APOE4/4 is linked to damaging lipid droplets in Alzheimer's disease microglia.

Several genetic risk factors for Alzheimer's disease implicate genes involved in lipid metabolism and many of these lipid genes are highly expressed in glial cells. However, the relationship between lipid metabolism in glia and Alzheimer's disease pathology remains poorly understood. Through single-nucleus RNA sequencing of brain tissue in Alzheimer's disease, we have identified a microglial state defined by the expression of the lipid droplet-associated enzyme ACSL1 with ACSL1-positive microglia being most abundant in patients with Alzheimer's disease having the APOE4/4 genotype.

APOE4-promoted gliosis and degeneration in tauopathy are ameliorated by pharmacological inhibition of HMGB1 release.

Apolipoprotein E4 (APOE4) is an important driver of Tau pathology, gliosis, and degeneration in Alzheimer's disease (AD). Still, the mechanisms underlying these APOE4-driven pathological effects remain elusive. Here, we report in a tauopathy mouse model that APOE4 promoted the nucleocytoplasmic translocation and release of high-mobility group box 1 (HMGB1) from hippocampal neurons, which correlated with the severity of hippocampal microgliosis and degeneration.

APOE4/4 is linked to damaging lipid droplets in Alzheimer's microglia.

Several genetic risk factors for Alzheimer's Disease (AD) implicate genes involved in lipid metabolism and many of these lipid genes are highly expressed in glial cells. However, the relationship between lipid metabolism in glia and AD pathology remains poorly understood. Through single-nucleus RNA-sequencing of AD brain tissue, we have identified a microglial state defined by the expression of the lipid droplet (LD) associated enzyme with ACSL1-positive microglia most abundant in AD patients with the genotype.

Defining the Magnetic Resonance Features of Renal Lesions and Their Response to Everolimus in a Transgenic Mouse Model of Tuberous Sclerosis Complex.

Tuberous sclerosis complex (TSC) is an inherited genetic disorder characterized by mutations in or class of tumor suppressers which impact several organs including the kidney. The renal manifestations are usually in the form of angiomyolipoma (AML, in 80% of the cases) and cystadenomas. mTOR inhibitors such as rapamycin and everolimus have shown efficacy in reducing the renal tumor burden.

CUB Domain-Containing Protein 1 (CDCP1) Is a Target for Radioligand Therapy in Castration-Resistant Prostate Cancer, including PSMA Null Disease.

Purpose: With the improvement in overall survival with 177Lu-PSMA 617, radioligand therapy (RLT) is now a viable option for patients with metastatic castration-resistant prostate cancer (mCRPC). However, responses are variable, in part due to low PSMA expression in 30% of patients. Herein, we evaluated whether the cell surface protein CUB domain-containing protein 1 (CDCP1) can be exploited to treat mCRPC with RLT, including in PSMA-low subsets.

Ferrous iron-activatable drug conjugate achieves potent MAPK blockade in KRAS-driven tumors.

KRAS mutations drive a quarter of cancer mortality, and most are undruggable. Several inhibitors of the MAPK pathway are FDA approved but poorly tolerated at the doses needed to adequately extinguish RAS/RAF/MAPK signaling in the tumor cell. We found that oncogenic KRAS signaling induced ferrous iron (Fe2+) accumulation early in and throughout mutant KRAS-mediated transformation.

Switchable assembly and function of antibody complexes in vivo using a small molecule.

The antigen specificity and long serum half-life of monoclonal antibodies have made them a critical part of modern therapeutics. These properties have been coopted in a number of synthetic formats, such as antibody-drug conjugates, bispecific antibodies, or Fc-fusion proteins to generate novel biologic drug modalities. Historically, these new therapies have been generated by covalently linking multiple molecular moieties through chemical or genetic methods.

Targeting a proteolytic neoepitope on CUB domain containing protein 1 (CDCP1) for RAS-driven cancers.

Extracellular proteolysis is frequently dysregulated in disease and can generate proteoforms with unique neoepitopes not found in healthy tissue. Here, we demonstrate that Abs that selectively recognize a proteolytic neoepitope on CUB domain containing protein 1 (CDCP1) could enable more effective and safer treatments for solid tumors. CDCP1 is highly overexpressed in RAS-driven cancers, and its ectodomain is cleaved by extracellular proteases.

In Vivo Profiling with F-YJH08 Reveals Diverse Tissue Patterns of Antagonist/Glucocorticoid Receptor Interactions.

