title: Identification of Anti-CA125 Antibody Responses in Ovarian Cancer Patients by a Novel Deep Sequence-Coupled Biopanning Platform.
abstract: High-grade epithelial ovarian cancer kills more women than any other gynecologic cancer and is rarely diagnosed at an early stage. We sought to identify tumor-associated antigens (TAA) as candidate diagnostic and/or immunotherapeutic targets by taking advantage of tumor autoantibody responses in individuals with ovarian cancer. Plasma-derived IgG from a pool of five patients with advanced ovarian cancer was subjected to iterative biopanning using a library of bacteriophage MS2 virus-like particles (MS2-VLPs) displaying diverse short random peptides. After two rounds of biopanning, we analyzed the selectant population of MS2-VLPs by Ion Torrent deep sequencing. One of the top 25 most abundant peptides identified (DISGTNTSRA) had sequence similarity to cancer antigen 125 (CA125/MUC16), a well-known ovarian cancer-associated antigen. Mice immunized with MS2-DISGTNTSRA generated antibodies that cross-reacted with purified soluble CA125 from ovarian cancer cells but not membrane-bound CA125, indicating that the DISGTNTSRA peptide was a CA125/MUC16 peptide mimic of soluble CA125. Preoperative ovarian cancer patient plasma (n = 100) was assessed for anti-DISGTNTSRA, anti-CA125, and CA125. Patients with normal CA125 (<35 IU/mL) at the time of diagnosis had significantly more antibodies to DISGTNTSRA and to CA125 than those patients who had high CA125 (>35 IU/mL). A statistically significant survival advantage was observed for patients who had either normal CA125 and/or higher concentrations of antibodies to CA125 at the time of diagnosis. These data show the feasibility of using deep sequence-coupled biopanning to identify TAA autoantibody responses from cancer patient plasma and suggest a possible antibody-mediated mechanism for low CA125 plasma concentrations in some ovarian cancer patients.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Frietze
authors.affiliation: Department of Pathology, The Johns Hopkins University, Baltimore, Maryland.
authors.forename: Richard B S
authors.initials: RB
authors.lastname: Roden
authors.affiliation: Biostatistics Shared Resource, University of New Mexico Cancer Center, Albuquerque, New Mexico.
authors.forename: Ji-Hyun
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Biostatistics Shared Resource, University of New Mexico Cancer Center, Albuquerque, New Mexico.
authors.forename: Yang
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico.
authors.forename: David S
authors.initials: DS
authors.lastname: Peabody
authors.affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico. BChackerian@salud.unm.edu.
authors.forename: Bryce
authors.initials: B
authors.lastname: Chackerian
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000917:Antibody Formation / Q000276:immunology*; D001323:Autoantibodies / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D018394:CA-125 Antigen / Q000737:chemistry / Q000276:immunology*; D000077216:Carcinoma, Ovarian Epithelial; D018985:Epitopes, B-Lymphocyte / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D005260:Female; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D051379:Mice; D009367:Neoplasm Staging; D009375:Neoplasms, Glandular and Epithelial / Q000235:genetics / Q000276:immunology; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000276:immunology* / Q000401:mortality / Q000473:pathology; D010455:Peptides / Q000737:chemistry / Q000235:genetics; D016016:Proportional Hazards Models
chemical_list: D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D018394:CA-125 Antigen; D018985:Epitopes, B-Lymphocyte; D007074:Immunoglobulin G; D010455:Peptides