A variant translocation t(2;18) in follicular lymphoma involves the 5' end of bcl-2 and Ig kappa light chain gene

We have examined three cases of human lymphoma bearing a t(2;18)(p11;q21) chromosome translocation. The bcl-2 gene appeared to be rearranged in all three cases and breakpoints were clustered in the 5' flanking region of the gene. In all three cases, bcl-2 was juxtaposed to J segments of the Ig kappa gene. This juxtaposition of the bcl-2 and Ig kappa genes is very similar to the variant chromosome translocations of Burkitt lymphoma that juxtapose the c-myc locus to IgL genes.     

Juxtaposition of human bcl-2 and immunoglobulin lambda light chain gene in chronic lymphocytic leukemia is the result of a reciprocal chromosome translocation between chromosome 18 and 22

The human bcl-2 gene is a oncogene candidate which is involved in the t(14;18) translocation specifically associated with follicular and diffuse B cell lymphomas. This translocation deregulates bcl-2 gene expression by placing it into immunoglobulin heavy chain locus (IgH). We have recently reported a case of chronic lymphocytic leukemia (CLL 1446) carrying a unique bcl-2 gene rearrangement with the immunoglobulin lambda light chain (Ig lambda) gene. This juxtaposition of the bcl-2 and Ig lambda genes resembles a variant chromosome translocation in Burkitt's lymphoma, although karyotype data of CLL 1446 is not available. In this paper, we completed the structural analysis of the bcl-2/Ig lambda gene rearrangement in CLL 1446 by cloning the corresponding partner of the rearrangement. This revealed that the juxtaposition of the bcl-2 and Ig lambda genes is a result of a reciprocal chromosome translocation between chromosomes 18 and 22 with deletions of 2 and 15 bp, respectively. Although a conserved immunoglobulin recombination signal (7mer-9mer) was absent around the breakpoint on chromosome 18, nonamer-like sequence was recognized within the deleted region at the breakpoint on chromosome 22. No extranucleotide was associated with both joining sites of the t(18;22) translocation. This is in sharp contrast to the t(14;18) translocation involving IgH locus in which the presence of extranucleotides is common and correlates well with the presence and absence of extranucleotides on V-(D)-J joining of IgH and light chain (L) genes, respectively. The data together suggest that the mechanism responsible for the physiological rearrangement of immunoglobulin genes is involved in this translocation.     

Potential Z-DNA elements surround the breakpoints of chromosome translocation within the 5' flanking region of bcl-2 gene

In follicular lymphoma the majority of t(14;18) chromosome translocations occur at the 3' region of the bcl-2 gene and are juxtaposed to the J region of the immunoglobulin heavy chain gene. Direct involvement of the putative V-(D)-J recombinase in the translocation has been proposed, since the hot spot region of the breakpoints on chromosome 18 possesses the 7/9 signal-like sequence. The 5' flanking region of bcl-2 gene is another hot spot of the translocations which are preferentially associated with chronic lymphocytic leukemia. The translocation in chronic lymphocytic leukemia results in the juxtaposition of the bcl-2 gene to various regions on the immunoglobulin light chain loci. No association of a 7/9 signal sequence and the heterogeneity of the breakpoints within the bcl-2 and IgL loci suggest that the translocations occurring at the 5'-flanking region of the bcl-2 gene might be mediated by a different mechanism from that of the t(14;18) translocation. Here we demonstrate that the breakpoints at the 5' flanking region of bcl-2 gene are surrounded by multiple alternating purine-pyrimidine elements (potential Z-DNA). The antibodies specific to Z-DNA showed that the regions containing the alternating purine-pyrimidine elements were confined to the 5' hot spot region. The data suggest that Z-DNA formation may be involved in chromosome translocations at the 5' flanking region of bcl-2 gene.     

Two Translocations: a Follicular Variant 2; 18 and a Burkitt 8;14 in a Small Non Cleaved Non Hodgkin's Lymphoma

The t(2;18)(p11;q21) has recently been described in two lymphoma cases as a variant of the t(14;18)(q32;q21) typical chromosome translocation in follicular lymphomas. Molecular investigations of t(2;18) confirmed juxtaposition of the bcl-2 gene to the immunoglobulin kappa (Igk) locus and described a new break point region on 18q21 found also in the recently reported, second follicular variant translocation (18;22)(q21;q11). Thus, cytogenetic and molecular studies established the same mechanism of (onco)gene activation by the heavy or light Ig gene in follicular lymphomas and Burkitt lymphomas.

