Tumor tissue characterization evaluating the luciferase activity under the control of a hsp70 promoter and MR imaging in three tumor cell lines

Abstract

We investigated the luciferase activity under the control of a hsp70 promoter and MR imaging for three tumor cell lines. Three tumor cell lines, SCCVII, NIH3T3 and M21 were transfected with a plasmid containing the hsp70 promoter fragment and the luciferase reporter gene and grown in mice. Bioluminescence imaging of the tumors was performed every other day. MR imaging, pre- and post-contrast T1-wt SE, T2-wt FSE, Diffusion-wt STEAM-sequence, T2-time determination were obtained on a 1.5-T GE MRI scanner at a tumor size of 600–800 mm 3 and 1400–1600 mm 3. Comparing the different tumor sizes the luciferase activity of the M21 tumors increased about 149.3%, for the NIH3T3 tumors about 47.4% and for the SCCVII tumors about 155.8%. Luciferase activity of the M21 tumors ( r = 0.82, p < 0.01) and the SCCVII tumors ( r = 0.62, p = 0.03) correlated significant with the diffusion coefficient. In the NIH3T3 tumors the best correlation between the luciferase activity and the MRI parameter was seen for the SNR (T2) values ( r = 0.78, p < 0.01). The luciferase activity per mm 3 tumor tissue correlated moderate with the contrast medium uptake ( r = 0.55, p = 0.01) in the M21 tumors. In the NIH3T3 and SCCVII tumors a negative correlation ( r = −0.78, p < 0.01, respectively, r = −0.49, p = 0.02) was found with the T2 time. Different tissue types have different luciferase activity under the control of the same hsp70 promoter. The combination of MR imaging with bioluminescence imaging improves the characterization of tumor tissue giving better information of this tissue on the molecular level.