Dataset Information

Evaluation of PET Imaging Performance of the TSPO Radioligand [18F]DPA-714 in Mouse and Rat Models of Cancer and Inflammation.

ABSTRACT:

Purpose

Many radioligands have been explored for imaging the 18-kDa translocator protein (TSPO), a diagnostic and therapeutic target for inflammation and cancer. Here, we investigated the TSPO radioligand [(18)F]DPA-714 for positron emission tomography (PET) imaging of cancer and inflammation.

Procedures

[(18)F]DPA-714 PET imaging was performed in 8 mouse and rat models of breast and brain cancer and 4 mouse and rat models of muscular and bowel inflammation.

Results

[(18)F]DPA-714 showed different uptake levels in healthy organs and malignant tissues of mice and rats. Although high and displaceable [(18)F]DPA-714 binding is observed ex vivo, TSPO-positive PET imaging of peripheral lesions of cancer and inflammation in mice did not show significant lesion-to-background signal ratios. Slower [(18)F]DPA-714 metabolism and muscle clearance in mice compared to rats may explain the elevated background signal in peripheral organs in this species.

Conclusion

Although TSPO is an evolutionary conserved protein, inter- and intra-species differences call for further exploration of the pharmacological parameters of TSPO radioligands.

SUBMITTER: Zheng J

PROVIDER: S-EPMC4722075 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Publications

Evaluation of PET Imaging Performance of the TSPO Radioligand [18F]DPA-714 in Mouse and Rat Models of Cancer and Inflammation.

Zheng Jinzi J Winkeler Alexandra A Peyronneau Marie-Anne MA Dollé Frédéric F Boisgard Raphaël R

Molecular imaging and biology 20160201 1

<h4>Purpose</h4>Many radioligands have been explored for imaging the 18-kDa translocator protein (TSPO), a diagnostic and therapeutic target for inflammation and cancer. Here, we investigated the TSPO radioligand [(18)F]DPA-714 for positron emission tomography (PET) imaging of cancer and inflammation.<h4>Procedures</h4>[(18)F]DPA-714 PET imaging was performed in 8 mouse and rat models of breast and brain cancer and 4 mouse and rat models of muscular and bowel inflammation.<h4>Results</h4>[(18)F] ...[more]

PMID: 26194010

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Project description:(18)F-DPA-714 is a PET tracer that recognizes macrophage translocator protein (TSPO), and (18)F-Alfatide II ((18)F-AlF-NOTA-E[PEG4-c(RGDfk)]2) is specific for integrin ?v?3. This study aims to apply these two tracers for longitudinal PET imaging of muscular inflammation, and evaluate the value of (18)F-DPA-714 in differentiating inflammation from tumor.RAW264.7 mouse macrophage cells were used for cell uptake analysis of (18)F-DPA-714. A mouse hind limb muscular inflammation model was established by intramuscular injection of turpentine oil. For the inflammation model, PET imaging was performed at different days using (18)F-DPA-714 and (18)F-Alfatide II. The specificity of the imaging probes was tested by co- or pre-injection of PK11195 or unlabeled RGD (Arg-Gly-Asp) peptide. PET imaging using (18)F-DPA-714 was performed in A549, HT29, U87MG, INS-1, and 4T1 xenograft models. Immunofluorescence staining was performed to evaluate infiltrated macrophages and angiogenesis in inflammation and/or tumors.Uptake of (18)F-DPA-714 in RAW264.7 cells was 45.5% at 1 h after incubation, and could be blocked by PK11195. PET imaging showed increased (18)F-DPA-714 and (18)F-Alfatide II uptake at inflammatory muscles. Peak uptake of (18)F-DPA-714 was seen on day 6 (4.02 ± 0.64 %ID/g), and peak uptake of (18)F-Alfatide II was shown on day 12 (1.87 ± 0.35 %ID/g) at 1 h p.i.. Tracer uptakes could be inhibited by PK11195 for (18)F-DPA-714 or cold RGD for (18)F-Alfatide II. Moreover, macrophage depletion with liposomal clodronate also reduced the local accumulation of both tracers. A549, HT29, U87MG, INS-1, and 4T1 tumor uptakes of (18)F-DPA-714 (0.46 ± 0.28, 0.91 ± 0.08, 1.69 ± 0.67, 1.13 ± 0.33, 1.22 ± 0.55 %ID/g at 1 h p.i., respectively) were significantly lower than inflammation uptake (All P < 0.05).PET imaging using (18)F-DPA-714 as a TSPO targeting tracer could evaluate the dynamics of macrophage activation and infiltration in different stages of inflammatory diseases. The concomitant longitudinal PET imaging with both (18)F-DPA-714 and (18)F-Alfatide II matched the causal relationship between macrophage infiltration and angiogenesis. Moreover, we found (18)F-DPA-714 uptake in several types of tumors is significantly lower than that in inflammatory muscles, suggesting (18)F-DPA-714 PET has the potential for better differentiation of tumor and non-tumor inflammation.

