A key role for early growth response-1 and nuclear factor-kappaB in mediating and maintaining GRO/CXCR2 proliferative signaling in esophageal cancer.
Although early growth response-1 (EGR-1) has been shown as a key transcription factor in controlling cell growth, proliferation, differentiation, and angiogenesis, its role in the development of esophageal cancer is poorly understood despite the high frequency of this disease in many parts of the world. Here, immunohistochemistry showed that EGR-1 is overexpressed in 80% of esophageal tumor tissues examined. Furthermore, EGR-1 is constitutively expressed in all esophageal cancer cell lines analyzed. Esophageal squamous carcinoma WHCO1 cells stably transfected with EGR-1 short hairpin RNA displayed a 55% reduction in EGR-1 protein levels, 50% reduction in cell proliferation, a 50% reduction in cyclin-dependent kinase 4 levels, and a 2-fold induction in p27(Kip1) levels associated with a G(2)-M cell cycle arrest. EGR-1 knockdown also caused a marked induction in IkappaBalpha expression, an effect also observed in GRObeta RNA interference-expressing WHCO1 cells, because EGR-1 lies downstream of GRO/CXCR2 signaling. Furthermore, p65 mRNA levels were also reduced in cells treated with either short hairpin RNA EGR-1 or small interfering RNA EGR-1. Immunohistochemical analysis indicated that p65 is elevated in 78% (n = 61) of esophageal tumor sections analyzed. Moreover, nuclear factor-kappaB inhibition with either sodium salicylate or p65 RNA interference led to a significant reduction in GROalpha and GRObeta expression. These results indicate that EGR-1 and nuclear factor-kappaB mediate GRO/CXCR2 proliferative signaling in esophageal cancer and may represent potential target molecules for therapeutic intervention.
Division of Medical Biochemistry, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa.
Bo
B
Wang
Levon M
LM
Khachigian
Luke
L
Esau
Michael J
MJ
Birrer
Xiaohang
X
Zhao
M Iqbal
MI
Parker
Denver T
DT
Hendricks
D015153:Blotting, Western; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D054360:Chemokine CXCL1 / Q000235:genetics / Q000378:metabolism; D054426:Chemokine CXCL2 / Q000235:genetics / Q000378:metabolism*; D051766:Early Growth Response Protein 1 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004938:Esophageal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D023063:Receptors, Interleukin-8B / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D012980:Sodium Salicylate / Q000494:pharmacology; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism; D014162:Transfection
C499706:CXCL2 protein, human; D018797:Cell Cycle Proteins; D054360:Chemokine CXCL1; D054426:Chemokine CXCL2; D051766:Early Growth Response Protein 1; D016328:NF-kappa B; D034741:RNA, Small Interfering; D023063:Receptors, Interleukin-8B; D051996:Transcription Factor RelA; D012980:Sodium Salicylate