ABSTRACT
Pretargeting is an imaging strategy different from the imaging of traditional radiolabeled antibody,in which the antibody and radioisotope are administered in turn and then combined by coupling system within the body.Due to the high specificity and affinity between the coupling systems,the radioisotope is localized to the target in vivo,and then the radioactive labeling is achieved for imaging.Nuclear imaging using pretargeting methods can decrease the circulation duration of the radioisotope so as to reduce the uptake of the radioactivity in normal tissues,and facilitate the use of short-lived radioisotopes.This article provides a bird's-eye view of 4 main strategies:biotin-streptavidin (SA) system,bispecific antibodies (BsAb) system,complementary oligonucleotides sequence,and bioorthogonal click chemistry system.
ABSTRACT
Pretargeting is an imaging strategy different from the imaging of traditional radiolabeled antibody, in which the antibody and radioisotope are administered in turn and then combined by coupling system within the body. Due to the high specificity and affinity between the coupling systems, the radioisotope is localized to the target in vivo, and then the radioactive labeling is achieved for imaging. Nuclear imaging using pretargeting methods can decrease the circulation duration of the radioisotope so as to reduce the uptake of the radioactivity in normal tissues, and facilitate the use of short-lived radioisotopes. This article provides a bird′s-eye view of 4 main strategies: biotin-streptavidin (SA) system, bispecific antibodies (BsAb) system, complementary oligonucleotides sequence, and bioorthogonal click chemistry system.
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Purpose To study the radioactive purity and activity of 131I labeled human single chain variable fragments antibodies (scFv) against anaplastic thyroid carcinoma (ATC),and to explore its distribution and radioimmunoimaging characteristics in tumor bearing nude mice model in vivo so as to provide a new method for anaplastic thyroid carcinoma diagnosis and treatment.Materials and Methods The nude mice model bearing human anaplastic thyroid carcinoma was constructed.The chloramine T method was used to label scFv with 131I and the Sephadex G25M was used for purification of labeled scFv.Labeling rate was determined by trichloroacetic acid method;radiochemical purity,room temperature stability and serum stability were examined using paper chromatography.131I-scFv was injected via tail vein in mice,and the distribution of 131I-scFv in body tissues and organs was analyzed at 12,24,48,72 h after injection.Static SPECT imaging was performed at 12,24,48,72 h after injection to observe the intratumoral accumulation of radioactivity.The SPECT/CT image fusion was performed when the tumor tissues were clearly visible.Results 131I-scFv was purified,and the labeling rate was 91.64％;the radiochemical purity was (93.3 ±0.3)％.The radiochemical purity of 131l-scFv placed at room temperature and the serum for 1,6,12,24 h were all ＞90％.The radioactive distribution of 131I-scFv in tumor,liver,kidney,intestine and blood was high.SPECT imaging showed 131I-scFv was selectively concentrated in tumor tissue;the target/non-target ratio was the highest at 48 h,and the imaging was most satisfactory.Conclusion 131I-scFv can be successfully prepared.SPECT imaging of 131I-scFv in nude mice model is satisfactory,which lays the foundation for further research in ATC diagnosis and treatment.
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Objective: To validate the clinical value of external fiducial frame in the fusion of single photon emission computed tomography (SPECT) radioimmunoimaging and CT imaging in tumor patients. Methods: The external fiducial frame was fixed on the body surface of back of the 6 patients. SPECT radioimmunoimaging and CT scan were performed on the 6 patients. The two styles of image were fused on the PC computer. Results: The images produced by SPECT radioimmunoimaging of the 6 patients were exactly fused with the CT image. The tumor lesions were correctly focused. Conclusion: The fusion of radioimmunoimaging and anatomic imaging would be accomplished by using the external fiducial frame. Image fusion increases the accuracy of location diagnosis.
