Conversion of a stem cell leukemia from a T-lymphoid to a myeloid phenotype induced by the adenosine deaminase inhibitor 2'-deoxycoformycin

To B- or not to B-: A review of lineage switched acute leukemia

Acute leukemia is a heterogeneous disorder of hematologic malignancies composed primarily of hematopoietic precursors that have acquired unregulated self-renewal and proliferation. Hematology classification systems typically divide these neoplasms into lymphoid (B- or T-) and myeloid-lineage subtypes, with therapy dependent upon this distinction. Infrequently, certain acute leukemias may undergo a complete lineage switch at relapse, subsequently complicating the diagnosis and treatment of these recurrent diseases. Transformation from B-lineage to myeloid lineage is the most common switch observed, and is frequently associated with a balanced 11q23 translocation, involving KMT2A. The mechanisms involved in the lineage-switch are unclear, but modern therapies targeting the B-cell-specific marker, CD19, have proven to promote this conversion as one means of treatment escape. Broadly speaking, therapy-mediated selection of alternate lineage-committed subclones derived from the same initial pluripotent progenitors, clonal evolution and reprogramming of lineage-committed blasts, and de novo clonally unrelated leukemias may account for the clinical impression of lineage switched acute leukemia during treatment. This review will explore the phenomenon and potential mechanisms of lineage transformation during the treatment of acute leukemia.

Repeated Lineage Switches in an Elderly Case of Refractory B-Cell Acute Lymphoblastic Leukemia With MLL Gene Amplification: A Case Report and Literature Review

Lineage switches in acute leukemia occur rarely, and the underlying mechanisms are poorly understood. Herein, we report the case of an elderly patient with leukemia in which the leukemia started as B-cell acute lymphoblastic leukemia (B-ALL) and later changed to B- and T-cell mixed phenotype acute leukemia (MPAL) and acute myeloid leukemia (AML) during consecutive induction chemotherapy treatments. A 65-year-old woman was initially diagnosed with Philadelphia chromosome-negative B-ALL primarily expressing TdT/CD34/HLA-DR; more than 20% of the blasts were positive for CD19/CD20/cytoplasmic CD79a/cytoplasmic CD22/CD13/CD71.The blasts were negative for T-lineage markers and myeloperoxidase (MPO). Induction chemotherapy with the standard regimen for B-ALL resulted in primary induction failure. After the second induction chemotherapy regimen, the blasts were found to be B/T bi-phenotypic with additional expression of cytoplasmic CD3. A single course of clofarabine (the fourth induction chemotherapy regimen) dramatically reduced lymphoid marker levels. However, the myeloid markers (e.g., MPO) eventually showed positivity and the leukemia completely changed its lineage to AML. Despite subsequent intensive chemotherapy regimens designed for AML, the patient’s leukemia was uncontrollable and a new monoblastic population emerged. The patient died approximately 8 months after the initial diagnosis without experiencing stable remission. Several cytogenetic and genetic features were commonly identified in the initial diagnostic B-ALL and in the following AML, suggesting that this case should be classified as lineage switching leukemia rather than multiple simultaneous cancers (i.e., de novo B-ALL and de novo AML, or primary B-ALL and therapy-related myeloid neoplasm). A complex karyotype was persistently observed with a hemi-allelic loss of chromosome 17 (the location of the TP53 tumor suppressor gene). As the leukemia progressed, the karyotype became more complex, with the additional abnormalities. Sequential target sequencing revealed an increased variant allele frequency of TP53 mutation. Fluorescent in situ hybridization (FISH) revealed an increased number of mixed-lineage leukemia (MLL) genes, both before and after lineage conversion. In contrast, FISH revealed negativity for MLL rearrangements, which are well-known abnormalities associated with lineage switching leukemia and MPAL. To our best knowledge, this is the first reported case of acute leukemia presenting with lineage ambiguity and MLL gene amplification.

