Search

Gastrin-releasing peptide receptor (GRPR) is overexpressed in various cancers and is a promising target for cancer diagnosis and therapy. However, the high pancreas uptake and/or metabolic instability observed for most reported GRPR-targeted radioligands might limit their clinical applications. Our group recently reported a GRPR-targeted antagonist tracer, [68Ga]Ga-TacsBOMB2 ([68Ga]Ga-DOTA-Pip-D-Phe6-Gln7-Trp8-Ala9-Val10-Gly11-His12-Leu13ψThz14-NH2), which showed a minimal pancreas uptake in a preclinical mouse model. In this study, we synthesized four derivatives with unnatural amino acid substitutions (Tle10-derived Ga-LW01158, NMe-His12-derived Ga-LW01160, α-Me-Trp8- and Tle10-derived Ga-LW01186, and Tle10- and N-Me-Gly11-derived Ga-LW02002) and evaluated their potential for detecting GRPR-expressing tumors with positron emission tomography (PET). The binding affinities (Ki(GRPR)) of Ga-LW01158, Ga-LW01160, Ga-LW01186, and Ga-LW02002 were 5.11 ± 0.47, 187 ± 17.8, 6.94 ± 0.95, and 11.0 ± 0.39 nM, respectively. [68Ga]Ga-LW01158, [68Ga]Ga-LW01186, and [68Ga]Ga-LW02002 enabled clear visualization of subcutaneously implanted human prostate cancer PC-3 tumor xenografts in mice in PET images. Ex vivo biodistribution studies showed that [68Ga]Ga-LW01158 had the highest tumor uptake (11.2 ± 0.65 %ID/g) and good tumor-to-background uptake ratios at 1 h post-injection. Comparable in vivo stabilities were observed for [68Ga]Ga-LW01158, [68Ga]Ga-LW01186, and [68Ga]Ga-LW02002 (76.5–80.7% remaining intact in mouse plasma at 15 min post-injection). In summary, the Tle10 substitution, either alone or combined with α-Me-Trp8 or NMe-Gly11 substitution, in Ga-TacsBOMB2 generates derivatives that retained good GRPR binding affinity and in vivo stability. With good tumor uptake and tumor-to-background imaging contrast, [68Ga]Ga-LW01158 is promising for detecting GRPR-expressing lesions with PET. [ABSTRACT FROM AUTHOR]

Some bispecific radiotracers have been developed to overcome the limitations of monospecific tracers and improve detection sensitivity for heterogeneous tumor lesions. Here, we aim to synthesize two bispecific tracers targeting prostate-specific membrane antigen (PSMA) and fibroblast activation protein (FAP), which are key markers expressed in prostate cancer. A pyridine-based FAP-targeted ligand was synthesized through multi-step organic synthesis and then connected to the 2-Nal-containing PSMA-targeted motif. The Ki(PSMA) values of Ga-complexed bispecific ligands, Ga-AV01084 and Ga-AV01088, were 11.6 ± 3.25 and 28.7 ± 6.05 nM, respectively, and the IC50(FAP) values of Ga-AV01084 and Ga-AV01088 were 10.9 ± 0.67 and 16.7 ± 1.53 nM, respectively. Both [68Ga]Ga-AV01084 and [68Ga]Ga-AV01088 enabled the visualization of PSMA-expressing LNCaP tumor xenografts and FAP-expressing HEK293T:hFAP tumor xenografts in PET images acquired at 1 h post-injection. However, the tumor uptake values from the bispecific tracers were still lower than those obtained from the monospecific tracers, PSMA-targeted [68Ga]Ga-PSMA-617 and FAP-targeted [68Ga]Ga-AV02070. Further investigations are needed to optimize the selection of linkers and targeted pharmacophores to improve the tumor uptake of bispecific PSMA/FAP tracers for prostate cancer imaging. [ABSTRACT FROM AUTHOR]