Project description:BACKGROUND:Magnetic resonance imaging (MRI)-guided pulsed focused ultrasound combined with the infusion of microbubbles (pFUS+MB) induces transient blood-brain barrier opening (BBBO) in targeted regions. pFUS+MB, through the facilitation of neurotherapeutics' delivery, has been advocated as an adjuvant treatment for neurodegenerative diseases and malignancies. Sterile neuroinflammation has been recently described following pFUS+MB BBBO. In this study, we used PET imaging with [18F]-DPA714, a biomarker of translocator protein (TSPO), to assess for neuroinflammatory changes following single and multiple pFUS+MB sessions. METHODS:Three groups of Sprague-Dawley female rats received MRI-guided pFUS+MB (Optison™; 5-8?×?107 MB/rat) treatments to the left frontal cortex and right hippocampus. Group A rats were sonicated once. Group B rats were sonicated twice and group C rats were sonicated six times on weekly basis. Passive cavitation detection feedback (PCD) controlled the peak negative pressure during sonication. We performed T1-weighted scans immediately after sonication to assess efficiency of BBBO and T2*-weighted scans to evaluate for hypointense voxels. [18F]DPA-714 PET/CT scans were acquired after the BBB had closed, 24 h after sonication in group A and within an average of 10 days from the last sonication in groups B and C. Ratios of T1 enhancement, T2* values, and [18F]DPA-714 percent injected dose/cc (%ID/cc) values in the targeted areas to the contralateral brain were calculated. Histological assessment for microglial activation/astrocytosis was performed. RESULTS:In all groups, [18F]DPA-714 binding was increased at the sonicated compared to non-sonicated brain (%ID/cc ratios >?1). Immunohistopathology showed increased staining for microglial and astrocytic markers in the sonicated frontal cortex compared to contralateral brain and to a lesser extent in the sonicated hippocampus. Using MRI, we documented BBB disruption immediately after sonication with resolution of BBBO 24 h later. We found more T2* hypointense voxels with increasing number of sonications. In a longitudinal group of animals imaged after two and after six sonications, there was no cumulative increase of neuroinflammation on PET. CONCLUSION:Using [18F]DPA-714 PET, we documented in vivo neuroinflammatory changes in association with pFUS+MB. Our protocol (utilizing PCD feedback to minimize damage) resulted in neuroinflammation visualized 24 h post one sonication. Our findings were supported by immunohistochemistry showing microglial activation and astrocytosis. Experimental sonication parameters intended for BBB disruption should be evaluated for neuroinflammatory sequelae prior to implementation in clinical trials.

