Qualitative flow metabolic phenotype of pancreatic cancer. A new prognostic biomarker?

BACKGROUND

Retrospective analysis to investigate the relationship between the flow-metabolic phenotype and overall survival (OS) of pancreatic ductal adenocarcinoma (PDAC) and its potential clinical utility.

METHODS

Patients with histopathologically proven PDAC between 2005 and 2014 using tumor attenuation on routine pre-operative CECT as a surrogate for the vascularity and [18F]FDG-uptake as a surrogate for metabolic activity on [18F]FDG-PET.

RESULTS

In total, 93 patients (50 male, 43 female, median age 63) were included. Hypoattenuating PDAC with high [18F]FDG-uptake has the poorest prognosis (median OS 7 ± 1 months), compared to hypoattenuating PDAC with low [18F]FDG-uptake (median OS 11 ± 3 months; p = 0.176), iso- or hyperattenuating PDAC with high [18F]FDG-uptake (median OS 15 ± 5 months; p = 0.004) and iso- or hyperattenuating PDAC with low [18F]FDG-uptake (median OS 23 ± 4 months; p = 0.035). In multivariate analysis, surgery combined with tumor differentiation, tumor stage, systemic therapy and flow metabolic phenotype remained independent predictors for overall survival.

DISCUSSION

The novel qualitative flow-metabolic phenotype of PDAC using a combination of CECT and [18F]FDG-PET features, predicted significantly worse survival for hypoattenuating-high uptake pancreatic cancers compared to the other phenotypes.

Longitudinal evaluation of the biodistribution and cellular internalization of the bispecific CD3xTRP1 antibody in syngeneic mouse tumor models

BACKGROUND

CD3 bispecific antibodies (CD3-bsAbs) require binding of both a tumor-associated surface antigen and CD3 for their immunotherapeutic effect. Their efficacy is, therefore, influenced by the tumor uptake and the extracellular dose. To optimize their currently limited efficacy in solid tumors, increased understanding of their pharmacokinetics and in vivo internalization is needed.

METHODS

Here, were studied the pharmacokinetics and in vivo internalization of CD3xTRP1, a fully murine Fc-inert bsAb, in endogenous TRP1-expressing immunocompetent male C57BL/6J mice bearing TRP1-positive and negative tumors over time. Matching bsAbs lacking TRP1-binding or CD3-binding capacity served as controls. BsAbs were radiolabeled with 111In to investigate their pharmacokinetics, target binding, and biodistribution through SPECT/CT imaging and ex vivo biodistribution analyses. Co-injection of 111In- and 125I-labeled bsAb was performed to investigate the in vivo internalization by comparing tissue concentrations of cellular residing 111In versus effluxing 125I. Antitumor therapy effects were evaluated by monitoring tumor growth and immunohistochemistry.

RESULTS

SPECT/CT and biodistribution analyses showed that CD3xTRP1 specifically targeted TRP1-positive tumors and CD3-rich lymphoid organ and uptake peaked 24 hours pi (KPC3-TRP1: 37.7%ID/g±5.3%ID/g, spleen: 29.0%ID/g±3.9%ID/g). Studies with control bsAbs demonstrated that uptake of CD3xTRP1 in TRP1-positive tumors and CD3-rich tissues was primarily receptor-mediated. Together with CD3xTRP1 in the circulation being mainly unattached, this indicates that CD3+ T cells are generally not traffickers of CD3-bsAbs to the tumor. Additionally, target-mediated clearance by TRP1-expressing melanocytes was not observed. We further demonstrated rapid internalization of CD3xTRP1 in KPC3-TRP1 tumors (24 hours pi: 54.9%±2.3% internalized) and CD3-rich tissues (spleen, 24 hours pi: 79.7%±0.9% internalized). Therapeutic effects by CD3xTRP1 were observed for TRP1-positive tumors and consisted of high tumor influx of CD8+ T cells and neutrophils, which corresponded with increased necrosis and growth delay.

CONCLUSIONS

We show that CD3xTRP1 efficiently targets TRP1-positive tumors and CD3-rich tissues primarily through receptor-mediated targeting. We further demonstrate rapid receptor-mediated internalization of CD3xTRP1 in TRP1-positive tumors and CD3-rich tissues. Even though this significantly decreases the therapeutical available dose, CD3xTRP1 still induced effective antitumor T-cell responses and inhibited tumor growth. Together, our data on the pharmacokinetics and mechanism of action of CD3xTRP1 pave the way for further optimization of CD3-bsAb therapies.

The diagnostic value of [18F]FDG-PET/CT in detecting septic thrombosis in patients with central venous catheter-related Staphylococcus aureus bacteremia

PURPOSE

Septic thrombosis often complicates Staphylococcus aureus bacteremia (SAB) in patients with a central venous catheter. Currently there is no reference standard for diagnosis. We describe the diagnostic value of [¹⁸F]FDG-PET/CT imaging in a patient cohort and the potential contribution of quantitative measurements in detecting septic thrombosis.

METHODS

We selected patients with catheter-related SAB from our institutional database (2013-2020). The contribution of [¹⁸F]FDG-PET/CT on clinical diagnosis of septic thrombosis was evaluated. Standardized Uptake Values (SUV) were measured and compared with a composite reference standard (clinical signs, initial [¹⁸F]FDG-PET/CT result, Multidisciplinary Team (MDT) meeting outcome) to identify a cut-off value for detecting septic thrombosis.

