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Background: Radiation therapy (RT) of hepatocellular carcinoma (HCC) is limited by low tolerance of the liver to radiation, whereas radiosensitizers are effective in reducing the required radiation dose. Multimodality gadolinium-based nanoparticles (AGuIX) are small and have enhanced permeability and retention effects; thus, they are very suitable for radiation sensitizer HCC RT. Here, we evaluated the potential value of AGuIX for theranostic MRI-radiosensitization in HCC.Methods: The radiosensitization effects of AGuIX were evaluated via in vitro and in vivo experiments. Tumor growth, apoptosis imaging, and immunohistochemistry were performed to verify the antitumor effects of RT with AGuIX.Results: In vitro evaluation of the efficacy of radiosensitivity of the AGuIX demonstrated that the presence of AGuIX significantly decreased HepG2 cell survival when combined with an X-ray beam. In vivo MRI imaging showed the ratio of tumor/liver concentration of the AGuIX was the highest 1 h after intravenous injection. For antitumor effects, we found that the tumor size decreased by RT-only and RT with AGuIX. The antitumor effects were more effective with high-dose AGuIX-mediated RT. Apoptosis imaging and immunohistochemistry both demonstrated that the degree of the cell apoptosis was highest with a high dose of AGuIX-mediated RT.Conclusions: This study provides compelling data that AGuIX can facilitate theranostic MRI-radiosensitization in HCC.

Site-specific imaging agents play a key role in tumor targeting, but only a few agents are currently available for inflammation targeting. Since the P2X7 receptor (P2X7R) is a promising molecular target for inflammation, we evaluated the potential value of the 18 F-labeled tracer 18 F-PTTP (5-{[2-Chloro-3-(trifluoromethyl)phenyl]carbonyl}-1-pyrimidin-2-yl-4,5,6,7-tetrahydro-1H-[1,2,3]triazolo[4,5-c]pyridin) for targeting P2X7Rs and thus differentiating inflammation from tumors. Methods: The radioligand 18 F-PTTP was achieved by a 1-step 18 Ftrifluoromethylation reaction. The binding affinity of the ligand for P2X7R and its stability were evaluated in vitro. Blood pharmacokinetics tests and biodistribution studies were performed in vivo. Dynamic 18 F-PTTP small-animal PET/CT imaging was performed for 60 min on A549 tumor-bearing mice and inflammation-model mice for targeting differentiation. Results: 18 F-PTTP was afforded with decay-corrected radiochemical yields of 2.5%-7.0%, specific activity of 296-370 MBq/μmol, and radiochemical purity over 95%. 18 F-PTTP showed excellent stability in 0.9% NaCl and 0.1% bovine serum albumin, good affinity to RAW264.7 cells, and rapid blood clearance in mice. In inflammation-model mice, uptake of 18 F-PTTP peaked at 5 min after injection and kept at an imageable level till 30 min, whereas no significant radioactivity uptake was found in tumor grafts till 1 h after injection. The specificity of 18 F-PTTP was verified by blocking studies and histologic analysis. Conclusion: The current study provides compelling data that 18 F-PTTP is a novel radioligand targeting P2X7R and has potential to screen new drugs, quantify peripheral inflammation, and distinguish inflammation from certain solid tumors.

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Currently, positron emission tomography/computed tomography (PET/CT) is an important method for the discovery and diagnosis of digestive system tumors. However, the shortage of specific imaging tracer limits the effectiveness of PET. Triggering receptor expressed on myeloid cells 2 (TREM2) as an M2-type macrophage biomarker is receiving much attention considering its high abundance and specificity, which could be an ideal target for PET imaging. First, the expression of TREM2 in tumors and corresponding normal tissues was analyzed using a database and was verified by tissue microarrays and murine model slices, and we found that the expression of TREM2 in tumor tissues was significantly higher than that in normal tissues and enteritis tissues. Then, we established a macrophage co-culture system to obtain tumor-associated macrophages (TAMs). Compared with M1-type macrophages and tumor cells, TAMs had a higher expression level of TREM2. The novel radioligand 68Ga-NOTA-COG1410 was successfully synthesized for TREM2 targeting PET imaging. The biodistribution and micro-PET/CT results showed high uptake of 68Ga-NOTA-COG1410 in the tumor but not in areas of inflammation. The data testified that 68Ga-NOTA-COG1410 was a specific radioligand targeting TREM2, which could be used to distinguish tumors from inflammation. Using 68Ga-NOTA-COG1410, the effectiveness of PET on digestive tumors imaging may be enhanced.