We describe a case of small non cleaved non Hodgkin's lymphoma in which translocation (2;18) coexisted with a typical (8;14) Burkitt translocation. Absent HLA-DR expression by the tumour cells was noted in this case. The possible implications of the cytogenetic and immunologic findings are discussed.     

Pre-B-cell leukemia with a t(8; 14) and a t(14; 18) translocation is preceded by follicular lymphoma

We have performed gene rearrangement studies on the leukemic blasts of a patient with acute pre-B-cell leukemia. The patient had a 5 year history of follicular lymphoma, which developed into acute pre-B-cell leukemia. The leukemic blasts revealed a karyotype with two translocations, t(8; 14) and t(14; 18), characteristic for Burkitt's lymphoma and follicular lymphoma. The cells are TdT positive, do not possess surface immunoglobulin, and they show immunoglobulin gene rearrangement. The mu heavy chain and kappa light chain constant (C mu and C kappa) loci are deleted, while the gamma and lambda light chain constant (C gamma and C lambda) region genes are rearranged. Both alleles of the heavy chain joining segment (JH) are rearranged on chromosome 14q+, one of them with the bcl-2 oncogene from chromosome 18. The breakpoint of the t(14; 18) translocation occurs in the major breakpoint cluster region in the 3' untranslated region of bcl-2. On chromosome 8 a c-myc rearrangement was mapped immediately 5' to the c-myc first exon in a region involved in sporadic Burkitt lymphoma. The data are consistent with our previous hypothesis on the evolution of B-cell malignancies: a rare pre-B cell develops a t(14; 18) translocation during immunoglobulin VDJ joining that results in an expansion of a follicular lymphoma clone carrying an activated bcl-2 gene. Within the clone of pre-B cells a second translocation, t(8; 14), occurs during heavy chain isotype switching that results in the deregulation of the c-myc involved in the translocation.     

Molecular structure of double reciprocal translocations: significance in B-cell lymphomagenesis

The molecular structure of reciprocal translocations associated with low grade and high grade non-Hodgkin's lymphomas occurring together was analysed in two tumors. Sequential biopsies documented histological transformation of a large cell lymphoma to an immunoblastic lymphoma bearing t(14;18)(q32;q21) and t(8;22)(q24;q11). A second tumor, a small non-cleaved cell lymphoma, demonstrated a t(8;14)(q24;q11) as well as t(18;22)(q21;q11). DNA analysis from these tumors showed rearrangements at the Ig heavy chain, kappa and lambda light chains, BCL2 and c-MYC loci. Utilizing multiple enzyme digests and different probes spanning the BCL2, c-MYC and Ig genes, mapping of DNA break-points was performed. In both these tumors primary translocation events dysregulating the BCL2 or c-MYC were identified to have occurred in a pre-B-cell. Based on these results and those published previously, a sequence of B-cell development during which somatic recombination errors lead to the genesis of specific translocations is proposed. From these studies it is inferred that secondary dysregulation of a c-MYC in a lymphoma tumor carrying dysregulated BCL2 gene leads to rapid progression to high grade disease.     

Translocation (14;19)(q32;q13.1) in a Young Patient who Developed a Large Cell Lymphoma after an Initial Diagnosis of CLL

A translocation (14;19)(q32;q13.1) was found in a 31 year old man with a large cell lymphoma which had evolved from chronic lymphocytic leukaemia (CLL). Molecular analysis showed a monoclonal proliferation of B cells with rearrangement of the immunoglobulin (Ig) heavy and kappa light chain genes, and of the bcl-3 gene on chromosome 19q. Nine cases with t(14;19) from the literature were reviewed; B cell lymphoma had been diagnosed in eight and acute biphenotypic leukaemia in one of these cases. Four had transformed from CLL to a more aggressive disease, as in the present case. Two out of seven patients as well as the present one, with t(14;19) and CLL were young (less than 40). The t(14;19) is usually associated with other cytogenetic abnormalities; in our case a (15;16)(q15;p13) translocation was found and appears to be an additional nonrandom aberration in t(14;19) disorders.     

