title: Imaging epidermal growth factor receptor phosphorylation in human colorectal cancer cells and human tissues.
abstract: In tumor cells, high phosphorylation levels of receptor tyrosine kinases may occur in the absence of exogenous ligands due to autocrine signaling or enhanced tyrosine kinase activity. Here we show that the phosphorylation state of the endogenous epidermal growth factor receptor (EGFR) can be quantitatively imaged in tumor cells and tissues by detecting fluorescence resonance energy transfer between fluorophores conjugated to antibodies against the receptor and phosphotyrosine, respectively. Five different human colorectal cell lines were analyzed for activity and expression of EGFR. All cell lines exhibited basal EGFR phosphorylation under serum starvation conditions. Phosphorylation levels increased after stimulation with EGF or pervanadate, dependent on the level of basal EGFR phosphorylation in the respective cell lines. This basal activity correlated inversely with receptor expression. Using the acceptor photobleaching fluorescence resonance energy transfer imaging approach, a significantly higher phosphorylation state of EGFR was also found in resected human colorectal tumor samples as compared with adjacent healthy tissue. Imaging of EGFR phosphorylation may thus serve as a valuable tool to investigate the role of receptor tyrosine kinase activity in malignant cell growth.
authors.affiliation: Surgical Clinic, University Hospital Mannheim, D-68167 Mannheim, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Keese
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Magdeburg
authors.forename: Torsten
authors.initials: T
authors.lastname: Herzog
authors.forename: Till
authors.initials: T
authors.lastname: Hasenberg
authors.forename: Martin
authors.initials: M
authors.lastname: Offterdinger
authors.forename: Rainer
authors.initials: R
authors.lastname: Pepperkok
authors.forename: Jörg W
authors.initials: JW
authors.lastname: Sturm
authors.forename: Philippe I H
authors.initials: PI
authors.lastname: Bastiaens
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003001:Cloning, Molecular; D015179:Colorectal Neoplasms / Q000378:metabolism*; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D066246:ErbB Receptors / Q000737:chemistry* / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D007700:Kinetics; D018613:Microscopy, Confocal / Q000379:methods*; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013997:Time Factors; D014638:Vanadates / Q000494:pharmacology
chemical_list: D016895:Culture Media, Serum-Free; D018076:DNA, Complementary; C076715:pervanadate; D019000:Phosphotyrosine; D014638:Vanadates; D012313:RNA; D066246:ErbB Receptors; D020794:Receptor Protein-Tyrosine Kinases