title: Beta2-microglobulin aberrations in diffuse large B-cell lymphoma of the testis and the central nervous system.
abstract: Human leukocyte antigen (HLA) class I molecules are expressed on the surface of all nucleated cells and present antigenic peptides to cytotoxic T cells, thereby playing an important role in initiating the cellular anti-tumor immune response. We previously reported that loss of HLA class I expression in diffuse large B-cell lymphoma (DLBCL) of the central nervous system (CNS) and the testis is a common event. Loss of expression and mutations of the light chain of the HLA class I molecule, beta(2)-microglobulin (beta(2)m) have been described in a variety of human tumors and cell lines. In our study, we screened 15 DLBCL cases with a combined loss of HLA class I and beta(2)m expression for mutations in the latter gene by direct sequencing. Frame shift mutations in repetitive sequences within the beta(2)m gene leading to loss of functional beta(2)m were detected in 2 cases. Loss of heterozygosity (LOH) and fluorescent in situ hybridization (FISH) analysis for chromosome 15 exhibited loss of the remaining copy of the beta(2)m gene in both cases but also hemizygous deletions and monosomies in 6 additional cases. Since similar mutations in the beta(2)m gene have been associated with microsatellite instability (MSI), we used 8 markers to study MSI involvement in DLBCL. Low MSI was more frequent (33%) as compared to nodal DLBCL (n=15) but did not correlate with the beta(2)m mutations. Our data indicate that multiple mechanisms lead to downregulation of beta(2)m and concomitant loss of HLA class I expression in DLBCL.
authors.affiliation: Department of Pathology, Leiden University Medical Center, The Netherlands. k.jordanova@lumc.nl
authors.forename: Ekaterina S
authors.initials: ES
authors.lastname: Jordanova
authors.forename: Sietske A
authors.initials: SA
authors.lastname: Riemersma
authors.forename: Katja
authors.initials: K
authors.lastname: Philippo
authors.forename: Ed
authors.initials: E
authors.lastname: Schuuring
authors.forename: Philip M
authors.initials: PM
authors.lastname: Kluin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000483:Alleles; D001932:Brain Neoplasms / Q000235:genetics*; D002352:Carrier Proteins; D002869:Chromosome Aberrations; D002872:Chromosome Deletion; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics; D017931:DNA Primers / Q000737:chemistry; D015342:DNA Probes / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D006680:HLA Antigens / Q000235:genetics; D006801:Humans; D007124:Immunoenzyme Techniques; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D007399:Interphase / Q000235:genetics; D019656:Loss of Heterozygosity / Q000235:genetics*; D016393:Lymphoma, B-Cell / Q000235:genetics*; D016403:Lymphoma, Large B-Cell, Diffuse / Q000235:genetics*; D008297:Male; D018895:Microsatellite Repeats; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009154:Mutation / Q000235:genetics; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D013736:Testicular Neoplasms / Q000235:genetics*; D001613:beta 2-Microglobulin / Q000235:genetics* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D017931:DNA Primers; D015342:DNA Probes; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; D006680:HLA Antigens; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D001613:beta 2-Microglobulin; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein