title: Comparison of 3D and 2D tumor models reveals enhanced HER2 activation in 3D associated with an increased response to trastuzumab.
abstract: Three-dimensional (3D) cell culture techniques are frequently used to model alterations in tissue architecture critically important for tumor development. Here, we report on a detailed comparison of a spheroid model of human epidermal growth factor receptor (HER2) overexpressing cancer cells with the traditional monolayer culture. In 2D culture, HER2 and HER3 form heterodimers, whereas in multicellular spheroids HER2 homodimers are formed. These homodimers localize in membrane rafts, resulting in enhanced inhibition of the proliferation of cancer cells with trastuzumab (Herceptin), a monoclonal antibody specifically targeting HER2. Within the tumor spheroids, HER2 homodimerization leads to enhanced activation of HER2 and results in a switch in signaling pathways from phosphoinositide 3-kinase (PI3K) to mitogen-activated protein kinase (MAPK). Diminished PI3K signaling is accompanied by the activation of the integrin beta4/Rac1/PAK 2 signaling cascade. We propose that the described 3D culture system may better reflect some in vivo aspects of HER signaling and can be used to further improve the understanding of the molecular mechanisms of trastuzumab action. Furthermore, the described human multicellular tumor spheroids may allow identification of new targets for the treatment of HER2-positive breast cancer patients who currently benefit suboptimally from trastuzumab treatment.
authors.affiliation: Roche Diagnostics GmbH, Pharmaceutical Research Oncology, Penzberg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Pickl
authors.forename: C H
authors.initials: CH
authors.lastname: Ries
mesh_terms: D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D018929:Cell Culture Techniques; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019281:Dimerization; D006801:Humans; D016023:Integrins / Q000378:metabolism; D021962:Membrane Microdomains; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D018874:Spheroids, Cellular / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000068878:Trastuzumab; D014407:Tumor Cells, Cultured; D054462:p21-Activated Kinases / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D016023:Integrins; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein; C107953:RAC1 protein, human