Microbeam-irradiated tumour tissue possesses a different infrared absorbance profile compared to broad beam and sham-irradiated tissue.
OBJECTIVE
To investigate biochemical changes in mouse tumour tissue following Microbeam Radiation Therapy (MRT) and Broad Beam (BB) irradiation using synchrotron Fourier-Transform Infrared (FTIR) microspectroscopy.


METHODS
Synchrotron FTIR microspectroscopy was carried out on mouse tumour sections previously irradiated with BB (11, 22 or 44 Gy), MRT (560 Gy in-beam, 25 μm wide, 200 μm peak separation) or sham-irradiation (0 Gy) from mice culled 4 hours post-irradiation.


RESULTS
MRT and BB-irradiated tumour sections showed clear chemical shifts in spectral bands corresponding to functional group vibrations in protein (1654-1630 cm(-1)), lipid (~1470, 1463 cm(-1)) and nucleic acid (1130-1050 cm(-1)). MRT peak and valley regions showed virtually identical absorbance patterns in protein and lipid regions. However, we observed chemical shifts corresponding to the nucleic acid region (1120-1050 cm(-1)) between the peak and valley dose regions. Chemical maps produced from integrating absorbance bands of interest over the scanned tumour area did not reveal any microbeam paths.


CONCLUSIONS
The lack of difference between MRT peak and valley irradiated areas suggests a holistic tissue response to MRT that occurs within 4 h, and might be the first evidence for a mechanism by which MRT kills the whole tumour despite only a small percentage receiving peak irradiation.
University of Melbourne, Department of Obstetrics & Gynaecology, Royal Women's Hospital, Parkville, Victoria, Australia.
Monica
M
Sharma
Jeffrey C
JC
Crosbie
Ljiljana
L
Puskar
Peter A W
PA
Rogers
D000818:Animals; D045744:Cell Line, Tumor; D005260:Female; D006657:Histones / Q000378:metabolism; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D015591:Microspectrophotometry; D011879:Radiotherapy Dosage; D017550:Spectroscopy, Fourier Transform Infrared; D017356:Synchrotrons
D006657:Histones; C475961:gamma-H2AX protein, mouse