Aleukemic extramedullary T lymphoid/myeloid bilineage hematopoietic and lymphoid malignancy with progression to bilineage leukemia at relapse: A case report

Bilineage T lymphoid and myeloid (T/My) neoplasms are rare entities among the hematopoietic and lymphoid malignancies. The majority of patients present with leukemic symptoms in which blasts are observed in the peripheral blood (PB) or bone marrow (BM) at a percentage of >20% of nucleated cells. Only a minimal number of cases of T/My bilineage hematopoietic and lymphoid malignancy have been reported with extramedullary infiltration as the initial symptom. The origin of the neoplastic cells in T/My bilineage malignancy has been documented as the hematopoietic stem cells. The present study reports the case of a 31-year-old man with a T/My bilineage malignancy, which initially showed cervical lymph node enlargement beyond the diagnostic criteria of leukemia in the PB and in the BM. Two distinct malignant populations were detected in the cervical lymph node and pleural effusion, one of which was positive for MPO-staining, while the other was positive for cytoplasmic cluster of differentiation 3. Mutations in platelet-derived growth factor receptor α, platelet-derived growth factor receptor β, fibroblast growth factor receptor 1 and other chromosome abnormalities were excluded. The patient obtained complete remission after conventional chemotherapy, but relapsed with bilineage leukemia within a short period of time. Lymphoid and myeloid lineages have been reported to be differentiated from multipotent progenitors asymmetrically. However, the cellular mutation stage in T/My bilineage malignancy remains unclear. The present study also reviews the origin, development and therapeutic strategies for extramedullary T/My bilineage malignancy.

Lineage Switch in MLL-Rearranged Infant Leukemia Following CD19-Directed Therapy

Rearrangements of the mixed lineage leukemia (MLL) gene occur frequently in infants with both acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). Conversions of leukemia cell lineage are rare, but occur most commonly in the setting of MLL-rearrangement. Blinatumomab is a bidirectional antibody targeting CD19 with significant activity in relapsed B-precursor ALL. We report an infant with ALL with t(4;11)(q21;q23) refractory to cytotoxic chemotherapy who was treated with blinatumomab. Following rapid initial clearance of peripheral lymphoblasts, bone marrow evaluation demonstrated a leukemic lineage switch to CD19-negative monoblastic AML. Complete remission was achieved with myeloid-directed chemotherapy.

Lineage switch at relapse of childhood acute leukemia: a report of four cases

Lineage switch in acute leukemia is an uncommon event at relapse, and therefore rarely reported in the literature. Here, we have described the clinical laboratory features of four cases in which the cell lineage switched from acute lymphoblastic leukemia (ALL) to acute myeloid leukemia (AML). One patient was initially diagnosed with B-ALL, switched to T-ALL at the first relapse, and eventually, AML at the second relapse. A lineage switch represented either relapse of the original clone with heterogeneity at the morphologic level or emergence of a new leukemic clone. Further sequential phenotypic and cytogenetic studies may yield valuable insights into the mechanisms of leukemic recurrence, with possible implications for treatment selection.

Very early onset of an acute myeloid leukemia in an adult patient with B-cell lymphoblastic leukemia

We report on a case of a 30-year-old male with acute B-lymphoblastic leukemia (B-ALL) with immunophenotype CD19(+), CD22(+), CD20(+), CD10(+), with aberrant expression of CD13 and CD117, and IgH gene rearrangements. Three months after treatment with GMALL-2003 and Ida/FLAG protocols bone marrow showed predominance of blasts with myeloid morphology and phenotype MPO(+), CD13(+), CD33(+), CD64(+), CD15(+), CD56(+), EVI-1 gene overexpression and lack of IgH rearrangements. The case is the first report of a very early emergence of myeloid leukemia during the induction treatment for B-ALL in an adult patient. Different pathogenetic mechanisms are discussed - clonal evolution or selection, lineage switch or development of a de novo or therapy-induced leukemia.

Alterations in S-adenosylhomocysteine metabolism decrease O6-methylguanine DNA methyltransferase gene expression without affecting promoter methylation

