Immunoglobulin gene organisation and expression in haemopoietic stem cell leukaemia

JAK2 is dispensable for maintenance of JAK2 mutant B-cell acute lymphoblastic leukemias

Kim et al. show that while expression of mutant Jak2 is necessary for B-cell acute lymphoblastic leukemia induction, neither its continued expression nor enzymatic activity is required to maintain leukemia survival and rapid proliferation.

Activating JAK2 point mutations are implicated in the pathogenesis of myeloid and lymphoid malignancies, including high-risk B-cell acute lymphoblastic leukemia (B-ALL). In preclinical studies, treatment of JAK2 mutant leukemias with type I JAK2 inhibitors (e.g., Food and Drug Administration [FDA]-approved ruxolitinib) provided limited single-agent responses, possibly due to paradoxical JAK2^Y1007/1008 hyperphosphorylation induced by these agents. To determine the importance of mutant JAK2 in B-ALL initiation and maintenance, we developed unique genetically engineered mouse models of B-ALL driven by overexpressed Crlf2 and mutant Jak2, recapitulating the genetic aberrations found in human B-ALL. While expression of mutant Jak2 was necessary for leukemia induction, neither its continued expression nor enzymatic activity was required to maintain leukemia survival and rapid proliferation. CRLF2/JAK2 mutant B-ALLs with sustained depletion or pharmacological inhibition of JAK2 exhibited enhanced expression of c-Myc and prominent up-regulation of c-Myc target genes. Combined indirect targeting of c-Myc using the BET bromodomain inhibitor JQ1 and direct targeting of JAK2 with ruxolitinib potently killed JAK2 mutant B-ALLs.

Sustained leukaemic phenotype after inactivation of BCR-ABLp190 in mice

Pharmacological inactivation of cancer genes or products is being used as a strategy for therapy in oncology. To investigate the potential role of BCR-ABLp190 cessation in leukaemia development, we generated mice carrying a tetracycline-repressible BCR-ABLp190 transgene. These mice were morphologically normal at birth, and developed leukaemias. Disease was characterized by the presence of B-cell blasts co-expressing myeloid markers, reminiscent of the human counterpart. BCR-ABLp190 activation can initiate leukaemia in both young and adult mice. Transitory expression of BCR-ABLp190 is enough to develop leukaemia. Suppression of the BCR-ABLp190 transgene in leukaemic CombitTA-p190 mice did not rescue the malignant phenotype, indicating that BCR-ABLp190 is not required to maintain the disease in mice. Similar results were obtained by inactivation of BCR-ABLp190 with STI571 (Gleevec; Novartis, East Hanover, NJ, USA) in leukaemic CombitTA-p190 mice. However, gradual suppression of BCR-ABLp190 in leukaemic CombitTA-p190 mice identified a minimum level of BCR-ABLp190 expression necessary to revert the specific block in B-cell differentiation in the leukaemic cells. Overall, the findings indicate that BCR-ABLp190 appears to cause epigenetic and/or genetic changes in tumour-maintaining cells that render them insensitive to BCR-ABLp190 inactivation.

Prenatal origin of hyperdiploid acute lymphoblastic leukemia in identical twins

Studies in identical twins and with neonatal blood spots (Guthrie cards) have backtracked the origin of childhood acute leukemia and their associated chromosomal translocations to before birth. High hyperdiploidy is the most common genetic abnormality in childhood acute lymphoblastic leukemia (ALL). Evidence for an in utero initiation of this important genetic event in ALL is available from blood spots but remains limited. Twin children with hyperdiploid ALL have not hitherto been reported. We describe a pair of 2-year-old monozygotic twins with concordant B-cell precursor ALL and hyperdiploid karyotypes. One twin's leukemic cells had two rearranged TCRD alleles and one of these was a clonotypic Vdelta2-Ddelta3 sequence shared with leukemic cells of the other twin. The twins' leukemic cells had several different IGH V(H)-J(H) rearrangements but shared two common D(H)-J(H) 'stem' sequences. We conclude that ALL in these twins is likely to have originated prenatally in one fetus before spreading to the other via intraplacental anastomoses. It is likely that one or more additional postnatal genetic events was required for overt leukemogenesis.

Protracted and Variable Latency of Acute Lymphoblastic Leukemia AfterTEL-AML1 Gene Fusion In Utero

We report a pair of identical twins with concordant acute lymphoblastic leukemia (ALL). Unusually, their diagnoses were spaced 9 years apart at ages 5 and 14. Leukemic cells in both twins had aTEL-AML1 rearrangement, which was characterized at the DNA level by an adaptation of a long distance polymerase chain reaction (PCR) method. The genomic fusion sequence was identical in the two leukemias, indicative of a single cell origin in one fetus, in utero. At the time twin 1 was diagnosed (aged 5 years), the bone marrow of twin 2 was hematologically normal. However, retrospective scrutiny of the DNA from an archived slide with clonotypic TEL-AML1 primers showed that the presumptive preleukemic clone was present and disseminated 9 years before a clinical diagnosis. These data provide novel insight into the natural history of childhood leukemia and suggest that consequent to a prenatal initiation of a leukemic clone, most probably by TEL-AML fusion itself, the latency of ALL can be both extremely variable and protracted. This, in turn, is likely to reflect the timing of critical secondary events.

Fetal origins of the TEL-AML1 fusion gene in identical twins with leukemia

The TEL (ETV6)-AML1 (CBFA2) gene fusion is the most common reciprocal chromosomal rearrangement in childhood cancer occurring in approximately 25% of the most predominant subtype of leukemia- common acute lymphoblastic leukemia. The TEL-AML1 genomic sequence has been characterized in a pair of monozygotic twins diagnosed at ages 3 years, 6 months and 4 years, 10 months with common acute lymphoblastic leukemia. The twin leukemic DNA shared the same unique (or clonotypic) but nonconstitutive TEL-AML1 fusion sequence. The most plausible explanation for this finding is a single cell origin of the TEL-AML fusion in one fetus in utero, probably as a leukemia-initiating mutation, followed by intraplacental metastasis of clonal progeny to the other twin. Clonal identity is further supported by the finding that the leukemic cells in the two twins shared an identical rearranged IGH allele. These data have implications for the etiology and natural history of childhood leukemia.

