Effect of Irradiation on Tumor Microenvironment and Bone Marrow Cell Migration in a Preclinical Tumor Model.

Abstract

PURPOSE:

To characterize the tumor microenvironment after standard radiation therapy (SRT) and pulsed radiation therapy (PRT) in Lewis lung carcinoma (LLC) allografts.

METHODS AND MATERIALS:

Subcutaneous LLC tumors were established in C57BL/6 mice. Standard RT or PRT was given at 2 Gy/d for a total dose of 20 Gy using a 5 days on, 2 days off schedule to mimic clinical delivery. Radiation-induced tumor microenvironment changes were examined after treatment using flow cytometry and antibody-specific histopathology. Normal tissue effects were measured using noninvasive (18)F-fluorodeoxyglucose positron emission tomography/computed tomography after naïve animals were given whole-lung irradiation to 40 Gy in 4 weeks using the same 2-Gy/d regimens.

RESULTS:

Over the 2 weeks of therapy, PRT was more effective than SRT at reducing tumor growth rate (0.31 ± 0.02 mm(3)/d and 0.55 ± 0.04 mm(3)/d, respectively; P<.007). Histopathology showed a significant comparative reduction in the levels of Ki-67 (14.5% ± 3%), hypoxia (10% ± 3.5%), vascular endothelial growth factor (2.3% ± 1%), and stromal-derived factor-1α (2.5% ± 1.4%), as well as a concomitant decrease in CD45(+) bone marrow-derived cell (BMDC) migration (7.8% ± 2.2%) after PRT. The addition of AMD3100 also decreased CD45(+) BMDC migration in treated tumors (0.6% ± 0.1%). Higher vessel density was observed in treated tumors. No differences were observed in normal lung tissue after PRT or SRT.

CONCLUSIONS:

Pulsed RT-treated tumors exhibited slower growth and reduced hypoxia. Pulsed RT eliminated initiation of supportive mechanisms utilized by tumors in low oxygen microenvironments, including angiogenesis and recruitment of BMDCs.

• Authors: Jonathan L Kane, Sarah A Krueger, Alaa Hanna, Thomas R Raffel, George D Wilson, Gerard J Madlambayan, Brian Marples
• Journal: International journal of radiation oncology, biology, physics (Int J Radiat Oncol Biol Phys) Vol. 96 Issue 1 Pg. 170-8 (09 01 2016) ISSN: 1879-355X [Electronic] United States
• PMID: 27511854 (Publication Type: Journal Article)
• Copyright: Copyright © 2016 Elsevier Inc. All rights reserved.

Topics

• Animals
• Bone Marrow Cells (radiation effects)
• Carcinoma, Lewis Lung (pathology, radiotherapy)
• Cell Line, Tumor
• Cell Movement (radiation effects)
• Dose-Response Relationship, Radiation
• Male
• Mice, Inbred C57BL
• Neoplasms, Experimental (pathology, radiotherapy)
• Radiation Dose Hypofractionation
• Treatment Outcome
• Tumor Burden (radiation effects)
• Tumor Microenvironment (radiation effects)