Objective:To establish a human monocyte cell line U937 stably expressing CD200.Methods:The eukaryotic expression vector pcDNA3-CD200 containing human CD200 cDNA and vector pcDNA3 were transferred into human monocyte U937 cell line by electrotransfer.These two cell lines were selected by G418, and the selected cell lines were subcultured. U937 cell line was enclosed as control group.The expression of CD200 mRNA and protein was detected by RT-PCR and flow cytometry.Results:After G418 selection,U937 cell line in control group was died, and the cell lines transferring pcDNA3 and recombined pcDNA3-CD200 were subcultured over 30 generations.The CD200 mRNA expression in pcDNA3-CD200 group was confirmed with RT-PCR.The CD200 expression in U937-pcDNA3-CD200,U937-pcDNA3 and U937 were 77.20%,3.20% and 2.10%,compared with other two groups (F=133 996.40,P0.05).Conclusion:Our study provides foundation for mechanism of action for CD200 in future.The human monocyte series U937 cell line that expresses CD200 protein stably is established successfully by gene transfection method.

Objective :Humna WAF1 gene was cloned,and WAF1-pcDNA3 recombinant plasmid was con-structed. Methods :Human WAF1 gene was amplified by RT-PCR from Hela cell,then cloned into pcDNA3vector. Results :Human WAF1-pcDNA3 recombinant plasmid was constructed,and DNA direct sequencingindicated that was correct. Conclusion:Our study laid the foundation for studying WAF1 gene expressionand it＇s biological effects.

Objective :To study mutation of Ps3 gene and its relationship with histologic grade and Dukes' stage in colorectal cancer. Methods :PCR-SSCP was used to detect mutations of Ps3 in 30 colorectal cancer patients. Results: It was found that 6 mutations (20. 0%) in the coding region of P53 gene. One mutation was located in exon4; 5 mutations were located in exon 5; none of mutation was found in exon 2 and 3. According to the histologic grade of of colorectal cancer,the frequencies of P53 gene mutation were 1/8 (12. 5%) in the well differentiated and in the moderately differentiated as well,3/10 (30. 0%) in the poorly differenctiated and 1/4 (25.0%) in the undifferentiated. In clinic, the frequencies of P53 gene mutation were associated with Dukes stage: 1/10 (10. 0 % ) in B stage, 2/12 (16. 7%) in C Stage,3/8(37. 5%) in D stage. Conclusion:The mutation of P53 gene is related to Dukes＇ stage,and the P53 gene mutation hardly occurs in exon 2,3 in coloretal cancer.