title: Antitumor activity of a monoclonal antibody targeting major histocompatibility complex class I-Her2 peptide complexes.
abstract: BACKGROUND
  Applications of trastuzumab are limited to breast cancer patients with high Her2-expressing tumors. We developed a T-cell receptor mimic (TCRm) monoclonal antibody (hereafter called RL1B) that targets the Her2-E75 peptide (residues 369-377)-HLA-A2 complex and examined its effects in Her2-expressing cancer cells.
  
  
  METHODS
  RL1B binding affinity was determined by surface plasmon resonance and specificity was demonstrated using Her2 antigen-positive and negative tumor cell lines. Immunohistochemistry was used to assess binding to frozen sections of human carcinomas (n = 3). Antitumor activity mediated by RL1B and trastuzumab against Her2(+) tumor cell lines was evaluated using the WST-1 cell viability assay and caspase-3 and poly(ADP-ribose) polymerase cleavage assays. A xenograft mouse model (n = 6 per group) was used to assess RL1B antitumor activity. Mechanisms of RL1B-mediated cytotoxicity were evaluated with confocal microscopy, flow cytometry, and histology. All statistical tests were two-sided.
  
  
  RESULTS
  RL1B bound with high specificity and affinity to the E75 peptide-HLA-A2 complex in all Her2(+) and HLA-A2(+) cancer cell lines and human carcinomas. Compared with control antibody, RL1B suppressed growth of low Her2-expressing breast tumors in mice (mean volume, RL1B vs control = 241 mm(3) vs 1531 mm(3); P = .0109) and statistically significantly increased mouse survival (P = .0098). It reduced viability compared to control monoclonal antibody-treated cells and statistically significantly increased caspase 3 activation of all Her2(+) carcinoma cell lines tested, whereas trastuzumab induced apoptosis only in high Her2-expressing cancer cells. Mechanisms of RL1B cytotoxicity were associated with antibody internalization and intracellular signaling.
  
  
  CONCLUSIONS
  The TCRm RL1B could be a new approach to immunotherapy of Her2-expressing malignancies.
authors.affiliation: Center for Immunotherapeutic Research and Department of Immunotherapeutics and Biotechnology, School of Pharmacy, Texas Tech University Health Sciences Center, Abilene, TX 79601, USA.
authors.forename: Rinki
authors.initials: R
authors.lastname: Jain
authors.forename: Amit
authors.initials: A
authors.lastname: Rawat
authors.forename: Bhavna
authors.initials: B
authors.lastname: Verma
authors.forename: Maciej M
authors.initials: MM
authors.lastname: Markiewski
authors.forename: Jon A
authors.initials: JA
authors.lastname: Weidanz
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy; D002277:Carcinoma / Q000188:drug therapy; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D005629:Frozen Sections; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D015789:HLA-A2 Antigen / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007163:Immunosorbent Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D053758:Nanoparticles; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000188:drug therapy; D010446:Peptide Fragments / Q000187:drug effects / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000819:agonists*; D015398:Signal Transduction / Q000187:drug effects; D000068878:Trastuzumab; D015854:Up-Regulation; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D053148:Caspase 3; D015789:HLA-A2 Antigen; D047908:Intracellular Signaling Peptides and Proteins; D015514:Oncogene Proteins, Fusion; D010446:Peptide Fragments; D011065:Poly(ADP-ribose) Polymerases; D018719:Erb-b2 Receptor Tyrosine Kinases; D011948:Receptors, Antigen, T-Cell; D000068878:Trastuzumab; C579076:RL1B monoclonal antibody; C508053:ERBB2 protein, human