Expressions of pro-apoptotic protein Smac and HtrA2 in children with acute leukemia and its clinical significance

Abstract

Objective To investigate the expression and clinical significance of Smac and HtrA2 in children with acute leukemia(AL). Methods Bone marrow samples were obtained from 77 children with AL(including 32 newly diagnosed children, 33 complete remission children and 12 relapsed children)and the control group of 15 children without malignant blood disease.The expressions of Smac and HtrA2 protein were measured by streptavidin/peroxidase immunoperoxidase technique(SP)in all children.SPSS 13.0 software was applied to analyze the statistical data. Results Protein Smac was detected only in some samples, but HtrA2 was detected in all samples.The levels of Smac and HtrA2 protein in newly diagnosed AL children were both higher than those of the complete remission children(χ2=17.38, F=2.36, all P 0.05). The levels of Smac and HtrA2 protein in complete remission children were both higher than those of the normal controls, and the difference had no statistical significance(χ2=1.20, F=2.23, all P>0.05). In the newly diagnosed children, the levels of Smac and HtrA2 protein in children with acute lymphocytic leukemia(ALL)were higher than those of the acute myeloid leukemia(AML), but the differences had no statistical significance(χ2=0.113, t=1.024, all P>0.05). In newly diagnosed AL children, the complete remission(CR) rate of the negative expression of Smac(Smac-, 90.9%)and the low expression of HtrA2(HtrA2low, 84.6%)in the level of protein were higher than those of the positive expression of Smac(Smac+ , 47.6%)and the high expression of HtrA2(HtrA2high, 47.4%), and there was statistical significance respectively(χ2=5.772, 4.596, all P<0.05). The CR rate of Smac- HtrA2low group (100%) was higher than that of Smac+ HtrA2high group(30.8%)in the children with AL, and the statistical data were of great significance(χ2=9.692, P<0.01). The protein level of Smac in newly diagnosed AL children was correlated with HtrA2 (r=0.979, P<0.001). Conclusions Pro-apoptotic protein Smac and HtrA2 may be involved in and affected each other in the pathogenesis and progression in AL, but levels of Smac and HtrA2 protein may be not correlated with the types of AL.In newly diagnosed AL children, the high expression of protein Smac and HtrA2 predicts poor prognosis. Key words: Smac; HtrA2; Leukemia; Streptavidin/peroxidase immunoperoxidase technique