MR Imaging Of Human Pancreatic Cancer Cell Labeled With Superparamagnetic Iron Oxide (SPIO) And The Xenograft Model In Nude Mice

Objective: The aim of this work was to approach the best concentration of Superparamagnetic Iron Oxide (SPIO) labeling human pancreatic cancer cell; to set up tumor xenografts model induced in nude mice by the subcutaneously inoculation of human pancreatic cancer cells labeled with SPIO; and to investigate the MRI findings of the tumor xenografts and to monitor the growth of the tumor by using MR imaging.Method:1 Different concentration of SPIO (4.2μg/ml, 8.4μg/ml, 21μg/ml, 42μg/ml, 84μg/ml) was used to label human pancreatic cancer cell. The morphology of the cells was evaluated on Prussian blue staining, and the masccline rate of labeled cells was analyzed.2 Both the labeled cells group (the human pancreatic cancer cell labeled by different concentration of SPIO) and the SPIO group (different concentration of SPIO without cells) were performed MR imaging on 1.5T MR scanner.3 The labeled cancer cells were subcutaneously inoculated into 11 nude mice to induce tumor xenografts (experimental group). The unlabelled cancer cells served as a control inoculated into 9 nude mice (control group).4 MR imaging was performed with 1.5T MR scanner for the tumor xenograft at the first, second and third week after the inoculation, respectively, and the pathomorphology of the tumor were evaluated by HE staining and Prussian blue staining.Result:1 The masccline rate of labeled by different concentration of SPIO (4.2μg/ml, 8.4μg/ml,21μg/ml, 42μg/ml, 84μg/ml) were 14.2%, 38.5%, 59.6%, 87.7%, 94.6% respectively.2 The MRI finding of SPIO group: the signal intensity trended to decrease after an initial ascent in SE-T1WI and SPGR-T1WI ,the lowest MR signal intensity is on 84μg/ml,4.2μg/ml, respectively; and to increase after an initial decline in FRFSE-T2WI, the lowest MR signal intensity is on 21μg/ml, and was a wave pattern (down-up-down) in 3D-FIESTA following the increase of the concentration of SPIO. The MRI finding of labeled cells group: the signal intensity tended to increase after an initial decline in SE-T1WI, SPGR-T1WI and FRFSE-T2WI, he lowest MR signal intensity is on 21μg/ml,and to decrease in 3D-FIESTA following the increase of the concentration of SPIO, the lowest MR signal intensity is on 84μg/ml.3 The incidence of tumor xenograft was 100% in nude mice for both groups (20/20) in the first week after the inoculation.4 The MRI finding of tumor xenografts model of nude mice: In SPIO group, the tumors showed homogeneously hypointense both on T1, T2 weighted and FIESTA images one week after inoculation. Two and three weeks after inoculation, the tumor center was kept hypointense on all above sequences. The tumor periphery showed isointense on T1 weighted, and hyperintense on T2 weighted and FIESTA images, respectively. The tumors in control group showed homogeneously hypointense or isointense on T1 weighted, and hyperintense on T2 weighted and FIESTA images in the first, second and third week after the inoculation. The size of tumor in both groups had increased subsequent to the inoculation, and the size and signal to noise rate (SNR) of tumor center in SPIO group had decreased subsequent to the inoculation in all T1, T2 weighted images and FIESTA.5 The Prussian blue stain showed a lot of blue grains were accumulated in the center of tumor and little blue grains were in the tumor periphery. The content of the blue grains had decreased subsequent to the distance to the center.Conclusion:1 The best concentration of SPIO to label human pancreatic cancer cell is 42μg/ml (the concentration of iron ions).2 The human pancreatic cancer cells can be labeled with SPIO without affection to the proliferation of it and the labeled cells can induce tumor xenograft in nude mice.3 MR imaging can monitor the distribution and concentration changes of SPIO in the tumor and also can be used to monitor the development of the tumor.