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Antitumor interaction of short-course endostatin and ionizing radiation. Cancer J 2000 Sep-Oct;6(5):287-93



Pubmed ID



PURPOSE: 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.

DISCUSSION: 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.

Author List

Hanna NN, Seetharam S, Mauceri HJ, Beckett MA, Jaskowiak NT, Salloum RM, Hari D, Dhanabal M, Ramchandran R, Kalluri R, Sukhatme VP, Kufe DW, Weichselbaum RR


Ramani Ramchandran PhD Professor in the Pediatrics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Antineoplastic Agents
Carcinoma, Lewis Lung
Cell Separation
Cells, Cultured
Cloning, Molecular
Collagen Type XVIII
Combined Modality Therapy
Dose-Response Relationship, Drug
Endothelium, Vascular
Escherichia coli
Flow Cytometry
Mice, Inbred C57BL
Neoplasm Transplantation
Peptide Fragments
Platelet Endothelial Cell Adhesion Molecule-1
Radiation, Ionizing
Recombinant Proteins
Time Factors
Tumor Cells, Cultured
Umbilical Veins
jenkins-FCD Prod-484 8aa07fc50b7f6d102f3dda2f4c7056ff84294d1d