PET imaging of microglia by targeting macrophage colony-stimulating factor 1 receptor (CSF1R).

While neuroinflammation is an evolving concept and the cells involved and their functions are being defined, microglia are understood to be a key cellular mediator of brain injury and repair. The ability to measure microglial activity specifically and noninvasively would be a boon to the study of neuroinflammation, which is involved in a wide variety of neuropsychiatric disorders including traumatic brain injury, demyelinating disease, Alzheimer's disease (AD), and Parkinson's disease, among others. We have developed [11C]CPPC [5-cyano-N-(4-(4-[11C]methylpiperazin-1-yl)-2-(piperidin-1-yl)phenyl)furan-2-carboxamide], a positron-emitting, high-affinity ligand that is specific for the macrophage colony-stimulating factor 1 receptor (CSF1R), the expression of which is essentially restricted to microglia within brain. [11C]CPPC demonstrates high and specific brain uptake in a murine and nonhuman primate lipopolysaccharide model of neuroinflammation. It also shows specific and elevated uptake in a murine model of AD, experimental allergic encephalomyelitis murine model of demyelination and in postmortem brain tissue of patients with AD. Radiation dosimetry in mice indicated [11C]CPPC to be safe for future human studies. [11C]CPPC can be synthesized in sufficient radiochemical yield, purity, and specific radioactivity and possesses binding specificity in relevant models that indicate potential for human PET imaging of CSF1R and the microglial component of neuroinflammation.

Design and synthesis of a novel BODIPY-labeled PSMA inhibitor.

Prostate-specific membrane antigen (PSMA) is a zinc-bound metalloprotease which is highly expressed in metastatic prostate cancer. It has been considered an excellent target protein for prostate cancer imaging and targeted therapy because it is a membrane protein and its active site is located in the extracellular region. We successfully synthesized and evaluated a novel PSMA ligand conjugated with BODIPY650/665. Compound 1 showed strong PSMA-inhibitory activity and selective uptake into PSMA-expressing tumors. Compound 1 has the potential to be utilized as a near infrared (NIR) optical imaging probe targeting PSMA-expressing cancers.

A Unique Core-Shell Structured, Glycol Chitosan-Based Nanoparticle Achieves Cancer-Selective Gene Delivery with Reduced Off-Target Effects.

The inherent instability of nucleic acids within serum and the tumor microenvironment necessitates a suitable vehicle for non-viral gene delivery to malignant lesions. A specificity-conferring mechanism is also often needed to mitigate off-target toxicity. In the present study, we report a stable and efficient redox-sensitive nanoparticle system with a unique core-shell structure as a DNA carrier for cancer theranostics. Thiolated polyethylenimine (PEI-SH) is complexed with DNA through electrostatic interactions to form the core, and glycol chitosan-modified with succinimidyl 3-(2-pyridyldithio)propionate (GCS-PDP) is grafted on the surface through a thiolate-disulfide interchange reaction to form the shell. The resulting nanoparticles, GCS-PDP/PEI-SH/DNA nanoparticles (GNPs), exhibit high colloid stability in a simulated physiological environment and redox-responsive DNA release. GNPs not only show a high and redox-responsive cellular uptake, high transfection efficiency, and low cytotoxicity in vitro, but also exhibit selective tumor targeting, with minimal toxicity, in vivo, upon systemic administration. Such a performance positions GNPs as viable candidates for molecular-genetic imaging and theranostic applications.

A prostate-specific membrane antigen (PSMA)-targeted prodrug with a favorable in vivo toxicity profile.

Prostate-specific membrane antigen (PSMA) is a promising target for the treatment of advanced prostate cancer (PC) and various solid tumors. Although PSMA-targeted radiopharmaceutical therapy (RPT) has enabled significant imaging and prostate-specific antigen (PSA) responses, accumulating clinical data are beginning to reveal certain limitations, including a subgroup of non-responders, relapse, radiation-induced toxicity, and the need for specialized facilities for its administration. To date non-radioactive attempts to leverage PSMA to treat PC with antibodies, nanomedicines or cell-based therapies have met with modest success. We developed a non-radioactive prodrug, SBPD-1, composed of a small-molecule PSMA-targeting moiety, a cancer-selective cleavable linker, and the microtubule inhibitor monomethyl auristatin E (MMAE). SBPD-1 demonstrated high binding affinity to PSMA (Ki = 8.84 nM) and selective cytotoxicity to PSMA-expressing PC cell lines (IC50 = 3.90 nM). SBPD-1 demonstrated a significant survival benefit in two murine models of human PC relative to controls. The highest dose tested did not induce toxicity in immunocompetent mice. The high specific targeting ability of SBPD-1 to PSMA-expressing tumors and its favorable toxicity profile warrant its further development.