Objective The uptake of 18F-fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) is known to be linked to programmed death ligand 1 (PD-L1) expression on tumor cells (TC). However, the association between PD-L1 expression on immune cells (IC) and 18F-FDG accumulation is still unclear. Here, we conducted a clinicopathological study to investigate the relationship between PD-L1 expression on TC/IC and 18F-FDG uptake in patients with surgically resected pulmonary adenocarcinoma (ADC). Methods A total of 450 ADC patients who underwent preoperative 18F-FDG-PET/CT imaging were analyzed retrospectively. Immunohistochemistry analysis was performed for PD-L1 expression on TC and IC in ADC specimens with SP142. PD-L1 expression was performed on whole-tissue sections and given scores (0/1/2/3) according to percent of PD-L1+ cells in TC and IC. Results Compared to TC0 and IC0, PD-L1 positive expression was 90.4% (407/450) in ADC specimens. Both PD-L1 expression score on TC and IC were associated with maximum standardized uptake (SUVmax). SUVmax augmented with increasing PD-L1 expression (TC0 and IC0, 4.3 ± 3.4; TC or IC1/2/3, 7.7 ± 5.6; TC or IC2/3, 8.1 ± 5.6; TC or IC3, 8.4 ± 5.4). The best cut-off value of PD-L1 expression, determined by receiver operating characteristic curve, was 5.1 for TC or IC1/2/3 [area under the curve (AUC) = 0.713, sensitivity 62.2%, specificity 72.1%]. Multivariate analysis demonstrated that TC or IC1/2/3 subset was correlated with histological subtype, PD-1 expression on IC and SUVmax. Conclusion High SUVmax is associated with PD-L1 expression on TC and IC in surgically resected pulmonary ADC. 18F-FDG-PET/CT imaging can be a potential tool to evaluate PD-L1 expression in pulmonary ADC.

Objective: To investigate the therapeutic efficacy of intratumoral injection of 125I-AA98 mAb for hepatocellular carcinoma (HCC) and its therapy efficacy assessment by 99mTc-HYNIC-duramycin and 99mTc-HYNIC-3PRGD2 SPECT/CT imaging.Methods: HCC xenograft tumor mice models were injected intratumorally with a single dose of normal saline, 10 microcurie (μCi) 125I-AA98 mAb, free 125I, AA98 mAb, 80 μCi 125I-AA98 mAb, and 200 μCi 125I-AA98 mAb. 99mTc-HYNIC-duramycin and 99mTc-HYNIC-3PRGD2 micro-SPECT/CT imaging were performed on days 3 and 7, respectively. The T/M ratio for each imaging was compared with the corresponding immunohistochemical staining at each time point. The relative tumor inhibition rates were documented.Results: In terms of apoptosis, the 200 μCi group demonstrated the highest apoptotic index (11.8 ± 3.8%), and its T/M ratio achieved by 99mTc-HYNIC-duramycin imaging on day 3 was higher than that of the normal saline group, 80 μCi group, 10 μCi group and free 125I group on day 3, respectively (all P < 0.05). On day 3, there was a markedly positive correlation between T/M ratio from 99mTc-HYNIC-duramycin imaging and apoptotic index by TUNEL staining (r = 0.6981; P < 0.05). Moreover, the 200 μCi group showed the lowest T/M ratio on 99mTc-HYNIC-3PRGD2 imaging (1.0 ± 0.5) on day 7 (all P < 0.05) comparing to other groups. The T/M ratio on day 7 was not correlated with integrin ανβ3 staining (P > 0.05). The relative inhibitory rates of tumor on day 14 in the AA98 mAb, 10 μCi, 80 μCi, free 125I, and 200 μCi groups were 26.3, 55.3, 60.5, 66.3, and 69.5%, respectively.Conclusion: 125I-AA98 mAb showed more effective apoptosis induced ability for CD146 high expression Hep G2 HCC cells and hold the potential for HCC treatment. Moreover, 99mTc-HYNIC-Duramycin (apoptosis-targeted) imaging and 99mTc-HYNIC-3PRGD2 (angiogenesis-targeted) imaging are reliable non-invasive methods to evaluate the efficacy of targeted treatment of HCC.

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