Demonstrating target engagement in vivo is an important milestone in drug development, both to establish on target, on tissue interactions but also to identify potentially undesirable off tissue binding. The glucocorticoid receptor (GR) is a long-studied yet vexing drug target that has recently re-emerged as a potential druggable driver of many solid tumor types including breast and prostate cancer, and several antagonists are currently in early phase clinical trials. Since GR is also ubiquitously expressed in normal tissues, understanding antagonist/GR interactions in normal tissues and tumor is crucial to defining a therapeutic index.

In Vivo Measurement of Granzyme Proteolysis from Activated Immune Cells with PET.

The biology of human granzymes remains enigmatic in part due to our inability to probe their functions outside of in vitro assays or animal models with divergent granzyme species. We hypothesize that the biology of human granzymes could be better elaborated with a translational imaging technology to reveal the contexts in which granzymes are secreted and biochemically active in vivo. Here, we advance toward this goal by engineering a Granzyme targeting Restricted Interaction Peptide specific to family member B (GRIP B) to measure secreted granzyme B (GZMB) biochemistry with positron emission tomography.

Molecular Imaging of Prostate Cancer Targeting CD46 Using ImmunoPET.

Purpose: We recently identified CD46 as a novel therapeutic target in prostate cancer. In this study, we developed a CD46-targeted PET radiopharmaceutical, [Zr]DFO-YS5, and evaluated its performance for immunoPET imaging in murine prostate cancer models.

Experimental Design: [Zr]DFO-YS5 was prepared and its binding affinity for CD46 was measured.

Ferronostics: Measuring Tumoral Ferrous Iron with PET to Predict Sensitivity to Iron-Targeted Cancer Therapies.

Although cancer has been known for decades to harbor an insatiable appetite for iron, only recently has the chemistry emerged to exploit this altered state therapeutically, by targeting the expanded cytosolic labile iron pool (LIP) of the cancer cell. The state of the art includes therapies that react with the LIP to produce cytotoxic radical species (in some cases also releasing drug payloads) and molecules that exacerbate LIP-induced oxidative stress to trigger ferroptosis. Effectively implementing LIP-targeted therapies in patients will require biomarkers to identify those tumors with the most elevated LIP and thus most likely to succumb to LIP-targeted interventions.

The Synthesis and Structural Requirements for Measuring Glucocorticoid Receptor Expression In Vivo with (±)-C-YJH08 PET.

Noninvasive methods to study glucocorticoid receptor (GR) signaling are urgently needed to elaborate the complexity of GR signaling in normal physiology and human disorders, as well as to identify selective GR modulators to treat diseases. Here, we report evidence supporting translational studies with (±)-C-5-(4-fluorobenzyl)-10-methoxy-2,2,4-trimethyl-2,5-dihydro-1H-chromeno[3,4-f]-quinoline ((±)-C-YJH08), a radioligand for PET that engages the ligand binding domain on GR. (±)-C-YJH08 was synthesized by reacting the phenol precursor with C-methyl iodide.

An Analysis of Isoclonal Antibody Formats Suggests a Role for Measuring PD-L1 with Low Molecular Weight PET Radiotracers.

Purpose: The swell of new and diverse radiotracers to predict or monitor tumor response to cancer immunotherapies invites the opportunity for comparative studies to identify optimal platforms. To probe the significance of antibody format on image quality for PD-L1 imaging, we developed and studied the biodistribution of a library of antibodies based on the anti-PD-L1 IgG1 clone C4.

Procedure: A C4 minibody and scFv were cloned, expressed, and characterized.

Theranostic Targeting of CUB Domain Containing Protein 1 (CDCP1) in Pancreatic Cancer.

Purpose: The recent emergence of radioligand therapies for cancer treatment has increased enthusiasm for developing new theranostic strategies coupling both imaging and cytotoxicity in the same entity. In this study, we evaluated whether CUB domain containing protein 1 (CDCP1), a single-pass transmembrane protein highly overexpressed in diverse human cancers, might be a target for cancer theranostics.

Experimental Design: The ectodomain of CDCP1 was targeted using radiolabeled forms of 4A06, a potent and specific recombinant human antibody that we developed.

A Novel Radioligand Reveals Tissue Specific Pharmacological Modulation of Glucocorticoid Receptor Expression with Positron Emission Tomography.

The complexity of glucocorticoid receptor (GR) signaling cannot be measured with direct tissue analysis in living subjects, which has stifled our understanding of GR's role in human physiology or disease and impeded the development of selective GR modulators. Herein, we report F-5-(4-fluorobenzyl)-10-methoxy-2,2,4-trimethyl-2,5-dihydro-1H-chromeno[3,4-]quinoline (F-YJH08), a radioligand that enables noninvasive measurements of tissue autonomous GR expression levels with positron emission tomography (PET). YJH08 potently binds GR ( ∼ 0.