Nanoparticle-mediated tumor cell expression of mIL-12 via systemic gene delivery treats syngeneic models of murine lung cancers.

Treatment of cancers in the lung remains a critical challenge in the clinic for which gene therapy could offer valuable options. We describe an effective approach through systemic injection of engineered polymer/DNA nanoparticles that mediate tumor-specific expression of a therapeutic gene, under the control of the cancer-selective progression elevated gene 3 (PEG-3) promoter, to treat tumors in the lungs of diseased mice. A clinically tested, untargeted, polyethylenimine carrier was selected to aid rapid transition to clinical studies, and a CpG-free plasmid backbone and coding sequences were used to reduce inflammation. Intravenous administration of nanoparticles expressing murine single-chain interleukin 12, under the control of PEG-3 promoter, significantly improved the survival of mice in both an orthotopic and a metastatic model of lung cancer with no marked symptoms of systemic toxicity. These outcomes achieved using clinically relevant nanoparticle components raises the promise of translation to human therapy.

A Glucose-Triptolide Conjugate Selectively Targets Cancer Cells under Hypoxia.

A major hurdle in the treatment of cancer is chemoresistance induced under hypoxia that is characteristic of tumor microenvironment. Triptolide, a potent inhibitor of eukaryotic transcription, possesses potent antitumor activity. However, its clinical potential has been limited by toxicity and water solubility. To address those limitations of triptolide, we designed and synthesized glucose-triptolide conjugates (glutriptolides) and demonstrated their antitumor activity in vitro and in vivo. Herein, we identified a lead, glutriptolide-2 with an altered linker structure. Glutriptolide-2 possessed improved stability in human serum, greater selectivity toward cancer over normal cells, and increased potency against cancer cells. Glutriptolide-2 exhibits sustained antitumor activity, prolonging survival in a prostate cancer metastasis animal model. Importantly, we found that glutriptolide-2 was more potent against cancer cells under hypoxia than normoxia. Together, this work provides an attractive glutriptolide drug lead and suggests a viable strategy to overcome chemoresistance through conjugation of cytotoxic agents to glucose.

Imaging CAR T cell therapy with PSMA-targeted positron emission tomography.

Chimeric antigen receptor (CAR) T cell therapy for hematologic malignancies is fraught with several unknowns, including number of functional T cells that engage target tumor, durability and subsequent expansion and contraction of that engagement, and whether toxicity can be managed. Non-invasive, serial imaging of CAR T cell therapy using a reporter transgene can address those issues quantitatively. We have transduced anti-CD19 CAR T cells with the prostate-specific membrane antigen (PSMA) because it is a human protein with restricted normal tissue expression and has an expanding array of positron emission tomography (PET) and therapeutic radioligands. We demonstrate that CD19-tPSMA(N9del) CAR T cells can be tracked with [18F]DCFPyL PET in a Nalm6 model of acute lymphoblastic leukemia. Divergence between the number of CD19-tPSMA(N9del) CAR T cells in peripheral blood and bone marrow and those in tumor was evident. These findings underscore the need for non-invasive repeatable monitoring of CAR T cell disposition clinically.

Kinetic Control in Assembly of Plasmid DNA/Polycation Complex Nanoparticles.

Polyelectrolyte complex (PEC) nanoparticles assembled from plasmid DNA (pDNA) and polycations such as linear polyethylenimine (lPEI) represent a major nonviral delivery vehicle for gene therapy tested thus far. Efforts to control the size, shape, and surface properties of pDNA/polycation nanoparticles have been primarily focused on fine-tuning the molecular structures of the polycationic carriers and on assembly conditions such as medium polarity, pH, and temperature. However, reproducible production of these nanoparticles hinges on the ability to control the assembly kinetics, given the nonequilibrium nature of the assembly process and nanoparticle composition. Here we adopt a kinetically controlled mixing process, termed flash nanocomplexation (FNC), that accelerates the mixing of pDNA solution with polycation lPEI solution to match the PEC assembly kinetics through turbulent mixing in a microchamber. This achieves explicit control of the kinetic conditions for pDNA/lPEI nanoparticle assembly, as demonstrated by the tunability of nanoparticle size, composition, and pDNA payload. Through a combined experimental and simulation approach, we prepared pDNA/lPEI nanoparticles having an average of 1.3 to 21.8 copies of pDNA per nanoparticle and average size of 35 to 130 nm in a more uniform and scalable manner than bulk mixing methods. Using these nanoparticles with defined compositions and sizes, we showed the correlation of pDNA payload and nanoparticle formulation composition with the transfection efficiencies and toxicity in vivo. These nanoparticles exhibited long-term stability at -20 °C for at least 9 months in a lyophilized formulation, validating scalable manufacture of an off-the-shelf nanoparticle product with well-defined characteristics as a gene medicine.

