs may be exported from cells within membranous nanovesicles termed exosomes. Exosomes might play a pivotal role in intercellular communication. Researchers at the Tohoku University Graduate School of Medicine aimed to clarify the microRNA signature of PSC-derived exosomes and their effects on pancreatic cancer cells.
Exosomes were prepared from the conditioned medium of immortalized human PSCs. MicroRNAs were prepared from the exosomes and their source PSCs, and the microRNA expression profiles were compared by microarray. The effects of PSC-derived exosomes on proliferation, migration, and the mRNA expression profiles were examined in pancreatic cancer cells.
Pancreatic stellate cell-derived exosomes contained a variety of microRNAs including miR-21-5p. Several microRNAs such as miR-451a were enriched in exosomes compared to their source PSCs. Pancreatic stellate cell-derived exosomes stimulated the proliferation, migration and expression of mRNAs for chemokine (C – X – C motif) ligands 1 and 2 in pancreatic cancer cells. The stimulation of proliferation, migration, and chemokine gene expression by the conditioned medium of PSCs was suppressed by GW4869, an exosome inhibitor.
Isolation of PSC-derived exosomes
Exosomes were isolated by the sequential ultracentrifugation of conditioned medium of immortalized human PSCs. A, Transmission electron microscopy showing the isolated vesicles. Original magnification: 25,000. Scale bar represents 100 nm. B, Exosomal (“Exo”) and cellular proteins (“Cell”) were prepared by lysing the isolated exosomes and their source PSCs, respectively. The levels of CD9, CD63, CD81, and GM130 were determined by Western blotting.
We clarified the microRNA expression profile in PSC-derived exosomes. Pancreatic stellate cell-derived exosomes might play a role in the interactions between PSCs and pancreatic cancer cells.