Studies Of¹³¹I-rMIF On Biodistribution And Tumor-targeting In Tumor-bearing Mice

Objective:Hepatocellular carcinoma (HCC) is one of the mostfrequently reported malignant tumors. Detection of HCC at anearlier stage is very important for patient’s prognosis. Althoughα-feto-protein (AFP) has been used as serum marker for HCC for decades, it is insufficient for HCC screening. The ability of abdominal imaging to detect HCC has improved dramatically over the last few decades. Although computed tomography (CT) and ultrasonography (US) usually accurately depict HCC, the attempts to improve the method s of stagingand follow up for patients with known HCC haveled to the evaluation of nuclear imaging systems. Therefore, efforts are being made to alternative tracers for screening and staging HCC in patients at risk.Macrophage migration inhibitory factor (MIF)has been considered as the most interesting factor because of its multifunction. MIF wassubsequently found to be involved in the development of pathological changes associated with severalacute and chronic inflammatory diseases. Recentlystudies have been shown that MIF plays an important role in the tumor formation. MIF has been shown to promote cell proliferation and tumor angio genesis and over-expression of MIF has been reported in cancers. In our preciously study, Na131I labeled anti-MIF monoclonal antibody(McAb) have been reported could focused in tumor tissues in vivo in HCC tumor-bearing model. But the molecular weight of McAbis larger; it is not suitable for clinic use. So, it is important to find a smaller fragment of MIF for nuclear medicine imaging in vivo. The purpose of this study is to evaluate whether rMIF could be used as an early imaging marker for HCC.Methods:1. The expression, purification and identification of rMIF were done.2. The rMIF was labeled with131I using Iodogen method and the labeled rate and stability were identified with paper chromatography. The biological activity of were determinated.3. The specific binding was analyzed by cells uptake assay.4. Hepatocellular-bearing mice model has been estabolished and the expression of MIF in tumor-bearing model was verificated with RT-PCR and Western-Blotting.5. The biodistribution and tumor targeting was analyzed after injection of131I-rMIF.Results:1. TherMIF was expressed and purified and identified with Western-Blotting.2. The rMIF was labeled with iodine131through Iodogen method. The labeled rate of131I-rMIF is87.34%, radiochemical purity is94.95%.131I-rMIF was relatively stable.3. The uptake of131I-rMIF by hepatocellular carcinoma cells was much higher than that of control (free Na131I) in0.5,1,2and4h (P＜0.05).4. Hepatocellular-bearing model were successfully estabolished.MIFmRNAwas expressedin hepatocellular-bearing model.5. It was shown that131I-rMIF mainly metabolized through liver and kidney. And the higher radioactivity was detected within tumor tissues (target), the T/NT (target-to-non-target) ratios at were2.701±0.230、3.931±0.281、4.242±0.111and3.587±0.241separately at1,3,6,24h after injection (P＜0.05). The result of autoradiography was shown that131I-rMIF could be specifically localized in tumors after6h. Conclusion:The results suggested that131I-labeled rMIF was stable, could be uptake and focused by tumor cells rapidly, and so may be used for hepatocellular carcinoma early detection.