Imaging of Glial Cell Activation and White Matter Integrity in Brains of Active and Recently Retired National Football League Players.

IMPORTANCE: Microglia, the resident immune cells of the central nervous system, play an important role in the brain's response to injury and neurodegenerative processes. It has been proposed that prolonged microglial activation occurs after single and repeated traumatic brain injury, possibly through sports-related concussive and subconcussive injuries. Limited in vivo brain imaging studies months to years after individuals experience a single moderate to severe traumatic brain injury suggest widespread persistent microglial activation, but there has been little study of persistent glial cell activity in brains of athletes with sports-related traumatic brain injury. OBJECTIVE: To measure translocator protein 18 kDa (TSPO), a marker of activated glial cell response, in a cohort of National Football League (NFL) players and control participants, and to report measures of white matter integrity. DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional, case-control study included young active (n = 4) or former (n = 10) NFL players recruited from across the United States, and 16 age-, sex-, highest educational level-, and body mass index-matched control participants. This study was conducted at an academic research institution in Baltimore, Maryland, from January 29, 2015, to February 18, 2016. MAIN OUTCOMES AND MEASURES: Positron emission tomography-based regional measures of TSPO using [11C]DPA-713, diffusion tensor imaging measures of regional white matter integrity, regional volumes on structural magnetic resonance imaging, and neuropsychological performance. RESULTS: The mean (SD) ages of the 14 NFL participants and 16 control participants were 31.3 (6.1) years and 27.6 (4.9) years, respectively. Players reported a mean (SD) of 7.0 (6.4) years (range, 1-21 years) since the last self-reported concussion. Using [11C]DPA-713 positron emission tomographic data from 12 active or former NFL players and 11 matched control participants, the NFL players showed higher total distribution volume in 8 of the 12 brain regions examined (P < .004). We also observed limited change in white matter fractional anisotropy and mean diffusivity in 13 players compared with 15 control participants. In contrast, these young players did not differ from control participants in regional brain volumes or in neuropsychological performance. CONCLUSIONS AND RELEVANCE: The results suggest that localized brain injury and repair, indicated by higher TSPO signal and white matter changes, may be associated with NFL play. Further study is needed to confirm these findings and to determine whether TSPO signal and white matter changes in young NFL athletes are related to later onset of neuropsychiatric symptoms.

ENC1 Modulates the Aggregation and Neurotoxicity of Mutant Huntingtin Through p62 Under ER Stress.

Huntington's disease (HD) is a devastating neurodegenerative disorder, which is caused by the expression and aggregation of polyQ-expanded mutant huntingtin protein (mtHTT). While toxic mtHTT aggregates are primarily eliminated through autophagy, autophagy dysfunction is often observed in HD pathogenesis. Here, we show that ectodermal-neural cortex 1 (ENC1), a novel binding partner of sequestosome 1 (p62), negatively regulates autophagy under endoplasmic reticulum (ER) stress. We found that ER stress significantly increases the expression of ENC1 via inositol-requiring enzyme 1 (IRE1)-TNF receptor-associated factor 2 (TRAF2)-c-Jun N-terminal kinase (JNK) pathway. Ectopic expression of ENC1 alone induces the accumulation of detergent-resistant mtHTT aggregates and downregulation of ENC1 alleviates ER stress-induced mtHTT aggregation. Simultaneously, ER stress-induced impairment of autophagy flux is ameliorated by downregulation of ENC1. From immunoprecipitation and immunocytochemical assays, we found that ENC1 binds to p62 through its BTB and C-terminal Kelch (BACK) domain and this interaction is enhanced under ER stress. In particular, ENC1 preferentially interacts with the phosphorylated p62 at Ser403 during ER stress. Interestingly, ENC1 colocalizes with mtHTT aggregates and its C-terminal Kelch domain is required for interfering with the access of p62 to ubiquitinated mtHTT aggregates, thus inhibiting cargo recognition of p62. Accordingly, knockdown of ENC1 expression enhances colocalization of p62 with mtHTT aggregates. Consequently, ENC1 knockdown relieves death of neuronal cells expressing mtHTT under ER stress. These results suggest that ENC1 interacts with the phosphorylated p62 to impair autophagic degradation of mtHTT aggregates and affects cargo recognition failure under ER stress, leading to the accumulation and neurotoxicity of mtHTT aggregates.

