No abstract

Combination treatment approaches are increasingly considered to overcome resistance to immunotherapy targeting immunoinhibitory molecules such as programmed death (PD)-1 and PD-ligand 1 (PD-L1). Previous studies have demonstrated that the therapeutic efficacy of anti-PD-L1 Abs is enhanced by combination treatment with cyclooxygenase-2 inhibitors, through downregulation of the immunosuppressive eicosanoid PGE 2 , although the underlying mechanism remains unclear. In this study, we show that serum PGE 2 levels are upregulated after anti-PD-L1 Ab administration in a bovine model of immunotherapy and that PGE 2 directly inhibits T cell activation via its receptor E prostanoid (EP) 4. Additionally, anti-PD-L1 Ab induces TNF-a production and TNF-a blockade reduces PGE 2 production in the presence of anti-PD-L1 Ab, suggesting that anti-PD-L1 Ab-induced TNF-a impairs T cell activation by PGE 2 upregulation. Our studies examining the therapeutic potential of the dual blockade of PD-L1 and EP4 in bovine and murine immune cells reveal that the dual blockade of PD-L1 and EP4 significantly enhances Th1 cytokine production in vitro. Finally, we show that the dual blockade decreases tumor volume and prolongs survival in mice inoculated with the murine lymphoma cell line EG7. Altogether, these results suggest that TNF-a induced by anti-PD-L1 Ab treatment is associated with T cell dysfunction via PGE 2 /EP4 pathway and that the dual blockade of PD-L1 and EP4 should be considered as a novel immunotherapy for cancer.

Cholesterol is a major component of the lipid bilayers of cellular membranes. The synthesis of cholesterol is acutely elevated during T‐cell activation to support T‐cell growth and proliferation. There is a limited understanding of cholesterol metabolism reprogramming during T‐cell activation. Retinoic acid receptor‐related orphan receptors (RORs) are ligand‐activated nuclear receptors that regulate the transcription of target genes. In this study, we demonstrated that the activation of RORs by a synthetic agonist (SR1078) impairs the proliferation and survival of postactivated CD8+ T cells. The inhibitory effects of SR1078 on CD8+ T‐cell proliferation and survival were attributed to cholesterol depletion and downregulated expression of cholesterol metabolism‐related genes. The overexpression of RORα or RORγt promoted apoptosis in the postactivated CD8+ T cells in vitro. The expression of RORα (but not that of RORγt) was markedly upregulated in the CD8+ T cells upon stimulation with an antigen in vivo. The functional deficiency of RORα enhanced CD8+ T‐cell expansion during the response to bacterial infection. These results suggest that RORs are involved in the regulation of CD8+ T‐cell‐mediated immune response through the regulation of cholesterol metabolism, which can be modulated by a synthetic ROR agonist. The findings of this study can aid in the development of immunotherapeutic methods that target nuclear receptors.

Background: As an essential physiological parameter, pH plays a critical role in maintaining cellular and tissue homeostasis. The ratiometric chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) method using clinically approved iodinated agents has emerged as one of the most promising noninvasive techniques for pH assessment.Methods: In this study, we investigated the ability to use the combination of two different nonequivalent amide protons, chosen from five iodinated agents, namely iodixanol, iohexol, iobitridol, iopamidol, and iopromide, for pH measurement. The ratio of two nonequivalent amide CEST signals was calculated and compared for pH measurements in the range of 5.6 to 7.6. To quantify the CEST signals at 4.3 and 5.5 parts per million (ppm), we employed two analytic methods: magnetization transfer ratio asymmetry and Lorentzian fitting analysis. Lastly, the established protocol was used to measure the pH values in healthy rat kidneys (n=5).Results: The combination of iodixanol and iobitridol at a ratio of 1:1 was found to be suitable for pH mapping. The saturation power level (B 1 ) was also investigated, and a low B 1 of 1.5 μT was adopted for subsequent pH measurements. Improved precision and an extended pH detection range were achieved using iodixanol and iobitridol (1:1 ratio) and a single low B 1 of 1.5 μT in vitro. In vivo renal pH values were measured as 7.23±0.09, 6.55±0.15, and 6.29±0.23 for the cortex, medulla, and calyx, respectively.Conclusions: These results show that the ratiometric CEST method using two iodinated agents with nonequivalent amide protons could be used for in vivo pH mapping of the kidney under a single low B 1 saturation power.

BackgroundConventional gadolinium (Gd)-enhanced MRI is currently used for stratifying the lesion activity of multiple sclerosis (MS) despite limited correlation with disability and disease activity. The stratification of MS lesion activity needs further improvement to better support clinics.PurposeTo investigate if the novel proton exchange rate (kex) MRI combined with quantitative susceptibility mapping (QSM) may help to further stratify non-enhanced (Gd-negative) MS lesions.Materials and methodsFrom December 2017 to December 2020, clinically diagnosed relapsing-remitting MS patients who underwent MRI were consecutively enrolled in this IRB-approved retrospective study. The customized MRI protocol covered conventional T2-weighted, T2-fluid-attenuated-inversion-recovery, pre- and post-contrast T1-weighted imaging, and quantitative sequences, including kex MRI based on direct-saturation removed omega plots and QSM. Each MS lesion was evaluated based on its Gd-enhancement as well as its susceptibility and kex elevation compared to the normal appearing white matter. The difference and correlation concerning lesion characteristics and imaging contrasts were analyzed using the Mann–Whitney U test or Kruskal–Wallis test, and Spearman rank analysis with p < 0.05 considered significant.ResultsA total of 322 MS lesions from 30 patients were identified with 153 Gd-enhanced and 169 non-enhanced lesions. We found that the kex elevation of all lesions significantly correlated with their susceptibility elevation (r = 0.30, p < 0.001). Within the 153 MS lesions with Gd-enhancement, ring-enhanced lesions showed higher kex elevation than the nodular-enhanced ones’ (p < 0.001). Similarly, lesions with ring-hyperintensity in QSM also had higher kex elevation than the lesions with nodular-QSM-hyperintensity (p < 0.001). Of the 169 Gd-negative lesions, three radiological patterns were recognized according to lesion manifestations on the kex map and QSM images: Pattern I (kex+ and QSM+, n = 114, 67.5%), Pattern II (only kex+ or QSM+, n = 47, 27.8%) and Pattern III (kex– and QSM–, n = 8, 4.7%). Compared to Pattern II and III, Pattern I had higher kex (p < 0.001) and susceptibility (p < 0.05) elevation. The percentage of Pattern I of each subject was negatively correlated with the disease duration (r = –0.45, p = 0.015).ConclusionAs a potential imaging biomarker for inflammation due to oxidative stress, in vivo kex MRI combined with QSM is promising in extending the clinical classification of MS lesions beyond conventional Gd-enhanced MRI.