Report of two novel chromosomal translocations in chronic lymphocytic leukemia

Two novel chromosomal translocations were identified in 2 patients with chronic lymphocytic leukemia (CLL). Case 1: 60 year-old male, stage Rai 0/Binet A, with mutated immunoglobulin heavy (IgH) and lambda (Igλ) light chain genes; karyotype: 46, XY, t(9;12)(q12;p11) [3]/ 46, XY [22]. Case 2: 56 year-old male, stage Rai 2/Binet B, with mutated IgH and unmutated Igλ genes; karyotype: 46, XY, add(10)(q26), t(13;18)(q14;q21) [8]/ 46, XY [27]. Although both translocations are novel, the involved breakpoints (especially 13q14 and 18q21) have been reported to participate in various aberrations in CLL patients. Aberrations affecting bands 9q12 and 12p11, as in case 1, are generally rare.     

Heterogeneity of immunoglobulin gene rearrangements in B-cell lymphomas

We have examined 69 B-cell non-Hodgkin's lymphomas (NHL) for rearrangements of the immunoglobulin (Ig) or T-cell antigen receptor (TCR) genes. The lymphomas were assigned to the categories of the Kiel classification and their B-cell nature was confirmed by immunostaining. Only 2 cases (with CLL) displayed clonal T beta-chain TCR gene rearrangements together with rearranged heavy- and light-chain Ig genes. The remaining 67 lymphomas had a germline beta-chain TCR-gene configuration. Three different patterns of Ig gene rearrangements were identified; (A) presence of both heavy- and light-chain rearrangements (H+L+); (B) rearrangement of heavy-chain gene only (H+L-); (C) heavy- and light-chain genes in germline configuration (H-L-). All the 45 low-grade NHLs and the 4 immunoblastic lymphomas exhibited pattern A and all had their kappa gene rearranged or deleted. Of 24 low-grade lymphomas tested, 13 (54%) had an addition rearrangement of the lambda light-chain gene. In contrast, the 19 high-grade centroblastic (cb) B-NHLs had distinct patterns of Ig-gene rearrangement: 12 with pattern A, 4 with B and 2 with C. In this group only 2 of 17 (12%) cases analyzed had evidence of lambda light-chain rearrangement whereas 12 of 18 (67%) had a kappa gene rearrangement or deletion. In one case expressing sIgM/lambda and with heavy chain Ig-rearrangement, no DNA was available for Ig light-chain analysis.     

Interphase FISH assays for the detection of translocations with breakpoints in immunoglobulin light chain loci

Many B-cell malignancies bear chromosomal translocations juxtaposing immunoglobulin (IG) genes with oncogenes, resulting in deregulated expression of the latter. Translocations affecting the IG heavy chain (IGH) locus in chromosomal region 14q32 are most prevalent. However, variant translocations involving the IG kappa (IGK) locus in 2p12 or the IG lambda (IGL) locus in 22q11 occur recurrently in B-cell neoplasias. No routine methods for the detection of all breakpoints involving IG light chain loci independently of the translocation partner have been described. For this reason, we have designed 2 novel interphase fluorescence in situ hybridization (FISH) assays using differentially labeled probes flanking the IGK and IGL locus, respectively. Based on extensive control studies, the diagnostic thresholds for the detection of breakpoints were set at 0.3% for IGK and 1.4% for IGL. Fifteen cases of B-cell malignancies with cytogenetically detectable chromosomal abnormalities in 2p11-14 were investigated with the FISH assay for IGK. Breakpoints affecting the IGK locus were detected in 7 cases including all 4 variant Burkitt's translocations t(2;8)(p12;q24) and a variant BCL2-associated translocation t(2;18)(p12;q21). Other translocation partners were chromosome bands 7q21 and 16q24. Ten cases with abnormalities in 22q11-12 were investigated with the FISH assay for IGL. Breakpoints in the IGL locus were diagnosed in 7 cases including both variant Burkitt's translocations t(8;22)(q24;q11) and a t(3;22)(q27;q11) involving the BCL6 locus. Other translocation partners were 2p13-14, 4q13 and 16p12. Our results show that these FISH assays provide flexible, simple and reliable tools in the diagnosis and characterization of genetic changes in B-cell malignancies.     

