title: Natural humoral immune response to ribosomal P0 protein in colorectal cancer patients.
abstract: BACKGROUND
  Tumor associated antigens are useful in colorectal cancer (CRC) management. The ribosomal P proteins (P0, P1, P2) play an important role in protein synthesis and tumor formation. The immunogenicity of the ribosomal P0 protein in head and neck, in breast and prostate cancer patients and the overexpression of the carboxyl-terminal P0 epitope (C-22 P0) in some tumors were reported.
  
  
  METHODS
  Sera from 72 colorectal tumor patients (67 malignant and 5 benign tumors) were compared with 73 healthy donor sera for the presence of antibodies to CEA, EGFR, ErbB2 and ribosomal P proteins by western blotting or ELISA. Expression of the C-22 P0 epitope on tissues and colon cancer cells was determined by immunoperoxidase staining and indirect immunofluorescence/western blotting, respectively, employing MAb 2B2. Biological effects of MAb 2B2 on colon cancer cells were assessed by the Sulforhodamine B cell proliferation assay, trypan blue exclusion test and cleaved caspase-3 detection. Fisher's exact test was used to compare the number of auto-antibodies positive patients with healthy donors. Variation in the C-22 P0 expression, and in the number of apoptotic cells was evaluated by Student's t-test. Variation in cell survival and cell death was evaluated by Newman-Keuls test.
  
  
  RESULTS
  No significant humoral response was observed to CEA, EGFR and ErbB2 in CRC patients. Conversely, 7 out of 67 CRC patient sera reacted to ribosomal P proteins. The prevalence of P proteins auto-antibodies in CRC patients was significant. Five patients showed restricted P0 immunoreactivity, while two patients reacted simultaneously to all P proteins. The C-22 P0 epitope was homogenously expressed both in malignant tumors and the adjacent mucosa, but the intensity of expression was higher in the tumor. Starved colon cancer cells showed a higher C-22 P0 epitope plasma membrane expression compared to control cells. MAb 2B2 inhibited colon cancer cell growth and induced cell death in a dose dependent manner.
  
  
  CONCLUSIONS
  Our study shows a spontaneous humoral immune response to ribosomal P0 protein in CRC patients and the inhibition of in vitro cancer cell growth after C-22 P0 epitope targeting. The ribosomal P0 protein might be a useful immunological target in CRC patients.
authors.affiliation: Department of Clinical Sciences and Translational Medicine, University of Rome "Tor Vergata", Rome, Italy. monicab4@hotmail.it.
authors.forename: Monica
authors.initials: M
authors.lastname: Benvenuto
authors.affiliation: Department of Experimental Medicine and Surgery, University of Rome "Tor Vergata", Rome, Italy. piersileri@yahoo.com.
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Sileri
authors.affiliation: Department of Experimental Medicine and Surgery, University of Rome "Tor Vergata", Rome, Italy. piero.rossi@uniroma2.it.
authors.forename: Piero
authors.initials: P
authors.lastname: Rossi
authors.affiliation: Department of Experimental Medicine, University of Rome "Sapienza", Rome, Italy. laura.masuelli@uniroma1.it.
authors.forename: Laura
authors.initials: L
authors.lastname: Masuelli
authors.affiliation: Department of Clinical Sciences and Translational Medicine, University of Rome "Tor Vergata", Rome, Italy. max.fantini@libero.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Fantini
authors.affiliation: Department of Clinical Sciences and Translational Medicine, University of Rome "Tor Vergata", Rome, Italy. nanni.monica@libero.it.
authors.forename: Monica
authors.initials: M
authors.lastname: Nanni
authors.affiliation: Department of Experimental Medicine and Surgery, University of Rome "Tor Vergata", Rome, Italy. luana.franceschilli@virgilio.it.
authors.forename: Luana
authors.initials: L
authors.lastname: Franceschilli
authors.affiliation: Laboratory of Tumor Immunology and Immunotherapy, Institute of Translational Pharmacology, Department of Medicine, CNR, Rome, Italy. sconocchiag@yahoo.com.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Sconocchia
authors.affiliation: Laboratory of Tumor Immunology and Immunotherapy, Institute of Translational Pharmacology, Department of Medicine, CNR, Rome, Italy. giulia.lanzilli@ift.cnr.it.
authors.forename: Giulia
authors.initials: G
authors.lastname: Lanzilli
authors.affiliation: Department of Systems Medicine, University of Rome "Tor Vergata", Rome, Italy. roberto.arriga@uniroma2.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Arriga
authors.affiliation: Centro Studi e Ricerche Sanità e Veterinaria Esercito, Rome, Italy. giovanni.faggioni@gmail.com.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Faggioni
authors.affiliation: Centro Studi e Ricerche Sanità e Veterinaria Esercito, Rome, Italy. romano.lista@gmail.com.
authors.forename: Florigio
authors.initials: F
authors.lastname: Lista
authors.affiliation: Department of Biomedicine and Prevention, University of Rome "Tor Vergata", Rome, Italy. orlandi@uniroma2.it.
authors.forename: Augusto
authors.initials: A
authors.lastname: Orlandi
authors.affiliation: Department of Clinical Sciences and Translational Medicine, University of Rome "Tor Vergata", Rome, Italy. manzari@med.uniroma2.it.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Manzari
authors.affiliation: Department of Experimental Medicine and Surgery, University of Rome "Tor Vergata", Rome, Italy. achille.gaspari@gmail.com.
authors.forename: Achille Lucio
authors.initials: AL
authors.lastname: Gaspari
authors.affiliation: Department of Clinical Sciences and Translational Medicine, University of Rome "Tor Vergata", Rome, Italy. modesti@uniroma2.it.
authors.forename: Andrea
authors.initials: A
authors.lastname: Modesti
authors.affiliation: Department of Clinical Sciences and Translational Medicine, University of Rome "Tor Vergata", Rome, Italy. bei@med.uniroma2.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Bei
mesh_terms: D000230:Adenocarcinoma / Q000097:blood / Q000276:immunology / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D001323:Autoantibodies / Q000097:blood; D002272:Carcinoembryonic Antigen / Q000276:immunology; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000097:blood / Q000276:immunology* / Q000473:pathology; D000939:Epitopes / Q000276:immunology; D066246:ErbB Receptors / Q000276:immunology; D005260:Female; D006801:Humans; D056724:Immunity, Humoral; D007413:Intestinal Mucosa / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008875:Middle Aged; D041681:NIH 3T3 Cells; D051381:Rats; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology; D012269:Ribosomal Proteins / Q000276:immunology*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D002272:Carcinoembryonic Antigen; D000939:Epitopes; D066246:ErbB Receptors; D018719:Erb-b2 Receptor Tyrosine Kinases; D012269:Ribosomal Proteins; C054675:ribosomal protein P0; C508053:ERBB2 protein, human