Predictive Value of [18F]ML-10 PET/CT in Early Response Evaluation of Combination Radiotherapy with Cetuximab on Nasopharyngeal Carcinoma.

PURPOSE: Apoptosis may be an indication of success therapy, and precise detection of apoptosis can provide instructional suggestions in the therapy management of malignant tumors. PROCEDURES: We used CNE-1 cell lines for in vitro experiments, and colony formation assay, CCK-8 assay, cell apoptosis analysis, and western blotting were performed. For in vivo experiments, subcutaneous xenotransplanted tumor models of CNE-1 in nude mice were established. Then, small animal positron emission tomography/X-ray computed tomography (PET/CT) images were acquired by tail intravenous injection of 2-(5-[18F]fluoropentyl)-2-methyl-malonic acid ([18F]ML-10) or 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) before and 24 h and 48 h after treatment. Moreover, expression of epidermal growth factor receptor (EGFR), Ki-67, Glut-1, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) was examined by immunohistochemical examination. Tumor volumes of mice were recorded every 2 days. RESULTS: In the presence of Cetuximab, the number of colonies of CNE-1 cells decreased significantly after irradiation at 1 and 2 Gy. In addition, Cetuximab increased the radiation-induced cytotoxicity and apoptosis of CNE-1 cells. Mechanistic studies demonstrated that Cetuximab enhanced radiosensitivity by suppressing the EGFR/PI3-K/AKT pathway. In PET/CT imaging, the tumors showed clear uptake of [18F]ML-10 at 24 h and 48 h after combined treatment, and the value of tumor/muscle (T/M) and SUVmax (the max of standard uptake value) was significantly higher than those of the other three groups. The T/M of [18F]ML-10 uptake showed a positive correlation of 0.926 with the apoptosis index (P < 0.001). However, the uptake of [18F]FDG in tumors exhibited no trend among the four groups. The T/M of [18F]FDG revealed a positive correlation of 0.926 with Glut-1 intensity (P < 0.001). CONCLUSIONS: Our work revealed that Cetuximab could increase the radiosensitivity of CNE-1 cells both in vitro and in vivo. Apoptosis imaging with [18F]ML-10 PET/CT is a promising modality for application in the response prediction of nasopharyngeal carcinoma.

Improved testing for vitamin B12 deficiency: correcting MMA for eGFR reduces the number of patients classified as vitamin B12 deficient.

Background Methylmalonic acid (MMA) can detect functional vitamin B12 deficiencies as it accumulates early when intracellular deficits arise. However, impaired clearance of MMA from blood due to decreased glomerular filtration rate (eGFR) also results in elevated plasma MMA concentrations. Alternative to clinical trials, a data mining approach was chosen to quantify and compensate for the effect of decreased eGFR on MMA concentration. Methods Comprehensive data on patient's vitamin B12, eGFR and MMA concentrations were collected ( n = 2906). The relationship between vitamin B12, renal function (eGFR) and MMA was modelled using weighted multiple linear regression. The obtained model was used to estimate the influence of decreased eGFR on MMA. Clinical impact was examined by comparing the number of patients labelled vitamin B12 deficient with and without adjustment in MMA. Results Adjusting measured MMA concentrations for eGFR in the group of patients with low-normal vitamin B12 concentrations (90-300 pmol/L) showed that the use of unadjusted MMA concentrations overestimates vitamin B12 deficiency by 40%. Conclusions Through a data mining approach, the influence of eGFR on the relation between MMA and vitamin B12 can be quantified and used to correct the measured MMA concentration for decreased eGFR. Especially in the elderly, eGFR-based correction of MMA may prevent over-diagnosis of vitamin B12 deficiency and corresponding treatment.

Molecular PET Imaging of Cyclophosphamide Induced Apoptosis with 18F-ML-8.

In this paper, a novel small-molecular apoptotic PET imaging probe, (18)F-ML-8 with a malonate motif structure, is presented and discussed. After study, the small tracer that belongs to a member of ApoSense family is proved to be capable of imaging merely apoptotic regions in the CTX treated tumor-bearing mice. The experimental result is further confirmed by in vitro cell binding assays and TUNEL staining assay. As a result, (18)F-ML-8 could be used for noninvasive visualization of apoptosis induced by antitumor chemotherapy.

Use of LC-MS for the quality control of radiopharmaceuticals: example of [(18)F]ML10.

[(18)F]ML10 is a promising novel low molecular weight positron emission tomography probe for apoptosis. As part of the quality control to support clinical studies for cancer therapy monitoring in the GSK Clinical Imaging Centre, a simple and sensitive liquid chromatography mass spectrometry method has been developed and validated for the quantification of total ML10 and impurity content in the final product. Chromatographic separation of ML10 and its radiolabelling precursor and impurities was achieved. Mass curves were constructed from a concentration range of ML10 and known impurities and were linear. Quantification was achieved by comparison of the area under the curve for ML10 content (m/z = 205) and the mass curve. The method was validated over a concentration range of 0.1-1 µg/ml.

Fumarase deficiency presenting with periventricular cysts.

A fumarase-deficient patient expressed a novel phenotype of congenital cerebral ventricular dilatation and periventricular cysts. The patient was a compound heterozygote for two mutations that are the only ones among the 12 published mutations that have been found in multiple, unrelated, fumarase-deficient patients.