Background: Overexpressed in various solid tumors, gastrin-releasing peptide receptor (GRPR) is a promising cancer imaging marker and therapeutic target. Although antagonists are preferable for the development of GRPR-targeted radiopharmaceuticals due to potentially fewer side effects, internalization of agonists may lead to longer tumor retention and better treatment efficacy. In this study, we systematically investigated unnatural amino acid substitutions to improve in vivo stability and tumor uptake of a previously reported GRPR-targeted agonist tracer, [68Ga]Ga-TacBOMB2 (68Ga-DOTA-Pip-D-Phe6-Gln7-Trp8-Ala9-Val10-Gly11-His12-Leu13-Thz14-NH2). Results: Unnatural amino acid substitutions were conducted for Gln7, Trp8, Ala9, Val10, Gly11 and His12, either alone or in combination. Out of 25 unnatural amino acid substitutions, tert-Leu10 (Tle10) and NMe-His12 substitutions were identified to be preferable modifications especially in combination. Compared with the previously reported [68Ga]Ga-TacBOMB2, the Tle10 and NMe-His12 derived [68Ga]Ga-LW01110 showed retained agonist characteristics and improved GRPR binding affinity (Ki = 7.62 vs 1.39 nM), in vivo stability (12.7 vs 89.0% intact tracer in mouse plasma at 15 min post-injection) and tumor uptake (5.95 vs 16.6 %ID/g at 1 h post-injection). Conclusions: Unnatural amino acid substitution is an effective strategy to improve in vivo stability and tumor uptake of peptide-based radiopharmaceuticals. With excellent tumor uptake and tumor-to-background contrast, [68Ga]Ga-LW01110 is promising for detecting GRPR-expressing cancer lesions with PET. Since agonists can lead to internalization upon binding to receptors and foreseeable long tumor retention, our optimized GRPR-targeted sequence, [Tle10,NMe-His12,Thz14]Bombesin(7–14), is a promising template for use for the design of GRPR-targeted radiotherapeutic agents. [ABSTRACT FROM AUTHOR]

A study was conducted to develop a method of separating lysozyme from egg white by an efficient and rapid method. Thus, egg whites from both hen and duck were reacted with anionic polysaccharides, specifically the carbohydrate polymers -carrageenan, high methoxy pectin, Na-carboxymethylcellulose and Na-alginate. Recovery, purification fold and storage ability of the lysozyme obtained from the precipitates of the reaction mixture were determined. It was found that only -carrageenan was effective.

Purpose: Mesenchymal stem cell-derived EVs (MSC-EVs) are demonstrated to have similar therapeutic effect as their cells of origin and represent an attractive cell-free stem cell therapy. With the potential to be the future medical regimen, the information of fate and behavior of MSC-EVs in the living subject should be urgently gathered. This study aimed to track MSC-EVs by 111In-labeling and μSPECT/CT imaging.Procedures: Wharton's jelly-MSC-EVs (WJ-MSC-EVs) were isolated using Exo-Prep kit followed by characterization of expressing markers and size. After labeled by 111In-oxine, 111In-EVs were injected into C57BL/6 mice followed by μSPECT/CT imaging. Organs were then taken out for ex vivo biodistribution analysis.Results: The radiochemical purity of 111In-EVs was > 90 % and remained stable up to 24 h. The image results showed that with injection of 111In-EVs, the signal mainly accumulated in the liver, spleen, and kidney, compared to that in lung and kidney after 111In-oxine injection. The ex vivo biodistribution showed the similar pattern to that of imaging. Chelation of free 111In with EDTA was found necessary to reduce the nonspecific accumulation of signal.Conclusion: This study demonstrated the feasibility of radiolabeling WJ-MSC-EVs with 111In-oxine for in vivo imaging and quantitative analysis in a mouse model. This simple and quick labeling method preserves the characteristics of WJ-MSC-EVs. The results in this study provide a thorough and objective basis for future clinical study. [ABSTRACT FROM AUTHOR]