Preclinical studies of a PARP targeted, Meitner-Auger emitting, theranostic radiopharmaceutical for metastatic ovarian cancer.

Advanced ovarian cancer currently has few therapeutic options. Poly(ADP-ribose) polymerase (PARP) inhibitors bind to nuclear PARP and trap the protein-inhibitor complex to DNA. This work investigates a theranostic PARP inhibitor for targeted radiopharmaceutical therapy of ovarian cancer in vitro and PET imaging of healthy mice in vivo. METHODS: [77Br]RD1 was synthesized and assessed for pharmacokinetics and cytotoxicity in human and murine ovarian cancer cell lines. [76Br]RD1 biodistribution and organ uptake in healthy mice were quantified through longitudinal PET/CT imaging and ex vivo radioactivity measurements. Organ-level dosimetry following [76/77Br]RD1 administration was calculated using RAPID, an in-house platform for absorbed dose in mice, and OLINDA for equivalent and effective dose in human. RESULTS: The maximum specific binding (Bmax), equilibrium dissociation constant (Kd), and nonspecific binding slope (NS) were calculated for each cell line. These values were used to calculate the cell specific activity uptake for cell viability studies. The half maximal effective concentration (EC50) was measured as 0.17 (95 % CI: 0.13-0.24) nM and 0.46 (0.13-0.24) nM for PARP(+) and PARP(-) expressing cell lines, respectively. The EC50 was 0.27 (0.21-0.36) nM and 0.30 (0.22-0.41) nM for BRCA1(-) and BRCA1(+) expressing cell lines, respectively. When measuring the EC50 as a function of cellular activity uptake and nuclear dose, the EC50 ranges from 0.020 to 0.039 Bq/cell and 3.3-9.2 Gy, respectively. Excretion through the hepatobiliary and renal pathways were observed in mice, with liver uptake of 2.3 ± 0.4 %ID/g after 48 h, contributing to estimated absorbed dose values in mice of 19.3 ± 0.3 mGy/MBq and 290 ± 10 mGy/MBq for [77Br]RD1 and [76Br]RD1, respectively. CONCLUSION: [77Br]RD1 cytotoxicity was dependent on PARP expression and independent of BRCA1 status. The in vitro results suggest that [77Br]RD1 cytotoxicity is driven by the targeted Meitner-Auger electron (MAe) radiotherapeutic effect of the agent. Further studies investigating the theranostic potential, organ dose, and tumor uptake of [76/77Br]RD1 are warranted.

Intermetallic cobalt-gallium targets for production of germanium radioisotopes.

Increasing interest in targeted radionuclide therapy motivates the development of new radionuclides. The unique emission spectrum from 71Ge make it an ideal candidate for probing microdosimetric effects of low energy electrons absent confounding photon dose. This work reports a novel intermetallic target of Co and Ga for accelerator production of no-carrier-added 69/71Ge and a new method to isolate the Ge in high yields and purities.

Relationship of amyloid beta and neurofibrillary tau deposition in Neurodegeneration in Aging Down Syndrome (NiAD) study at baseline.

IMPORTANCE: Adults with Down syndrome (DS) are at high-risk of revealing Alzheimer's disease (AD) pathology, in part due to the triplication of chromosome 21 encoding the amyloid precursor protein. Adults with DS are uniformly affected by AD pathology by their 30's and have a 70% to 80% chance of clinical dementia by their 60's. Our previous studies have assessed longitudinal changes in amyloid beta (Aß) accumulation in DS. OBJECTIVE: The goal of the present study was to assess the presence of brain tau using [18F]AV-1451 positron emission tomography (PET) in DS and to assess the relationship of brain tau pathology to Aß using Pittsburgh Compound B (PiB)-PET. DESIGN: Cohort study. SETTING: Multi-center study. PARTICIPANTS: Participants consisted of a sample of individuals with DS and sibling controls recruited from the community; exclusion criteria included contraindications for magnetic resonance imaging (MRI) and/or a medical or psychiatric condition that impaired cognitive functioning. EXPOSURES: PET brain scans to assess Aß ([11C]PiB) and tau ([18F]AV-1451) burden. MAIN OUTCOMES AND MEASURES: Multiple linear regression models (adjusted for chronological age, sex and performance site) were used to examine associations between regional [18F]AV-1451 standard uptake value ratio (SUVR) (based on regions associated with Braak stages 1-6) and global [11C]PiB SUVR (as both a continuous and dichotomous variable). RESULTS: A cohort of 156 participants (mean age = 39.05, SD(8.4)) were examined. These results revealed a significant relationship between in vivo Aß and tau pathology in DS. As a dichotomous variable, [18F]AV-1451 retention was higher in each Braak region in PiB(+) participants. We also found, based on our statistical models, starting with the Braak 3 region of interest (ROI), an acceleration of [18F]AV-1451 SUVR deposition with [11C]PiB SUVR increases.

Cyclotron production and radiochemical separation of 55Co and 58mCo from 54Fe, 58Ni and 57Fe targets.

