Effects of ionizing radiation on normal and tumor-associated lymphatic vessels

Lymphatic vessels play a crucial role in both the pathophysiology of tumors and in the spread cancer cells to lymph nodes. The effects of radiation on these vessels, however, are largely unknown. Here, we seek to describe the effects of ionizing radiation on normal and tumor-associated lymphatic vessels in vitro and in vivo. Clonogenic assays were employed to study the radiation dose response of lymphatic endothelial cells. Putative lymphatic endothelial cell mitogens and antiproliferative agents, including vascular endothelial growth factor-A (VEGF-A), VEGF-C and AZD2171, a tyrosine kinase inhibitor of the VEGF receptors, were tested as radiation sensitizers and protectors. Our results indicate that VEGF-A and VEGF-C are radiosensitizers while AZD2171 did not modulate the radioresponse. In vivo, normal lymphatics were studied with the experimental group receiving a single fraction of 8 Gy and the control group receiving no radiation. We observed no difference in the average lymphatic vessel diameter between these two groups over the course of 6 months. VEGF-C overexpressing tumor-associated lymphatic vessels were studied in vivo with four treatment groups: control animals (no irradiation), 8 Gy two weeks prior to implantation, 8 Gy at the time of implantation and 16 Gy given in two fractions before implantation (two weeks prior to and at the time of implantation). The average lymphatic vessel diameter and frequency of lymph node metastasis in these four groups indicates that the ability of radiation to prevent VEGF-C driven lymph node metastases is time-dependent; radiation must be delivered in close proximity to VEGF-C overexpressing tumor cell implantation to impact nodal metastases. This suggests that VEGF-C may be a functional lymphatic vessel radiosensitizer in vivo.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Lobo, Jennifer D

Advisor dc:contributor.advisor

• David G. Cory.

• Nuclear Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/41685

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/41685