The DNA repair enzyme O(6)-methylguanine DNA methyltransferase (MGMT) protects cells against the cytotoxic effects of alkylating agents. Therefore, modulation of MGMT expression in tumors is a possible strategy for improving the efficiency of cancer therapy. MGMT expression and activity is lost frequently in association with DNA hypermethylation of the MGMT promoter region. Since DNA and mRNA methylation are controlled by intracellular S-adenosylmethionine (AdoMet) and S-adenosylhomocysteine (AdoHcy) levels, we hypothesized a role for AdoMet/AdoHcy ratio in the regulation of MGMT promoter methylation and mRNA expression. Our initial studies showed that AdoMet/AdoHcy ratios vary over a wide range (7.0-50) in different glioblastoma and hepatoma cell lines. The studied cell lines exhibit distinct MGMT promoter methylation patterns: MGMT promoter was completely unmethylated in LN-18 and Tu 132 cells, hypermethylated in LN-229, U87-MG, and Tu 113 cells, and partially methylated in HepG2 cells. Furthermore, MGMT promoter methylation patterns and global DNA methylation are not related to intracellular AdoMet/AdoHcy ratio under control conditions. To lower AdoMet/AdoHcy ratio to values <1 we used AdoHcy hydrolase inhibitor adenosine-2',3'-dialdehyde (30 microM) and found that neither short-term (24 h) nor long-term changes (7 weeks) in AdoMet/AdoHcy ratio altered global or MGMT promoter methylation. However, experimentally elevated AdoHcy levels significantly decreased MGMT mRNA levels by >50% in all MGMT-expressing cell lines, which is most likely the result of impaired mRNA methylation. Thus, the present study suggests elevation of AdoHcy levels by AdoHcy hydrolase inhibition as a novel pharmacological approach to modulate MGMT expression and to increase the responsiveness to alkylating agents.

Altered intracellular and extracellular signaling leads to impaired T-cell functions in ADA-SCID patients

Mutations in the adenosine deaminase (ADA) gene are responsible for a form of severe combined immunodeficiency (SCID) caused by the lymphotoxic accumulation of ADA substrates, adenosine and 2'-deoxy-adenosine. The molecular mechanisms underlying T-cell dysfunction in humans remain to be elucidated. Here, we show that CD4(+) T cells from ADA-SCID patients have severely compromised TCR/CD28-driven proliferation and cytokine production, both at the transcriptional and protein levels. Such an impairment is associated with an intrinsically reduced ZAP-70 phosphorylation, Ca(2+) flux, and ERK1/2 signaling and to defective transcriptional events linked to CREB and NF-kappaB. Moreover, exposure to 2'-deoxy-adenosine results in a stronger inhibition of T-cell activation, mediated by the aberrant A(2A) adenosine receptor signaling engagement and PKA hyperactivation, or in a direct apoptotic effect at higher doses. Conversely, in T cells isolated from patients after gene therapy with retrovirally transduced hematopoietic stem/progenitor cells, the biochemical events after TCR triggering occur properly, leading to restored effector functions and normal sensitivity to apoptosis. Overall, our findings provide a better understanding of the pathogenesis of the immune defects associated with an altered purine metabolism and confirm that ADA gene transfer is an efficacious treatment for ADA-SCID. The trials in this study are enrolled at www.ClinicalTrials.gov as #NCT00598481 and #NCT0059978.

An in vivo functional genetic screen for suppressors of the Rag1-/- T-cell defect

Functional genetic screens on mutant backgrounds have been successfully used in lower organisms to investigate biological processes. However, few identical screens have been performed in mice. Recombinase activating gene-1 deficient (Rag1-/-) mice have a severe T-cell developmental block owing to lack of rearrangement of their T-cell receptor (TCR) genes. Using a retroviral cDNA library derived from wild-type embryonic thymocytes we performed a suppressor screen in Rag1-/- hematopoietic cells and recovered TCRbeta. This is the first demonstration that targeted genetic screens are feasible using transduced primary cells in vivo. Consequently, this technique can be used to interrogate multiple blood lineages using diverse hematopoietic mouse mutants.

T-cell acute lymphoblastic leukemia relapsing as acute myelogenous leukemia

We present the unusual case of a 16-year-old girl with T-cell acute lymphoblastic leukemia (ALL) with an early thymocyte immunophenotype without myeloid markers, who after 13 months of complete hematological remission relapsed as acute myelogenous leukemia (AML) with minimal differentiation and died of her disease. Whether the AML represented a relapse with lineage switch of the original immature T-cell clone or a new secondary malignancy, could not be proven due to the absence of molecular or clonal markers. This report suggests that a subset of CD7+ T-cell leukemias without mature T-cell antigens (CD4-, CD8-) are minimally differentiated and can relapse as AML.