Neoplastic kappa and lambda cells in a B-PLL with chromosome translocations of both light chain gene regions

We describe a chromosome translocation t(2;13) (p11-12;p11) involving the kappa (kappa) light chain gene region (2p11-12), and a subsequent translocation t(11;22) (q23;11) involving the lambda (lambda) light chain gene region (22q11) within the same clone, in a patient with B-cell prolymphocytic leukaemia (B-PLL), of whose peripheral mononuclear cells 82% expressed (kappa) chains and 8% expressed (lambda) chains. Electron microscope (EM) studies using the immunogold method showed that both kappa- and lambda-producing cells were prolymphocytes. Immunoglobulin (Ig) gene analysis by Southern blotting demonstrated rearrangement of both Ig heavy (H) chain genes and one kappa gene. Although a lambda gene rearrangement corresponding to the minor lambda-positive population was not detected, a small monoclonal (M) band of IgM-lambda was present in the serum. The chromosome translocations and the pattern of light chain expression, particularly the lambda-producing cells, are discussed in the light of the restricted light chain expression observed in Burkitt's lymphomas with variant translocations involving the light chain genes.     

Clonal evolution of t(14;18) follicular lymphomas demonstrated by immunoglobulin genes and the 18q21 major breakpoint region

A 2.8-kilobase major breakpoint region on chromosome segment 18q21 is the site of most t(14;18) translocations typical of human follicular lymphomas. Breaks are focused at the 5' end of joining (JH) regions of immunoglobulin (Ig) on chromosome 14, indicating that the translocation occurs at a pre-B-cell stage during attempted heavy (H) chain joining. A new gene from 18q21 (Bcl-2) is placed in the H chain locus creating a unique, translocation-specific JH;18q21 rearrangement that presumably represents a transformation event. In addition, normal Ig gene joining occurs in a H before light (L) chain and K before lambda cascade, creating ordered clonal markers. These serial markers were examined to determine if variations in Ig gene patterns during the natural history of lymphomas represent the emergence of truly separate neoplasms or heterogeneity of a single neoplasm. We examined 45 serial biopsies from 16 B follicular lymphoma patients; six cases showed variation in Ig gene patterns over time. Seven individuals had a detectable JH;18q21 rearrangement present, and it remained unchanged over 5-10 years. Further rearrangements of H chain genes occurred on the normal chromosome 14 within evolving subclones of the original tumor. Lambda L chains also underwent additional rearrangements in two instances, while K gene patterns remained unchanged. All variations in the normal H and L chain genes were 2 degrees rearrangements occurring at a mature B-cell stage following the initial successful rearrangement of a H and L chain. In contrast the t(14;18) breakpoint was conserved in each individual, indicating that evolving neoplastic subpopulations arose from a common clonal progenitor cell.     

Concurrent activation of c-myc and inactivation of bcl-2 by chromosomal translocation in a lymphoblastic lymphoma cell line

We have characterized a chromosomal translocation in a cell line (SU-DUL5) established from a patient with lymphoblastic lymphoma in which the c-myc gene on chromosome 8 was juxtaposed to a t(14;18). Cytogenetic analysis of this cell line showed 14q+, 18q-, and 8p+q+ marker chromosomes in the absence of t(14;18). Genomic Southern blot analysis showed juxtaposition of the immunoglobulin heavy chain joining region (JH) with chromosome 18 near the minor breakpoint cluster region (mcr) of the bcl-2 gene. There was also a rearranged c-myc gene detectable with a 5' c-myc probe. Molecular cloning studies showed that the c-myc gene was joined to chromosome 18 DNA. Nucleotide sequence analysis of cloned breakpoint DNA revealed that the crossover between chromosomes 8 and 18 occurred at the 3' end of the bcl-2 gene resulting in replacement of the bcl-2 gene on the 14q+ chromosome with the c-myc gene. As a result of this translocation the SU-DUL5 cell line contains no detectable bcl-2 mRNA or protein but has abundant levels of c-myc mRNA. Our data suggest that bcl-2 inactivation occurred simultaneously with c-myc translocation in a B cell lymphoblastic lymphoma.     

Amplified and rearranged bcl-2 gene in two lymphoma cell lines, FL-218 and FL-318, carrying a 14;18 translocation

Two human B-cell lines carrying a 14;18 chromosome translocation [t(14;18)(q32;q21)], designated FL-218 and FL-318, were established from effusion cells of two Japanese patients manifesting the transformed histology of follicular lymphoma. The FL-218 and FL-318 cell lines were composed of cells in the hyperdiploid range, which had two and three or four 18q- chromosomes, respectively. These 18q- chromosomes were not distinguishable from an 18q- chromosome derived from t(14;18) since they exhibited the same banding pattern. Southern blot analysis revealed that in both cell lines, breakage of the bcl-2 gene occurred within the major breakpoint cluster region and the truncated gene juxtaposed to an immunoglobulin heavy chain gene locus. The autoradiographic intensity of the retained fragment each on 18q- chromosome was more enhanced than that of the translocated fragment on 14q+ chromosome. These findings suggest that the extra 18q- chromosome found in t(14;18)-positive cancer does not arise from de novo independent t(14;18) but from duplication of a preexisting 18q- chromosome.     

