title: HLA-E surface expression is independent of the availability of HLA class I signal sequence-derived peptides in human tumor cell lines.
abstract: Human leukocyte antigen (HLA)-E is a nonclassic HLA class I molecule whose expression at the cell surface of tumor cells might allow them to escape T- and natural killer (NK)-cell immune surveillance. In this study, we analyzed HLA-E expression in a panel of human HLA-typed tumor cell lines of different histotypes by flow cytometry with anti-HLA-E monoclonal antibodies and by reverse transcriptase-polymerase chain reaction. Although specific HLA-E transcripts were detected in all cell lines, except in HELA, surface expression was detected at different intensities on seven (23%) of 30 cell lines with higher frequency and intensity among osteosarcoma cell lines. HLA-E-positive tumor cell lines mainly expressed the HLA-A*02 class I allele. Some tumor cell lines demonstrating HLA class I A* or Cw* alleles, which we expected to allow HLA-E surface expression on the basis of reported data on lymphoid cells, instead were HLA-E negative. All tumor cell lines were either tapasin and TAP-1 positive by flow cytometry, except two osteosarcoma cell lines, a finding that suggests an intact assembly machinery for peptide loading. We conclude that the concomitant presence of the appropriate HLA class I alleles with leader sequence-derived peptides and HLA-E heavy chain may not be sufficient to allow HLA-E surface expression in tumor cell lines as opposed to lymphoid cells.
authors.affiliation: Department of Biology, University of Genova, Italy.
authors.forename: Giulio Lelio
authors.initials: GL
authors.lastname: Palmisano
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Contardi
authors.forename: Anna
authors.initials: A
authors.lastname: Morabito
authors.forename: Vittoria
authors.initials: V
authors.lastname: Gargaglione
authors.forename: Giovanni Battista
authors.initials: GB
authors.lastname: Ferrara
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Pistillo
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000276:immunology; D000483:Alleles; D017920:Antiporters / Q000276:immunology*; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000276:immunology* / Q000378:metabolism; D005434:Flow Cytometry; D006680:HLA Antigens / Q000096:biosynthesis / Q000276:immunology*; D019073:HT29 Cells; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis / Q000276:immunology*; D006801:Humans; D007136:Immunoglobulins / Q000276:immunology*; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals / Q000235:genetics; D000097625:HLA-E Antigens
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D017920:Antiporters; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D000097625:HLA-E Antigens; C073119:TAP1 protein, human; C107762:tapasin