title: Comparison of the effects of carbon ion and photon irradiation on the angiogenic response in human lung adenocarcinoma cells.
abstract: OBJECTIVE
  Radiotherapy resistance is a commonly encountered problem in cancer treatment. In this regard, stabilization of endothelial cells and release of angiogenic factors by cancer cells contribute to this problem. In this study, we used human lung adenocarcinoma (A549) cells to compare the effects of carbon ion and X-ray irradiation on the cells' angiogenic response.
  
  
  METHODS
  A549 cells were irradiated with biologically equivalent doses for cell survival of either carbon ions (linear energy transfer, 170 keV/μm; energy of 9.8 MeV/u on target) or X-rays and injected with basement membrane matrix into BALB/c nu/nu mice to generate a plug, allowing quantification of angiogenesis by blood vessel enumeration. The expression of angiogenic factors (VEGF, PlGF, SDF-1, and SCF) was assessed at the mRNA and secreted protein levels by using real-time reverse transcription-PCR and enzyme-linked immunosorbent assay. Signal transduction mediated by stem cell factor (SCF) was assessed by phosphorylation of its receptor c-Kit. For inhibition of SCF/c-Kit signaling, a specific SCF/c-Kit inhibitor (ISCK03) was used.
  
  
  RESULTS
  Irradiation of A549 cells with X-rays (6 Gy) but not carbon ions (2 Gy) resulted in a significant increase in blood vessel density (control, 20.71 ± 1.55; X-ray, 36.44 ± 3.44; carbon ion, 16.33 ± 1.03; number per microscopic field). Concordantly, irradiation with X-rays but not with carbon ions increased the expression of SCF and subsequently caused phosphorylation of c-Kit in endothelial cells. ISCK03 treatment of A549 cells irradiated with X-rays (6 Gy) resulted in a significant decrease in blood vessel density (X-ray, 36.44 ± 3.44; X-ray and ISCK03, 4.33 ± 0.71; number of microscopic field). These data indicate that irradiation of A549 cells with X-rays but not with carbon ions promotes angiogenesis.
  
  
  CONCLUSIONS
  The present study provides evidence that SCF is an X-ray-induced mediator of angiogenesis in A549 cells, a phenomenon that could not be observed with carbon ion irradiation. Thus, in this model system evaluating angiogenesis, carbon ion irradiation may have a therapeutic advantage. This observation should be confirmed in orthotopic lung tumor models.
authors.affiliation: Department of Radiotherapy and Radiooncology, Philipps-University, Marburg, Germany. Kamlah@staff.uni-marburg.de
authors.forename: Florentine
authors.initials: F
authors.lastname: Kamlah
authors.forename: Jörg
authors.initials: J
authors.lastname: Hänze
authors.forename: Andrea
authors.initials: A
authors.lastname: Arenz
authors.forename: Ulrike
authors.initials: U
authors.lastname: Seay
authors.forename: Diya
authors.initials: D
authors.lastname: Hasan
authors.forename: Janko
authors.initials: J
authors.lastname: Juricko
authors.forename: Birgit
authors.initials: B
authors.lastname: Bischoff
authors.forename: Oana R
authors.initials: OR
authors.lastname: Gottschald
authors.forename: Claudia
authors.initials: C
authors.lastname: Fournier
authors.forename: Gisela
authors.initials: G
authors.lastname: Taucher-Scholz
authors.forename: Michael
authors.initials: M
authors.lastname: Scholz
authors.forename: Werner
authors.initials: W
authors.lastname: Seeger
authors.forename: Rita
authors.initials: R
authors.lastname: Engenhart-Cabillic
authors.forename: Frank
authors.initials: F
authors.lastname: Rose
mesh_terms: D000230:Adenocarcinoma / Q000098:blood supply* / Q000378:metabolism / Q000532:radiotherapy*; D000077192:Adenocarcinoma of Lung; D000818:Animals; D002244:Carbon / Q000627:therapeutic use*; D002289:Carcinoma, Non-Small-Cell Lung / Q000098:blood supply / Q000378:metabolism / Q000532:radiotherapy; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D054377:Chemokine CXCL12 / Q000378:metabolism; D063193:Heavy Ion Radiotherapy; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D018499:Linear Energy Transfer; D008175:Lung Neoplasms / Q000098:blood supply* / Q000378:metabolism / Q000532:radiotherapy*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D010766:Phosphorylation; D017785:Photons / Q000627:therapeutic use*; D019009:Proto-Oncogene Proteins c-kit / Q000037:antagonists & inhibitors / Q000378:metabolism; D019089:Stem Cell Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: C528178:4-t-butylphenyl-N-(4-imidazol-1-ylphenyl)sulfonamide; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D007093:Imidazoles; D008565:Membrane Proteins; D009363:Neoplasm Proteins; C098069:PIGF protein, human; D019089:Stem Cell Factor; D013449:Sulfonamides; D042461:Vascular Endothelial Growth Factor A; D002244:Carbon; D019009:Proto-Oncogene Proteins c-kit