title: Autocrine impact of VEGF-A on uveal melanoma cells.
abstract: OBJECTIVE
  Tumor-derived VEGF-A, apart from expediting sufficient vascularization, subsequent tumor growth, and metastatic spread, can act on malignant cells themselves provided that VEGF receptors 1 or 2 (VEGF-R1, -R2) are co-expressed. The study goal was to investigate whether such autocrine VEGF-A signaling exists in uveal melanoma (UM).
  
  
  METHODS
  Primary (MEL-270, OM-431) and metastatic (OMM-2.3, OMM-2.5) UM cell lines were analyzed for VEGF-A, VEGF-R1, and VEGF-R2 expression by RT-PCR, ELISA (VEGF-A protein), and immunocytochemistry (VEGF receptors). Proliferation of UM cells incubated with neutralizing anti-VEGF-A antibody bevacizumab (≤ 2.5 mg/mL), or VEGF-A (≤ 100 ng/mL) was assessed by bromodeoxyuridine (BrdU) ELISA. It was measured by real-time PCR, whether VEGF-A (100 ng/mL) modulated the expression ratio of VEGF-A itself and its antiangiogenic antagonist pigment epithelium-derived factor (PEDF).
  
  
  RESULTS
  All UM cells expressed VEGF-A, VEGF-R1, VEGF-R2 mRNA, and protein. In each cell line, the proliferation was stimulated by VEGF-A or inhibited by blocking VEGF-A, or both: bevacizumab significantly decreased the proliferation in MEL-270 (P = 0.005), OMM-2.3 (P = 0.001), and OMM-2.5 (P = 0.011). Increased VEGF-A signaling significantly raised the proliferation in MEL-270, OM-431 (P < 0.001, respectively), and OMM-2.3 (P = 0.043) in a dose-dependent manner but did not significantly change the VEGF-A/PEDF mRNA expression ratio.
  
  
  CONCLUSIONS
  Autocrine VEGF-A signaling seems to be present in UM, sustaining the proliferation of both primary and metastatic UM cells. Apparently, VEGF-A signaling in UM cells neither acts retroactively on VEGF-A expression, in the sense of a feedback loop, nor contributes to a pro-angiogenic shift of the VEGF-A/PEDF ratio.
authors.affiliation: Department of Ophthalmology, University of Cologne, Cologne, Germany.
authors.forename: Konrad R
authors.initials: KR
authors.lastname: Koch
authors.forename: Nasrin
authors.initials: N
authors.lastname: Refaian
authors.forename: Deniz
authors.initials: D
authors.lastname: Hos
authors.forename: Simona L
authors.initials: SL
authors.lastname: Schlereth
authors.forename: Jacobus J
authors.initials: JJ
authors.lastname: Bosch
authors.forename: Claus
authors.initials: C
authors.lastname: Cursiefen
authors.forename: Ludwig M
authors.initials: LM
authors.lastname: Heindl
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D018450:Disease Progression; D004797:Enzyme-Linked Immunosorbent Assay; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D012334:RNA, Neoplasm / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D014604:Uveal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics*; D000098943:Uveal Melanoma
chemical_list: D012334:RNA, Neoplasm; D042461:Vascular Endothelial Growth Factor A
keywords: VEGF-A; autocrine signaling; bevacizumab; proliferation; tumor growth; uveal melanoma