Measuring Dynamic Changes in the Labile Iron Pool in Vivo with a Reactivity-Based Probe for Positron Emission Tomography.

Redox cycling of iron powers various enzyme functions crucial for life, making the study of iron acquisition, storage, and disposition in the whole organism a worthy topic of inquiry. However, despite its important role in biology and disease, imaging iron in animals with oxidation-state specificity remains an outstanding problem in biology and medicine. Here we report a first-generation reactivity-based probe of labile ferrous iron suitable for positron emission tomography studies in live animals.

Quantitative and Qualitative Improvement of Low-Count [Ga]Citrate and [Y]Microspheres PET Image Reconstructions Using Block Sequential Regularized Expectation Maximization Algorithm.

Purpose: There are several important positron emission tomography (PET) imaging scenarios that require imaging with very low photon statistics, for which both quantitative accuracy and visual quality should not be neglected. For example, PET imaging with the low photon statistics is closely related to active efforts to significantly reduce radiation exposure from radiopharmaceuticals. We investigated two examples of low-count PET imaging: (a) imaging [Y]microsphere radioembolization that suffers the very small positron emission fraction of Y-90's decay processes, and (b) cancer imaging with [Ga]citrate with uptake time of 3-4 half-lives, necessary for visualizing tumors.

Tumor-conditional anti-CTLA4 uncouples antitumor efficacy from immunotherapy-related toxicity.

While immune checkpoint blockade leads to potent antitumor efficacy, it also leads to immune-related adverse events in cancer patients. These toxicities stem from systemic immune activation resulting in inflammation of multiple organs, including the gastrointestinal tract, lung, and endocrine organs. We developed a dual variable domain immunoglobulin of anti-CTLA4 antibody (anti-CTLA4 DVD, where CTLA4 is defined as cytotoxic T lymphocyte-associated antigen-4) possessing an outer tumor-specific antigen-binding site engineered to shield the inner anti-CTLA4-binding domain.

Targeting iron metabolism in high-grade glioma with 68Ga-citrate PET/MR.

Noninvasive tools that target tumor cells could improve the management of glioma. Cancer generally has a high demand for Fe(III), an essential nutrient for a variety of biochemical processes. We tested whether 68Ga-citrate, an Fe(III) biomimetic that binds to apo-transferrin in blood, detects glioma in preclinical models and patients using hybrid PET/MRI.

A Preclinical Assessment of Zr-atezolizumab Identifies a Requirement for Carrier Added Formulations Not Observed with Zr-C4.

The swell of experimental imaging technologies to noninvasively measure immune checkpoint protein expression presents the opportunity for rigorous comparative studies toward identifying a gold standard. Zr-atezolizumab is currently in man, and early data show tumor targeting but also abundant uptake in several normal tissues. Therefore, we conducted a reverse translational study both to understand if tumor to normal tissue ratios for Zr-atezolizumab could be improved and to make direct comparisons to Zr-C4, a radiotracer that we showed can detect a large dynamic range of tumor-associated PD-L1 expression.

Measuring glucocorticoid receptor expression with PET.

The glucocorticoid receptor (GR) is an emerging drug target for several common and deadly solid tumors like breast and prostate cancer, and clinical trials studying the antitumor effects of GR antagonists are beginning. Since GR expression can be variable in tumor cells, and virtually all normal mammalian tissues express some GR, we hypothesized that an imaging tool capable of detecting GR positive tumors and/or measuring GR occupancy by drug in tumor and normal tissues could improve the precision application of anti-GR therapies in the clinic. To this end, we developed a fluorine-18 labeled corticosteroid termed GR02 that potently binds the endogenous ligand binding pocket on full length GR.

Imaging PD-L1 Expression with ImmunoPET.

High sensitivity imaging tools could provide a more holistic view of target antigen expression to improve the identification of patients who might benefit from cancer immunotherapy. We developed for immunoPET a novel recombinant human IgG1 (termed C4) that potently binds an extracellular epitope on human and mouse PD-L1 and radiolabeled the antibody with zirconium-89. Small animal PET/CT studies showed that Zr-C4 detected antigen levels on a patient derived xenograft (PDX) established from a non-small-cell lung cancer (NSCLC) patient before an 8-month response to anti-PD-1 and anti-CTLA4 therapy.