RESULTS

We identified 93 patients with a catheter-related SAB. Quantitative measurements were possible for 43/56 patients in whom a [¹⁸F]FDG-PET/CT scan was performed. Septic thrombosis was clinically diagnosed in 30% (13/43) of the cases. In 85% of these cases, significant [¹⁸F]FDG-PET/CT uptake at the site of the thrombus was the deciding factor for diagnosis of septic thrombosis during the MDT meeting. All mean SUV's of thrombotic lesions were higher in patients with clinically proven septic thrombosis compared to patients in whom this diagnosis was rejected (p < 0.001). A SUV_peak thrombus/SUV_mean blood ratio of 1.6 (AUC-ROC value 0.982) as cut-off to differentiate between septic thrombosis and non-septic thrombosis had a sensitivity of 92% (95% CI 64-100) and specificity of 89% (95% CI 65-99). An algorithm was designed to guide diagnosis of septic thrombosis.

CONCLUSION

Quantitative [¹⁸F]FDG-PET/CT-derived parameters seem helpful to differentiate between septic and non-septic thrombosis in patients with catheter-related SAB.

Management of Respiratory Motion Artefacts in 18F-fluorodeoxyglucose Positron Emission Tomography using an Amplitude-Based Optimal Respiratory Gating Algorithm

Positron emission tomography (PET) combined with X-ray computed tomography (CT) is an important molecular imaging platform that is required for accurate diagnosis and clinical staging of a variety of diseases. The advantage of PET imaging is the ability to visualize and quantify a myriad of biological processes in vivo with high sensitivity and accuracy. However, there are multiple factors that determine image quality and quantitative accuracy of PET images. One of the foremost factors influencing image quality in PET imaging of the thorax and upper abdomen is respiratory motion, resulting in respiration-induced motion blurring of anatomical structures. Correction of these artefacts is required for providing optimal image quality and quantitative accuracy of PET images. Several respiratory gating techniques have been developed, typically relying on acquisition of a respiratory signal simultaneously with PET data. Based on the respiratory signal acquired, PET data is selected for reconstruction of a motion-free image. Although these methods have been shown to effectively remove respiratory motion artefacts from PET images, the performance is dependent on the quality of the respiratory signal being acquired. In this study, the use of an amplitude-based optimal respiratory gating (ORG) algorithm is discussed. In contrast to many other respiratory gating algorithms, ORG permits the user to have control over image quality versus the amount of rejected motion in the reconstructed PET images. This is achieved by calculating an optimal amplitude range based on the acquired surrogate signal and a user-specified duty cycle (the percentage of PET data used for image reconstruction). The optimal amplitude range is defined as the smallest amplitude range still containing the amount of PET data required for image reconstruction. It was shown that ORG results in effective removal of respiration-induced image blurring in PET imaging of the thorax and upper abdomen, resulting in improved image quality and quantitative accuracy.

OR04-2 Aldosterone Induces Trained Immunity via Fatty Acid Synthesis

Hyperaldosteronism is associated with an increased cardiovascular risk in humans. Animal models show that aldosterone accelerates the development of atherosclerotic plaques, and suggest that this is, at least in part, mediated by activation of innate immune cells by aldosterone (1). Human data are scarce. We recently showed that monocytes can adopt a long-term pro-inflammatory phenotype after brief stimulation, which has been termed ‘trained immunity’ (2). Therefore, we tested the hypothesis that aldosterone induces ‘trained immunity’ by investigating the functional, immunometabolic and epigenetic effects of aldosterone on human monocytes in vitro. Human monocytes were exposed to vehicle, aldosterone (10nM) or serum obtained from patients with primary hyperaldosteronism (PA) with and without addition of a mineralocorticoid receptor (MR) antagonist for 24 hours, and differentiated to macrophages. We assessed the ability of these cells to produce ROS and cytokines upon re-stimulation. Changes in immunometabolism were assessed via extracellular flux measurements with Seahorse XF technology and further explored at the genome level with RNA microarray. Chromatin immunoprecipitation was performed to assess histone modifications in aldosterone-exposed cells. In vitro exposure of human monocytes with both aldosterone and PA serum induced a trained immunity phenotype characterized by augmented IL-6 and TNF-α responses, as well as ROS production to re-stimulation, an effect that was prevented by the MR antagonist spironolactone. Aldosterone-trained cells showed no differences in glycolysis or oxidative phosphorylation compared to vehicle treated cells. Instead, RNA microarray showed upregulation of the fatty acid synthesis (FAS) pathway, which we validated with qPCR. Pharmacological inhibition of FAS abolished the induction of training by aldosterone. Moreover, the aldosterone-trained phenotype was associated with enrichment of the transcriptionally-permissive histone mark H3K4me3, at the level of the promoters of central genes in the fatty acid synthesis pathway. In conclusion, aldosterone induces a form of trained immunity which is dependent on activation of the MR and induction of fatty acid synthesis. This novel pathway of immune activation uncovers potential pharmacological targets for patients with hyperaldosteronism. To translate these findings, we have recruited 15 patients with proven primary hyperaldosteronism and 15 matched patients with essential hypertension and comprehensively assessed systemic inflammation and monocyte phenotype as well as vascular wall inflammation with fluorodeoxyglucose-positron emission tomography. The results of these analyses will be available at the time of ENDO 2019. (1) van der Heijden et al. Cardiovasc Res. 2018 Jun 1;114(7):944-953. (2) Netea et al. Science. 2016 Apr 22;352(6284)