C-myc but not Hif-1α-dependent downregulation of VEGF influences the proliferation and differentiation of HL-60 cells induced by ATRA

Abstract

Vascular endothelial growth factor (VEGF) plays an important role in solid tumor growth, progression and metastasis as well as in the proliferation and differentiation of hematological malignancies. However, the molecular mechanism that modulates VEGF expression and secretion in leukemia cells has not yet to be elucidated. The purpose of the present study was to investigate the role of the signal pathway in modulating the expression of VEGF in HL-60 cells. Specific siRNAs targeting VEGF were transfected into HL-60 cells and the VEGF expression was measured with reverse transcription-polymerase chain reaction (RT-PCR) and western blot assay. The cell proliferation of HL-60 cells was detected by the cell counting kit-8 (CCK-8) assay and the differentiation of HL-60 cells induced by all-trans-retinoic acid (ATRA) was detected by the RT-PCR assay and flow cytometry assay for CD11b. The upstream transcription factors that were related to VEGF expression such as P53, SP-1, c-jun, VHL, cox-2, c-myc and stat3 were detected by RT-PCR assay. In addition, the chromatin immunoprecipitation (ChIP) assay was used to reveal the role of c-myc by binding the target gene VEGF. The results demonstrated the hypoxia-inducible factor1α-related signaling pathway, not the same as in solid tumors, might not play a key role in modulating VEGF expression. c-myc contributes to the modulation of VEGF expression by targeting the promoter of VEGF, which was indicated by the ChIP assay. In conclusion, our data demonstrate that VEGF plays an important role in the differentiation and proliferation of HL-60 cells; c-myc-dependent downregulation of VEGF induced by ATRA contributes to the differentiation of HL-60 cells.