Experimental research on the inhibition of SALL4 expression in acute myeloid leukemia THP-1 cells by RNA interference

Abstract

Objective To inhibit the expression level of SALI4 in AML cell line THP-1 and investigate its potential effects on pathogenesis of leukemia. Methods AML cell line THP-1 was transfected with plasmids that expressed small interfering RNA targeting SALL4. The samples were divided into 4 groups:(1) blank group: samples with not any treatments; (2) control group: cells with empty pRS vector alone;(3) test1 group:cells with SALL4-shRNA-pRS-1 plasmid transfection complex; (4) test2 group:cells with SALL4-shRNA-pRS-2 plasmid transfection complex. The expression levels of SALL4 mRNA and protein were measured by real time fluorescence quantitative PCR and WB. C-myc, Cyclin D1 and β-catenin were important components of Wnt/β-catenin signaling pathway and their expression levels in SALL4 knockdown THP-1 cells were detected by real-time fluorescence PCR. Furthermore, THP-1 apoptosis was analyzed by flow cytometry after Annexin V-PI staining. Results Real time fluorescent quantitative PCR illustrated that the expression of SALL4 in testl group, test2 group, control group and blank group were ( 36. 0 ± 4. 3 ) %,(32. 0 ± 2. 4) %, ( 102. 0 ± 6.5 ) % and ( 100. 0 ± 2. 6 ) % respectively. There was statistical significance ( F = 226. 3, P < 0. 05 ). The expression of SALL4 in testl and test2 group respectively were significant lower than that in blank group (t = 19.7,19. 1, P<0. 05). The expression of SALL4 had no significant difference between blank group and control group (t = 1.1, P ＞0. 05). Western blot analysis revealed SALL4 protein in testl and test2 group were significantly decreased compared with those of control and blank group. All above data indicated the high efficiency of RNA interference targeting SALL4. Comparing with the blank group, the relative expression of C-myc, Cyclin D1 and β-catenin mRNA in test1, test2 and control group were(44.0 ±6.2)%,(44.0 ±5.1)% and (107.0±13.6)%;(22.0±4.5)%,(25.0±3.5)% and (48.0 ± 7. 6 ) %; ( 42.0 ± 3.5 ) %, ( 59. 0 ± 3.7 ) % and ( 79. 0 ± 5.6 ) %. The expression of C-myc,β-catenin and Cyclin D1 mRNA in testl and test2 group were significant lower than that in blank group (t = 10. 1,9. 5, 23. 3, 22. 9; 17.4, 12. 4; P < 0. 05). The percentage of apoptotic cells in group of test1,test2,control, blank were (57.2 ±9.1)%, (34.4 ±8.6)%, (14.4 ±3.6)% and (14.8 ±4.8)%respectively. There was statistical significance ( F = 42. 5, P < 0. 05 ). After the inhibition of SALL4, the percentages of apoptotic cell in testl and test2 group were significantly increased( t =9. 7, 4. 5 ;P <0. 05).Conclusion The inhibition of SALL4 in leukemia cell line THP-1 downregulates the expression of cell proliferation related genes such as C-myc, Cyclin D1,β-catenin and promoted apoptosis. Key words: Leukemia; Cell line, tumor; Transcription factors; RNA interference; Apoptosis