A BCR-ABLp190 Fusion Gene Made by Homologous Recombination Causes B-Cell Acute Lymphoblastic Leukemias in Chimeric Mice With Independence of the Endogenous bcr Product

BCR-ABLp190 oncogene is the result of a reciprocal translocation between chromosomes 9 and 22 and is associated with B-cell acute lymphoblastic leukemia (B-ALL) in humans. Current models expressing the BCR-ABLp190 chimeric gene fail to consistently reproduce the phenotype with which the fusion gene is associated in human pathology, mainly due to the difficulty of being expressed in the appropriate cell type in vivo. We have used here homologous recombination in ES cells to create an in-frame fusion of BCR-ABLp190 that mimics the consequences of the human chromosomal translocation by fusion of BCR-ABL coding sequences into the bcr endogenous gene. The chimeric mice generated with the mutant embryonic stem cells systematically develop B-ALL. Using these chimeric mice, we further show that BCR-ABL oncogene does not require the endogenous bcr product in leukemogenesis. Our results show that BCR-ABLp190 chimeric mice are a new model to study the biology of the BCR-ABL oncogene and indicate the efficacy of this strategy for studying the role of specific chromosome abnormalities in tumor development.

A BCR-ABLp190 Fusion Gene Made by Homologous Recombination Causes B-Cell Acute Lymphoblastic Leukemias in Chimeric Mice With Independence of the Endogenous bcr Product

BCR-ABLp190 oncogene is the result of a reciprocal translocation between chromosomes 9 and 22 and is associated with B-cell acute lymphoblastic leukemia (B-ALL) in humans. Current models expressing the BCR-ABLp190 chimeric gene fail to consistently reproduce the phenotype with which the fusion gene is associated in human pathology, mainly due to the difficulty of being expressed in the appropriate cell type in vivo. We have used here homologous recombination in ES cells to create an in-frame fusion of BCR-ABLp190 that mimics the consequences of the human chromosomal translocation by fusion of BCR-ABL coding sequences into the bcr endogenous gene. The chimeric mice generated with the mutant embryonic stem cells systematically develop B-ALL. Using these chimeric mice, we further show that BCR-ABL oncogene does not require the endogenous bcr product in leukemogenesis. Our results show that BCR-ABLp190 chimeric mice are a new model to study the biology of the BCR-ABL oncogene and indicate the efficacy of this strategy for studying the role of specific chromosome abnormalities in tumor development.

Monoclonal Origin of Concordant T-Cell Malignancy in Identical Twins

Acute leukemia has a high concordance rate in young identical twins and in infants this is known, from molecular analysis, to reflect an in utero origin in one twin followed by prenatal metastasis to the other twin via intraplacental anastomoses. The situation in older twins with leukemia has been less clear. We describe a pair of identical twins who were diagnosed with a T-cell malignancy at 9 and 11 years of age, one with T-cell non-Hodgkin's lymphoma and the other with T-cell acute lymphoblastic leukemia. Leukemic cells from the twins shared the same TCRβ gene rearrangement with an identical 11 bp N region. The most plausible interpretation of this result is that these malignancies were initiated in one twin fetus in utero, in a single T-lineage cell that had stable bi-allelic TCRβ rearrangements. Progeny of this cell then spread to the other twin before birth via shared placental vasculature. This was then followed by a 9- and 11-year preleukemic latent period before clinical disease manifestation as leukemia or lymphoma. This result has considerable implications for the etiology and natural history of pediatric leukemia.

Monoclonal Origin of Concordant T-Cell Malignancy in Identical Twins

Acute leukemia has a high concordance rate in young identical twins and in infants this is known, from molecular analysis, to reflect an in utero origin in one twin followed by prenatal metastasis to the other twin via intraplacental anastomoses. The situation in older twins with leukemia has been less clear. We describe a pair of identical twins who were diagnosed with a T-cell malignancy at 9 and 11 years of age, one with T-cell non-Hodgkin's lymphoma and the other with T-cell acute lymphoblastic leukemia. Leukemic cells from the twins shared the same TCRβ gene rearrangement with an identical 11 bp N region. The most plausible interpretation of this result is that these malignancies were initiated in one twin fetus in utero, in a single T-lineage cell that had stable bi-allelic TCRβ rearrangements. Progeny of this cell then spread to the other twin before birth via shared placental vasculature. This was then followed by a 9- and 11-year preleukemic latent period before clinical disease manifestation as leukemia or lymphoma. This result has considerable implications for the etiology and natural history of pediatric leukemia.

Differences in T-cell-receptor gene rearrangement and transcription in nasal lymphomas of natural killer and T-cell types: implications on cellular origin

Although nasal lymphomas showing midfacial destructive lesions had been classified as T-cell lymphomas, their exact cellular origin is still unclear. Although they usually express a restricted number of T-cell-related antigens, namely, CD2, CD43, and CD45RO, other pan-T or subset-T-lineage antigens, such as CD3 (membrane), CD5, CD4, CD8, and CD7, are frequently absent. Conversely, they often express a natural killer (NK) cell-associated antigen, CD56, but lack other mature NK markets. To study their cellular origin further, the authors analyzed T-cell receptor (TCR) gene transcription in three cases of nasal lymphomas and correlated the findings with the phenotype and gene rearrangement data. Two cases of nasal lymphomas with CD2+CD3(Leu4)-CD19-CD56+ phenotype were shown to express truncated 1.0-kb Tbeta and multiple unrearranged Tdelta transcripts with germline TCR beta, gamma, delta, and immunoglobulin heavy-chain joining region (JH) genes, consistent with NK cell lineage. In contrast, one case of nasal lymphoma with CD2+CD3(Leu4)+CD8+CD19-CD56+ phenotype expressed full-length Talpha, Tbeta, and Tgamma transcripts rearranged TCR beta, gamma, and deleted TCR delta genes, indicating T-lineage, These results support the view that nasal lymphomas can separated into NK-cell and T-cell neoplasms, based on differences genotypic characteristics. The possibility of these tumors being derived from a putative common precursor cell merits further investigation.

