CORRESPONDENCE

More About: B-Cell Non-Hodgkin's Lymphoma: Evidence for the t(14;18) Translocation in All Hematopoietic Cell Lineages

John Apostolidis, Debra M. Lillington, Lindsey K. Goff, Emma L. Jones, T. Andrew Lister, Rajnish K. Gupta

Affiliation of authors: Imperial Cancer Research Fund (ICRF), Medical Oncology Unit, St. Bartholomew's Hospital, London, U.K.

Correspondence to: Rajnish K Gupta, B.Sc., Ph.D., FRCP, ICRF Medical Oncology Unit, St. Bartholomew's Hospital, 45 Little Britain, West Smithfield, London EC1A 7BE U.K. (e-mail: r.gupta{at}icrf.icnet.uk).

Follicular lymphoma is a mature B-cell lymphoma, characterized by the presence of the t(14;18) translocation that juxtaposes the BCL2 locus on chromosome 18q21 to the immunoglobulin H (IgH) locus on chromosome 14q32, resulting in overexpression of the antiapoptotic protein Bcl2 (1). In a previous issue of the Journal, Yarkoni et al. (2) demonstrated t(14;18) fluorescence in situ hybridization (FISH) signals in nearly 100% of fluorescence-activated cell-sorted (FACS) fractionated CD34+ hematopoietic stem cells and (B-cell, T-cell, myeloid, erythroid, and megakaryocytic) committed progenitor cells derived from this lineage in seven of the eight t(14;18)-positive patients with non-Hodgkin's lymphoma analyzed. The authors concluded that the t(14;18) occurs in an early multilineage progenitor stem cell. A subsequent letter by Siebert et al. (3) disagreed and stated that it was unlikely that, in the majority of B-cell lymphomas, the t(14;18) translocation occurs in a very early multilineage progenitor cell.

Currently, positive selection of the CD34+ hematopoietic progenitor cell fraction is being evaluated as a strategy to eliminate t(14;18)-bearing cells from reinfused grafts. In our experience at St. Bartholomew's Hospital, CD34+ selection by use of an avidin-biotin immunoadsorption device can eliminate all polymerase chain reaction (PCR)-detectable t(14;18)-bearing cells from 50% of contaminated peripheral blood progenitor cell collections obtained from patients with follicular lymphoma (4). The purity of the CD34+ fraction obtained with this device is highly variable, suggesting that tumor cells escape the positive selection process and continue to contaminate the reinfused CD34 concentrate. To investigate whether the CD34+ compartment in these CD34 concentrates contributes to contamination with t(14;18)-bearing cells, a FISH assay using 40-kilobase cosmids for the IgH (constant) region and BCL2 (major breakpoint region) was combined with immunophenotyping for CD34 (FICTION technique) (3,5). Cells were also subjected to immunohistochemistry to detect Bcl2 protein.

Control studies were performed on lymphocytes from normal individuals, and the cutoff level for a false-positive FISH signal was set at 2% (±0.4% standard deviation). Cytospin preparations made from cryopreserved CD34 concentrates from seven patients with follicular lymphoma who received high-dose chemotherapy and reinfusion of CD34 concentrates were analyzed. Five of these concentrates contained a PCR-detectable t(14;18) translocation. FICTION analysis demonstrated t(14;18) fusion signals above the cutoff level in CD34+ cells from three patients—15%, 4.8%, and 4.6%, respectively. In one patient's sample, the high percentage of t(14;18) colocalization signals in the CD34+ compartment (Fig. 1)Go as opposed to that in the CD34- compartment of the CD34 concentrate (15% versus 7%, respectively) (data not shown) lends further support to the hypothesis that the t(14;18) translocation occurs in CD34+ cells. In the remaining four patients, the detection of t(14;18) fusion signals in 2.5%-3% of CD34+ cells was difficult to interpret in view of the false-positive rate. The low number of cells expressing Bcl2 (0%-1.5%) suggests that the majority of CD34+ t(14;18)-bearing cells do not have increased expression of Bcl2 protein and may well correspond to detectable "physiological" rearrangements, similar to those detected in normal individuals (6).



View larger version (96K):
[in this window]
[in a new window]
 
Fig. 1. A CD34+ cell (aminomethyl coumarin acetic acid [AMCA]-anti-CD34, blue signal) with a positive fluorescence in situ hybridization signal (red-green signal, arrowhead) from one patient (original magnification x250).

 
In partial agreement with results reported by Yarkoni et al. (2), our results also demonstrate that the t(14;18) translocation is detected in CD34+ cells. However, we observed positive FISH signals in only a small proportion of cells. This finding favors the hypothesis that the t(14;18) translocation occurs during early B-cell development (CD34+19+) at the pro-B cell (7) rather than in an early multilineage hematopoietic stem cell. This finding also lends support to the hypothesis that nonmalignant t(14;18)-positive CD34+ cells are "regularly" generated in the bone marrow.

EDITOR'S NOTE

Shai Yarkoni et al. declined to respond to John Apostolidis et al.'s correspondence.

REFERENCES

1 Cleary ML, Smith SD, Sklar J. Cloning and structural analysis of cDNAs for bcl-2 and a hybrid bcl-2/immunoglobulin transcript resulting from the t(14;18) translocation. Cell 1986;47:19-28.[Medline]

2 Yarkoni S, Lishner M, Tangi I, Nagler A, Lorberboum-Galski H. B-cell non-Hodgkin's lymphoma: evidence for the t(14;18) translocation in all hematopoietic cell lineages. J Natl Cancer Inst 1996;88:973-9.[Abstract/Free Full Text]

3 Siebert R, Weber-Matthiesen K, Matthiesen P, Zhang Y, Schlegelberger B. Re: B-cell non-Hodgkin's lymphoma: evidence for the t(14;18) translocation in all hematopoietic cell lineages [letter]. J Natl Cancer Inst 1997;89:93-5.[Free Full Text]

4 Apostolidis J, Gupta RK, Summers K, Ledchumykanthan K, Okukenu E, Salam A, et al. Concentrated CD34+ cells derived from the blood to support myeloablative therapy in patients with follicular lymphoma [abstract]. Blood 1997;90(Suppl):350b.

5 Poetsch M, Weber-Matthiesen K, Plendl HJ, Grote W, Schlegelberger B. Detection of the t(14;18) chromosomal translocation by interphase cytogenetics with yeast-artificial-chromosome probes in follicular lymphoma and nonneoplastic lymphoproliferation. J Clin Oncol 1996;14:963-9.[Abstract]

6 Liu Y, Hernandez AM, Shibata D, Cortopassi GA. BCL2 translocation frequency rises with age in humans. Proc Natl Acad Sci U S A 1994;91:8910-4.[Abstract]

7 Macintyre EA, Belanger C, Debert C, Canioni D, Turhan AG, Azagury M, et al. Detection of clonal CD34+19+ progenitors in bone marrow of BCL2-IgH-positive follicular lymphoma patients. Blood 1995;86:4691-8.[Abstract/Free Full Text]



             
Copyright © 1999 Oxford University Press (unless otherwise stated)
Oxford University Press Privacy Policy and Legal Statement