Mechanism of polypyrimidine tract-binding protein 1 on the proliferation and metastasis of gastric cancer cells / 中华消化杂志

ABSTRACT

Objective:To explore the expression of polypyrimidine tract-binding protein 1 (PTBP1) in gastric cancer (GC) tissues and GC cell lines, and the role of PTBP1 in the proliferation and metastasis of GC cells.Methods:From January to June in 2019 at The First Affiliated Hospital of Xi′an Jiaotong University, the cancer tissues and corresponding para-cancer tissues of GC patients underwent surgical resection were collected. The Kaplan-Meier Plotter database was used to analyze the survival of GC patients. The expression of PTBP1 was down-regulated by transfecting small interfering RNA (siRNA) in human GC cell lines SGC7901 and AGS with relatively high expression of PTBP1. The cells were divided into blank control group, negative control group, and PTBP1 knockdown group. The expression of PTBP1 at mRNA and protein level were detected by real-time fluorescence quantification polymerase chain reaction (RT-qPCR) and Western blotting. At 24, 48, 72 and 96-hour after transfection, the effect of PTBP1 on the proliferation of GC cells was observed by 3-(4, 5 dimethylthiazol)-2, 5 diphenyltetrazolium bromide (MTT) experiment. The changes of invasion and migration of GC cells after down-regulation of PTBP1 were detected by transwell assay. The expression changes of epithelial-mesenchymal transition (EMT) markers E-cadherin, N-cadherin and vimentin after down-regulation of PTBP1 in GC cells were determined by Western blotting. Indenpendent samples t test, analysis of variance and rank sum test were used for statistical analysis. Results:The Kaplan-Meier Plotter prognostic analysis showed that the overall survival of GC patients with high PTBP1 expression was shorter than that of GC patients with low PTBP1 expression (9.2 months, 6.2 months to 17.2 months vs. 19.0 months, 14.5 months to 28.4 months), and the difference was statistically significant ( Z=5.31, P<0.05). The results of RT-qPCR showed that in GC cell lines SGC7901 and AGS, the expression of PTBP1 at mRNA level of PTBP1 knockdown group was lower than that of blank control group and negative control group (SGC7901: 0.78±0.11 vs.3.10±0.19 and 2.99±0.23; AGS: 0.80±0.09 vs. 3.55±0.24 and 3.50±0.18), and the differences were statistically significant ( tSGC7901=10.57 and 8.08, tAGS=10.91 and 13.42; all P<0.01). The results of Western blotting indicated that in GC cell lines SGC7901 and AGS, the expression of PTBP1 at protein level of PTBP1 knockdown group was lower than those of blank control group and negative control group (SGC7901: 0.38±0.04 vs. 1.42±0.05 and 1.35±0.09; AGS: 0.17±0.02 vs. 1.52±0.08 and 1.38±0.45), and the differences were statistically significant ( tSGC7901=15.94 and 10.57, tAGS=16.60 and 20.80; all P<0.01). The results of MTT showed that at 48, 72 and 96-hour after transfection the absorbance values of PTBP1 knockdown group decreased by 0.25±0.01, 0.38±0.02, and 0.84±0.04 as compared with those of negative control group, and the decrease was the most significant at 96-hour after transfection, and the differences were statistically significant ( t=10.21、14.32, both P<0.01). The results of transwell experiment demonstrated that the number of invasion and migration cells of PTBP1 knockdown group were both less than that of the blank control group and the negative control group (SGC7901: 42.00±5.91 vs. 116.40±10.23 and 114.40±10.43; 39.60±6.77 vs. 125.80±11.51 and 122.40±5.90; AGS: 40.20±7.25 vs. 115.60±14.63 and 117.40±9.12; 36.00±5.20 vs. 122.40±12.10 and 125.40±12.74), and the differences were statistically significant ( tSGC7901=14.07, 13.50, 14.43 and 20.62; tAGS=10.27, 14.75, 14.68 and 16.76; all P<0.01). The results of Western blotting showed that the expression of E-cadherin of PTBP1 knockdown group was higher than that of the blank control group and the negative control group (SGC7901: 1.42±0.05 vs. 0.53±0.05 and 0.57±0.03; AGS: 1.34±0.04 vs. 0.54±0.03 and 0.61±0.01), however the expression levels of N-cadherin and vimentin were both lower than those of the blank control group and the negative control group (SGC7901: 0.50±0.03 vs. 1.64±0.05 and 1.46±0.07; 0.32±0.07 vs. 1.42±0.07 and 1.33±0.07; AGS: 0.37±0.06 vs. 1.47±0.04 and 1.36±0.04; 0.41±0.04 vs. 1.53±0.06 and 1.37±0.04), and the differences were statistically significant ( tSGC7901=11.63, 13.19, 18.83, 11.68, 11.43 and 10.43; tAGS= 15.02, 16.23, 14.67, 12.97, 14.45 and 17.18; all P<0.01). Conclusions:The expression levels of PTBP1 increase in GC tissues and cells, which may be involved in regulating the proliferation, metastasis and EMT of GC cells.