[64Cu]XYIMSR-06: A dual-motif CAIX ligand for PET imaging of clear cell renal cell carcinoma.

Carbonic anhydrase IX (CAIX) is a cell surface enzyme that is over-expressed in approximately 95% of cases of clear cell renal cell carcinoma (ccRCC), the most common renal cancer. We synthesized and performed in vitro and in vivo evaluation of a dual-motif ligand, [64Cu]XYIMSR-06, for imaging CAIX expression on ccRCC tumors using positron emission tomography (PET). [64Cu]XYIMSR-06 was generated in yields of 51.0 ± 4.5% (n=5) and specific activities of 4.1 - 8.9 GBq/µmol (110-240 Ci/mmol). Tumor was visualized on PET images by 1 h post-injection with high tumor-to-background levels (>100 tumor-to-blood and -muscle) achieved within 24 h. Biodistribution studies demonstrated a maximum tumor uptake of 19.3% injected dose per gram of radioactivity at 4 h. Tumor-to-blood, -muscle and -kidney ratios were 129.6 ± 18.8, 84.3 ± 21.0 and 2.1 ± 0.3, respectively, at 8 h post-injection. At 24 h a tumor-to-kidney ratio of 7.1 ± 2.5 was achieved. These results indicate pharmacokinetics superior to those of previously reported imaging agents binding to CAIX. [64Cu]XYIMSR-06 is a new low-molecular-weight PET ligand targeting CAIX, which can image localized and metastatic ccRCC.

iRhom1 regulates proteasome activity via PAC1/2 under ER stress.

Proteasome is a protein degradation complex that plays a major role in maintaining cellular homeostasis. Despite extensive efforts to identify protein substrates that are degraded through ubiquitination, the regulation of proteasome activity itself under diverse signals is poorly understood. In this study, we have isolated iRhom1 as a stimulator of proteasome activity from genome-wide functional screening using cDNA expression and an unstable GFP-degron. Downregulation of iRhom1 reduced enzymatic activity of proteasome complexes and overexpression of iRhom1 enhanced it. Native-gel and fractionation analyses revealed that knockdown of iRhom1 expression impaired the assembly of the proteasome complexes. The expression of iRhom1 was increased by endoplasmic reticulum (ER) stressors, such as thapsigargin and tunicamycin, leading to the enhancement of proteasome activity, especially in ER-containing microsomes. iRhom1 interacted with the 20S proteasome assembly chaperones PAC1 and PAC2, affecting their protein stability. Moreover, knockdown of iRhom1 expression impaired the dimerization of PAC1 and PAC2 under ER stress. In addition, iRhom1 deficiency in D. melanogaster accelerated the rough-eye phenotype of mutant Huntingtin, while transgenic flies expressing either human iRhom1 or Drosophila iRhom showed rescue of the rough-eye phenotype. Together, these results identify a novel regulator of proteasome activity, iRhom1, which functions via PAC1/2 under ER stress.

Identification of glucose-6-phosphate transporter as a key regulator functioning at the autophagy initiation step.

Autophagy is a catabolic process involving autophagosome formation via lysosome. However, the initiation step of autophagy is largely unknown. We found an interaction between ULK1 and ATG9 in mammalian cells and utilized the interaction to identify novel regulators of autophagy upstream of ULK1. We established a cell-based screening assay employing bimolecular fluorescence complementation. By performing gain-of-function screening, we identified G6PT as an autophagy activator. G6PT enhanced the interaction between N-terminal Venus-tagged ULK1 and C-terminal Venus-tagged ATG9, and increased autophagic flux independent of its transport activity. G6PT negatively regulated mTORC1 activity, demonstrating that G6PT functions upstream of mTORC1 in stimulating autophagy.

Overexpression of Atg5 in mice activates autophagy and extends lifespan.

Autophagy has been implicated in the ageing process, but whether autophagy activation extends lifespan in mammals is unknown. Here we show that ubiquitous overexpression of Atg5, a protein essential for autophagosome formation, extends median lifespan of mice by 17.2%. We demonstrate that moderate overexpression of Atg5 in mice enhances autophagy, and that Atg5 transgenic mice showed anti-ageing phenotypes, including leanness, increased insulin sensitivity and improved motor function. Furthermore, mouse embryonic fibroblasts cultured from Atg5 transgenic mice are more tolerant to oxidative damage and cell death induced by oxidative stress, and this tolerance was reversible by treatment with an autophagy inhibitor. Our observations suggest that the leanness and lifespan extension in Atg5 transgenic mice may be the result of increased autophagic activity.