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Use of in vivo bioluminescence and MRI to determine hyperthermia‐induced changes in luciferase activity under the control of an hsp70 promoter
Author(s) -
Hundt Walter,
Schink Christian,
Steinbach Silke,
O'ConnellRodwell Caitlin E.,
Mayer Dirk,
Burbelko Mykhaylo,
Kießling Andreas,
Guccione Samira
Publication year - 2012
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.2811
Subject(s) - luciferase , in vivo , bioluminescence imaging , hyperthermia , bioluminescence , chemistry , hsp70 , microbiology and biotechnology , nuclear magnetic resonance , heat shock protein , magnetic resonance imaging , nuclear medicine , transfection , biology , medicine , gene , physics , biochemistry , radiology , paleontology
We investigated the in vivo effect of hyperthermia on the expression of heat shock proteins and MRI changes in three tumor cell lines. Three tumor cell lines (SCCVII, NIH3T3, M21) were transfected with a plasmid containing the heat shock protein 70 gene ( hsp70 ) promoter fragment and the luciferase reporter gene, and injected into mice. Tumors of 1100 mm 3 in size were exposed to five different temperatures (38, 40, 42, 44 and 46 °C) in a water bath. Bioluminescence and MRI were performed at set time intervals. The MRI scan protocol was as follows: T 1 ‐weighted spin echo ± contrast medium, T 2 ‐weighted fast spin echo, dynamic contrast‐enhanced MRI, diffusion‐weighted stimulated echo acquisition mode sequence, T 2 time obtained on a 1.5T General Electric MRI scanner. Immunoblotting was also performed. hsp70 transcription was strongly induced at 42 and 44 °C, reaching values as high as 8531.5 ± 432.1‐fold above baseline in NIH3T3 tumors. At these temperatures, significant increases in the uptake of contrast medium, slope of initial enhancement, Ak ep values and apparent diffusion coefficient (ADC) were observed in the 8‐h scan of the NIH3T3 cell line. In SCCVII tumors, ADC increased by about 23% ( p = 0.010) in the scans performed at 8, 24, 48 and 96 h. At 46 °C, luciferase activity was reduced significantly in the three cell lines. In all tumor types, a significant increase in ADC was observed, which was highest in SCCVII tumors (33.8%; p < 0.01). In accordance with the bioluminescence results, significant Hsp70 protein production was shown by immunoblot analysis. The best correlation coefficient between luciferase activity and immunoblotting results was found for M21 tumors ( r = 0.93, p < 0.0001). Different tissue types display distinct patterns of hsp70 transcription. MRI can be used, in combination with optical imaging, to provide information on hsp70 transcription and protein production. The major finding of the present study was that heat‐related biochemical changes in tumor tissue can be determined by MRI. Copyright © 2012 John Wiley & Sons, Ltd.