Linker structure-activity relationships in fluorodeoxyglucose chlorambucil conjugates for tumor-targeted chemotherapy.

Nitrogen mustards, such as chlorambucil (CLB), can cause adverse side-effects due to ubiquitous distribution in non-target organs. To minimize this toxicity, strategies of tumor-targeting drug delivery have been developed, where a cytotoxic warhead is linked to a tumor-cell-specific small ligand. Malignant cells exhibit marked glucose avidity and an accelerated metabolism by aerobic glycolysis, known as the Warburg effect, and recognized as a hallmark of cancer. A targeting approach exploiting the Warburg effect by conjugation of CLB to 2-fluoro-2-deoxyglucose (FDG) was previously reported and identified two peracetylated glucoconjugates 2 and 3 with promising antitumor activities in vivo. These results prompted us to investigate the importance of the spacer in this tumor-targeting glucose-based conjugates. Here we report the chemical synthesis and an in vitro cytotoxicity evaluation, using a 5-member panel of human tumor cell lines and human fibroblasts, of 16 new CLB glucoconjugates in which the alkylating drug is attached to the C-1 position of FDG via different linkages. We studied the structure-activity relationships in the linker, and evidenced the positive impact of an aromatic linker on in vitro cytotoxicity: compound 51 proved to be the most active FDG-CLB glucoside, characterized by a bis-aromatic spacer tethered to CLB through an amide function.

Radioprotective efficacy of plastic polymer against the toxicogenomic effects of radiopharmaceutical 18F-FDG on human lymphocytes.

BACKGROUND: Healthcare workers occupationally exposed to 18F-FDG cannot wear protective equipment, such as lead aprons, since the interaction between high energy radiation (511 keV) and metal increases the dose of radiation absorption. The objective of this study was to evaluate the shielding efficacy of a plastic polymer against the toxicogenomic effects of ionizing radiation in human lymphocytes, using cytokinesis-block micronucleus assays. METHODS: Human peripheral blood lymphocytes were isolated from three subjects and cultured under standard conditions. The cultures were exposed to 300 mCi of 18F-FDG at a distance of 10 cm for 10 min, in the absence of shielding or with lead, polymer, and lead + polymer shields. RESULTS: Lead shielding was found to increase the number of counts detected by Geiger-Müller radiation monitors as a consequence of the photoelectron effect. Conversely, the lead + polymer shield reduced the number of counts. The lead, polymer, and lead + polymer shields significantly reduced the frequency of micronuclei, nucleoplasmic bridges, and nuclear buds induced by ionizing radiation. Regarding cytotoxicity, only the lead + polymer shield re-established the cell cycle at the level observed for the negative control. CONCLUSIONS: Lead aprons that are internally coated with polymer increased the radiological protection of individuals occupationally exposed to 18F-FDG PET/CT, especially during examinations.

18F-FDG-induced DNA damage, chromosomal aberrations, and toxicity in V79 lung fibroblast cells.

18F-FDG PET/CT imaging is used in the diagnosis of diseases, including cancers. The principal photons used for imaging are 511 ke V gamma photons resulting from positron annihilation. The absorbed dose varies among body organs, depending on administered radioactivity and biological clearance. We have attempted to evaluate DNA double-strand breaks (DSB) and toxicity induced in V79 lung fibroblast cells in vitro by 18F-FDG, at doses which might result from PET procedures. Cells were irradiated by 18F-FDG at doses (14.51 and 26.86 mGy), comparable to absorbed doses received by critical organs during PET procedures. The biological endpoints measured were formation of γ-H2AX foci, mitochondrial stress, chromosomal aberrations, and cell cycle perturbation. Irradiation induced DSB (γH2AX assay), mitochondrial depolarization, and both chromosome and chromatid types of aberrations. At higher radiation doses, increased aneuploidy and reduced mitotic activity were also seen. Thus, significant biological effects were observed at the doses delivered by the 18F-FDG exposure and the effects increased with dose.

Positron Emission Tomography for the Development and Characterization of Corneal Permanence of Ophthalmic Pharmaceutical Formulations.

Purpose: This work is aimed at describing the utility of positron emission tomography/computed tomography (PET/CT) as a noninvasive tool for pharmacokinetic studies of biopermanence of topical ocular formulations. Methods: The corneal biopermanence of a topical ophthalmic formulation containing gellan gum and kappa carragenan (0.82% wt/vol) labeled with 18Fluorine (18F) radiotracers (18F-FDG and 18F-NaF) was evaluated by using a dedicated small-animal PET/CT, and compared with the biopermanence of an aqueous solution labeled with the same compounds. Regions of interest (ROIs) were manually drawn on the reconstructed PET images for quantifying the radioactivity concentration in the eye. The biopermanence of the formulations was determined by measuring the radioactivity concentration at different times after topical application. Additionally, cellular and ex vivo safety assays were performed to assess the safety of the performed procedures. Results: Differences were observed in the ocular pharmacokinetics of the two formulations. After 1.5 hours of contact, 90% of the hydrogel remained in the ocular surface, while only 69% of the control solution remained. Furthermore, it was observed that flickering had a very important role in the approach of the trial. The application of 18F-FDG in the eye was neither irritating nor cytotoxic for human corneal epithelial cells. Conclusions: The use of small-animal PET and 18F radiotracers in ocular pharmacokinetics of ophthalmic formulations is feasible and could be a safe method for future ocular pharmacokinetic studies in humans.

A Pilot Study Into the Use of FDG-mNP as an Alternative Approach in Neuroblastoma Cell Hyperthermia.

Herein, we present a pilot study concerning the use of fluorodeoxy glucose conjugated magnetite nanoparticles (FDG-mNP) as a potential agent in magnetic nanoparticle mediated neuroblastoma cancer cell hyperthermia. This approach makes use of the 'Warburg effect', utilizing the fact that cancer cells have a higher metabolic rate than normal cells. FDG-mNP were synthesized, then applied to the SH-SY5Y neuroblastoma cancer cell line and exposed to an ac magnetic field. 3D Calorimetry was performed on the FDG-mNP compound. Simulations were performed using SEMCAD X software using Thelonious, (an anatomically correct male child model) in order to understand more about the end requirements with respect to cancer cell destruction. We investigated FDG-mNP mediated neuroblastoma cytotoxicity in conjunction with ac magnetic field exposure. Results are presented for 3D FDG-mNP SAR mnp (10.86 ± 0.99 W/g of particles) using a therapeutic dose of 0.83 mg/ mL. Human model simulations suggest that 43 W/kg SAR Theo would be required to obtain 42 °C within the centre of a liver tumor (Tumor size, bounding box x = 64, y = 61, z = 65 [mm]), and that the temperature distribution is inhomogeneous within the tumor. Our study suggests that this approach could potentially be used to increase the temperature within cells that would result in cancer cell death due to hyperthermia. Further development of this research will also involve using whole tumors removed from living organisms in conjunction with magnetic resonance imaging and positron emission tomography.