title: High interstitial fluid pressure is associated with low tumour penetration of diagnostic monoclonal antibodies applied for molecular imaging purposes.
abstract: The human epithelial cell adhesion molecule (EpCAM) is highly expressed in a variety of clinical tumour entities. Although an antibody against EpCAM has successfully been used as an adjuvant therapy in colon cancer, this therapy has never gained wide-spread use. We have therefore investigated the possibilities and limitations for EpCAM as possible molecular imaging target using a panel of preclinical cancer models. Twelve human cancer cell lines representing six tumour entities were tested for their EpCAM expression by qPCR, flow cytometry analysis and immunocytochemistry. In addition, EpCAM expression was analyzed in vivo in xenograft models for tumours derived from these cells. Except for melanoma, all cell lines expressed EpCAM mRNA and protein when grown in vitro. Although they exhibited different mRNA levels, all cell lines showed similar EpCAM protein levels upon detection with monoclonal antibodies. When grown in vivo, the EpCAM expression was unaffected compared to in vitro except for the pancreatic carcinoma cell line 5072 which lost its EpCAM expression in vivo. Intravenously applied radio-labelled anti EpCAM MOC31 antibody was enriched in HT29 primary tumour xenografts indicating that EpCAM binding sites are accessible in vivo. However, bound antibody could only be immunohistochemically detected in the vicinity of perfused blood vessels. Investigation of the fine structure of the HT29 tumour blood vessels showed that they were immature and prone for higher fluid flux into the interstitial space. Consistent with this hypothesis, a higher interstitial fluid pressure of about 12 mbar was measured in the HT29 primary tumour via "wick-in-needle" technique which could explain the limited diffusion of the antibody into the tumour observed by immunohistochemistry.
authors.affiliation: Institute of Anatomy and Experimental Morphology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. ma.heine@uke.uni-hamburg.de
authors.forename: Markus
authors.initials: M
authors.lastname: Heine
authors.forename: Barbara
authors.initials: B
authors.lastname: Freund
authors.forename: Peter
authors.initials: P
authors.lastname: Nielsen
authors.forename: Caroline
authors.initials: C
authors.lastname: Jung
authors.forename: Rudolph
authors.initials: R
authors.lastname: Reimer
authors.forename: Heinrich
authors.initials: H
authors.lastname: Hohenberg
authors.forename: Uwe
authors.initials: U
authors.lastname: Zangemeister-Wittke
authors.forename: Hans-Juergen
authors.initials: HJ
authors.lastname: Wester
authors.forename: Georg H
authors.initials: GH
authors.lastname: Lüers
authors.forename: Udo
authors.initials: U
authors.lastname: Schumacher
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D000912:Antibodies, Neoplasm / Q000276:immunology / Q000494:pharmacology*; D000951:Antigens, Neoplasm / Q000276:immunology / Q000378:metabolism*; D001665:Binding Sites; D018938:Caco-2 Cells; D015815:Cell Adhesion Molecules / Q000276:immunology / Q000378:metabolism*; D000071858:Epithelial Cell Adhesion Molecule; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000276:immunology / Q000378:metabolism*; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D011312:Pressure; D011859:Radiography; D014183:Transplantation, Heterologous
chemical_list: D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; C499379:EPCAM protein, human; D000071858:Epithelial Cell Adhesion Molecule; D009363:Neoplasm Proteins