Risk of acute myeloid leukaemia and multiple myeloma in workers exposed to benzene

OBJECTIVE

To determine the risk of developing acute myeloid leukaemia (AML) and multiple myeloma in a cohort of workers exposed to benzene. The results were used to show the importance of taking specificity of disease into consideration in causation analysis.

METHODS

Data were derived from a cohort of workers employed at two Goodyear plants in Ohio in the manufacture of Pliofilm. Based on data in the Pliofilm study, several papers that examined the relation between exposure to benzene and leukaemia (all cell types combined) have been published. In the current analyses based on updated data in the study, standardised mortality ratios (SMRs) and 95% confidence intervals (95% CIs) were calculated for AML and multiple myeloma by cumulative exposure to benzene. The results based on AML were compared with those for leukaemia (all cell types combined) published previously.

RESULTS

An exposure response relation was shown between cumulative exposure to benzene and AML. No increased risk of AML was detected for cumulative exposure to benzene below 200 ppm-years (SMR 0.91). Above 200 ppm-years, risk of AML rose drastically; reaching a significant SMR of 98.37 for > 400 ppm-years. For multiple myeloma, no relation with exposure to benzene was detected.

CONCLUSION

Analysis specific to AML shows the importance of taking specificity of disease into consideration in causation analysis. This investigation shows that previous analyses based on all leukaemia cell types combined have incorrectly set the estimated threshold too low, and have underestimated risk above the threshold. Current regulatory policies that rely on previous analyses based on all leukaemia cell types combined should be re-examined.

Cytogenetic and immunogenotypic alterations of blast crisis cells in chronic myelogenous leukemia independently linked to immunophenotypic expression

Chronic myelogenous leukemia (CML) is a disease of the hematopoietic stem cells, which can differentiate into either B-lymphoid or myeloid cells, because most of them develop either lymphoid or myeloid blast crisis. Immunophenotypic, genotypic, and cytogenetic analyses of 22 patients (24 episodes) with Philadelphia (Ph) positive CML in blast crisis were performed to determine the genetic alterations of the blast crisis cells. In B-lymphoid blast crisis, all the five patients had immunoglobulin heavy-chain (IgH) rearrangements and most of them showed normal karyotypes. Among the five patients, T-cell receptor (TCR) genes were rearranged at the following occurrence rates: 20% in TCR-beta, 60% in TCR-gamma, and 40% in TCR-delta chain genes. A high incidence of additional chromosome changes was noted in patients with B-lymphoid/myeloid-mixed blast crisis, but about 80% of them had rearranged IgH and about 40% had TCR rearrangements. In contrast, most of the patients with non-lymphoid blast crisis showed further chromosomal abnormalities, including +8, +19, i(17q), and double Ph, and most of them had germline configurations of IgH and TCR-gamma chain genes. Notably, only one patient (dual lymphoid and myelomegakaryoblast crisis) in this group exhibited IgH rearrangement, and TCR-beta and TCR-delta rearrangements were also rarely noted. Rearrangement of the IgH gene in CML blast crisis might be linked to expression of lymphoid markers, especially CD19.

In utero rearrangements in the trithorax-related oncogene in infant leukaemias

The majority (approximately 75%) of infant acute leukaemias have a reciprocal translocation between chromosome 11q23 and one of several partner chromosomes. The gene at 11q23 (named MLL, ALL-1, HRX or HTRX-1; refs 2-6) has been cloned and shares homology with the Drosophila developmental gene trithorax. Rearrangements of this gene (called HRX here) occur in introns and cluster in a region of approximately 10 kb; individual patients have different breakpoints. Here we describe three pairs of infant twins with concordant leukaemia who each share unique (clonal) but non-constitutive HRX rearrangements in their leukaemic cells, providing evidence that the leukaemogenic event originates in utero and unequivocal support for the intra-placental 'metastasis' hypothesis for leukaemia concordance in twins.

Regressing atypical histiocytosis, a regressing cutaneous phase of Ki-1-positive anaplastic large cell lymphoma. Immunocytochemical, nucleic acid, and cytogenetic studies of a new case in view of current opinion

BACKGROUND

Regressing atypical histiocytosis is a rare multifocal cutaneous tumor characterized by large, spontaneously regressing, ulcerating skin nodules. Although initially self-remitting, the condition may progress to systemic lymphoma.

METHODS

Using material from one patient, an attempt was made to clarify the nature of this condition with immunophenotyping, genotyping, and chromosome studies.

RESULTS

Immunophenotyping studies indicated the condition was of T-cell lineage, although T-cell receptor gene studies showed polyclonal rearrangement. This case progressed to systemic lymphoma.

CONCLUSIONS

The authors believe regressing atypical histiocytosis is a regressing phase of Ki-1-positive anaplastic large cell lymphoma of the skin.

