In Vivo Evaluation of Sgc8-c Aptamer as a Molecular Imaging Probe for Colon Cancer in a Mouse Xenograft Model.

Recent biotechnological applications in the field of clinical oncology led to the identification of new biomarkers as molecular targets of cancer, and to broad developments in the field of personalized medicine. Aptamers are oligonucleotides (ssDNA or RNA) that are selected to specifically recognize a molecular target with high affinity and specificity. Based on this, new horizons for their use as molecular imaging probes are being explored. The objective of this work was to evaluate the Sgc8-c aptamer conjugated with Alexa Fluor 647 fluorophore as an imaging probe in a colon tumor xenograft mouse model, with potential application in molecular imaging. In this study, the LS174T cell line was used to induce colorectal adenocarcinoma in nude mice. After confirmation of PTK7 overexpression by immunohistochemistry, in vivo studies were performed. Pharmacokinetic, in vivo and ex vivo biodistribution imaging, and a competition assay were evaluated by fluorescence imaging. In vivo visualization of the probe in the tumors was assessed two hours after aptamer probe administration, exhibiting excellent tumor-to-background ratios in biodistribution studies and high specificity in the competition test. Our results demonstrated the functionality of Scg8-c as an imaging probe for colon cancer, with potential clinical applications.

T908 Polymeric Micelles Improved the Uptake of Sgc8-c Aptamer Probe in Tumor-Bearing Mice: A Co-Association Study between the Probe and Preformed Nanostructures.

Aptamers are oligonucleotides that have the characteristic of recognizing a target with high affinity and specificity. Based on our previous studies, the aptamer probe Sgc8-c-Alexa647 is a promising tool for molecular imaging of PTK7, which is an interesting biomarker in cancer. In order to improve the delivery of this probe as well as create a novel drug delivery nanosystem targeted to the PTK7 receptor, we evaluate the co-association between the probe and preformed nanostructures. In this work, preformed pegylated liposomes (PPL) and linear and branched pristine polymeric micelles (PMs), based on PEO-PPO-PEO triblock copolymers were used: poloxamer F127® and poloxamines T1307® and T908®. For it, Sgc8-c-Alexa647 and its co-association with the different nanostructures was exhaustively analyzed. DLS analysis showed nanometric sizes, and TEM and AFM showed notable differences between free- and co-associated probe. Likewise, all nanosystems were evaluated on A20 lymphoma cell line overexpressing PTK7, and the confocal microscopy images showed distinctness in cellular uptake. Finally, the biodistribution in BALB/c mice bearing lymphoma-tumor and pharmacokinetic study revealed an encouraging profile for T908-probe. All data obtained from this work suggested that PMs and, more specifically T908 ones, are good candidates to improve the pharmacokinetics and the tumor uptake of aptamer-based probes.

Preparation and primary bioevaluation of 99mTc-labeled-1-thio-ß-D-glucose as melanoma targeting agent.

The development of specific radiolabeled probes towards molecular markers in vivo has gained interest as targeted imaging agents for a more accurate detection of diseases. The aim of this study was to evaluate early detection of melanoma tumor based on 1-thio-ß-D-glucose (1-TG) radiolabeled with technetium-99m. 99mTc-1-TG has been synthesized and evaluated in vitro and in vivo for melanoma uptake. Tumor-cell uptake of the 99mTc complex was performed with cultured B16F1 murine melanoma cells which were also used for the in vivo studies. The methodology consisted in radiopharmaceutical synthesis followed by intravenous administration of 99mTc-1-TG in melanoma bearing mice and scintigraphic imaging. 1-thio-ß-D-glucose was labeled with 99mTc under reductive conditions using SnCl2. Radiolabeling efficiency was > 96%. 99mTc-1-TG showed high melanoma uptake in vitro. This was confirmed in vivo since a significant difference of 99mTc-1- TG uptake between melanoma model and the control joint was observed. General biodistribution showed renal uptake. The scintigraphic images showed tumor selective uptake of the 1-TG labeled, in tumor-bearing mice This study indicates effective labeling of 1-thio-ß-D-glucose with 99mTc that shows potential as a new type of specific probe for melanoma detection.

Biological evaluation of glucose and deoxyglucose derivatives radiolabeled with [99mTc(CO)3(H2O)3]+ core as potential melanoma imaging agents.

Glucose 9 and 2-deoxyglucose 10 were successfully synthesized and radiolabeled with [(99m)Tc(CO)(3)(H(2)0)(3)](+) intermediate in high yield. The complexes were characterized by HPLC and its stability with histidine over time was challenged. Cell uptake and biodistribution studies in melanoma-bearing C57BL/6 mice were performed. Both compounds showed accumulation in tumor tissue with high tumor-to-muscle ratios. Thus, D-glucose- and D-2-deoxyglucose-(99m)Tc complex could be considered as agents for melanoma diagnosis.