A new variant 15; 16 translocation in mouse plasmacytoma leads to the juxtaposition of c-myc and immunoglobulin lambda.

Mouse plasmacytomas (MPCs) induced by pristane oil, or by a combination of pristane oil and Abelson virus, carry one of two chromosomal translocations. The typical 12; 15 translocation leads to the juxtaposition of c-myc and immunoglobulin heavy-chain sequences, whereas the 6; 15 translocation links the kappa light-chain locus with the pvt-1 (plasmacytoma variant translocation) locus, located at least 75kb 3' of c-myc [Cory, S., Graham, M., Webb, E., Corcoran, L. & Adams, J. (1985). EMBO J., 4, 675-681]. Unlike the human Burkitt's lymphoma-associated translocation, the lambda/myc juxtaposed variant translocation has not been found previously in MPCs. Using unconventional MPC induction systems in which the tumor precursor cell was induced to proliferate in a secondary host, we have recently identified a 15; 16 translocation in six of the derived MPCs [Wiener, F., Silva, S., Sugiyama, H., Babonits, M. & Klein, G. (1990). Genes Chromosomes Cancer, 2, 36-43]. Chromosome 16 harbors the lambda light-chain gene. To explore whether the 15; 16 translocation represents the lambda/myc juxtaposition, we have mapped the breakpoints on chromosomes 15 and 16 by pulsed-field gel electrophoresis (PFGE). The pvt-1 region was mapped to approximately 220 kb 3' of c-myc. The breakpoint on chromosome 15 in ABPC-Ch-163-10, one of the six 15; 16 translocation-carrying MPCs, was situated approximately 80 kb 3' of c-myc and 140 kb 5' of pvt-1b, the major breakpoint cluster region of the previously analysed 6; 15 variant MPCs. The breakpoint on chromosome 16 was found to cut between the V1 and C3 regions of the lambda locus. Co-migration experiments showed that the C3 and the myc gene were juxtaposed head to tail on the 15; 16 translocation chromosome. On the reciprocal product V1 was juxtaposed to pvt-1.     

Establishment and characterization of a new human B-cell line (ONHL-1) from non-Hodgkin's lymphoma: constant expression of bcl-2 gene during mitogen-induced growth inhibition

A new B-cell line (ONHL-1) was established from non-Hodgkin's lymphoma. ONHL-1 was free from Epstein-Barr virus nuclear antigen and expressed CD20, CD24, and slg (mu, delta, gamma and kappa), thus being equivalent to the mature B-cell stage. Chromosome analysis revealed a markedly abnormal pattern including 14q+ and 6q-. In accordance with the positive expression of surface kappa light chains, one of the kappa genes was found to be rearranged. However, rearrangement of the lambda locus was also detected, contrary to the supposed hierarchy for the rearrangement of the light-chain genes. Further, the rearranged fragments of the JH, C lambda, and bcl-2 genes were of the same size in the EcoRI and HindIII digests on the same filter. This may suggest that the bcl-2 gene is juxtaposed with the JH and C lambda locus. The proliferation of ONHL-I was inhibited by adding Staphylococcus aureus Cowan 1 or 12-O-tetradecanoyl-phorbol-13-acetate. During this growth inhibition, the expression of c-myc decreased, while that of bcl-2 mRNA remained steady. This result suggests that not the bcl-2 gene but other oncogenes, such as c-myc, play a key role in the proliferation of ONHL-1. This agrees with the hypothesis that the bcl-2 gene is not concerned with aggressive proliferation but with cell survival. This new cell line will therefore be of value in studying the differentiation and tumorigenesis of B cells.     

A new non-Hodgkin's B-cell line (DoHH2) with a chromosomal translocation t(14;18)(q32;q21).

