Nuclear medicine and biology最新文献

Immunorecognition provides an excellent basis for targeted imaging techniques covering a wide range from basic research to diagnostics and from single cells to whole organisms. Fluorescence- or radioisotope-labeled antibodies, antibody fragments or nanobodies enable a direct signal readout upon binding and allow for versatile imaging from microscopy to whole-body imaging. However, as the signal intensity directly correlates with the number of labeled antibodies bound to their epitopes (1:1 binding), sensitivity for low-expressing epitopes can be limiting for visualization. For the first time, we developed poly-epitope tags with multiple copies (1 to 7) of a short peptide epitope, specifically the MoonTag, that are recognized by a labeled nanobody and aimed at signal amplification in microscopy and cell-specific PET imaging. In transiently transfected HeLa cells or stably transduced A4573 cells we characterized complex formation and in vitro signal amplification. Indeed, using fluorescently and radioactively labeled nanobodies we found an approximately linear signal amplification with increasing numbers of epitope copies in vitro. To test the poly-epitope approach in vivo, A4573 tumor cells were injected subcutaneously into the shoulder of NSG mice, with A4573 tumor cells expressing a poly-epitope of 7 MoonTags on one side and WT cells on the other side. Using a [⁶⁸Ga]-labeled NODAGA-conjugated MoonTag nanobody, we performed PET/CT imaging at day 8–9 after tumor implantation. Specific binding of a [⁶⁸Ga]-labeled NODAGA-conjugated MoonTag nanobody was observed in 7xMoonTag tumors (1.7 ± 0.5%ID/mL) by PET imaging, showing significantly higher radiotracer accumulation compared to the WT tumors (1.1 ± 0.3%ID/mL; p < 0.01). Ex vivo gamma counter measurements confirmed significantly higher uptake in 7xMoonTag tumors compared to WT tumors (p < 0.001). In addition, MoonTag nanobody binding was detected by autoradiography which was spatially matched with histological analysis of the tumor tissues. In conclusion, we expect nanobody-based poly-epitope tag strategies to be widely applicable for multimodal imaging techniques given the advantageous properties of nanobodies and their amenability to genetic and chemical engineering.

Heat shock protein 90 (HSP90) plays a crucial role in cancer cell growth and metastasis by stabilizing overexpressed signaling proteins. Inhibiting HSP90 has emerged as a promising anti-cancer strategy. In this study, we aimed to develop and characterize a HSP90-targeted molecular imaging probe, [⁶⁴Cu]Cu-DOTA-BDA-GM, based on a specific HSP90 inhibitor, geldanamycin (GM), for PET imaging of cancers. GM is modified at the C-17 position with 1,4-butane-diamine (BDA) and linked to 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) for ⁶⁴Cu radiolabeling. We evaluated the probe's specific binding to HSP90-expressing cells using Chinese hamster ovary (CHO) cells and breast cancer cells including MDA-MB-231, MDA-MB-435S, MCF7, and KR-BR-3 cell lines. A competition study with non-radioactive GM-BDA yielded an IC50 value of 1.35 ± 0.14 nM, underscoring the probe's affinity for HSP90. In xenograft models of MDA-MB-231 breast cancer, [⁶⁴Cu]Cu-DOTA-BDA-GM showcased targeted tumor localization, with significant radioactivity observed up to 18 h post-injection. Blocking studies using unlabeled GM-BDA and treatment with the anticancer drug Vorinostat (SAHA), which can affect the expression and activity of numerous proteins, such as HSPs, confirmed the specificity and sensitivity of the probe in cancer targeting. Additionally, PET/CT imaging in a lung metastasis mouse model revealed increased lung uptake of [⁶⁴Cu]Cu-DOTA-BDA-GM in metastatic sites, significantly higher than in non-metastatic lungs, illustrating the probe's ability to detect metastatic breast cancer. In conclusion, [⁶⁴Cu]Cu-DOTA-BDA-GM represents a sensitive and specific approach for identifying HSP90 expression in breast cancer and metastases, offering promising implications for clinical diagnosis and monitoring.

Purpose

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer that lacks effective diagnostic and therapeutic options. Membrane type 1 matrix metalloproteinase (MT1-MMP) is an attractive biomarker for improving patient selection. This study aimed to develop a theranostic tool using a highly tumour-selective anti-MT1-MMP antibody (LEM2/15) radiolabelled with ⁸⁹Zr for PET and ¹⁷⁷Lu for therapy in a TNBC murine model.

