title: Antitumor interaction of short-course endostatin and ionizing radiation.
abstract: OBJECTIVE
  The purpose of this study was to evaluate whether endostatin, an antiangiogenic cleavage fragment of collagen XVIII, enhances the antitumor effects of ionizing radiation (IR). Endostatin was injected to coincide with fractionated radiotherapy.
  
  
  METHODS
  Xenografts of radioresistant SQ-20B tumor cells were established in athymic nude mice. Lewis lung carcinoma cells were injected into C57BI/6 mice. Mice bearing SQ-20B xenografts were injected intraperitoneally with 2.5 mg/kg/day of murine recombinant endostatin 5 times per week for 2 weeks 3 hours before IR treatment (50 Gy total dose). Mice bearing Lewis lung carcinoma tumors were injected intraperitoneally with endostatin (2.5 mg/kg/day) four times; the first injection was given 24 hours before the first IR dose (15 Gy) and then 3 hours before IR (15 Gy/day) for 3 consecutive days. Microvascular density was assessed on tumor tissue sections by use of CD31 immunohistochemistry and light microscopy. Endothelial cell survival analyses were employed to evaluate endostatin effects on human aortic endothelial cells and human umbilical vein endothelial cells. Endothelial cell apoptosis was examined by use of FACS analysis and DAPI microscopy.
  
  
  RESULTS
  In SQ-20B xenografts, combined treatment with endostatin and IR produced tumor growth inhibition that was most pronounced at the nadir of regression (day 21). By day 35, tumors receiving combined treatment with endostatin and IR were 47% smaller than tumors treated with endostatin alone. Interactive cytotoxic treatment effects between endostatin and IR were also demonstrated in mice bearing Lewis lung carcinoma tumors. Significant tumor growth inhibition was observed in the endostatin/IR group at days 11 and 13 compared with IR alone. Histologic analyses demonstrated a reduction in microvascular density after combined treatment with endostatin and IR compared with endostatin treatment alone. Survival analyses confirmed interactive cytotoxicity between endostatin and IR in both human aortic endothelial cells and human umbilical vein endothelial cells but not in SQ-20B tumor cells. Combined treatment with endostatin and IR produced an increase in cow pulmonary artery endothelial apoptosis compared with either treatment alone.
  
  
  CONCLUSIONS
  The tumor regression observed after combined treatment with endostatin and IR suggests additive antitumor effects in both human and murine tumors. Importantly, the concentrations of endostatin employed produced little tumor regression when endostatin was employed as a single agent. The results from the clonogenic and apoptosis assays support the hypothesis that the endothelial compartment is the target for the endostatin/IR interaction.
authors.affiliation: Department of Radiation and Cellular Oncology, University of Chicago, Illinois, USA.
authors.forename: N N
authors.initials: NN
authors.lastname: Hanna
authors.forename: S
authors.initials: S
authors.lastname: Seetharam
authors.forename: H J
authors.initials: HJ
authors.lastname: Mauceri
authors.forename: M A
authors.initials: MA
authors.lastname: Beckett
authors.forename: N T
authors.initials: NT
authors.lastname: Jaskowiak
authors.forename: R M
authors.initials: RM
authors.lastname: Salloum
authors.forename: D
authors.initials: D
authors.lastname: Hari
authors.forename: M
authors.initials: M
authors.lastname: Dhanabal
authors.forename: R
authors.initials: R
authors.lastname: Ramchandran
authors.forename: R
authors.initials: R
authors.lastname: Kalluri
authors.forename: V P
authors.initials: VP
authors.lastname: Sukhatme
authors.forename: D W
authors.initials: DW
authors.lastname: Kufe
authors.forename: R R
authors.initials: RR
authors.lastname: Weichselbaum
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis; D018827:Carcinoma, Lewis Lung / Q000188:drug therapy; D002469:Cell Separation; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003094:Collagen / Q000627:therapeutic use*; D043170:Collagen Type XVIII; D003131:Combined Modality Therapy; D004305:Dose-Response Relationship, Drug; D043169:Endostatins; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects; D004926:Escherichia coli / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008833:Microcirculation / Q000187:drug effects / Q000528:radiation effects; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000532:radiotherapy*; D010446:Peptide Fragments / Q000627:therapeutic use*; D010843:Pichia / Q000378:metabolism; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000096:biosynthesis; D011839:Radiation, Ionizing; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014471:Umbilical Veins / Q000166:cytology / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D043170:Collagen Type XVIII; D043169:Endostatins; D010446:Peptide Fragments; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011994:Recombinant Proteins; D003094:Collagen