Methylmalonic acid, a biochemical hallmark of methylmalonic acidurias but no inhibitor of mitochondrial respiratory chain.

Methylmalonic acidurias are biochemically characterized by an accumulation of methylmalonic acid and alternative metabolites. An impairment of energy metabolism plays a key role in the pathophysiology of this disease, resulting in neurodegeneration of the basal ganglia and renal failure. It has become the subject of intense debates whether methylmalonic acid is the major toxin, inhibiting respiratory chain complex II. To elucidate whether methylmalonic acid is a respiratory chain inhibitor, we used spectrophotometric analysis of complex II activity in submitochondrial particles from bovine heart, radiometric analysis of 14C-labeled substrates (pyruvate, malate, succinate), and analysis of ATP production in muscle from mice. Methylmalonic acid revealed no direct effects on the respiratory chain function, i.e. on single electron transferring complexes I-IV, ATPase, and mitochondrial transporters. However, we identified a variety of variables that must be carefully controlled to avoid an artificial inhibition of complex II activity. In summary, the study verifies our hypothesis that methylmalonic acid is not the major toxic metabolite in methylmalonic acidurias. Inhibition of respiratory chain and tricarboxylic acid cycle is most likely induced by synergistically acting alternative metabolites, in particular 2-methylcitric acid, malonic acid, and propionyl-CoA.

Determination of calpha chemical shift tensor orientation in peptides by dipolar-modulated chemical shift recoupling NMR spectroscopy.

We present a new method for determining the orientation of chemical shift tensors in polycrystalline solids with site resolution and demonstrate its application to the determination of the Calpha chemical shift tensor orientation in a model peptide with beta-sheet torsion angles. The tensor orientation is obtained under magic angle spinning by modulating a recoupled chemical shift anisotropy (CSA) pattern with various dipolar couplings. These dipolar-modulated chemical shift patterns constitute the indirect dimension of a 2D spectrum and are resolved according to the isotropic chemical shifts of different sites in the direct dimension. These dipolar-modulated CSA spectra are equivalent to the projection of a 2D static separated-local-field spectrum onto its chemical shift dimension, except that its dipolar dimension is multiplied with a modulation function. Both (13)C-(1)H and (13)C-(15)N dipolar couplings can modulate the CSA spectra of the Calpha site in an amino acid and yield the relative orientations of the chemical shift principal axes to the C-H and C-N bonds. We demonstrate the C-H and C-N modulated CSA experiments on methylmalonic acid and N-tBoc-glycine, respectively. The MAS results agree well with the results of the 2D separated-local-field spectra, thus confirming the validity of this MAS dipolar-modulation approach. Using this technique, we measured the Val Calpha tensor orientation in N-acetylvaline, which has beta-sheet torsion angles. The sigma(11) axis is oriented at 158 degrees (or 22 degrees) from the C-H bond, while the sigma(22) axis is tilted by 144 degrees (or 36 degrees) from the C-N bond. Both the orientations and the magnitude of this chemical shift tensor are in excellent agreement with quantum chemical calculations.

Extended form of a retro-inverso peptide stabilized by beta-sheet unidirectional H-bonds: Crystallographic and NMR evidence.

The crystallographic investigation of the retro-inverso peptide Bz-S-gAla-R-mAla-NHPh reveals an extended backbone conformation where the NH groups of the gem-diamino alkyl moiety and the CO groups of the malonyl residue face side by side. This extended conformation, presenting all carbonyls on opposite sides of the NH groups, is stabilized by interstrand H-bonds running in a single direction of the parallel beta-sheets that characterize the crystal packing. These sheets differ from the beta-sheets formed by native amino acids only. (1)H-NMR nuclear Overhauser effect spectroscopy (NOESY) experiments suggest that a conformation similar to that found in the crystal also prevails in dimethylsulfoxide solution. Previous potential energy calculations of gem-diamino alkyl (g) and malonyl (m) Ala residues predicted that extended forms were less stable than the helical ones because of strong electrostatic repulsions between the parallel polar groups. Similar arguments were invoked to give more weight to helical forms of the retro-peptide units in the proposal of packing models of some nylons in their crystalline polar regions. The present findings show that both g and m Ala residues can experience the extended conformation in the beta-sheet aggregation. The energy increase occurring in one strand, due to the parallel orientation of consecutive peptide dipoles, is more than compensated by favorable cooperative interactions among head-to-tail aligned peptide dipoles of facing strands, resulting in the formation of two C==O...H==N H-bonds per residue.

Conformational study of alanine and alpha-aminoisobutyric psi [NHCO]-retroamide peptide analogues.

The minimum-energy conformations of N,N'-dimethyl-2-methylmalondiamide (2mMA) and N,N'-dimethyl-2-dimethylmalondiamide (2dmMA) have been computed using the AM1 method. The results show that molecules tend to form an intramolecular six-membered ring hydrogen-bond system. The same trend is observed in crystals of malonamide derivatives substituted in the central carbon atom. The results are also compared with previous molecular-mechanics calculations. The conformational trends of 2mMA and 2dmMA are very similar to those showed by N,N'-dimethylmalondiamide. Details of the computed conformational energy maps for 2mMA and 2dmMA compounds are given.