Abstract:

Objective To investigate the effects of human glycolipid transfer protein （GLTP） on proliferation， migration and invasion of pancreatic cancer （PC） cells， and to elucidate their mechanisms. Methods The difference in the expression levels of GLTP proteins between PC tissue and normal pancreas tissue was analyzed by University of Alabama at Birmingham Cancer Data Analysis Platform（UALCAN） Database， as well as the difference in the expression levels of GLTP protein between PC tissue and normal pancreas tissue of the PC patients with different clinicopathological characteristics. The PANC-1 cells were cultured in vitro anddivided into control group （transfected with pFLAG-CMV4 plasmid） and GLTP-overexpression（GLTP-OE） group （transfected with pFLAG-GLTP plasmid）. The stably GLTP transfected cells were established using the antibiotic screening method. Knock-down experiments were performed using non-specific siRNA transfected PANC-1 cells as control group and si-GLTP transfected PANC-1 cells as si-GLTP group. Western blotting method was used to detect the expression of GLTP protein in the cells in various groups， cell counting kit-8 （CCK-8） method was used to detect the proliferation activities of PANC-1 cells， clone formation assay was used to detect the number of clone formation， and Transwell chamber assay were used to detect the numbers of migration and invasion cells in various groups. Transcriptomics sequencing analyses were conducted to assess the possible mechanism of GLTP in the PANC-1 cells. Western blotting method was employed to detect the expression levels of phosphatidylinositol 3-kinase （PI3K）， phosphorylated PI3K （p-PI3K）， protein kinase B （Akt）， and phosphorylated Akt （p-Akt） proteins in the PANC-1 cells in various groups； Real-time fluorescence quantitative PCR （RT-qPCR） was used to assess the expression levels of amphiregulin （AREG） and kinase insertion domain receptor （KDR） mRNA in the cells in various groups. The mice were randomly divided into control group （injected with pFLAG-GMV4 transfected PANC-1 cells） and experimental group （injected with pFLAG-GLTP stably transfected PANC-1 cells）， and the subcutaneously transplanted tumor models were prepared； the volumes and weights of the transplanted tumors of the mice in two groups were measured. Results UALCAN database analysis showed that the expression level of GLTP protein in PC tissue was lower than that in normal pancreas tissue （P<0.01）， and there were statistically significant differences in the GLTP protein expression between PC tissue and normal pancreas tissue of the PC patients with different cancer stages （P<0.05）， tumor grades （P<0.05）， ages （P<0.001）， and genders （P<0.05）. Compared with control group， the proliferation activity （P<0.01） and the number of clone formation （P<0.001） of the cells in GLTP-OE group were decreased， while the numbers of migration cells （P<0.001） and invasion cells （P<0.01） were decreased. In the knock-down experiment， compared with control group， the proliferation activity （P<0.01） and the number of clone formation （P<0.05） of the cells in GLTP-OE group were increased， while the numbers of migration cells （P<0.001） and invasion cells （P<0.001） were increased. Compared with control group， the tumor weight and volume of the mice in experimental group were decreased （P<0.01）， following the injection of tumor cells for a period of four weeks. In the over-expression experiment， compared with control group， the expression levels of p-PI3K （P<0.01）， p-Akt-S473 （P<0.01）， and p-Akt-T308 （P<0.05） proteins in the cells in GLTP-OE group were decreased； the expression levels of AREG （P<0.01） and KDR （P<0.01） mRNA were decreased. In the knock-down experiment， compared with control group， the expression levels of p-PI3K （P<0.01）， p-Akt-S473 （P<0.01）， and p-Akt-T308 （P<0.01） in the cells in si-GLPT group were increased， and the expression levels of AREG （P<0.01） and KDR （P<0.05） mRNA were increased. Conclusion Low expression levels of GLTP in PC tissue are present. The over-expression of GLTP can inhibit the proliferation， migration and invasion of PANC-1 cells， as well as the growth of subcutaneously transplanted tumors in the nude mice； its possible mechanism may be related to decreasing the activity of the PI3K/Akt signaling pathway.

Key words: Glycolipid transfer protein, Pancreas neoplasms, Human pancreatic cancer cells, Cell proliferation, Phosphatidylinositol 3-kinase, Protein kinase B