Constitutively active beta-catenin confers multilineage differentiation potential on lymphoid and myeloid progenitors

Beta-catenin-mediated Wnt signaling may contribute to the self-renewal of hematopoietic stem cells and proliferation in some malignancies. We now show that expression of constitutively active beta-catenin in normal lymphoid or myeloid progenitors generated uncommitted cells with multilineage differentiation potential. Inappropriate gene expression occurred in cells destined to produce either cell type and caused corresponding changes in their characteristics. For example, forced activation of beta-catenin quickly increased C/EBPalpha while reducing EBF and Pax-5 in lymphoid progenitors that then generated myeloid cells. Inversely, EBF dramatically increased in transduced myeloid progenitors and lymphocytes were produced. The results indicate that ectopic activation of beta-catenin destabilizes lineage fate decisions and confers some, but not all, stem cell properties on committed progenitors.

Multilineage involvement of light microscopic myeloperoxidase-negative acute leukemia

The classification of acute leukemia has traditionally been based on a combination of morphology and cytochemical staining data, including myeloperoxidase (MPO) reaction; however, a recent World Health Organization (WHO) classification entails use of cytogenetic and molecular findings in addition to the classic morphological and immunophenotypic analyses. Nevertheless, there have been rare cases in which blastic cells show multilineage phenotypes. These cases may be classified as acute leukemia of ambiguous lineage in the recent WHO classification. We report the case of a 49-year-old man with acute leukemia with multilineage phenotypes. Morphological findings led to a diagnosis of acute myeloid leukemia M2 by the French-American-British classification, but at light microscopy the results of MPO staining were negative for blast cells. In contrast, results of reverse transcription polymerase chain reaction and fluorescence-activated cell sorter analyses were positive for expression of MPO messenger RNA and protein. The blast cells expressed CD4, CD19, CD22, CD33, CD38, CD79a, and HLA-DR and showed rearrangement of the immunoglobulin heavy chain and TCR-3 genes. Results of immunoelectron microscopic analysis of the blast cells were positive for MPO, CD19, CD33, CD34, CD38 and glycophorin A but not for platelet peroxidase. According to these results, the blast cells had at least 4 lineage phenotypes. We concluded that the multiparameter analyses conducted in this case, including immunological and ultrastructural assays, were important in arriving at the appropriate diagnosis of acute leukemia of ambiguous lineage in the new WHO classification.

Important roles of reversible acetylation in the function of hematopoietic transcription factors

Hematopoiesis is a very complex process whose proper functioning requires the regulated action of a number of transcription factors. Histone acetyltransferases (HATs) and histone deacetylases (HDACs) play significant roles in the regulation of hematopoietic transcription factors activity. Transcription factors such as GATA-1, EKLF, NF-E2, GATA-1, PU.1 recruit HATs and HDACs to chromatin, leading to histone acetylation and deacetylation, that affect chromatin structure and result in gene expression changes. On the other hand, transcription factors themselves can be acetylated and deacetylated by HATs and HDACs, respectively. Consequently, some important functions of these transcription factors are influenced, including DNA binding, transcription activation, repressor activity and proteinprotein interactions. The regulation of hematopoietic transcription factors activity by HATs and HDACs may serve as a good model for studying how tissue-specific and lineage-specific gene expression is controlled through acetylation/ deacetylation of histone/nonhistone proteins.

New insights into adenosine-receptor-mediated immunosuppression and the role of adenosine in causing the immunodeficiency associated with adenosine deaminase deficiency

There is growing interest in manipulating adenosine (Ado) signal transduction to control inflammation and autoimmunity. This concept probably originated with the discovery of severe combined immunodeficiency disease (SCID) in infants with inherited deficiency of adenosine deaminase (ADA). However, the basis for immunosuppression by Ado has not been well defined, and effects of 2'-deoxyadenosine (dAdo), which does not activate Ado receptors, have also been implicated in causing SCID. Here I discuss recent evidence that Ado, acting through its A2A receptor, interferes with NF-kappa B activation in antigen-receptor-stimulated B and T lymphocytes. I also assess the relative contributions of Ado and dAdo to the pathogenesis of ADA-deficient SCID.