Methods

The LEM2/15 antibody and IgG isotype control were radiolabelled with ⁸⁹Zr. PET imaging was performed in a TNBC orthotopic mouse model at 1, 2, 4, and 7 days after administration. Tissue biodistribution and pharmacokinetic parameters were analysed and Patlak linearisation was used to calculate the influx rate of irreversible uptake. The TNBC mice were treated with [¹⁷⁷Lu]Lu-DOTA-LEM2/15 (single- or 3-dose regimen) or saline. Efficacy of [¹⁷⁷Lu]Lu-DOTA-LEM2/15 was evaluated as tumour growth and DNA damage (γH2AX) in MDA 231-BrM2-831 tumours.

Results

At 7 days post-injection, PET uptake in tumour xenografts revealed a 1.6-fold and 2.4-fold higher tumour-to-blood ratio for [⁸⁹Zr]Zr-Df-LEM2/15 in the non-blocked group compared to the blocked and IgG isotype control groups, respectively. Specific uptake of LEM2/15 in TBNC tumours mediated by MT1-MMP-binding was demonstrated by the Patlak linearisation method, providing insights into the potential efficacy of LEM2/15-based treatments. A similar uptake was found for [⁸⁹Zr]Zr-Df-LEM2/15 and [¹⁷⁷Lu]Lu-DOTA-LEM2/15 in tumours 7 days post-injection (6.80 ± 1.31 vs. 5.61 ± 0.66 %ID/g). Tumour doubling time was longer in the [¹⁷⁷Lu]Lu-DOTA-LEM2/15 3-dose regimen treated group compared to the control (50 vs. 17 days, respectively). The percentage of cells with γH2AX-foci was higher in tumours treated with [¹⁷⁷Lu]Lu-DOTA-LEM2/15 3-dose regimen compared to tumours non-treated or treated with [¹⁷⁷Lu]Lu-DOTA-LEM2/15 single-dose (12 % vs. 4–5 %).

Conclusions

The results showed that the ⁸⁹Zr/¹⁷⁷Lu-labelled anti-MT1-MMP mAb (LEM2/15) pair facilitated immune-PET imaging and reduced tumour growth in a preclinical TNBC xenograft model.

The radiotherapeutic ^195mPt is among the most effective Auger electron emitters of the currently studied radionuclides that have a potential theranostic application in nuclear medicine. Production of ^195mPt through double neuron capture of enriched ¹⁹³Ir followed by β⁻-decay to the radioisotope of interest carried out at the research reactor IBR-2 is described. Because of the high radiation background, radiochemical purification procedure of ^195mPt from bulk of iridium was needed to be developed and is detailed here as well. For the first time, cross section and resonance integral for the reaction ¹⁹⁴Ir(n,γ)^195mIr were determined. Resonance neutrons contribution was established to exceed that of thermal neutrons, and resonance integral for the reaction ¹⁹⁴Ir(n,γ)^195mIr is calculated to be 2900 b. Specific activity of ^195mPt was estimated to reach a value of 38.7 GBq/(g Pt) at IBR-2 by the end of bombardment (EOB).

Background

Osteosarcoma (OS) is a prevalent primary bone cancer affecting both humans and canines. This study describes initial insights into the interaction of the human monoclonal antibody IF3 to an insulin-like growth factor 2 receptor (IGF2R) radiolabeled with either alpha-emitting Actinium-225 (²²⁵Ac) or beta-emitting Lutetium-177 (¹⁷⁷Lu) radionuclides with the OS cells and tumor microenvironment (TME) in experimental human and canine OS.

Basic procedures

SCID mice bearing canine Gracie or human OS-33 OS tumors were treated with ¹⁷⁷Lu- or ²²⁵Ac-labeled IF3 antibody, sacrificed at 24, 72 or 168 h post-treatment and their tumors were analyzed by immunohistochemistry (IHC) for the presence of OS cells, various elements of TME as well as for the double DNA strand breaks with γH2AX and caspase 3 assays.

Main findings

IHC revealed a reduction in IGF2R-positive OS cells and OS stem cell populations post therapy with ²²⁵Ac- and ¹⁷⁷Lu-labeled IF3 antibody. Notably, radiolabeled IF3 antibody effectively diminished pro-tumorigenic M2 macrophages, highlighting its therapeutic promise. The study also unveiled varied responses of natural killer (NK) cells and M1 macrophages, shedding light on the intricate TME interplay. Time-dependent increase in γ-H2AX staining in canine Gracie and human OS-33 tumors treated with [¹⁷⁷Lu]Lu-IF3 and [²²⁵Ac]Ac-IF3 was observed at 24 and 72 h post-RIT.

Principal conclusions

These findings suggest that radiolabeled antibodies offer a hopeful avenue for personalized OS treatment, emphasizing the importance of understanding their impact on the TME and potential synergies with immunotherapy.