Knight, Joshua A.

Abstract Purpose The thyroid-stimulating hormone receptor (TSHR) is a cell-surface receptor predominantly expressed on benign and malignant thyroid cells, making it a viable target for developing radiotheranostics for metastatic thyroid cancer imaging and therapy. This study reports the radiosynthesis and preclinical evaluation of a 64Cu-labelled human antibody for positron emission tomography (PET) imaging of TSHR expression in thyroid cancer mouse models. Methods Human anti-TSHR recombinant antibody K1-70™ (TSHR-Ab) was conjugated with a bifunctional chelator, 2-S-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA), and then labelled with [64Cu]Cu2+, yielding radiotracer [64Cu]Cu-NOTA-TSHR-Ab. The specificity and binding affinity of the radiotracer to TSHR-positive (THJ529TTSHR(+)) or wild-type (THJ529TWT) cells were assessed in vitro. A series of immnuoPET imaging with [64Cu]Cu-NOTA-TSHR-Ab were conducted in mice bearing dual-flank tumors (THJ529TWT on the left and THJ529TTSHR(+) on the right) at multiple time points (1, 2, 4, 18, 24, and 48 h) post-injection (p.i.). Radiotracer co-injection studies with varying doses of unlabelled (cold) TSHR-Ab (100, 50, 25, 0 µg) were studied to assess its effect on radiotracer uptake in tumors and off-target organs. Biodistribution and immunohistochemistry (IHC) were performed to verify the immnuoPET imaging results. Results [64Cu]Cu-NOTA-TSHR-Ab was synthesised with a radiochemical yield of 46.89 ± 3.74%, radiochemical purity of 98.77 ± 0.89%, and specific activity >1.42 GBq/mg (n = 5). In vitro cell studies demonstrated [64Cu]Cu-NOTA-TSHR-Ab had high specificity and nanomolar affinity for THJ529TTSHR(+) cells, with a dissociation constant (Kd) of 4.74 nM and an inhibition constant (Ki) of 0.92 nM. The immnuoPET imaging studies showed that the radiotracer could reach tumor quickly and showed high uptake in TSHR-positive thyroid tumors (SUVmax: 3.63 ± 0.42, 3.82 ± 0.44, and 4.09 ± 0.56 at 18, 24, and 48 h p.i., respectively). Co-injection with cold TSHR-Ab at doses ranging from 25 to 100 µg effectively reduced background signals, especially in spleen, liver, and bone. Notably, a dose of 25 µg cold TSHR-Ab reduced off-target signals without affecting tumor uptake. The biodistribution and IHC analyses further supported PET imaging findings. Conclusion TSHR-targeted radiotracer [64Cu]Cu-NOTA-TSHR-Ab was synthesized with high radiochemical purity. Our preclinical evaluation results demonstrate it is a promising radiotracer for PET imaging of TSHR-positive thyroid cancer, which may guide and monitor TSHR-targeted therapies. High radiotracer uptake in tumor, prolonged retention time, and favourable pharmacokinetics with the support of cold antibody co-injection, pave the way for the development of paired radiotherapeutics to treat TSHR-positive thyroid cancers.