A spontaneously growing EBV-negative B-cell line (DoHH2) was established from the pleural fluid cells of a 60-year-old man with centroblastic/centrocytic non-Hodgkin's lymphoma, that had transformed into an immunoblastic lymphoma. The pleural fluid cells and the DoHH2 cells expressed IgG lambda, were reactive with CD10 and CD19 monoclonal antibodies, and showed by cytogenetic analysis 48,XY, +7, +del(12)(q24), t(14;18)(q32;q21). Southern blot analysis of mini-satellite DNA patterns, and of rearrangements of the immunoglobulin genes and bcl-2, confirmed that the cell line was derived from the patient's clonal lymphoma cells. Direct nucleotide sequence analysis on polymerase chain reaction (PCR) products of the t(14;18) junction revealed an identical sequence for the JH-bcl-2 junction at JH6 and in the major breakpoint region of bcl-2 in both the original tumor cells and the DoHH2 cell line. The cell line was valuable as a standard quantification control for PCR analysis of the t(14;18) breakpoint. Titration experiments demonstrated the detection of up to one tumor cell in 10(5) normal blood lymphocytes.     

New recurrent structural chromosome aberrations in non-Hodgkin's lymphoma

Identification, and subsequent molecular dissection, of recurring structural chromosome aberrations has led to a substantial increase in our understanding of lymphomagenesis. Thus we have reviewed the published literature on cytogenetic findings in non-Hodgkin's lymphoma (NHL) in search of previously unrecognized recurring chromosome aberrations. Thirty-four balanced rearrangements, including 32 reciprocal translocations and two inversions, and 25 unbalanced translocations, each observed in at least two different cases of NHL and previously unrecognized as recurring, have been ascertained. Among the 32 reciprocal translocations, 10 involved bands harboring one of the immunoglobulin (Ig) genes. In nine of these, the following bands or regions may be sites of putative oncogenes that are activated through juxtaposition to Ig loci: 1p35-36, 5q11, 6q21, 9p24, 12q13, 13q11, 15p11, 15q21-22 and 15q23-24. In one instance, t(21;22)(q22;q11), Ig lambda chain gene involvement is unlikely, because the t(21;22) has been identified in two NHLs of T-cell lineage. An additional four reciprocal translocations and one inversion affected the band 3q27, containing the BCL6/LAZ3 gene, and one of the following bands: 1q25, 3q12, 6p21, 7p13, 12p13. Three other reciprocal translocations had the breakpoint at 11q13 known to harbor the BCL1 gene. Among the 16 remaining balanced rearrangements, one translocation involved a band containing a gene for a T-cell receptor, i.e. 7q35. Almost all chromosomes in the human karyotype (except 3, 8, 20 and 21) were implicated in at least one of the 25 recurrent unbalanced translocations. The distribution of resulting chromosomal imbalances is highly nonrandom, however, because 17 translocations involved the long arm of chromosome 1 (1q) invariably resulting in partial trisomy of 1q. We suggest that these unbalanced translocations of Iq are best regarded as non-specific secondary abnormalities that may contribute to lymphoma progression.     

BCL-2 gene in lymphocytic malignancy

In t(14;18) (q32;q21) lymphomas, bcl-2 gene is activated by the juxtaposition of immunoglobulin (Ig) gene. The fused bcl-2-Ig gene generates chimeric mRNAs which consist of bcl-2 at 5' portion and Ig at 3' portion. Chimeric mRNA does not disrupt the bcl-2 coding frame of 239 amino acid polypeptide. Bcl-2-Ig transgenic mice demonstrated the extended B cell survival and the follicular lymphoproliferation, but they did not develop a malignancy until 25 weeks. Ten percent of them, however, developed malignant diffuse large-cell lymphomas after a long latency. Forty percent of these malignancies demonstrated the c-myc rearrangement, indicating that multiple step changes are required for malignant transformation in bcl-2 activated cells. Study on the bcl-2 gene rearrangement in Japanese B cell lymphoma and B-CLL revealed that 10 out of 32 cases of follicular lymphoma (31%), 5 out of 56 cases of diffuse lymphoma (9%) and 2 out of 30 cases of B-CLL (7%) were rearranged. Less frequency of B cell lymphoma, particularly follicular lymphoma in Japan might be partly due to the less bcl-2 involvement than in American cases. The ratio of bcl-2 involvement in B-CLL is not significantly different between Japan and U.S.A.. bcl-2 rearrangement at 5' promoter region is noted for Japanese B-CLL which was demonstrated for American cases. The clinical application of polymerase chain reaction for bcl-2 translocation was also discussed.