Hypoxia-inducible factor (HIF)-1 alpha directly enhances the transcriptional activity of stem cell factor (SCF) in response to hypoxia and epidermal growth factor (EGF).
Stem cell factor (SCF) plays important roles in tumor growth and angiogenesis. However, its regulatory mechanism remains largely undefined. Here, we report that hypoxia upregulated the expression of SCF in MCF-7 breast cancer cells in both messenger RNA and protein levels. When hypoxia-inducible factor (HIF)-1 alpha expression was knocked down by RNA interference, the MCF-7 cell expression of SCF was decreased significantly. Furthermore, the SCF receptor, c-kit phosphorylation was significantly strengthened by the condition culture media from hypoxic MCF-7 and MCF-7-c cells. The survival of A549 cells was more dependent on SCF under hypoxia. Analysis of SCF promoter 5'-flanking region revealed a potential hypoxia-response element (HRE; 5'-GCGTG-3') located at -68 to -64 relative to the transcriptional start site. Chromatin immunoprecipitation assay demonstrated that HIF-1 alpha directly bound to this region under normoxia, and this binding activity was significantly enhanced under hypoxia. Overexpression of HIF-1 alpha significantly upregulated the expression of luciferase reporter gene under control of the SCF promoters in both MCF-7 cells and human embryonic kidney 293 cells, but mutation of the HRE site completely blocked this effect. Epidermal growth factor was also able to enhance the SCF expression under normoxia in MCF-7 cells, which was dependent on HIF-1 alpha. Taken together, our data demonstrated that HIF-1 alpha was a key regulator of SCF expression in breast cancer cells. Hypoxia and epidermal growth factor receptor signal coexisted in the tumor microenvironment and might promote angiogenesis through HIF-1 alpha-mediated upregulation of SCF and other angiogenic factors.
Han
Zhi-Bo
ZB
The State Key Laboratory of Experimental Hematology, Institute of Hematology and Hospital of Blood Diseases, Chinese Academy of Medical Sciences and Peking Union of Medical College, Tianjin 300020, China.
Ren
He
H
Zhao
Hui
H
Chi
Ying
Y
Chen
Ke
K
Zhou
Bin
B
Liu
Yong-jun
YJ
Zhang
Lei
L
Xu
Bin
B
Liu
Bin
B
Yang
Renchi
R
Han
Zhong-Chao
ZC
D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000502:physiology*; D009389:Neovascularization, Pathologic / Q000209:etiology; D011401:Promoter Regions, Genetic; D019009:Proto-Oncogene Proteins c-kit / Q000502:physiology; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019089:Stem Cell Factor; D004815:Epidermal Growth Factor; D019009:Proto-Oncogene Proteins c-kit