title: Changes in [18F]Fluoro-2-deoxy-D-glucose incorporation induced by doxorubicin and anti-HER antibodies by breast cancer cells modulated by co-treatment with metformin and its effects on intracellular signalling.
abstract: OBJECTIVE
  Metformin, currently undergoing clinical trials as an adjuvant for the treatment of breast cancer, modulates the activity of key intracellular signalling molecules which affect 2-[(18)F]Fluoro-2-deoxy-D-glucose ([(18)F]FDG) incorporation. Here, we investigate the effect of drugs used in the treatment of breast cancer combined with metformin on [(18)F]FDG incorporation in HER2- or HER1-overexpressing breast cancer cells to determine whether or not metformin may obscure changes in [(18)F]FDG incorporation induced by clinically utilised anticancer drugs in the treatment of breast cancer.
  
  
  METHODS
  Three breast cancer cell lines expressing HER2 and one HER2 negative but HER1 positive were exposed to metformin, doxorubicin and trastuzumab or cetuximab. Cytotoxicity was measured by the MTT assay. Expression of active (phospho-) AMPK, PKB (Akt) and ERK was determined by Western blotting. [(18)F]FDG incorporation by cells exposed to drug combinations with metformin was determined. Glucose transport was assessed by measuring the initial rate of uptake of [(3)H]O-methyl-D-glucose ([(3)H]OMG). Phosphorylation of [(18)F]FDG was determined in intact cells after exposure to [(18)F]FDG.
  
  
  RESULTS
  Phospho-AMPK was increased by metformin in all cell lines whilst phospho-Akt and phospho-ERK expressions were decreased in two. Metformin treatment increased [(18)F]FDG incorporation in all cell lines, and treatment with anti-HER antibodies or doxorubicin only produced minor modulations in the increase induced by metformin alone. Glucose transport was increased in BT474 cells and decreased in SKBr3 and MDA-MB-468 cells after treatment with metformin. The fraction of phosphorylated [(18)F]FDG was increased in metformin-treated cells compared with controls, suggesting that hexokinase efficiency was increased by metformin.
  
  
  CONCLUSIONS
  This is the first study to show that increased [(18)F]FDG incorporation by breast cancer cells induced by metformin overwhelms the effect of doxorubicin and anti-HER treatments on [(18)F]FDG incorporation. Metformin-induced increased [(18)F]FDG incorporation was consistently associated with enhanced [(18)F]FDG phosphorylation.
authors.affiliation: Biomedical Physics Building, School of Medicine and Dentistry, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, Scotland, UK, alasdair.c.cooper.10@aberdeen.ac.uk.
authors.forename: Alasdair C
authors.initials: AC
authors.lastname: Cooper
authors.forename: Ian N
authors.initials: IN
authors.lastname: Fleming
authors.forename: Su M
authors.initials: SM
authors.lastname: Phyu
authors.forename: Tim A D
authors.initials: TA
authors.lastname: Smith
mesh_terms: D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000276:immunology / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D000068818:Cetuximab / Q000008:administration & dosage / Q000494:pharmacology; D004317:Doxorubicin / Q000008:administration & dosage / Q000494:pharmacology*; D004347:Drug Interactions; D066246:ErbB Receptors / Q000276:immunology; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008687:Metformin / Q000008:administration & dosage / Q000494:pharmacology*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015398:Signal Transduction / Q000187:drug effects; D000068878:Trastuzumab / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D004317:Doxorubicin; D008687:Metformin; D066246:ErbB Receptors; D053148:Caspase 3; D053179:Caspase 7; D000068878:Trastuzumab; D000068818:Cetuximab