Stromal cell-derived factor-1alpha and CXCR4 expression in hemangioblastoma and clear cell-renal cell carcinoma: von Hippel-Lindau loss-of-function induces expression of a ligand and its receptor.
The genetic hallmark of hemangioblastomas and clear cell-renal cell carcinomas (CC-RCCs) is loss-of-function of the von Hippel-Lindau (VHL) tumor suppressor protein. VHL is required for oxygen-dependent degradation of hypoxia-inducible factor-1alpha (HIF-1alpha). In hemangioblastomas and CC-RCCs, HIF-1alpha is constitutively overexpressed leading to increased transcription of HIF-1-regulated genes, including vascular endothelial growth factor (VEGF). Because loss of VHL function is associated with increased expression of the chemokine receptor CXCR4 in CC-RCCs, we investigated the expression of HIF-1alpha, CXCR4, and its ligand stromal cell-derived factor-1alpha (SDF-1alpha) in hemangioblastomas and CC-RCCs. Immunohistochemistry revealed overexpression of both CXCR4 and SDF-1alpha within tumor cells and endothelial cells of hemangioblastomas and CC-RCCs. HIF-1alpha was detected in tumor cell nuclei of both hemangioblastomas and CC-RCCs. A specific ELISA showed that hemangioblastomas and CC-RCCs expressed SDF-1alpha protein at levels that were significantly higher than those found in normal tissue. Analysis of the VHL-null RCC line 786-0 revealed that SDF-1alpha mRNA levels were 100-fold higher than in a subclone transfected with the wild-type VHL gene. Expression of CXCR4 and SDF-1alpha mRNA was significantly decreased in HIF-1alpha-null compared with wild-type mouse embryo fibroblasts (MEFs). ELISA and Western blot studies for SDF-1alpha and CXCR4 protein expression confirmed the RNA findings in RCC lines and MEFs. These results suggest that loss-of-function of a single tumor suppressor gene can up-regulate the expression of both a ligand and its receptor, which may establish an autocrine signaling pathway with important roles in the pathogenesis of hemangioblastoma and CC-RCC.
Zagzag
David
D
Microvascular and Molecular Neuro-oncology Laboratory, New York, New York, USA. dz4@nyu.edu
Krishnamachary
Balaji
B
Yee
Herman
H
Okuyama
Hiroaki
H
Chiriboga
Luis
L
Ali
M Aktar
MA
Melamed
Jonathan
J
Semenza
Gregg L
GL
D018262:Adenocarcinoma, Clear Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002528:Cerebellar Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000096:biosynthesis* / Q000235:genetics; D003600:Cytosol / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018325:Hemangioblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008875:Middle Aged; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D019718:Receptors, CXCR4 / Q000096:biosynthesis* / Q000235:genetics; D015398:Signal Transduction; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000502:physiology*; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics; D051794:Von Hippel-Lindau Tumor Suppressor Protein
C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; C515256:Cxcl12 protein, mouse; D012333:RNA, Messenger; D019718:Receptors, CXCR4; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; C497446:VHL protein, human