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Objective To explore the levels of neuron-specific enolase(NSE) and tumor necrosis factor-?(TNF-?)concentrations of serum and cerebrospinal fluid(CSF) in children with epilepsy,and evaluate its relationships with neuronal damage.Methods Sixty-two epilepsy children were divided into 2 groups:severe group including 28 cases of frenquent seizures ≥3 vices or time of master single test seizures≥15 min,mild group including 34 cases of infrenquent seizures
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Objective To further improve the amount of gadolinium located on tumor, a gadolinium chelate enhanced magnetic resonance imaging pretargeting with avidin-biotin system technique was adopted and the enhancing characteristics of difference of signal intensity at various scan timing were investigated in our experiment. Methods (1) Anti-CEA antibody CL -3 was biotinylated in a mixture with antibody to NHS-LS-biotin with a molar ratio of 1/30-50. (2) After the reaction of GdCl 3 and DTPA-B, the unconjugated gadolinium was removed by chromatography on G-10 column. (3) Steps for pretargeting tumor: First step, McAb-B was injected intravenously into nude mice on the first day. Second step, avidin (Av) and streptavidin (SA) were injected intraperitoneally 24 hours later. Third step, Gd-DTPA-Bt was injected intravenously 48 hours after the first injection. MRI was performed with plain scans, enhanced scans at 20 minutes, 2 hours, 8 hours, and 24 hours after the third step. Signal intensities of tumor and muscles were measured. The pretargeting effect was compared with those of Gd-DTPA-McAb and Gd-DTPA. Results (1) Each monoclonal antibody conjugated with 11-23 biotin and the immunoactivity of biotinylated antibody with 12 biotin/antibody was 94.9%. (2) The enhancing effect of pretargeting approach was tumor specific. Contrarily that of Gd-DTPA was not. (3) The enhancing rate of signal intensity specificity of pretargeting approach was 43%, while that of McAb-Gd-DTPA was 17.9% only, so the enhancing ratio was 2.4. Conclusion Pretargeting approach using avidin -biotin system improves the amounts of gadolinium locating on tumors and yields a specific enhancing effect. It is a promising modality which promotes the ability of Gd labeled magnetic resonance immunoimaging in the detection of colon cancer and its recurrence.
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ObjectiveTo evaluate mammaglobin (hMAM) mRNA expression as a tumor marker for micrometastatic carcinoma cells in the peripheral blood of patients with breast cancer (BC). MethodsTotal RNA extracted from a breast carcinoma cell line SKBR3 was subjected to analysis of hMAM mRNA expression by RT-PCR. The sensitivity of FQ-PCR to detect a SKBR3 cell at a level of 10 7 was established. Peripheral blood of 63 BC patients was examined by this method. ResultsBlood samples were positive in 19 out of 63 (30%) patients with breast carcinomas. None of the patients with other cancer (25 cases) or benign breast disease (13 cases) was positive and only 1 out of 31 healthy volunteers was found with detectable hMAM mRNA expression in the peripheral blood. ConclusionFluorescence quantitative (FQ) PCR combined with nest PCR was a sensitive method in detecting micrometastases of breast cancer.
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The biodistribution and the radio activity in blood clearance of 99m Tc AMLCA were determined in 5 normal dogs by whole body imaging and measuring the radio activity in blood samples at 2,4,8 and 24h after 99m Tc AMLCA injection. The feasibility of imaging of the site of myocardial infarct was determined in 2 of the experimental MI dogs by demonstration of the left ventricle blood pool imaging (LVBPI) with 99m Tc AMLCA and by subsequent imaging of the excised heart. The results showed that the plasma concentration of 99m Tc AMLCA decreased rapidly from 51 5%?5 2% at 2nd hr to 27 3%?3 1% at 4th, 12 3%?1 8% at 8 hr and 5 6%?0 6% at 24th after the injection. The LVBPI in one MI dog showed that the region of the radionuclide concentration of 99m Tc AMLCA corresponded to region of absence of 99m Tc MIBI. The scintigraphy in another MI dog heart slices showed that the region of the radionuclide concentrate of 99m Tc AMLCA corresponded to the region of triphenyltetrazolium chloride (TTC) staining. The measurement of double radionuclides in the double interesting region in the MI dog heart slices indicated that the infarct myocardium uptook 99m Tc AMLCA specifically. These findings suggested that 99m Tc AMLCA scintigraphy might be a new approach for detecting and localizing MI