Serum exosome-mediated lncRNA HOTTIP regulates cisplatin resistance in gastric cancer cells through the miR-138-5p/TJP1 axis / 中华消化外科杂志

ABSTRACT

Objective:To investigate the effects of serum exosomes of patients with gastric cancer on cisplatin resistance, clonal formation, migration, invasion and apoptosis of the AGS gastric cancer cells, and the corresponding molecular mechanisms.Methods:The experimental study was conducted. The exosomes of patients with gastric cancer was separated from their serum, and the expression of lncRNA HOTTIP was analyzed using the quantitative real time polymerase chain reaction (qRT-PCR). Normal gastric epithelial cell line GES1, gastric cancer cell line AGS and human embryonic kidney cell 293T were cultured in vitro. AGS cells were incubated with exosomes (Exo),with phos-phate buffered saline (PBS) treatment as control, and transfected with si-NC or si-HOTTIP-3, named as Exo group, PBS group, si-NC+Exo group, and si-HOTTIP-3+Exo group. The AGS cells were trans-fected with si-NC, si-HOTTIP-1, si-HOTTIP-2, si-HOTTIP-3, oe-HOTTIP, vector, oe-HOTTIP+miR-138-5p mimic, oe-HOTTIP+mimic NC, miR-138-5p inhibitor, inhibitor NC, miR-138-5p inhibitor+si-TJP1 and miR-138-5p inhibitor+si-NC. They were recorded as si-NC group, si-HOTTIP-1 group, si-HOTTIP-2 group, si-HOTTIP-3 group, oe-HOTTIP group, vector group, oe-HOTTIP+miR-138-5p mimic group, oe-HOTTIP+mimic NC group, miR-138-5p inhibitor group, inhibitor NC group, miR-138-5p inhibitor+si-TJP1 group and miR-138-5p inhibitor+si-NC group. The 293T cells transfected with mimic NC+HOTTIP wt, miR-138-5p mimic+HOTTIP wt, mimic NC+HOTTIP mut, miR-138-5p mimic+HOTTIP mut, mimic NC+TJP1 3'UTR wt, miR-138-5p mimic+TJP1 3'UTR wt, mimic NC+TJP1 3'UTR mut, miR-138-5p mimic+TJP1 3'UTR mut were recorded as the mimic NC+HOTTIP wt group, miR-138-5p mimic+HOTTIP wt group, mimic NC+HOTTIP mut group, miR-138-5p mimic+HOTTIP mut group, mimic NC+TJP1 3'UTR wt group, miR-138-5p mimic+TJP1 3'UTR wt group, mimic NC+TJP1 3'UTR mut group, miR-138-5p mimic+TJP1 3'UTR mut group. The cell counting kit-8 (CCK8) was used to analyze the cisplatin sensitivity of gastric cancer cells. The colony formation experiment was used to analyze the colony formation of gastric cancer cells. The Transwell experiment was used to analyzed cell migration and invasion of gastric cancer cells. The flow cytometry experiment was used to analyze cell apoptosis of gastric cancer cells. The Western bolt assay was used to analyze the expression of exosome marker proteins, including the CD63 and CD81, and the protein of TJP1, the drug-resistance related proteins, including the P-gp and MCL-1. The dual-luciferase assay was used to analyze the targeted relationships among lncRNA HOTTIP, miR-138-5p and TJP1. Observation indicators: (1) expression of lncRNA HOTTIP; (2) resistance of gastric cancer cells to cisplatin regulated by exosome-mediated lncRNA HOTTIP; (3) regulation of cisplatin resistance in gastric cancer cells mediated by miR-138-5p through lncRNA HOTTIP overexpression; (4) targeting of TJP1 gene 3′-untranslated region (UTR) by miR-138-5p; (5) regulation of cisplatin resistance in gastric cancer cells by TJP1 through miR-138-5p inhibition. Measurement data with normal distribution were represented as Mean± SD, and comparison between groups was conducted using the t test. The one-way ANOVA was used for comparison for multiple groups and the Tukey′s test was used for further pairwise compari-son. Count data were described as absolute numbers, and the chi-square test was used for comparison. Correlation analysis was conducted using the Pearson′s test. Results:(1) Expression of lncRNA HOTTIP. The expression of lncRNA HOTTIP in the serum exosome of patients with gastric cancer was higher than that in healthy volunteers, showing a significant difference ( P<0.05). Results of transmi-ssion electron microscopy examination showed that the serum exosomes were circular or oval in shape. Results of Western bolt assay showed the expression of marker proteins of CD63 and CD81 in serum exosomes. (2) Resistance of gastric cancer cells to cisplatin regulated by exosome-mediated lncRNA HOTTIP. Compared with the PBS group, the biochemical half maximal inhibitory concentra-tion (IC50), the number of clone formation, the number of invasive cell, the number of migratory cell, expression of P-gp protein, expression of MCL-1 protein in the Exo group increased, while the cell apoptosis rate decreased, showing significant differences between them ( P<0.05). Compared with the si-NC+Exo group, the IC50, the number of clone formation, the number of invasive cell, the number of migratory cell, expression of P-gp protein, expression of MCL-1 protein in the si-HOTTIP-3+Exo group decreased, while the cell apoptosis rate increased, showing significant differences between them ( P<0.05). (3) Regulation of cisplatin resistance in gastric cancer cells mediated by miR-138-5p through lncRNA HOTTIP overexpression. Compared with the vector group, the IC50, the number of clone formation, the number of invasive cell, the number of migratory cell, expression of P-gp protein, expression of MCL-1 protein in the oe-HOTTIP group increased, while the cell apoptosis rate decreased, showing significant differences between them ( P<0.05). Compared with the oe-HOTTIP+mimic NC group, the IC50, the number of clone formation, the number of invasive cell, the number of migratory cell, expression of P-gp protein, expression of MCL-1 protein in the oe-HOTTIP+miR-138-5p mimic group increased, while the cell apoptosis rate decreased, showing significant differences between them ( P<0.05). (4) Targeting of TJP1 gene 3′-UTR by miR-138-5p. Results of dual-luciferase assay showed that the luciferase activity in 293T cells treatment with mimics of control+vectors of wild type of TJP1 gene 3′-UTR and 293T cells treatment with mimics of miR-138-5p+vectors of wild type of TJP1 gene 3′-UTR was 1.00±0.09 and 0.21±0.03, respectively, showing a significant difference between them ( t=15.02, P<0.05). (5) Regulation of cisplatin resistance in gastric cancer cells by TJP1 through miR-138-5p inhibition. Compared with the inhibitor group, the IC50, the number of clone formation, the number of invasive cell, the number of migratory cell, expression of P-gp protein, expression of MCL-1 protein in the miR-138-5p inhibitor group increased, while the cell apoptosis rate decreased, showing significant differences between them ( P<0.05). Compared with the miR-138-5p inhibitor+si-NC group, the IC50, the number of clone formation, the number of invasive cell, the number of migratory cell, expression of P-gp protein, expression of MCL-1 protein in the miR-138-5p inhibitor+si-TJP1 group decreased, while the cell apoptosis rate increased, showing significant differences between them ( P<0.05). Conclusion:Serum exosomes-mediated lncRNA HOTTIP can promote cisplatin resistance, clonal formation, migration, invasion and apoptosis of gastric cancer cells and inhibit cell apoptosis of gastric cancer cells through regulating the expression of miR-138-5p/TJP1.