This work presents the production with a cyclotron of the positron emitter 55Co via the 54Fe(d,n) and 58Ni(p,α) reactions and the Auger electron emitter 58mCo via the 57Fe(d,n) reaction after high current (40µA p and 60µA d) irradiation on electroplated targets. High specific activity radionuclides (up to 55.6 GBq/µmol 55Co and 31.8GBq/µmol 58mCo) with high radionuclidic purity (99.995% 55Co from 54Fe, 98.8% 55Co from 58Ni, and 98.7% 58mCo from 57Fe at end of bombardment, EoB), in high activity concentration (final separated radionuclide in < 0.6mL) and with almost quantitative overall activity separation yield (> 92%) were obtained after processing of the irradiated targets with novel radiochemical separation methods based on HCl dissolution and the resin N,N,N',N'-tetrakis-2-ethylhexyldiglycolamide (DGA, branched). One hour long irradiations using 38-65, 110-214 and 59-78mg of enriched 54Fe (99.93%), 58Ni (99.48%) and 57Fe (95.06%), respectively, electroplated over a 1.0cm2 surface, yielded 582 ± 66MBq 55Co, 372 ± 14MBq 55Co and 810 ± 186MBq 58mCo, respectively, decay corrected to EoB. The separation methods allow for the recovery of the costly enriched target materials, which were reconstituted into metallic targets after novel electroplating methods, with an overall recycling efficiency of 93 ± 4% for iron. The produced radionuclides were used to radiolabel the angiogenesis marker antibody TRC105 conjugated to the chelator NOTA as a demonstration of their quality.

Production and decay of element 114: high cross sections and the new nucleus 277Hs.

The fusion-evaporation reaction 244Pu(48Ca,3-4n){288,289}114 was studied at the new gas-filled recoil separator TASCA. Thirteen correlated decay chains were observed and assigned to the production and decay of {288,289}114. At a compound nucleus excitation energy of E{*}=39.8-43.9 MeV, the 4n evaporation channel cross section was 9.8{-3.1}{+3.9} pb. At E^{*}=36.1-39.5 MeV, that of the 3n evaporation channel was 8.0{-4.5}{+7.4} pb. In one of the 3n evaporation channel decay chains, a previously unobserved α branch in 281Ds was observed (probability to be of random origin from background: 0.1%). This α decay populated the new nucleus 277Hs, which decayed by spontaneous fission after a lifetime of 4.5 ms.

New superheavy element isotopes: ²4²Pu(48Ca,5n) ²85114.

The new, neutron-deficient, superheavy element isotope ²85114 was produced in 48Ca irradiations of ²4²Pu targets at a center-of-target beam energy of 256 MeV (E*=50 MeV). The α decay of ²85114was followed by the sequential α decay of four daughter nuclides, 281Cn, 277Ds, 273Hs, and 269Sg. 265Rf was observed to decay by spontaneous fission. The measured α-decay Q values were compared with those from a macroscopic-microscopic nuclear mass model to give insight into superheavy element shell effects. The²4²Pu (48Ca,5n²)²85114 cross section was 0.6(-0.5)+0.9 pb.

Independent verification of element 114 Production in the ;{48}Ca + ;{242}Pu reaction.

Independent verification of the production of element 114 in the reaction of 244-MeV ;{48}Ca with ;{242}Pu is presented. Two chains of time- and position-correlated decays have been assigned to ;{286}114 and ;{287}114. The observed decay modes, half-lives, and decay energies agree with published results. The measured cross sections at a center-of-target energy of 244 MeV for the ;{242}Pu(;{48}Ca,3-4n);{287,286}114 reactions were 1.4_{-1.2};{+3.2} pb each, which are lower than the reported values.

Kinetics of smooth muscle heavy meromyosin with one thiophosphorylated head.

Actin-activated MgATPase of smooth muscle heavy meromyosin is activated by thiophosphorylation of two regulatory light chains, one on each head domain. To understand cooperativity between heads, we examined the kinetics of heavy meromyosin (HMM) with one thiophosphorylated head. Proteolytic gizzard heavy meromyosin regulatory light chains were partially exchanged with recombinant thiophosphorylated His-tagged light chains, and HMM with one thiophosphorylated head was isolated by nickel-affinity chromatography. In vitro motility was observed. By steady-state kinetic analysis, one-head thiophosphorylated heavy meromyosin had a similar K(m) value for actin but a V(max) value of approximately 50% of the fully thiophosphorylated molecule. However, single turnover analysis, which is not sensitive to small amounts of active heads, showed that one-head thiophosphorylated heavy meromyosin was 46-120 times more active than unphosphorylated HMM but only 7-19% as active as the fully thiophosphorylated molecule. Discrepancy between the single turnover and steady-state values could be explained by a small fraction of rigor heads. These rigor heads would have a large effect on the steady-state kinetics of one-head thiophosphorylated HMM. In summary, thiophosphorylation of one head leads to a molecule with unique intermediate kinetics suggesting that thiophosphorylation of one head cooperatively alters the kinetics of the partner head and vice versa.

Intrinsic crotonase activity in a bacterial butyryl-CoA dehydrogenase.

Butyryl-CoA, crotonyl-CoA or 3-hydroxybutyryl-CoA all ultimately form an enzyme-acetoacetyl-CoA complex upon aerobic addition to butyryl-CoA dehydrogenase purified from Megasphaera elsdenii, implying the presence of crotonase activity. This behaviour remains even after treatment with 6M urea, which destroys the activity of the main crotonase fraction from M. elsdenii. Flavin-sensitised photoinactivation destroys residual crotonase and dehydrogenase activities in parallel. Butyryl-CoA dehydrogenase thus has intrinsic crotonase activity with a turnover rate (0.05 min-1) about 0.02% of the figure for dehydrogenase activity. Mechanistic implications are discussed.

Endometrial carcinoma: feasibility of case-finding in a family physician's office.

To study the feasibility of endometrial sampling in a family physician's office we examined 42 asymptomatic women 50 years of age or older with the use of a Milan-Markley helix to obtain cytopathologic material. Nine procedures could not be completed because of stenosis of the introitus or cervix. The procedure took less than 3 minutes to complete for 30 women, and there was no technical difficulty for 27. Adequate amounts of tissue for diagnosis were obtained from 32 women. One or more risk factors for endometrial carcinoma were present in 34 women. Nine samples showed atypical hyperplasia. Although 37 women experienced discomfort and 19 experienced spotting, 35 were willing to have the procedure repeated annually or as indicated by their physician.