Molecular characterization of complete and incomplete immunoglobulin heavy chain gene rearrangements in hairy cell leukemia.
OBJECTIVE
We analyzed patients with hairy cell leukemia (HCL) to achieve a better understanding of the differentiation stage reached by HCL cells and to define the key role of the diversification of cell surface makers, especially CD25 expression.


METHODS
We analyzed 38 previously untreated patients with HCL to characterize their complete (VDJ(H)) and incomplete (DJ(H)) immunoglobulin (Ig) heavy chain (IgH) rearrangements, including somatic hypermutation pattern and gene segment use.


RESULTS
A correlation between immunophenotypic profile and molecular data was seen. All 38 cases showed monoclonal amplifications: VDJ(H) in 97%, DJ(H) in 42%, and both in 39%. Segments from the D(H)3 family were used more in complete compared with incomplete rearrangements (45% vs. 12%; P < .005). Furthermore, comparison between molecular and immunophenotypic characteristics disclosed differences in the expression of CD25 antigen; CD25(-) cases, a phenotype associated with HCL variant, showed complete homology to the germline in 3 of 5 cases (60%), whereas this characteristic was never observed in CD25(+) cases (P < .005). Moreover, V(H)4-34, V(H)1-08, and J(H)3 segments appeared in 2, 1, and 2 CD25(-) cases, respectively, whereas they were absent in all CD25(+) cases.


CONCLUSIONS
These results support that HCL is a heterogeneous entity including subgroups with different molecular characteristics, which reinforces the need for additional studies with a larger number of patients to clarify the real role of gene rearrangements in HCL.
Martín-Jiménez
Patricia
P
Servicio de Hematología, Hospital Universitario de Salamanca, Centro de Investigación del Cáncer, Universidad de Salamanca, Spain.
García-Sanz
Ramón
R
González
David
D
Balanzategui
Ana
A
Pérez
José J
JJ
Caballero
M Dolores
MD
Sarasquete
M Eugenia
ME
Galende
Josefina
J
Orfao
Alberto
A
López-Berges
M Consuelo
MC
San Miguel
Jesús F
JF
González
Marcos
M
D015321:Gene Rearrangement; D015894:Genome, Human; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D016130:Immunophenotyping; D007943:Leukemia, Hairy Cell / Q000235:genetics* / Q000276:immunology*; D009154:Mutation; D050441:VDJ Exons
D007143:Immunoglobulin Heavy Chains