Background and purpose:Researches had indicated that about over 85%of malignant tumors highly express telomerase activity. So telomerase has become one of the important methods in the research field of tumor diagnosis and treatment. Nowadays, several reports about malignant tumor which over expresses hTERT targeting imaging with radionuclide labeled hTERT ASON had been published. In these reports, high quality of pictures can hardly be acquired because of poor anatomical and spacial resolution in nuclear imaging itself. Accordingly, in this study, we developed a method of detecting human telomerase in vivo with magnetic resonance imaging (MRI) and evaluate its feasibility. Methods:Firstly, Uniformly phosphorothioate-modified human telomerase reverse transcriptase antisense oligonucleotide (hTERT ASON) was labeled with Gd3+ through the bifunctional chelator 1, 4, 7, 10-tetraazacyclododecane-N, N’, N’’, N’’’-tetraacetic acid (DOTA) and iv vitro experiments were performed to characterize the antisense probes (for biodistribution and cellular uptake, 99mTc-DOTA-ASON was used in stead of Gd-DOTA-ASON). Then Gd-DOTA-ASON was injected intraperitoneally in pulmonary adenocarcinoma A375 nude mice tumor-bearing BALB/c for in vivo imaging using 7.0 T Micro MRI periodically, tumors and their surrounding tissues were defined as region of interest (ROI) to calculate the signal to noise ratio (SNR) of tumor to muscle using Gd-DTPA as control. Finally, immunohistochemical analysis of telomerase activity of each xenograft was operated 2 days after imaging. Results:The binding efficiency of Gd-DOTA-ASON reached was as high as 65%(63.2±2.4, n=6). And it can maintain 61%in fresh human serum and normal saline at 37℃over 24 h;A375 cells showed an uptake of 8.5%when incubated with 99mTc-DOTA-ASON;In comparing with DOTA-ASON and Gd-DTPA, cells transected with Gd-DOTA-ASON had higher SI when performed MRI with T1WI. The hTERT-expressing xenografts were obviously enhanced by Gd-DOTA-ASON at 0.5-6 h after injection and the SNR can reach 2.37, whereas obvious enhancement only could be found within 2 h after injection of Gd-DTPA. Both labeled and non-labeled antisense probes can suppress the activity of telomerase of A375 cells either in vitro or in vitro. Conclusion:Our research offers proof that Gd-DOTA-ASON can be used as tumor specific targeting MR probe for diagnosing malignant tumors with high expression of telomerase.

Background: and Purpose To evaluate whether the thrombus enhancement sign (TES) can be used to differentiate embolic large vessel occlusion (LVO) from in situ intracranial atherosclerotic stenosis (ICAS)-related LVO in the anterior circulation of patients with acute ischemic stroke (AIS). Methods: Patients with LVO in the anterior circulation who underwent both non-contrast computed tomography (CT) and CT angiography and mechanical thrombectomy were retrospectively enrolled. Both embolic LVO (embo-LVO) and in situ ICAS-related LVO (ICAS-LVO) were confirmed by two neurointerventional radiologists after reviewing the medical and imaging data. TES was assessed to predict embo-LVO or ICAS-LVO. The associations between occlusion type and TES, along with clinical and interventional parameters, were investigated using logistic regression analysis and a receiver operating characteristic curve. Results: A total of 288 patients with AIS were included and divided into an embo-LVO group (n=235) and an ICAS-LVO group (n=53). TES was identified in 205 (71.2%) patients and was more frequently observed in those with embo-LVO, with a sensitivity of 83.8%, specificity of 84.9%, and area under the curve (AUC) of 0.844. Multivariate analysis showed that TES (odds ratio [OR], 22.2; 95% confidence interval [CI], 9.4–53.8; P<0.001) and atrial fibrillation (OR, 6.6; 95% CI, 2.8–15.8; P<0.001) were independent predictors of embolic occlusion. A predictive model that included both TES and atrial fibrillation yielded a higher diagnostic ability for embo-LVO, with an AUC of 0.899. Conclusion TES is an imaging marker with high predictive value for identifying embo- and ICAS-LVO in AIS and provides guidance for endovascular reperfusion therapy.