Molecular Imaging of P‑glycoprotein in Chemoresistant Tumors Using a Dual-Modality PET/Fluorescence Probe

Overexpression of P-glycoprotein (Pgp) has been considered a primary cause for multidrug resistance in a variety of cancers for three decades. However, clinical translation of Pgp targeted therapeutics has been hindered by lack of patient preselection based on the Pgp presence in tumors. We aim to develop a molecularly targeted probe for imaging tumoral Pgp <i>in vivo</i> with positron emission tomography (PET) and fluorescence, and to provide a tool for preselecting the patients with tumoral Pgp expression. Thus, a Pgp monoclonal antibody 15D3 was chemically modified with IRDye800 (IR800) and DOTA chelator. The specificity of the antibody conjugates DOTA-Pab-IR800 was verified in Pgp-expressing 3T3-MDR1 and control 3T3 cells. After radiolabeling with ⁶⁴Cu, the probe was applied in small animal PET imaging of Pgp in a mouse xenograft model of NCI/ADR-Res cells, which are chemoresistant through overexpression of Pgp. Quantification analysis of the PET images demonstrated that the tumor uptake of the radioactive probe was 9.9 ± 1.4, 12.1 ± 1.2, and 10.5 ± 1.0%ID/g at 4, 24, and 48 h post injection. The tumor-to-muscle ratio was 20.9 at 48 h post injection based on biodistribution studies. Fluorescence imaging was performed following PET experiments, and it demonstrated excellent tumor accumulation of this dual-modality probe in the NCI/ADR-Res tumors. Further, an image-guided surgery was successfully performed using the fluorescence modality of the probe, demonstrating potential utility of this probe in image-guided surgical removal of Pgp-positive drug resistant tumors in the patients. In conclusion, this study clearly demonstrated that the Pgp-targeted antibody probe, ⁶⁴Cu-DOTA-Pab-IR800, could provide a promising diagnosis tool for detection of Pgp-expressing tumors <i>in vivo</i>

Development of [¹⁸F]AlF-NOTA-NT as PET Agents of Neurotensin Receptor‑1 Positive Pancreatic Cancer

Several studies have suggested that neurotensin receptors (NTRs) and neurotensin (NT) greatly affect the growth and survival of pancreatic ductal adenocarcinoma (PDAC). Developing NTR-targeted PET probes could therefore be important for the management of a pancreatic cancer patient by providing key information on the NTR expression profile noninvasively. Despite the initial success on the synthesis of ¹⁸F-labeled NT PET probes, the labeling procedure generally requires lengthy steps including azeotropic drying of ¹⁸F. Using a straightforward chelation method, here we report the simple preparation of aluminum-¹⁸F-NOTA-NT starting from aqueous ¹⁸F. The cell binding test demonstrated that [¹⁹F]­AlF-NOTA-NT maintained high receptor-binding affinity to NTR1. This probe was then further evaluated in NTR1 positive pancreatic tumor models (AsPC-1 and PANC-1). After the administration of [¹⁸F]­AlF-NOTA-NT, small animal PET studies showed a high contrast between tumor and background in both models at 1 and 4 h time points. A blocking experiment was performed to demonstrate the receptor specificity: the tumor uptake in AsPC1 without and with blocking agent was 1.0 ± 0.2 and 0.1 ± 0.0%ID/g, respectively, at 4 h post injection. In summary, a NTR specific PET agent, [¹⁸F]­AlF-NOTA-NT, was prepared through the simple chelation method. This NTR-targeted PET probe may not only be used to detect NTR1 positive pancreatic tumors (diagnosis), but also it may be fully integrated to NTR target therapy leading to personalized medicine (theranostic)

Scatter plot of the relationship between the PCC-right medial superior frontal gyrus functional connectivity and hemoglobin levels in the patients.

<p>Scatter plot of the relationship between the PCC-right medial superior frontal gyrus functional connectivity and hemoglobin levels in the patients.</p

Within-group DMN patterns and between-group differences.

<p>The color bars represent the T scores. The results were mapped onto the brain surface using the BrainNet viewer software.</p

Radiolabeling Diaminosarcophagine with Cyclotron-Produced Cobalt-55 and [⁵⁵Co]Co-NT-Sarcage as a Proof of Concept in a Murine Xenograft Model

Cobalt–sarcophagine complexes exhibit high kinetic inertness under various stringent conditions, but there is limited literature on radiolabeling and in vivo positron emission tomography (PET) imaging using no carrier added 55Co. To fill this gap, this study first investigates the radiolabeling of DiAmSar (DSar) with 55Co, followed by stability evaluation in human serum and EDTA, pharmacokinetics in mice, and a direct comparison with [55Co]CoCl2 to assess differences in pharmacokinetics. Furthermore, the radiolabeling process was successfully used to generate the NTSR1-targeted PET agent [55Co]Co-NT-Sarcage (a DSar-functionalized SR142948 derivative) and administered to HT29 tumor xenografted mice. The [55Co]Co-DSar complex can be formed at 37 °C with purity and stability suitable for preclinical in vivo radiopharmaceutical applications, and [55Co]Co-NT-Sarcage demonstrated prominent tumor uptake with a low background signal. In a direct comparison with [64Cu]Cu-NT-Sarcage, [55Co]Co-NT-Sarcage achieved a higher tumor-to-liver ratio but with overall similar biodistribution profile. These results demonstrate that Sar would be a promising chelator for constructing Co-based radiopharmaceuticals including 55Co for PET and 58mCo for therapeutic applications

Demographics and clinical characteristics of all participants.

<p>Demographics and clinical characteristics of all participants.</p

Protein Nanocage Mediated Fibroblast-Activation Protein Targeted Photoimmunotherapy To Enhance Cytotoxic T Cell Infiltration and Tumor Control

Carcinoma-associated fibroblasts (CAFs) are found in many types of cancer and play an important role in tumor growth and metastasis. Fibroblast-activation protein (FAP), which is overexpressed on the surface of CAFs, has been proposed as a universal tumor targeting antigen. However, recent studies show that FAP is also expressed on multipotent bone marrow stem cells. A systematic anti-FAP therapy may lead to severe side effects and even death. Hence, there is an urgent need of a therapy that can selectively kill CAFs without causing systemic toxicity. Herein we report a nanoparticle-based photoimmunotherapy (nano-PIT) approach that addresses the need. Specifically, we exploit ferritin, a compact nanoparticle protein cage, as a photosensitizer carrier, and we conjugate to the surface of ferritin a FAP-specific single chain variable fragment (scFv). With photoirradiation, the enabled nano-PIT efficiently eliminates CAFs in tumors but causes little damage to healthy tissues due to the localized nature of the treatment. Interestingly, while not directly killing cancer cells, the nano-PIT caused efficient tumor suppression in tumor-bearing immunocompetent mice. Further investigations found that the nano-PIT led to suppressed C–X–C motif chemokine ligand 12 (CXCL12) secretion and extracellular matrix (ECM) deposition, both of which are regulated by CAFs in untreated tumors and mediate T cell exclusion that prevents physical contact between T cells and cancer cells. By selective killing of CAFs, the nano-PIT reversed the effect, leading to significantly enhanced T cell infiltration, followed by efficient tumor suppression. Our study suggests a new and safe CAF-targeted therapy and a novel strategy to modulate tumor microenvironment (TME) for enhanced immunity against cancer