Clonal Epstein-Barr virus genome in T-cell-rich lymphomas of B or probable B lineage

Seventeen nodal lymphomas (originally diagnosed as T-cell lymphomas based on histological features and immunohistochemical staining results) were studied for the presence of Epstein-Barr virus (EBV) genome, and the results correlated with immunoglobulin and T-cell receptor gene rearrangement analyses performed on the same tissue samples. All four EBV positive cases had clonal rearrangement of the joining region of the immunoglobulin heavy chain (IgJH) gene without clonal T-cell receptor beta-chain (TCR beta) gene rearrangement. Of these, two cases also showed clonally rearranged light chain gene, and they were reclassified as T-cell rich B-cell lymphomas (TRBL). The other two cases lacked clonal kappa or lambda light chain rearrangement and they were reclassified as T-cell rich lymphomas of probable B lineage, based on their isolated IgJH clonal rearrangement. These B-cell lymphomas may be easily misdiagnosed as T-cell lymphomas owing to the presence of an abundant reactive T-cell infiltrate masking the tumor population. The florid T-cell reaction may represent an unusual host response towards a clonal proliferation of EBV bearing B cells.

Human antiglioma monoclonal antibodies from patients with astrocytic tumors

The current management of malignant gliomas is unsatisfactory compared to that of other solid tumors; the expected median survival period is less than 1 year with the patient undergoing conventional surgery, radiotherapy, and chemotherapy treatment. Immunological reagents could be a useful adjunct. Human monoclonal antibodies derived from patients with astrocytic tumors might recognize subtle antigenic specificities that would differ from those recognized by xenogeneic (murine) systems. Five hybridomas, designated as BT27/1A2, BT27/2A3, BT32/A6, BT34/A5, and BT54/B8, were produced from the fusion of peripheral blood lymphocytes of four patients with astrocytic tumors to the human myeloma-like cell line TM-H2-SP2. This cell line has a 46, XX karyotype and is negative for hypoxanthine guanine phosphoribosyltransferase. All five human monoclonal antibodies produced 2.4 to 44 micrograms/ml of immunoglobulin M, had a similar but not identical pattern of reactivity against a panel of human tumor cell lines, and failed to react with normal human astrocytes. Labeling of four neuroectodermal tumor explant cultures by BT27/2A3 was demonstrated by flow cytometry. Karyotyping of three of the five hybridomas demonstrated that two were pseudodiploid (2-3n) and one hypodiploid (less than 2n). The monoclonality of the hybridomas was evaluated by Southern blot analysis of JH gene rearrangements, revealing two types of rearrangements for each hybridoma, both consistent with monoclonality. Preliminary antigen characterization indicated that at least four of the five human monoclonal antibodies were directed to cell-surface glycolipids.

Immunophenotypic, genomic and clinical characteristics of blast crisis of chronic myelogenous leukaemia

We have studied phenotypic and clinical features in a consecutive series of 45 patients with chronic myelogenous leukaemia (CML) in blast crisis (BC). In addition, in 22 of these patients we have analysed the genotypic characteristics including immunoglobulin, T-cell receptor (TCR) and major breakpoint cluster region (M-bcr) gene organization. The granulomonocytic and megakaryoblastic lineages are the most commonly involved in these BC of CML (33% and 33% of cases, respectively); only 18% of our cases displayed a lymphoid phenotype. Moreover, both morphological and immunophenotypic studies revealed the frequent coexistence of two or three cell populations, especially when the megakaryoblast component is involved. The lymphoid BC displayed the highest incidence of complete remissions although this was not associated with a longer survival. Only minor differences between the different myeloid subgroups were observed. Immunoglobulin heavy chain (IgH) gene rearrangement was found in five of the six lymphoid BC and in one myeloid BC. Only one case showed k light chain gene rearrangement. In all but one myeloid BC the TCR-beta gene was in germline configuration. The TCR-gamma gene was rearranged in all lymphoid and one myeloid BC, while TCR-delta gene rearrangement was detected in 67% and 16% of the lymphoid and myeloid BC, respectively. Most of the lymphoid BC (4/5) had the M-bcr breakpoint in subregion 3, while the myeloid BC had the breakpoint either in subregion 2 or 3. No differences between the different myeloid phenotypic subgroups were observed in relation to breakpoint.

Non-lymphoid blast crisis of CML with rearrangement of immunoglobulin and T-cell receptor delta genes

We report a patient with chronic myeloid leukaemia (Philadelphia-positive with M-BCR rearrangement) in transformation whose blast cells had myelomonocytic morphology, absent terminal deoxynucleotidyl transferase expression and non-lymphoid cell surface markers (CD10-, CD19-, CD33+, CD14+, CD11+). Leukaemia cell DNA showed rearrangement of both immunoglobulin heavy chain and T-cell receptor delta genes. Such rearrangements may be a feature of a small proportion of patients with non-lymphoid transformation of CML as they are in a minority of cases of de novo acute non-lymphoblastic leukaemia.

Malignant cell detection in Burkitt's lymphoma using third-complementarity-determining region (CDRIII), clone-specific probe developed by sequencing DNA from stored slides

The DNA sequence of the third-complementarity-determining region (CDRIII) of the immunoglobulin heavy chain (IgH) gene in a case of Burkitt's lymphoma was determined by polymerase chain reaction (PCR) using template DNA extracted from a smear stored at room temperature for more than one year. The DNA sequence obtained from the stored slide was compared with that of DNA from a frozen lymph node biopsied at the initial presentation. The sequences were shown to be identical, implying that DNA from a smear on a stored slide can be used as a source of DNA for PCR amplification, sequencing, and development of a clone-specific probe. Using oligonucleotides generated from one of the CDRIII sequences of the IgH gene as molecular probes, a retrospective study for the malignant clone on the smears was carried out. Malignant cells were detectable in the peripheral blood at an early stage of bone marrow relapse but not in the peripheral blood or bone marrow at the initial presentation. No malignant clone was detected in the bone marrow when testicular infiltration was diagnosed by examination of a pathological specimen. Thus, the technique permits molecular analysis of hematologic malignancies of B-cell lineage in cases where fresh or frozen specimens are not available.

