Construction of has-miR-335 lentiviral vector and verification of the target gene of miR-335 / 南方医科大学学报

<p><b>OBJECTIVE</b>To construct a lentiviral vector of miR-335 gene and verify the target gene of miR-335.</p><p><b>METHODS</b>The precursor sequence of miR-335 gene was amplified from the genomic DNA by PCR and cloned into the lentiviral vector PLVTHM labeled with GFP. Real-time quantitative RT-PCR was used to detect miR-335 and RASA1 expression in different colorectal cancer cell lines. A recombinant vector psiCHECK-2-RASA1 containing RASA1 3'UTR was constructed followed by site-directed mutagenesis of RASA1 3'UTR to establish the vector psiCHECK-2-RASA1-Mut. Co-transfection of hsa-mir-335 or a NC with these recombined vectors in HEK293A and SW480 cells was performed, and dual-luciferase reporter assay was utilized to examine the changes in luciferase activities. The recombinant PLVTHM-miR335 plasmid was packaged into mature lentivirus by 293FT cells and used to infect SW620 cells. Flow cytometry was employed for sorting the GFP+ cells. The expression of miR-335 and RASA1 were determined by qRT-PCR, and Western blotting was used to detect the expression of RASA1 protein in SW620 cell lines.</p><p><b>RESULTS</b>The recombinant lentiviral vector PLVTHM-miR335, psiCHECK-2-RASA1 and the mutation expression vector psiCHECK-2-RASA1-Mut were successfully constructed. Dual-luciferase reporter assay showed that miR-335 decreased luciferase activity in cells co-transfected with psiCHECK-2-RASA1. The expression of miR-335 in SW620 cells infected with the lentivirus PLVTHM-miR335 was significantly increased, but the expression of RASA1 showed only slight changes. Overexpression of miR-335 suppressed the expression of RASA1 protein in SW620 cells.</p><p><b>CONCLUSION</b>We have successfully constructed the lentiviral vector containing mir-335 gene and a SW620 cell line with miR-335 overexpression. MiR-335 can suppress RASA1 gene expression by targeting the specific sequence of RASA1 3'UTR.</p>

Selection and identification of specific-binding peptides for cancer stem cell surface marker CD133 / 南方医科大学学报

<p><b>OBJECTIVE</b>To select the peptides that specifically bind human cancer stem cell surface marker CD133 from the Ph.D.-7>(TM) phage peptide library.</p><p><b>METHODS</b>With a biotinylated extracellular fragment of human cancer stem cell surface marker CD133 as the target protein, the CD133 high-affinity peptides were screened from the phage peptide library by liquid phase panning. The clones with high-binding force with human CD133 were then identified by sandwich ELISA and their single-stranded DNA was extracted to test the specificity by competitive ELISA. The amino acid sequences of the selected peptides derived from the phage DNA sequences were synthesized after sequence alignment analysis, and their capacity of binding with colorectal carcinoma cells was assessed by immunofluorescence technique.</p><p><b>RESULTS</b>After 4 rounds of liquid phase selection, the phages capable of specific binding with human CD133 were effectively enriched, with an enrichment ratio of 388 times compared to that at the fourth and first rounds. Thirteen out of the 20 clones from the fourth round of panning were identified as positive clones, among which 11 had identical amino acid sequence of TISWPPR, and 2 had the sequence of STTKLAL, and the former sequence showed a stronger binding specificity to CD133.</p><p><b>CONCLUSION</b>We have successfully obtained a peptide that specifically binds human CD133 from the Ph.D.-7(TM) phage peptide library, demonstrating the feasibility of screening small molecule high-affinity polypeptides from phage peptide library by liquid-phase panning.</p>

Touchdown PCR and overlap extension PCR for generating CD133(+) cancer stem cell-selective adenovirus vector / 南方医科大学学报

<p><b>OBJECTIVE</b>To construct a replication-incompetent adenovirus vector targeting cancer stem cells by modified touchdown PCR and overlap extension PCR and investigate its infection efficiency in CD133(+) SW480 cells in vitro.</p><p><b>METHODS</b>The two portions of the fiber gene encoding the Ad5 fiber knob domain with the HI loop deleted were amplified using two pairs of designed primers and then linked by overlap extension PCR. The product obtained was identified by sequencing and inserted into prokaryotic expression vector pEGFP-N1. The product, pEGFP-N1 KNOBδHI, contained a unique EcoRV restriction site in the deleted portion of the sequence encoding the HI loop. The gene sequences of the adenovirus fiber were amplified using both common PCR and overlap extension PCR, then identified by sequencing and inserted into pNEB193, resulting in pNEB-F5. CD133(+) SW480 cells were infected with the generated adenovirus vectors Ad5-GFP and Ad5FHI-GFP to investigate the infection efficiency using fluorescent microscope.</p><p><b>RESULTS</b>The target fragments of expected sizes were amplified by touchdown PCR and overlap extension PCR, but not by common PCR. Ad5FHI-GFP showed a higher infection efficiency than Ad5-GFP in CD133(+) SW480 cells.</p><p><b>CONCLUSION</b>Compared with common PCR, touchdown PCR and overlap extension PCR can significantly improve the specificity and efficiency of the PCR products for constructing CD133(+) cancer stem cell-selective adenovirus type 5 vector, which provides carriers for tumor-targeted gene therapy.</p>