U-2932: two clones in one cell line, a tool for the study of clonal evolution

• Published in: Leukemia Vol. 27; no. 5; pp. 1155 - 1164
• Main Authors: Quentmeier, H, Amini, R M, Berglund, M, Dirks, W G, Ehrentraut, S, Geffers, R, MacLeod, R A F, Nagel, S, Romani, J, Scherr, M, Zaborski, M, Drexler, H G
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-05-2013; Nature Publishing Group
• Subjects: 631/67/1990/291/1621/1915; 631/67/2329; 631/67/395; 692/420/2780/2152/2040; ADP-ribosyl Cyclase 1 - analysis; Antigens, CD20 - analysis; B-cell lymphoma; Base Sequence; Bcl-6 protein; BCL2; BCL6; Cancer Research; CD20 antigen; CD38 antigen; Cell culture; Cell Line, Tumor; Cell surface; Chromosome Aberrations; Clonal Evolution; Cloning; Critical Care Medicine; Cytogenetics; DLBCL; DNA methylation; DNA microarrays; DNA-Binding Proteins - genetics; Ectopic expression; Epigenesis, Genetic; Epigenetics; Functional analysis; Gene expression; Gene silencing; Genes; Genes, bcl-2; Genetic aspects; Genetic transcription; Health aspects; Hematology; Heterogeneity; Humans; Hybridization; Immunoglobulins; Immunophenotyping; Intensive; Internal Medicine; Leukemia; Lymphocytes B; Lymphoma; Lymphoma, Large B-Cell, Diffuse - genetics; Lymphoma, Large B-Cell, Diffuse - immunology; Medicine; Medicine & Public Health; Microorganisms; Molecular Sequence Data; MYC; Myc protein; Non-Hodgkin's lymphomas; Oncogenes; Oncology; original-article; Populations; Proto-Oncogene Proteins c-bcl-6; Receptors, CXCR4 - genetics; Somatic Hypermutation, Immunoglobulin; Surface markers; Transcription; Transcriptome; Tumors; Germany; United States > US; Sweden; BCL2; DLBCL; BCL6; clonal evolution; MYC
• ISSN: 0887-6924; 1476-5551; 1476-5551
• DOI: 10.1038/leu.2012.358

Genetic heterogeneity is common in tumors, explicable by the development of subclones with distinct genetic and epigenetic alterations. We describe an
in vitro
model for cancer heterogeneity, comprising the diffuse large B-cell lymphoma cell line U-2932 which expresses two sets of cell surface markers representing twin populations flow-sorted by CD20 vs CD38 expression. U-2932 populations were traced to subclones of the original tumor with clone-specific immunoglobulin IgV
H
4–39 hypermutation patterns.
BCL6
was overexpressed in one subpopulation (R1),
MYC
in the other (R2), both clones overexpressed
BCL2
. According to the combined results of immunoglobulin hypermutation and cytogenetic analysis, R1 and R2 derive from a mother clone with genomic
BCL2
amplification, which acquired secondary rearrangements leading to the overexpression of
BCL6
(R1) or
MYC
(R2). Some 200 genes were differentially expressed in R1/R2 microarrays including transcriptional targets of the aberrantly expressed oncogenes. Other genes were regulated by epigenetic means as shown by DNA methylation analysis. Ectopic expression of
BCL6
in R2 variously modulated new candidate target genes, confirming dual silencing and activating functions. In summary, stable retention of genetically distinct subclones in U-2932 models tumor heterogeneity
in vitro
permitting functional analysis of oncogenes against a syngenic background.