T-lymphoid blast crisis in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is considered to be a pleuripotential stem cell disorder with the capacity to differentiate into myeloid, erythroid, megakaryocytic, and lymphoid cell lines. Consequently, blast crisis (BC) involving each of the above lineages has been well described. Among lymphoblastic crises, differentiation frequently occurs along B-cell lineage. We report four patients of CML who terminated in T-cell extramedullary BC in lymph nodes after a variable duration of chronic phase. The T-lineage was established by characteristic cytochemical staining and reactivity with a panel of anti-T-cell monoclonal antibodies. All four cases were Philadelphia (Ph) chromosome positive and demonstrated the Ph chromosome and associated anomalies (extra Ph, +19) in the lymph nodes. Our data adds to the growing evidence that CML is a disorder of the common stem cell from which T, B, and myeloid precursors originate.

Presence of Epstein-Barr virus DNA in nasal lymphomas of B and 'T' cell type

We studied 12 tumours from 11 Chinese patients with primary nasal lymphoma for presence of Epstein-Barr Virus (EBV) DNA, using Southern-blot analysis. These results were correlated with immunophenotype and T-cell receptor (TcR) or immunoglobulin gene rearrangement patterns. EBV DNA was detected in all nine tumours with a 'T' phenotype, in both primary and secondary sites. When the structure of the viral genomic termini was studied using the EcoRI-Dhet probe, a single clonal episomal band was demonstrated in five tumour samples, with one other case showing a biclonal pattern. However, none of these cases showed clonal rearrangement of TcR beta chain gene, and TcR gamma rearrangement was found only in one. The lineage of these phenotypic 'T' lymphomas therefore require further studies for confirmation. Two out of three B-lymphomas were also EBV DNA+; clonal EBV DNA was found in one. Their B-lineage was confirmed by detection of clonal immunoglobulin gene rearrangements. The association of EBV with an increasing number of lymphomas of different types highlights the need for continued study into its role in oncogenesis.

Expansion of B lymphocytes with an unusual immunoglobulin rearrangement associated with atypical lymphocytosis and cigarette smoking

Persistent polyclonal lymphocytosis has been described in a group of female patients who all have the HLA-DR7 antigen in common and who are all heavy cigarette smokers. Immunoglobulin heavy chain gene rearrangement was analyzed by hybridization with specific immunoglobulin heavy chain genes to restriction enzyme-digested genomic DNA samples. The results in two of these patients showed that the lymphocytosis was associated with an expanded subpopulation of B-lineage cells represented by the presence of an unusual immunoglobulin gene rearrangement pattern. Expansion of this subpopulation of B cells appeared to be linked to cigarette smoking since the intensity of the cell population harboring the rearranged gene was much stronger in patients who were smoking heavily compared with the same patients who were temporarily not smoking.

DEL cell line: a "malignant histiocytosis" CD30+ t(5;6)(q35;p21) cell line

A new cell line DEL, established in vitro, was isolated from a pleural effusion of a boy who died of malignant histiocytosis. Its principal characteristics are: strong positivity with monoclonal antibodies (MAbs) to CD25, CD30, CD45R, KiM7, EMA, HLA Cl I and II; constant presence of acid phosphatase, ANAE, alpha-anti-trypsin, alpha-anti-chymotrypsin and NBT reductase activity; rearrangement of the immunoglobulin heavy-chain gene (JH) and a germ-line configuration of the T-chain gene; and finally a translocation between chromosomes 5-6 with a breakpoint in 5q35. The DEL cell line is appropriate for studying the role of the 5q localized c-fms oncogene and of the genes of the mononuclear phagocyte growth factor (CSFI) and of their receptors in the dynamics and etiology of malignant hemopathies associated with a 5q35 breakpoint.

Genetic heterogeneity in blast crisis of chronic myelocytic leukemia

Fourteen patients with lymphoid and mixed blast crisis (BC) of chronic myelocytic leukemia were studied by immunophenotyping and genotyping. Rearrangements of immunoglobulin heavy chain (IgH), T-cell receptor (TcR) gamma and TcR beta genes were detected in all 14, in nine and in four patients, respectively. Interestingly, more than two rearranged bands of IgH gene in three lymphoid BC and two rearranged bands with germ line band in 1 biphenotypic BC indicated the genetic heterogeneity of the blasts. Some blastic transformations are thought to occur at a more immature stage of hematopoietic differentiation than that indicated by the phenotype and genotype of BC cells.

Immunoglobulin heavy chain gene rearrangements and mixed lineage characteristics in acute leukemias with the 11;19 translocation

Although the origin of acute leukemia with the 4;11 translocation has been shown to be an early myeloid progenitor cell or a stem cell with the potential for differentiation into both lymphoid and myeloid lineage, few precise studies on acute leukemia with the 11;19 translocation have thus far been reported. This study focused on the clinical, morphologic, ultrastructural, and immunologic characteristics as well as the DNA in three cases of acute leukemia with the 11;19 translocation. All three patients were infants and showed hyperleukocytosis. The morphologic feature was French-American-British (FAB)-L2 in two patients, in one of which a few monocytoid blasts were also seen by electron microscopy. Cells from the third patient underwent morphologic changes from FAB-L2 at the time of diagnosis to M5b at relapse. Immunologic marker studies revealed that the blast cells from all three patients expressed Ia and B4, but none expressed B1, CALLA(J5), T antigens, or SIg. Cells from one patient simultaneously expressed myeloid antigen (MCS-II) both at diagnosis and relapse. Cells from two patients expressed myeloid antigen after being cultured for a short time in vitro. An analysis of immunoglobulin genes and T-cell receptor genes revealed rearrangements of the heavy chain genes and germ line configurations of the kappa and lambda light chain genes, and of the T-cell receptor beta chain genes. These findings suggest that acute leukemia with the 11;19 translocation has mixed lineage characteristics as a result of leukemogenesis in a stem cell with the potential for both lymphoid and myeloid, especially monocytic, differentiation.

