RESUMO
The sialyl Lewis X (SLex) antigen encoded by the FUT7 gene is the ligand of endotheliam-selectin (E-selectin).The combination of SLex antigen and E-selectin represents an important way for malignant tumor metastasis.In the present study,the effect of the SLeX-binding DNA aptamer on the adhesion and metastasis of hepatocellular carcinoma HepG2 cells in vitro was investigated.Reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence staining were conducted to detect the expression of FUT7 at both transcriptional and translational levels.The SLex expression in HepG2 cells treated with different concentrations of SLeX-binding DNA aptamer was detected by flow cytometry.Besides,the adhesion,migration,and invasion of HepG2 cells were measured by cell adhesion assay,and the Transwell migration and invasion assay.The results showed that the FUT7 expression was up-regulated at both mRNA and protein levels in HepG2 cells.SLeX-binding DNA aptamer could significantly decrease the expression of SLex in HepG2 cells.The cell adhesion assay revealed that the SLeX-binding DNA aptamer could effectively inhibit the interactions between E-selectin and SLex in the HepG2 cells.Additionally,SLeX-binding DNA aptamers at 20 nmol/L were found to have the similar effect to the monoclonal antibody CSLEX-1.The Transwell migration and invasion assay revealed that the number of penetrating cells on the down-side of Transwell membrane was significantly less in cells treated with 5,10,20 nmol/L SLeX-binding DNA aptamer than those in the negative control group (P＜0.01).Our study demonstrated that the SLeX-binding DNA aptamer could significantly inhibit the in vitro adhesion,migration,and invasion of HepG2 cells,suggesting that the SLeX-binding DNA aptamer may be used as a potential molecular targeted drug against metastatic hepatocellular carcinoma.
RESUMO
Objective To obtain DNA oligonucleotide aptamers which can specifically bind to MPT64 protein from Mycobacterium tuberculosis by SELEX(systematic evolution of ligands by exponential enrichment)technology. Methods A random ssDNA library with in vitro synthesized 78 nucleotides in length was subiected to 12 rounds of selection by SELEX method against MPT64 protein. The binding ability of the aptamers to the protein was examined by biotin-streptavidin-horseradish peroxidase system. Results The selective system used was as follows:in PCR amplification,annealing temperature was 65℃ and the concentration of Mg2+ was 1.5 mmol/L in optimizing library, and when preparation of ssDNA with asymmetrical PCR amplification, 0.75 mmol/L of Mg2+ was used. When using the plate for ELISA as the substrate for the selection, the pattern of electrophoretic band of PCR product after the tenth round selection became unitary and denser than that of the first round. The binding assay demonstrated that A value at 450 nm of the tenth round increased by 9.18 times as compared with that of the first round. The results showed that the affinities of the aptamers were different. The highest A value at 450 nm was 1.606, and the lowest 0.572. Conclusion A set of aptamers with considerable binding affinity to MPT64 protein are successfully picked out from the initial random DNA library.