Irradiation-dependent effects on tumor perfusion and endogenous and exogenous hypoxia markers in an A549 xenograft model.
OBJECTIVE
Hypoxia is a major determinant of tumor radiosensitivity, and microenvironmental changes in response to ionizing radiation (IR) are often heterogenous. We analyzed IR-dependent changes in hypoxia and perfusion in A549 human lung adenocarcinoma xenografts.


METHODS
Immunohistological analysis of two exogenously added chemical hypoxic markers, pimonidazole and CCI-103F, and of the endogenous marker Glut-1 was performed time dependently after IR. Tumor vessels and apoptosis were analyzed using CD31 and caspase-3 antibodies. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and fluorescent beads (Hoechst 33342) were used to monitor vascular perfusion.


RESULTS
CCI-103F signals measuring the fraction of hypoxic areas after IR were significantly decreased by approximately 50% when compared with pimonidazole signals, representing the fraction of hypoxic areas from the same tumors before IR. Interestingly, Glut-1 signals were significantly decreased at early time point (6.5 h) after IR returning to the initial levels at 30.5 h. Vascular density showed no difference between irradiated and control groups, whereas apoptosis was significantly induced at 10.5 h post-IR. DCE-MRI indicated increased perfusion 1 h post-IR.


CONCLUSIONS
The discrepancy between the hypoxic fractions of CCI-103F and Glut-1 forces us to consider the possibility that both markers reflect different metabolic alterations of tumor microenvironment. The reliability of endogenous markers such as Glut-1 to measure reoxygenation in irradiated tumors needs further consideration. Monitoring tumor microvascular response to IR by DCE-MRI and measuring tumor volume alterations should be encouraged.
Fokas
Emmanouil
E
Department of Radiotherapy and Radiation Oncology, University Hospital Marburg, Medical Faculty of Philipps University, Marburg, Germany. emmanouil.fokas@yahoo.de
Hänze
Jörg
J
Kamlah
Florentine
F
Eul
Bastian G
BG
Lang
Nico
N
Keil
Boris
B
Heverhagen
Johannes T
JT
Engenhart-Cabillic
Rita
R
An
Hanxiang
H
Rose
Frank
F
D000230:Adenocarcinoma / Q000098:blood supply / Q000378:metabolism / Q000532:radiotherapy; D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D001562:Benzimidazoles / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D053148:Caspase 3 / Q000032:analysis / Q000276:immunology; D015687:Cell Hypoxia / Q000528:radiation effects; D003287:Contrast Media / Q000378:metabolism; D005682:Gadolinium / Q000378:metabolism; D051272:Glucose Transporter Type 1 / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000098:blood supply / Q000378:metabolism / Q000532:radiotherapy; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence; D009593:Nitroimidazoles / Q000378:metabolism*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis / Q000276:immunology; D013997:Time Factors; D014183:Transplantation, Heterologous; D005466:Fluorocarbons
D001562:Benzimidazoles; D015415:Biomarkers; D053148:Caspase 3; D003287:Contrast Media; D005682:Gadolinium; D051272:Glucose Transporter Type 1; D009593:Nitroimidazoles; D019408:Platelet Endothelial Cell Adhesion Molecule-1; C049948:CCI 103F; D005466:Fluorocarbons; C033815:pimonidazole; C017807:bisbenzimide ethoxide trihydrochloride