Immunohistological diagnosis of primary brain lymphoma using monoclonal antibodies: confirmation of B-cell origin

The antigenic characteristics of 20 primary cerebral lymphomas have been defined by their reactivity with a panel of monoclonal antibodies recognizing differentiation antigens of lymphocytes and other cell types. In 7 out of 20 cases (35%), immunohistological results were diagnostically crucial and this approach appeared almost to double the detection rate of brain lymphomas over a 10-year period. All 20 tumours were confirmed as B-cell neoplasms by the use of a monoclonal antibody (B-1) specific for B-lymphocytes, rather than by the demonstration of immunoglobulin production. Further immunophenotyping with antibody FMC7 indicated that the neoplastic B-cells had been 'arrested' at a relatively mature stage of differentiation. The importance of monoclonal antibody markers in the accurate diagnosis and characterization of primary cerebral lymphomas has now been established.

Unique fusion of bcr and c-abl genes in Philadelphia chromosome positive acute lymphoblastic leukemia

The Philadelphia (Ph) chromosome, the product of t(9:22), is the cytogenetic hallmark of chronic myelogenous leukemia. The c-abl oncogene on chromosome 9 is translocated to the Ph chromosome and linked to a breakpoint cluster region (bcr), which is part of a large bcr gene. This results in the formation of a bcr-c-abl fusion gene, which is transcribed into an 8.5 kb chimeric mRNA encoding a 210 kd bcr-c-abl fusion protein. The Ph chromosome is also found in acute lymphoblastic leukemia (Ph+ ALL). Although the c-abl is translocated and a new 190 kd c-abl protein has been identified, no breakpoints are observed in the bcr (Ph+bcr- ALL). Here we show that in Ph+bcr- ALL, breakpoints in chromosome 22 occur within the same bcr gene, but more 5' of the bcr. Cloning of a chimeric bcr-c-abl cDNA demonstrates that the fusion gene is transcribed into a 7 kb mRNA, encoding a novel fusion protein.

Phenotype versus immunoglobulin and T-cell receptor genotype of Hodgkin-derived cell lines: activation of immature lymphoid cells in Hodgkin's disease

Three Hodgkin-derived cell lines (L428, L540, and CO) were studied for rearrangements and expression of immunoglobulin and T-cell receptor genes, and their genotype was compared to the phenotype. As far as the genotype is concerned, all 3 cell lines have characteristics of lymphoid cells; L428 of B, and L540 and CO of T-cell origin. L428 cells have one Ig heavy chain allele rearranged to C gamma and transcribed into RNA, while the second is deleted. Furthermore, L428 cells show an unusual immunoglobulin kappa light chain gene rearrangement involving deletion of the kappa constant gene in one allele, while the remaining kappa and lambda loci are in germline configuration. L540 and CO have, in contrast to L428 cells, the immunoglobulin genes in germline and T-cell receptor genes rearranged. The T-cell receptor beta and gamma genes are rearranged in both L540 and CO, whereas a rearrangement in the alpha locus was detected in L540 cells only. RNA of the size of functional beta chain transcripts was found in CO cells and of the size of functional alpha chain transcripts in L540 cells. All 3 cell lines are classified as immature lymphoid cells with respect to the limited expression of B- and T-cell antigens, respectively, and to the incomplete expression of their antigen receptor. The immaturity of lymphoid differentiation contrasts with the expression of activation antigens, i.e. Ki-1, Ki-24, HLA-DR, and IL-2 receptor. The immaturity of the cells excludes the possibility that the cells were activated along the physiological pathway, i.e. by interaction of the cell with antigen. The results obtained on the cell lines are in accordance with in vivo studies and suggest that Hodgkin and Sternberg-Reed cells are immature lymphoid cells which are activated by a still unknown mechanism.

Application of a bcr-specific probe in the classification of human leukaemia

A genomic probe derived from the breakpoint cluster region (bcr) on chromosome 22q11 was used to assess whether Philadelphia (Ph) chromosome positive chronic myelogenous leukaemia patients have unique patterns of bcr rearrangements and whether this pattern is modified as the disease progresses from stable phase to blast crisis. The data indicated that bcr rearrangements are fairly unique to each patient and are not subject to additional modifications during the course of the disease. We have also found bcr rearrangements in acute lymphocytic leukaemia (ALL) patients, usually of the cALL phenotype. For the majority of Ph+ ALL patients, the breakpoint on 22q11 was in bcr. However, we describe a case of Ph+ ALL without bcr rearrangement, indicating heterogeneity of Ph chromosomes in ALL at the molecular level. Contrary to previous reports, a bcr rearrangement was also identified in a childhood cALL.

Undifferentiated leukemia of infancy with t(11:17) chromosomal rearrangement. Coexpressing myeloid and B cell restricted antigens

It has been suggested that the malignant transformation, in some of the acute leukemias, may involve totipotent stem cells resulting in a biphenotypic leukemia expressing both myeloid, and lymphoid characteristics. We describe here a hybrid cell acute leukemia, in a 16-day-old infant, in whom leukemic cells coexpressed myeloid and lymphoid B cell antigens. Blast cells in the bone marrow showed L2 morphology according to the French American British (FAB) classification, with positive periodic-acid Schiff, and nonspecific esterase staining. Sudan black, and specific esterase were negative. Terminal deoxynucleotidyl transferase, was strongly positive in 5% of blasts, and faintly reactive with the rest. Karyotypic analysis demonstrated a translocation of t(11:17);(q23;p13). Immunoglobulin gene analysis revealed rearrangement of the heavy chain genes. The blasts' phenotype was HLA/DR+ B4+ My7+ My9+ common acute lymphoblastic leukemia antigen (CALLA) B1- T11-. Dual immunofluorescence staining using anti My7, and My9 fluorescein isothiocyanate, and anti B4 pycoerythrin conjugated monoclonal antibodies, and flow cytofluorometry, revealed a labeling pattern of 25% B4+; 10% to 15% My7+; 17% My9+; and 50% of cells coexpressing B4 My7, and My9 antigens. These results provide evidence for a hybrid leukemia with lymphomyeloblasts being part of a single clone, which may indicate the origin of this leukemic clone from a pluripotent (lymphoid/myeloid) stem cell.

