Development of anti-MUC1 DNA aptamers for the imaging and radiotherapy of breast cancer

Aptamers are novel oligonucleotide-based recognition molecules which can bind to almost any target, including extracellular proteins, antibodies, peptides and small molecules. Aptamers can be rapidly generated, and offer reduced immunogenicity, good tumour penetration, rapid uptake and clearance, and can thus be used as alternatives to monoclonal antibodies in molecular targeted radiotherapy and diagnostic imaging

Development of anti-MUC1 DNA aptamers for the imaging and radiotherapy of breast cancer

Background Aptamers have shown great potential as novel targeted radiopharmaceutical entities for the diagnosis and imaging of disease. They offer reduced immunogenicity, good tumour penetration, rapid uptake and clearance compared with their monoclonal antibody counterparts. In previous work we have reported the labelling of such aptamers against breast-cancer-related biomarkers with radionuclide ligands. Methods We have now conjugated previously selected aptamers against the protein core of the MUC1 glycoprotein tumour marker with chelating agents and labelled them with 99mTc, for the diagnostic imaging of breast cancer. The conjugation is achieved using standard peptide coupling reactions between an amino modification on the aptamer and the carboxylic group on the ligands. Labelling with 99mTc used tin chloride as the reducing agent, and analysis was by HPLC where both the UV and the gamma emission was monitored. Radiolabelled aptamer conjugates were separated from free, unconjugated 99mTc using microcon filters. For the analysis of the pharmacokinetic properties of the aptamer–radionucleotide conjugate we used gamma-camera imaging in MCF-7 breast cancer tumour model systems. Results We coupled the aptamer with the highest affinity for the MUC1 glycoprotein to different ligands (MAG2 or meso-2,3-dimercaptosuccinic acid) and labelled it with active 99mTc to obtain stable complexes that were used in pharmacokinetic studies. This allows us to compare the properties of a single conjugate with a biaptamer conjugate, as two of the DMSA–aptamer conjugates can coordinate the metal core. An efficient and convenient labelling of the aptamer with short half-life radioisotopes was achieved as the last step of the synthesis (postconjugation labelling). The labelled aptamers were separated from free 99mTc using microcon filter separation and were monitored by HPLC at all stages, to ensure that only radiolabelled aptamers were injected and imaged for their pharmacokinetic properties. Conclusion The aptamer–chelator conjugates have strong 99mTc binding properties and the resulting complexes are highly stable in vivo both in terms of nuclease degradation and leaching of the metal. The presence of more than one molecule of aptamer per complex alters the binding and pharmacokinetic properties of the radiolabelled products, allowing the complex to remain longer in circulation and thus offering improved tumour imaging properties, without affecting the tumour penetration of the aptamer. Furthermore, different ligands affect accumulation of the aptamer in different organs, as they alter the lipophilic properties of the conjugate. These results aim to open new possibilities for the diagnostic imaging of, and potentially the targeted radiotherapy of, breast cancer. </br

A general [F-18]AlF radiochemistry procedure on two automated synthesis platforms

The first general [18F]AIF automated radiolabelling procedure developed on the GE Tracerlab FX FN (Left) and Trasis AllInOne (Right) platforms.</p

Evaluation of DFO-HOPO as an octadentate chelator for zirconium-89.

The future of 89Zr-based immuno-PET is reliant upon the development of new chelators with improved stability compared to the currently used deferoxamine (DFO). Herein, we report the evaluation of the octadentate molecule DFO-HOPO (3) as a suitable chelator for 89Zr and a more stable alternative to DFO. The molecule showed good potential for the future development of a DFO-HOPO-based bifunctional chelator (BFC) for the radiolabelling of biomolecules with 89Zr. This work broadens the selection of available chelators for 89Zr in search of improved successors to DFO for clinical 89Zr-immuno-PET

Radiosynthesis of the anticancer nucleoside analogue Trifluridine using an automated 18F-trifluoromethylation procedure.

Trifluoromethyl groups are widespread in medicinal chemistry, yet there are limited 18F-radiochemistry techniques available for the production of the complementary PET agents. Herein, we report the first radiosynthesis of the anticancer nucleoside analogue trifluridine, using a fully automated, clinically-applicable 18F-trifluoromethylation procedure. [18F]Trifluridine was obtained after two synthetic steps in 99%, and a molar activity of 0.4 GBq μmol-1 ± 0.05. Biodistribution and PET-imaging data using HCT116 tumour-bearing mice showed a 2.5 %ID g-1 tumour uptake of [18F]trifluridine at 60 minutes post-injection, with bone uptake becoming a prominent feature thereafter. In vivo metabolite analysis of selected tissues revealed the presence of the original radiolabelled nucleoside analogue, together with deglycosylated and phosphorylated [18F]trifluridine as the main metabolites. Our findings suggest a potential role for [18F]trifluridine as a PET radiotracer for elucidation of drug mechanism of action

Estudo etnobotânico junto aos ervatários da área central de Pelotas-RS.

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HER3-Mediated Resistance to Hsp90 Inhibition Detected in Breast Cancer Xenografts by Affibody-Based PET Imaging.

Purpose: Recent studies have highlighted a role of HER3 in HER2-driven cancers (e.g., breast cancer), implicating the upregulation of the receptor in resistance to HER-targeted therapies and Hsp90 inhibitors (e.g., AUY922). Therefore, we have developed an affibody-based PET radioconjugate that quantitatively assesses HER3 changes induced by Hsp90 inhibition in vivoExperimental Design: ZHER3:8698 affibody molecules were conjugated via the C-terminus cysteine to DFO-maleimide for 89Zr radiolabeling. The probe was characterized in vitro and in vivo in a panel of human breast cell lines and xenograft models with varying HER3 receptor levels. In addition, the radioconjugate was investigated as a tool to monitor the outcome of AUY922, an Hsp90 inhibitor, in an MCF-7 xenograft model.Results: We demonstrated that 89Zr-DFO-ZHER3:8698 can track changes in receptor expression in HER3-positive xenograft models and monitor the outcome of AUY922 treatment. Our in vitro findings showed that MCF-7 cells, which are phenotypically different from BT474, develop resistance to treatment with AUY922 through HER3/IGF-1Rβ-mediated signaling. Of note, the lack of response in vitro due to HER3 recovery was confirmed in vivo using 89Zr-DFO-ZHER3:8698-based imaging. Upon AUY922 treatment, higher radioconjugate uptake was detected in treated MCF-7 xenografts, correlating with an AUY922-induced HER3 upregulation concomitant with an increase in IGF-1Rβ expression.Conclusions: These data underline the potential of HER3-based PET imaging to noninvasively provide information about HER3 expression and to identify patients not responding to targeted therapies due to HER3 recovery. Clin Cancer Res; 24(8); 1853-65. ©2018 AACR