Distinct mechanisms lead to HPRT gene mutations in leukemic cells

Leukemias are considered malignant clonal disorders arising from the accumulation of mutations in hematopoietic cells; the majority of these mutations are thought to be acquired somatically. Measurement of mutation frequency (Mf) at the hypoxanthine phosphoribosyltransferase (HPRT) locus has been developed as a method for estimating genomic instability. We investigated the Mf in 16 leukemic cell lines to determine whether these cell lines showed evidence of genomic instability. Although some leukemic cell lines had markedly elevated Mfs, the Mfs at the HPRT locus in leukemic cell lines were not always higher than those of B-lymphoblastoid cell lines and T lymphocytes from normal individuals. We were able to identify the HPRT mutation for 159 of 160 individual HPRT mutants. The HPRT mutations were characterized at a molecular level and classified as either gross chromosomal rearrangements (GCRs) or point mutations, such as single-nucleotide substitutions, insertions, or deletions. With rare exceptions, individual leukemic cell lines showed either point mutations or GCR, but not both. Of note, all the cell lines that primarily showed point mutations are known to be defective in mismatch repair machinery.

A novel c-kit positive biphenotypic acute leukemia cell line, TMBL-1, carrying a p53 point mutation

We established and characterized a c-kit positive cell line from the bone marrow of a patient with biphenotypic acute leukemia (BAL). The cell line, designated TMBL-1, carried a His-175 mutant p53. The immunophenotype of the primary leukemia cells at diagnosis was cytoplasmic CD3+, CD7+, CD13+, CD33-, interleukin-7 (IL-7) receptor+ and c-kit -. However, leukemia cells in relapse and TMBL-1 cells were CD33+ and c-kit +. Immunophenotypically, TMBL-1 is a BAL cell line that coexpresses T-lymphoid and myeloid markers which fulfill the criteria of the European Group for the Immunological Characterization of Leukemia. Stem cell factor (SCF), a key regulator of hematopoiesis signaling through c-kit, enhanced the proliferation of TMBL-1 cells. Direct sequencing revealed the conversion at codon 175 of the p53 gene in the TMBL-1 cells. Primary leukemia cells in relapse also carried the same point mutation but not at diagnosis. Moreover, TMBL-1 cells are sensitive to paclitaxel, which could induce p53-independent apoptosis. The biphenotypic features and p53 mutation may be associated with progression to a more malignant type. This cell line may provide new information on the role of SCF in the overlapping area between early T-lymphoid/myeloid cells, and help in the design of new therapies targeted towards p53 mutations.

Transcriptional regulation of erythropoiesis. Fine tuning of combinatorial multi-domain elements

Haematopoiesis, the differentiation of haematopoietic stem cells and progenitors into various lineages, involves complex interactions of transcription factors that modulate the expression of downstream genes and mediate proliferation and differentiation signals. Commitment of pluripotent haematopoietic stem cells to the erythroid lineage induces erythropoiesis, the production of red blood cells. This process involves a concerted progression through an erythroid burst forming unit (BFU-E), an erythroid colony forming unit (CFU-E), proerythroblast and an erythroblast. The terminally differentiated erythrocytes, in mammals, lose their nucleus yet function several more months. A well-coordinated cohort of transcription factors regulates the formation, survival, proliferation and differentiation of multipotent progenitor into the erythroid lineage. Here, we discuss broad-spectrum factors essential for self-renewal and/or differentiation of multipotent cells as well as specific factors required for proper erythroid development. These factors may operate solely or as part of transcriptional complexes, and exert activation or repression. Sequence comparisons reveal evolutionarily conserved modular composition for these factors; X-ray crystallography demonstrates that they include multidomain elements (e.g. HLH or zinc finger motifs), consistent with their complex interactions with other proteins. Finally, transfections and genomic studies show that the timing of each factor's expression during the hematopoietic process, the cell lineages affected and the existing combination of other factors determine the erythroid cell fate.

Two consecutive immunophenotypic switches in a child with immunogenotypically stable acute leukaemia

A 12-year-old girl presented with a CD33+ precursor B-acute lymphoblastic leukaemia (ALL) and seemed to respond well to ALL treatment. However, 2 weeks after diagnosis her leucocyte count rose rapidly with a predominance of myeloid blasts with M5b morphology and CD19+ myeloid immunophenotype. Acute myeloid leukaemia (AML) treatment was started and remission was achieved after one course of chemotherapy; the AML treatment was continued for 6 months. Two months after cessation of chemotherapy, the patient developed a bone marrow relapse, this time with an undifferentiated blast morphology and a precursor B immunophenotype. Molecular analysis of the immunoglobulin and T-cell receptor genes showed several clonal gene rearrangements at diagnosis: two IGH, two IGK and two TCRD gene rearrangements. All rearrangements were also detected during the AML phase of the disease, suggesting a phenotypic shift of the same leukaemia. At relapse, 8 months later, all rearrangements were preserved except for one TCRD (Vdelta2-Ddelta3) rearrangement. The first phenotypic shift in the genotypically stable leukaemia was remarkably fast. The most probable explanation for our observations is an oncogenic event in an undifferentiated haematopoietic progenitor clone, with a highly versatile phenotype.

