High-density screening reveals a different spectrum of genomic aberrations in chronic lymphocytic leukemia patients with 'stereotyped' IGHV3-21 and IGHV4-34 B-cell receptors.
BACKGROUND
The existence of multiple subsets of chronic lymphocytic leukemia expressing 'stereotyped' B-cell receptors implies the involvement of antigen(s) in leukemogenesis. Studies also indicate that 'stereotypy' may influence the clinical course of patients with chronic lymphocytic leukemia, for example, in subsets with stereotyped IGHV3-21 and IGHV4-34 B-cell receptors; however, little is known regarding the genomic profile of patients in these subsets.


METHODS
We applied 250K single nucleotide polymorphism-arrays to study copy-number aberrations and copy-number neutral loss-of-heterozygosity in patients with stereotyped IGHV3-21 (subset #2, n=29), stereotyped IGHV4-34 (subset #4, n=17; subset #16, n=8) and non-subset #2 IGHV3-21 (n=13) and non-subset #4/16 IGHV4-34 (n=34) patients.


RESULTS
Over 90% of patients in subset #2 and non-subset #2 carried copy-number aberrations, whereas 75-76% of patients in subset #4 and subset #16 showed copy-number aberrations. Subset #2 and non-subset #2 patients also displayed a higher average number of aberrations compared to patients in subset #4. Deletion of 13q was the only known recurrent aberration detected in subset #4 (35%); this aberration was even more frequent in subset #2 (79%). del(11q) was more frequent in subset #2 and non-subset #2 (31% and 23%) patients than in subset #4 and non-subset #4/16 patients. Recurrent copy-number neutral loss-of-heterozygosity was mainly detected on chromosome 13q, independently of B-cell receptor stereotypy.


CONCLUSIONS
Genomic aberrations were more common in subset #2 and non-subset #2 than in subset #4. The particularly high frequency of del(11q) in subset #2 may be linked to the adverse outcome reported for patients in this subset. Conversely, the lower prevalence of copy-number aberrations and the absence of poor-prognostic aberrations in subset #4 may reflect an inherently low-proliferative disease, which would prevent accumulation of genomic alterations.
Marincevic
Millaray
M
Department of Genetics and Pathology, Rudbeck Laboratory, Uppsala University, SE-751-85 Uppsala, Sweden.
Cahill
Nicola
N
Gunnarsson
Rebeqa
R
Isaksson
Anders
A
Mansouri
Mahmoud
M
Göransson
Hanna
H
Rasmussen
Markus
M
Jansson
Mattias
M
Ryan
Fergus
F
Karlsson
Karin
K
Adami
Hans-Olov
HO
Davi
Fred
F
Jurlander
Jesper
J
Juliusson
Gunnar
G
Stamatopoulos
Kostas
K
Rosenquist
Richard
R
D000368:Aged; D000369:Aged, 80 and over; D002869:Chromosome Aberrations; D005260:Female; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics* / Q000276:immunology; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D011379:Prognosis; D011947:Receptors, Antigen, B-Cell
D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D011947:Receptors, Antigen, B-Cell