Bromocriptine promotes secretion of exosomes and drug resistance of rat prolactinoma MMQ cells in vitro / 肿瘤

ABSTRACT

Objective: To investigate the effect of bromocriptine on the secretion of exosomes and the role of exosomes in drug resistance of rat prolactinoma MMQ cells. Methods: The effect of different concentrations of bromocriptine on the proliferation of MMQ cells was detected by CCK-8 assay, and the half maximal inhibitory concentration (IC50) was calculated. MMQ cells were exposed to bromocriptine for 48 h, then the exosomes were isolated by differential centrifugation. The morphology of exosomes was observed by transmission electron microscopy, the particle size of exosomes was analyzed by nanoparticle tracking analysis (NTA), and the expression of exosomal marker CD63 was detected by Western blotting. MMQ cells uptaking PKH67-labeled exosomes were observed by laser confocal microscopy. Then the sensitivity of MMQ cells to bromocriptine was tested again by CCK-8 method. The expression level of PR domain zinc finger protein 2 (PRDM2) mRNA in MMQ cells treated with exosomes was detected by real-time fluorescent quantitative PCR. The expression levels of PRDM2, dopamine 2 receptor (D2R), extracellular signal-regulated kinase 1/2 (ERK1/2) and phospho-ERK1/2 (p-ERK1/2) proteins in MMQ cells treated with exosomes were determined by Western blotting. Results: The IC50 of bromocriptine on MMQ cells was (52.91±1.48) µmol/L. Compared with the exosomes collected from MMQ cells not treated with bromocriptine, the particles and proteins in exosomes collected from MMQ cells treated with 50 µmol/L bromocriptine were significantly increased (both P < 0.01). The expression of CD63 was only observed in the exosomes. The exosomes collected from MMQ cells treated with bromocriptine were uptaken by MMQ cells. After the exosomes were absorbed by MMQ cells, the IC50 of bromocriptine [(73.74±1.17) µmol/L] was increased on MMQ cells (P < 0.01). In exosome-treated MMQ cells, the expression levels of PRDM2 mRNA and protein (both P < 0.05) and D2R protein (P < 0.05) were down-regulated, while the expression level of p-ERK1/2 was higher than that in the control group (P < 0.05). Conclusion: Bromocriptine can promote the secretion of exosomes in MMQ cells, and the exosomes may be involved in the transmission of information through intercellular communication of tumors, which can make MMQ cells to obtain drug resistance.