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J Dermatol Sci. 2017 Nov;88(2):238-246. doi: 10.1016/j.jdermsci.2017.07.008. Epub 2017 Jul 26.

Molecular analysis of immunoglobulin variable genes supports a germinal center experienced normal counterpart in primary cutaneous diffuse large B-cell lymphoma, leg-type.

Author information

1
INSERM U1053, Team 3 Oncogenesis of Cutaneous Lymphomas, Univ. Bordeaux, 146 rue Léo Saignat, 33076 Bordeaux, France; Dermatology Department, CHU Bordeaux,1 avenue Jean Burguet, 33000 Bordeaux, France. Electronic address: anne.pham@ledard.org.
2
INSERM U1053, Team 3 Oncogenesis of Cutaneous Lymphomas, Univ. Bordeaux, 146 rue Léo Saignat, 33076 Bordeaux, France.
3
UMR CNRS 7276, Univ. Limoges,2 avenue Martin Luther King, 87042 Limoges, France.
4
INSERM U1053, Team 3 Oncogenesis of Cutaneous Lymphomas, Univ. Bordeaux, 146 rue Léo Saignat, 33076 Bordeaux, France; Dermatology Department, CHU Bordeaux,1 avenue Jean Burguet, 33000 Bordeaux, France.
5
INSERM U1053, Team 3 Oncogenesis of Cutaneous Lymphomas, Univ. Bordeaux, 146 rue Léo Saignat, 33076 Bordeaux, France; Pathology Department, CHU Bordeaux,Avenue de Magellan, 33604 Pessac, France.
6
INSERM U1053, Team 3 Oncogenesis of Cutaneous Lymphomas, Univ. Bordeaux, 146 rue Léo Saignat, 33076 Bordeaux, France; Tumor Bank and Tumor Biology Laboratory,Avenue de Magellan, CHU Bordeaux, 33604 Pessac, France.

Abstract

BACKGROUND:

Immunophenotype of primary cutaneous diffuse large B-cell lymphoma, leg-type (PCLBCL-LT) suggests a germinal center-experienced B lymphocyte (BCL2+ MUM1+ BCL6+/-).

OBJECTIVES:

As maturation history of B-cell is "imprinted" during B-cell development on the immunoglobulin gene sequence, we studied the structure and sequence of the variable part of the genes (IGHV, IGLV, IGKV), immunoglobulin surface expression and features of class switching in order to determine the PCLBCL-LT cell of origin.

METHODS:

Clonality analysis with BIOMED2 protocol and VH leader primers was done on DNA extracted from frozen skin biopsies on retrospective samples from 14 patients. The clonal DNA IGHV sequence of the tumor was aligned and compared with the closest germline sequence and homology percentage was calculated. Superantigen binding sites were studied. Features of selection pressure were evaluated with the multinomial Lossos model.

RESULTS:

A functional monoclonal sequence was observed in 14 cases as determined for IGHV (10), IGLV (2) or IGKV (3). IGV mutation rates were high (>5%) in all cases but one (median:15.5%), with superantigen binding sites conservation. Features of selection pressure were identified in 11/12 interpretable cases, more frequently negative (75%) than positive (25%). Intraclonal variation was detected in 3 of 8 tumor specimens with a low rate of mutations. Surface immunoglobulin was an IgM in 12/12 cases. FISH analysis of IGHM locus, deleted during class switching, showed heterozygous IGHM gene deletion in half of cases. The genomic PCR analysis confirmed the deletions within the switch μ region. IGV sequences were highly mutated but functional, with negative features of selection pressure suggesting one or more germinal center passage(s) with somatic hypermutation, but superantigen (SpA) binding sites conservation. Genetic features of class switch were observed, but on the non functional allele and co-existing with primary isotype IgM expression.

CONCLUSION:

These data suggest that cell-of origin is germinal center experienced and superantigen driven selected B-cell, in a stage between germinal center B-cell and plasma cell.

KEYWORDS:

Cell-of-origin; Class switch recombination; IGV gene mutation; Leg-type; Primary cutaneous diffuse large B-cell lymphoma; Superantigen

PMID:
28838616
DOI:
10.1016/j.jdermsci.2017.07.008
[Indexed for MEDLINE]

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