Pancreatic cancer cell-secreted exosomes promote apoptosis of β cells via activation of mitochondrial apoptotic pathways / 中国病理生理杂志

ABSTRACT

AIM:To investigate the effects of exosomes secreted by pancreatic cancer cells on the viability and function of βcells and the possible mechanism .METHODS:ExoQuick-TC kit was used to extract exosomes in the super-natants of mouse pancreatic cancer Pan 02 and MPC-83 cells, and the extracted exosomes were identified by transmission electron microscopy.Fluorescence-labeled exosomes were incubated with mouse insulinoma MIN 6 cells for 48 h to detect whether exosomes secreted by pancreatic cancer cells were uptaken by MIN 6 cells.MTT and glucose-stimulated insulin se-cretion ( GSIS) assays were conducted to examine cell viability and insulin secretion of MIN 6 cells after incubating with ex-osomes.The expression of miR-204 and Bcl-2 mRNA in MIN6 cells was detected by qPCR .The protein expression of Bcl-2, Bax, caspase-3 and cytochrome C (Cyt-C) in MIN6 cells was determined by Western blot .RESULTS:The results of transmission electron microscopy showed that both Pan 02 cells and MPC-83 cells secreted exosomes , and Pan02 cells secre-ted more.The co-incubation results of fluorescence-labeled exosomes and MIN6 cells confirmed that MIN6 cells were able to ingest large amounts of exosomes secreted by pancreatic cancer cells .The results of MTT and GSIS assays showed that the viability and the level of high glucose-stimulated insulin secretion of MIN 6 cells in exosome treatment group significantly decreased compared with nontreatment group (P<0.01).The results of qPCR showed that the exosomes secreted by pan-creatic cancer cells were rich in miR-204, and the mRNA expression of Bcl-2 in MIN6 cells was significantly down-regula-ted by exosome incubation ( P<0.01) .The results of Western blot showed that the protein expression of Bcl-2 in the MIN6 cells treated with exosomes was significantly down-regulated (P<0.05), and the protein levels of Bax, cleaved caspase-3 and Cyt-C in exosomes treatment group were significantly up-regulated ( P<0.01 ) .CONCLUSION: Pancreatic cancer cells secrete exosomes .The exosomes secreted by pancreatic cancer cells are ingested by βcells, and reduce the viability and insulin secretion of βcells.The mechanism may be related to the increase in exosomal miR-204 in the βcells.In-creasing miR-204 may inhibit the expression of Bcl-2 and promote the activation of mitochondrial apoptosis in βcells.