What can we learn from leukemia as for the process of lineage commitment in hematopoiesis?

Most contemporary models of hematopoiesis assume lineage fidelity of early progenitor cells. Along with this concept normal hematopoietic cells and the majority of leukemias express exclusively myeloid or lymphoid specific antigens. On the other hand, growing evidence exists challenging the lineage fidelity model. Chronic myeloid leukemia (CML) in the blast crisis may switch to acute lymphoblastic leukemia (ALL) and as a result of the chemotherapy ALL may converse to acute myeloid leukemia (AML). Furthermore, a substantial portion of leukemia cases, named acute mixed-lineage leukemia (AMLL), show simultaneous expression of both myeloid and lymphoid antigens. Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements, correlating with myeloid-lymphoid immunophenotype in AMLL, support the hypothesis of lineage infidelity of early progenitor cells, rather than the aberrant antigen expression. Based on a detailed characterization of AMLL we present a modified model of a "common myeloid/lymphoid progenitor cell". This hypothetical very early hematopoietic progenitor cell shows a transient expression of myeloid and B- or T-lymphoid antigen and may also have rearranged its Ig and/or TCR genes. Subsequently, myeloid or lymphoid markers are downregulated and the hematopoietic cell enters either myeloid, T-lymphoid or B-lymphoid differentiation pathway.

The extracellular versus intracellular mechanisms of inhibition of TCR-triggered activation in thymocytes by adenosine under conditions of inhibited adenosine deaminase

The absence or low levels of adenosine deaminase (ADA) in humans result in severe combined immunodeficiency (SCID), which is characterized by hypoplastic thymus, T lymphocyte depletion and autoimmunity. Deficiency of ADA causes increased levels of both intracellular and extracellular adenosine, although only the intracellular lymphotoxicity of accumulated adenosine is considered in the pathogenesis of ADA SCID. It is shown that extracellular but not intracellular adenosine selectively inhibits TCR-triggered up-regulation of activation markers and apoptotic events in thymocytes under conditions of ADA deficiency. The effects of intracellular adenosine are dissociated from effects of extracellular adenosine in experiments using an adenosine transporter blocker. We found that prevention of toxicity of intracellular adenosine led to survival of TCR-cross-linked thymocytes in long-term (4 days) assays, but it was not sufficient for normal T cell differentiation under conditions of inhibited ADA. Surviving TCR-cross-linked thymocytes had a non-activated phenotype due to extracellular adenosine-mediated, TCR-antagonizing signaling. Taken together the data suggest that both intracellular toxicity and signaling by extracellular adenosine may contribute to pathogenesis of ADA SCID. Accordingly, extracellular adenosine may act on thymocytes, which survived intracellular toxicity of adenosine during ADA deficiency by counteracting TCR signaling. This, in turn, could lead to failure of positive and negative selection of thymocytes, and to additional elimination of thymocytes or autoimmunity of surviving T cells.

Developmental regulation of lymphocyte-specific protein 1 (LSP1) expression in thymus during human T-cell maturation

The lymphocyte specific protein 1 (LSP1) phosphoprotein is an F-actin binding molecule restricted to cells of hematopoietic origin in mice and humans. LSP1 is localized to the internal surface of the plasma membrane, the cytoplasm, and NP-40-insoluble actin filaments and is thought to mediate cytoskeleton-driven responses in activated leukocytes that involve receptor capping, cell-cell interactions and cell motility. Here, we generated two monoclonal antibodies (MAbs), 5E3 and 14G8, that are specific for human LSP1 to define the expression of LSP1 throughout human T-cell development. Both MAbs reacted with a 52-kDa protein in BW5147 cells transfected with human LSP1 cDNA in pcDNA3, but not in cells transfected with cDNA in an antisense orientation, indicating the specificity of 5E3 and 14G8 for human LSP1. In developing T cells, LSP1 was expressed on human fetal liver CD7+ NK and T-cell precursors, the CD7+, CD3-, CD4-, CD8- human stem cell line DU-528, and on CD4-, CD8- double-negative (DN) thymocytes. Immunohistochemistry and three-color flow cytometry analysis of fetal or postnatal thymocytes revealed that LSP1 was increasingly expressed during intrathymic human T-cell maturation. While immature CD4+CD8+ double-positive (DP) thymocytes expressed low to undetectable levels of LSP1, mature CD4+CD8- and CD4-CD8+ single-positive (SP) thymocytes expressed high levels of LSP1. Thus, LSP1 is developmentally regulated during T-cell maturation within the human thymus and may play a functional role in the motility of DN and SP thymocytes.

