ABSTRACT
UNLABELLED: Signaling via the MET receptor tyrosine kinase has been implicated in crosstalk with cellular responses to DNA damage. Our group previously demonstrated that MET inhibition in tumor cells with deregulated MET activity results in radiosensitization via downregulation of the ATR-CHK1-CDC25 pathway, a major signaling cascade responsible for intra-S and G2-M cell-cycle arrest following DNA damage. Here we aimed at studying the potential therapeutic application of ionizing radiation in combination with a MET inhibitor, EMD-1214063, in p53-deficient cancer cells that harbor impaired G1-S checkpoint regulation upon DNA damage. We hypothesized that upon MET inhibition, p53-deficient cells would bypass both G1-S and G2-M checkpoints, promoting premature mitotic entry with substantial DNA lesions and cell death in a greater extent than p53-proficient cells. Our data suggest that p53-deficient cells are more susceptible to EMD-1214063 and combined treatment with irradiation than wild-type p53 lines as inferred from elevated γH2AX expression and increased cytotoxicity. Furthermore, cell-cycle distribution profiling indicates constantly lower G1 and higher G2-M population as well as higher expression of a mitotic marker p-histone H3 following the dual treatment in p53 knockdown isogenic variant, compared with the parental counterpart. IMPLICATIONS: The concept of MET inhibition-mediated radiosensitization enhanced by p53 deficiency is of high clinical relevance, as p53 is frequently mutated in numerous types of human cancer. The current data point for a therapeutic advantage for an approach combining MET targeting along with DNA-damaging agents for MET-positive/p53-negative tumors.
Subject(s)
Cell Cycle Checkpoints/drug effects , Proto-Oncogene Proteins c-met/antagonists & inhibitors , Pyridazines/pharmacology , Pyrimidines/pharmacology , Radiation-Sensitizing Agents/pharmacology , Tumor Suppressor Protein p53/deficiency , Apoptosis , Cell Cycle Checkpoints/radiation effects , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Proliferation/radiation effects , Cell Survival/drug effects , Cell Survival/radiation effects , Gene Expression Regulation, Neoplastic/drug effects , Gene Expression Regulation, Neoplastic/radiation effects , HumansABSTRACT
2-Deoxy-2-[18F]fluoro-D-glucose ([18F] FDG), the most popular positron emitting radiopharmaceutical, may oxidise by autoradiolysis in aqueous solution. The aim of this work was to use LC-MS for determination of the oxidation products of fluorodeoxyglucose and glucose (Glc) obtained by oxidation with Fenton's reagent. Asahipak NH2P-50 polyamide silica column and acetonitrile-0.025% aqueous ammonium formate (80:20 (v/v)) eluent were utilised with an Agilent 1100 HPLC-MS instrument. Ten major oxidation products of FDG and Glc were separated and identified by mass spectrometry: 2-fluorogluconic acid, 2-fluoroglucuronic acid, 2-oxoerythronic acid, arabinose, arabonic acid, araburonic acid, erythrose, erythrulose, gluconic acid, and glucuronic acid. The most intensive electrospray ionisation signals were found in the negative ion spectra and were due to HCOO- adducts, the other acids being in their lactone forms.