Establishment and characterization of three new malignant lymphoid cell lines

We have established 3 new EBV-negative cell lines, designated Sc-1, Ri-1 and Ci-1, from patients with B-cell lymphoma/leukemia. We characterized them by cytogenetics and by study of surface membrane antigens with a panel of monoclonal antibodies (MAbs), surface and cytoplasmic immunoglobulin (Ig) expression and Ig heavy- and light-chain genes. All 3 lines had a 14q+ abnormality. Ri-1 also had translocations involving chromosomes 2, 8 and 18. Ci-1 also had abnormalities involving chromosomes 2, 8 and 22 and its karyotype was 46, XX, t(2;8), t(14;22). The t(2;8) had the same breakpoints as those reported in some cases of Burkitt's lymphoma. We also studied a classical Ph1-positive cell line previously established by Pegoraro et al. (1983) and designated BV173. The phenotypes of these 4 lines based on Ig expression and marker studies correlated well with their respective genotypes. Our results are in keeping with the notion that leukaemic cell populations are clonal expansions of cells "frozen" at a particular stage in their differentiation. Specifically, BV173 cells are at an early stage of B-cell differentiation, Ri-1 and Ci-1 cells are at intermediate stages and Sc-1 cells are at a relatively late stage in the B-cell lineage.

The arrangement of immunoglobulin and T cell receptor genes in human lymphoproliferative disorders

Immunoglobulin and T cell antigen receptor genes in their germ-line form are organized as discontinuous DNA elements that are joined by recombinations during lymphocyte development. The analysis of immunoglobulin gene structure and arrangement has been of great value in the study of human lymphoid neoplasms. The analysis of rearranged immunoglobulin and T cell receptor genes has been of value in defining the lineage (T or B cell) of neoplasms that were of controversial origin previously, determining the clonality of abnormal lymphocyte proliferations, diagnosing and monitoring the therapy of lymphoid malignancies, determining the state of maturation and the causes for failure of maturation of cells of the B cell series, and providing major insights into the cause of malignant transformation of B and T lymphoid cells. Thus, the application of this molecular genetic approach has great potential for complementing conventional marker analysis, cytogenetics, and histopathology, thus broadening the scientific basis for the classification, diagnosis, and monitoring of the therapy of lymphoid neoplasia.

Differentiation-linked leukemogenesis in lymphocytes

Most human lymphoid malignancies preserve a pattern of gene expression reflecting their proliferative activity and the development level of clonal expansion and maturation arrest. Characteristics of leukemia and other cancer cells frequently considered to reflect aberrant differentiation may more often reflect clonal selection of cell types that are normally infrequent and transitory. The differentiation status of progenitor or mature lymphoid cells influences which genetic elements are at risk of being exploited, via mutation, recombination, or deletion, for clonal advantage. These alterations may frequently arise spontaneously as a consequence of the unique developmental and functional programs of lymphoid cells and have as a major phenotypic consequence the stabilization of transitory cellular phenotypes.

Developmentally regulated rearrangement and expression of genes encoding the T cell receptor-T3 complex

Human leukemic cells corresponding to the earliest identifiable stages of intrathymic T cell differentiation lack cell surface expression of the T cell receptor(TCR alpha/beta)-T3 complex but transcribe TCR beta mRNA from either germ-line configuration (1/13) or partially (DJ) or fully (VDJ) rearranged (12/13) genes. These cells do not produce TCR alpha mRNA, but do contain T3 delta and T3 epsilon mRNA and accumulate T3 polypeptides, primarily in the perinuclear envelope. Equivalent normal T cells isolated from thymus have a predominantly germ-line configuration of TCR beta but contain intracellular T3 proteins. T3 gene expression is therefore a very early event in T cell differentiation. TCR alpha chain production appears to be the limiting maturation-linked event in the transport, assembly, and cell surface membrane insertion of the TCR alpha/beta-T3 complex.

Immunoglobulin chain gene rearrangements in a t(4;11) acute leukaemia with monocytoid blasts

We report a case of acute leukaemia with the t(4;11) chromosomal translocation which, at initial diagnosis, had L-1 lymphoblasts that were positive for terminal deoxynucleotidyl transferase (TdT) and HLA-DR but negative for myeloid cytochemical markers. At last relapse the patient had mostly monocytoid blasts which were not TdT negative but were positive for HLA-DR, weakly positive for Sudan Black B (SB), periodic acid Schiff's (PAS), naphthol AS-D acetate esterase (NSE), chloroacetate esterase (CAE) and negative for acid phosphatase (AP) and nitroblue tetrazolium (NBT) reduction. Treatment with 12-o-tetradecanoylphorbol-13-acetate (TPA) in vitro induced differentiation to macrophage-like cells that were strongly positive for SB, PAS, NSE, AP, CAE and NBT reduction, indicating a latent monocyte-like phenotype. Thus the leukaemic cell clone or a precursor clone with the t(4;11) translocation manifested a lymphoid phenotype at initial diagnosis and a monocytoid phenotype at relapse. Immunoglobulin gene analysis of the monocytoid relapse blasts revealed rearrangements of the heavy chain gene alleles and germline light chain genes. Thus, the leukaemia clone with the t(4;11) chromosomal translocation could be a bipotential cell with heavy chain gene rearrangements occurring in a primitive cell which may retain the ability to differentiate along the myeloid-monocytoid lineage in response to the appropriate stimulus. Alternatively, these characteristics may result from a transformation associated event.