Project description:PurposeNeuroinflammation is involved in several brain disorders and can be monitored through expression of the translocator protein 18 kDa (TSPO) on activated microglia. In recent years, several new PET radioligands for TSPO have been evaluated in disease models. [(18)F]DPA-714 is a TSPO radiotracer with great promise; however results vary between different experimental models of neuroinflammation. To further examine the potential of [(18)F]DPA-714, it was compared directly to [(11)C]PK11195 in experimental cerebral ischaemia in rats.MethodsUnder anaesthesia, the middle cerebral artery of adult rats was occluded for 60 min using the filament model. Rats were allowed recovery for 5 to 7 days before one hour dynamic PET scans with [(11)C]PK11195 and/or [(18)F]DPA-714 under anaesthesia.ResultsUptake of [(11)C]PK11195 vs [(18)F]DPA-714 in the ischemic lesion was similar (core/contralateral ratio: 2.84±0.67 vs 2.28±0.34 respectively), but severity of the brain ischemia and hence ligand uptake in the lesion appeared to vary greatly between animals scanned with [(11)C]PK11195 or with [(18)F]DPA-714. To solve this issue of inter-individual variability, we performed a direct comparison of [(11)C]PK11195 and [(18)F]DPA-714 by scanning the same animals sequentially with both tracers within 24 h. In this direct comparison, the core/contralateral ratio (3.35±1.21 vs 4.66±2.50 for [(11)C]PK11195 vs [(18)F]DPA-714 respectively) showed a significantly better signal-to-noise ratio (1.6 (1.3-1.9, 95%CI) fold by linear regression) for [(18)F]DPA-714.ConclusionsIn a clinically relevant model of neuroinflammation, uptake for both radiotracers appeared to be similar at first, but a high variability was observed in our model. Therefore, to truly compare tracers in such models, we performed scans with both tracers in the same animals. By doing so, our result demonstrated that [(18)F]DPA-714 displayed a higher signal-to-noise ratio than [(11)C]PK11195. Our results suggest that, with the longer half-life of [(18)F] which facilitates distribution of the tracer across PET centre, [(18)F]DPA-714 is a good alternative for TSPO imaging.

Project description:Acute intoxication with organophosphates (OPs) can trigger status epilepticus followed by persistent cognitive impairment and/or electroencephalographic abnormalities. Neuroinflammation is widely posited to influence these persistent neurological consequences. However, testing this hypothesis has been challenging, in part because traditional biometrics preclude longitudinal measures of neuroinflammation within the same animal. Therefore, we evaluated the performance of noninvasive positron emission tomography (PET), using the translocator protein (TSPO) radioligand [18F]PBR111 against classic histopathologic measures of neuroinflammation in a preclinical model of acute intoxication with the OP diisopropylfluorophosphate (DFP). Adult male Sprague Dawley rats administered pyridostigmine bromide (0.1 mg/kg, im) 30 min prior to administration of DFP (4 mg/kg, sc), atropine sulfate (2 mg/kg, im) and 2-pralidoxime (25 mg/kg, im) exhibited moderate-to-severe seizure behavior. TSPO PET performed prior to DFP exposure and at 3, 7, 14, 21, and 28 days postexposure revealed distinct lesions, as defined by increased standardized uptake values (SUV). Increased SUV showed high spatial correspondence to immunohistochemical evidence of neuroinflammation, which was corroborated by cytokine gene and protein expression. Regional SUV metrics varied spatiotemporally with days postexposure and correlated with the degree of neuroinflammation detected immunohistochemically. Furthermore, SUV metrics were highly correlated with seizure severity, suggesting that early termination of OP-induced seizures may be critical for attenuating subsequent neuroinflammatory responses. Normalization of SUV values to a cerebellar reference region improved correlations to all outcome measures and seizure severity. Collectively, these results establish TSPO PET using [18F]PBR111 as a robust, noninvasive tool for longitudinal monitoring of neuroinflammation following acute OP intoxication.

Dataset Information

Evaluation of PET Imaging Performance of the TSPO Radioligand [18F]DPA-714 in Mouse and Rat Models of Cancer and Inflammation.

Purpose

Procedures

Results

Conclusion

Publications

Evaluation of PET Imaging Performance of the TSPO Radioligand [18F]DPA-714 in Mouse and Rat Models of Cancer and Inflammation.

Similar Datasets

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