Abstract Metastatic castration-resistant prostate cancer (mCRPC) is an aggressive malignancy with poor outcomes. To investigate novel therapeutic strategies, we characterized three new metastatic prostate cancer patient derived-tumor xenograft (PDTX) models and developed 3D spheroids from each to investigate molecular targeted therapy combinations including CDK4/6 inhibitors (CDK4/6i) with AKT inhibitors (ATKi). Metastatic prostate cancer tissue was collected and three PDTX models were established and characterized using whole-exome sequencing. PDTX 3D spheroids were developed from these three PDTXs to show resistance patterns and test novel molecular-targeted therapies. CDK4/6i's were combined with AKTi's to assess synergistic antitumor response to prove our hypothesis that blockade of AKT overcomes drug resistance to CDK4/6i. This combination was evaluated in PDTX three-dimensional (3D) spheroids and in vivo experiments with responses measured by tumor volumes, PSA, and Ga-68 PSMA-11 PET-CT imaging. We demonstrated CDK4/6i's with AKTi's possess synergistic antitumor activity in three mCRPC PDTX models. These models have multiple unique pathogenic and deleterious genomic alterations with resistance to single-agent CDK4/6i's. Despite this, combination therapy with AKTi's was able to overcome resistance mechanisms. The IHC and Western blot analysis confirmed on target effects, whereas tumor volume, serum PSA ELISA, and radionuclide imaging demonstrated response to therapy with statistically significant SUV differences seen with Ga-68 PSMA-11 PET-CT. These preclinical data demonstrating antitumor synergy by overcoming single-agent CDK 4/6i as well as AKTi drug resistance provide the rational for a clinical trial combining a CDK4/6i with an AKTi in patients with mCRPC whose tumor expresses wild-type retinoblastoma 1.

TREM2 is exclusively expressed by microglia in the brain and is strongly linked to the risk for Alzheimer’s disease (AD). As microglial responses modulated by TREM2 are central to AD pathogenesis, enhancing TREM2 signaling has been explored as an AD therapeutic strategy. However, the effective therapeutic window targeting TREM2 is unclear. Here, by using microglia-specific inducible mouse models overexpressing human wild-type TREM2 (TREM2-WT) or R47H risk variant (TREM2-R47H), we show that TREM2-WT expression reduces amyloid deposition and neuritic dystrophy only during the early amyloid seeding stage, whereas TREM2-R47H exacerbates amyloid burden during the middle amyloid rapid growth stage. Single-cell RNA sequencing reveals suppressed disease-associated microglia (DAM) signature and reduced DAM population upon TREM2-WT expression in the early stage, whereas upregulated antigen presentation pathway is detected with TREM2-R47H expression in the middle stage. Together, our findings highlight the dynamic effects of TREM2 in modulating AD pathogenesis and emphasize the beneficial effect of enhancing TREM2 function in the early stage of AD development.

Abstract Background: The p.H157Y variant of TREM2 (Triggering Receptor Expressed on Myeloid Cells 2) has been reported to increase Alzheimer’s disease (AD) risk. This mutation in the extracellular domain of TREM2 localizes at the cleavage site and was shown to enhance shedding and impair phagocytosis in vitro by ectopic expression of TREM2-H157Y in HEK293 cells. However, the physiological and AD-related outcomes of TREM2 H157Y mutation in vivo remain unknown.Methods: We generated a novel Trem2 H157Y knock-in mouse model through CRISPR-Cas9 technology and investigated how Trem2 H157Y mutation impacts TREM2 proteolytic processing, synaptic function, and AD-related amyloid pathology by conducting biochemical assays, immunofluorescent staining, hippocampal electrophysiology, and in vivo micro-dialysis in awake, free-moving animals.Results: Consistent with previous in vitro findings, TREM2-H157Y increases the amount of soluble TREM2 (sTREM2) in the cortex and serum of mutant mice compared to the wild type controls. Interestingly, the Trem2 H157Y variant enhances synaptic plasticity without affecting microglial density and morphology. In the presence of amyloid pathology, TREM2-H157Y surprisingly accelerates Aβ clearance and reduces amyloid burden and microgliosis. Conclusion: Taken together, our findings support a beneficial effect of the Trem2 H157Y mutation in synaptic function and in mitigating amyloid pathology. Considering the genetic association of TREM2 p.H157Y with AD, we speculate TREM2-H157Y might increase AD risk through an amyloid-independent pathway, as such its effects on tauopathy and neurodegeneration merit further investigation.

A rare APOE variant APOE3 -Jac reduces self-aggregation and promotes healthy brain aging.

APOE4 exacerbates α-synuclein pathology in a synucleinopathy mouse model, and APOE4 genotype associates with increased α-synuclein pathology in humans.