Expression of the human immunoglobulin heavy chain gene of the 14q+ chromosome in a t(8;14)-positive Burkitt lymphoma cell line demonstrated in somatic cell hybrids

A newly isolated Burkitt lymphoma cell line, ROS-1, carrying the specific translocation (8;14) has been studied using somatic cell hybridization techniques. As in other reported Burkitt cell lines, the oncogene c-myc was found to be translocated from the 8q- to the 14q+ chromosome. In contrast to other reports, expression of the mu immunoglobulin (Ig) heavy chain correlated with the presence of the 14q+ derivative and not of its normal homologue. These results indicate that the translocation (8;14) is not necessarily an abortive event for the production of the mu Ig heavy chain by the 14q+ derivative.

Rearrangement of immunoglobulin heavy chain genes and T3 expression in the absence of rearrangement of T-cell receptor beta-chain gene in a patient with T-cell malignant lymphoma

We describe the rearrangement of immunoglobulin genes and T3 expression in the absence of rearrangement of T-cell receptor beta-chain genes in a patient with T-cell malignant lymphoma. He had a mediastinal mass and his lymphoma cells expressed T-cell antigens (OKT3+, OKT9+, and OKT10+). When we examined genomic DNA from the lymphoma cells, we detected the rearrangement of immunoglobulin heavy chain genes with a germ-line configuration of light chain genes and no rearrangement of T-cell receptor beta-chain gene. These results indicated that the rearrangement of immunoglobulin genes could occur in T-cell malignant lymphoma, and that T3 antigen could be expressed prior to the rearrangement of T-cell receptor beta-chain genes under certain circumstances.

Single allelic C mu gene rearrangements in patients with T cell and undifferentiated leukemia

By using a panel of monoclonal antibodies in combination with conventional morphological and histochemical studies, seven leukemic patients were diagnosed as having T-cell lymphocytic leukemia (ALL) and three patients were classified as having acute undifferentiated leukemia (AUL). When genomic DNA from each patient was analysed by the Southern blot hybridization technique, two out of seven cases with T-cell ALL and two of three cases with AUL demonstrated immunoglobulin (Ig) mu gene rearrangements. Interestingly, the patterns of C mu gene rearrangement found in these four cases as well as in the T-cell line HSB-2 were quite similar with rearrangement of a single allele and germ line configuration retained in the other allele. Ig gene rearrangement is an essential property of cells of B-lineage, but detection of an Ig gene rearrangement by itself seems insufficient to assign commitment to B-lineage differentiation. The significance of Ig gene rearrangements in T-cell ALL is unclear, but this heterogeneity at the DNA level among T-cell ALL may reflect differences in leukemogeneis and have prognostic and therapeutic implications.

Lineage specific classification of leukaemia: results of the analysis of sixty cases of childhood leukaemia

In addition to conventional morphological, histochemical and immunological marker studies, cells from 60 children with leukaemia were further analysed using the Southern blot hybridization technique to look at differences in the organization of immunoglobulin (Ig) genes. Of the 60 patients studied by conventional means, 47 were diagnosed as acute lymphocytic leukaemia (ALL) and 13 as non-lymphocytic leukaemia. Seven patients were initially classified as T ALL and 40 as non-T, non-B ALL. Further subclassification of the 40 patients with non-T, non-B ALL indicated three pre-B ALL and 29 patients diagnosed as common ALL, expressing Ia and CALLA antigens. All 29 patients with common ALL demonstrated C mu gene rearrangements with or without light chain (kappa and lambda) genes rearrangement. Based on the developmental hierarchy of Ig gene rearrangement, it was possible to further subclassify the patients with common ALL into different stages of B cell development. Eight (of the 40) patients with non-T, non-B ALL were identified as CALLA- but further analysis indicated T-lineage origin in two patients and three patients were reclassified as acute undifferentiated leukaemia (AUL). C mu gene rearrangements were detected in two patients with T ALL, two patients with AUL and one patient with acute myelogenous leukaemia (AML). In contrast to the patients with common ALL, Ig gene rearrangement observed in these non-B-lineage cells was restricted to a single C mu gene while retaining germ-line configuration of the other allele of the C mu gene and both light chain genes.

Phenotypic heterogeneity at the DNA level in childhood leukemia with a mediastinal mass

Although phenotypic heterogeneity of childhood T-cell acute lymphocytic leukemia (T-ALL) which bear receptors for sheep red blood cells (E-rosettes) and/or T-cell-associated antigens has been reported, there are certain clinical features which are shared by most patients. A mediastinal mass is one of the most characteristic presentations in this particular disorder. This report describes four children with ALL, who presented with a mediastinal mass. Three patients were E-rosette-negative and one was E-rosette-positive. Individual surface phenotypes, defined by a panel of monoclonal antibodies, were quite different. Since Ig gene organization is an essential property of cells of B-lineage, it was surprising to find that analysis of genomic DNA revealed immunoglobulin (Ig) gene rearrangements in two of them. These findings suggest that there is significant heterogeneity even among those leukemias associated with a mediastinal mass, and that a mediastinal mass may not clearly indicate origin from cells of T-lineage. This heterogeneity may reflect differences in leukemogenesis and may have prognostic and therapeutic implications.

Contribution of immunophenotype to the classification and differential diagnosis of acute leukaemia

The diagnostic value of a panel of monoclonal antibodies was assessed in 100 consecutive patients with acute leukaemia. 97 patients were clearly phenotyped. Clinical and haematological feedback showed that the immunological data made a critical contribution to the final haematological diagnosis in 19 patients and provided useful confirmatory data in another 78. Immunophenotype also provided the basis for a subset classification of known prognostic relevance to acute lymphoblastic leukaemia (ALL). Immunophenotype and haematological findings conflicted in 2 cases, and 3 cases were unclassifiable with the antibody panel. In these difficult cases leukaemic-cell DNA was investigated for immunoglobulin gene rearrangement. Immunophenotyping with selective probes may be used in conjunction with other laboratory analyses (eg, karyotyping) in the routine investigation of patients with acute leukaemia.