Abstract:Objective To analyze the different expression of RecQ5 in different tissues and cells,inferring the relationship between RecQ5 expression and the degree of malignancy in different tissues.Methods 35 OS samples,20 tumor adjacent tissues samples and 20 normal bone samples were chosen for the research.We compared the expression of RecQ5 among OS tissues,tumor adjacenttissues and bone tissues by immunohistochemical method and analyzed the relationship between expression intensity of RecQ5 and malignant degree of tissues,including AJCC staging.Moreover,Real-time PCR and Western blot were used to detect the mRNA and protein level of RecQ5 in hFOB1.19,U2OS and MG-63 cell lines.Results RecQ5 expression decreased inhuman osteosarcoma tissue.According to immunohistochemical results,the positive rate of RecQ5 expression was 100%(20/20)in normal bone tissues and positive rate was 90%(18/20) in tumor adjacent tissues,while the positive rate was 68.5%(24/35)in osteosarcoma tissues,which had statistically significant difference between the former two(P=0.004),but no significant difference in the former two(P>0.05).Further analysis of relationship between expression intensity and malignancy degree of tissues found that the expression intensity of RecQ5 decreased with increasing of malignant degree of tissues(P<0.05)and OS staging(P<0.005),which showed the expression of RecQ5 was negatively correlated with malignancy degree of tissues.Both Real-time PCR and Western blot showed the mRNA and protein level of RecQ5 expression was reduced in MG-63 and U2OS cells,compared to hFOB 1.19 cells(P<0.05).Conclusion The expression level of RecQ5is negatively correlated with the malignancy degree of tissues.Deletion of RecQ5 is associated with the occurrence of osteosarcoma.