Large granular lymphocytic leukaemia with a mixed T-cell/B-cell phenotype

We report a case of large granular lymphocytic leukaemia (LGLL) with mixed T-cell/B-cell phenotypes. The LGLL cells expressed T-cell markers such as CD1, CD2, CD3, CD5, CD7, CD8 and CD57. The CD8+ LGLL cells coexpressed B-cell markers including CD20 and PCA-1, and a fraction of purified CD8+ LGLL cells secreted double isotypes of immunoglobulins (IgG-kappa and IgA-kappa). Both TCRB and IGH genes were clonally rearranged. The LGLL cells could be divided into at least three subpopulations that were cytogenetically distinct, and all subpopulations involved the 11q23. The expression of both T- and B-cell markers on the LGLL cells suggests the involvement of a putative common lymphoid progenitor in leukaemic transformation.

Induction of differentiation of human myeloid leukemia cells by 2'-deoxycoformycin in combination with 2'-deoxyadenosine

2'-Deoxycoformycin (dCF), a specific and potent inhibitor of adenosine deaminase, has demonstrated significant antitumor effect on lymphoid malignancies. The drug induced functional and morphologic differentiation of myeloid leukemia cells in combination with 2'-deoxyadenosine (dAd), but not dCF alone. NB4, a cell line derived from a patient with t(15; 17) acute promyelocytic leukemia (APL) underwent granulocytic differentiation when treated with all-trans retinoic acid (ATRA) or dCF plus dAd, but not with cytosine arabinoside. Pre-exposure of NB4 cells to ATRA greatly potentiated differentiation induced by dCF plus dAd, but pretreatment with dCF plus dAd before exposure to ATRA was less effective. Differentiation of NB4 cells was effectively induced by clinically applicable concentrations of dCF in combination with dAd. These findings may provide useful information about induction of differentiation in vivo.

Clinical expression, genetics and therapy of adenosine deaminase (ADA) deficiency

Adenosine deaminase (ADA) deficiency was the first known cause of primary immunodeficiency. Over the past 25 years the basis for immune deficiency has largely been established. Now it appears that ADA deficiency may also cause hepatic toxicity, raising new questions about its pathogenesis. The ADA gene has been sequenced and the ADA three-dimensional structure solved. The relationship between genotype and phenotype is being analysed, and ADA deficiency has become a focus for novel approaches to enzyme replacement and gene therapy.

Genomic instability in 1p and human malignancies

Both cytogenetic and molecular genetic approaches have unveiled non-random genomic alterations in 1p associated with a number of human malignancies. These have been interpreted to suggest the existence of cancer-related genes in 1p. Earlier studies had employed chromosome analysis or used molecular probes mapped by in situ hybridization. Further, studies of the various tumor types often involved different molecular probes that had been mapped by different technical approaches, like linkage analysis, radioactive or fluorescence in situ hybridization, or by employing a panel of mouse x human radiation reduced somatic cell hybrids. The lack of maps fully integrating all loci has complicated the generation of a comparative and coherent picture of 1p damage in human malignancies even among different studies on the same tumor type. Only recently has the availability of genetically mapped, highly polymorphic loci at (CA)n repeats with sufficient linear density made it possible to scan genomic regions in different types of tumors readily by polymerase chain reaction (PCR) with a standard set of molecular probes. This paper aims at presenting an up-to-date picture of the association of 1p alterations with different human cancers and compiles the corresponding literature. From this it will emerge that the pattern of alterations in individual tumor types can be complex and that a stringent molecular and functional definition of the role that Ip alterations might have in tumorigenesis will require a more detailed analysis of the genomic regions involved.

TCR delta gene rearrangements in acute myeloid leukemia with T-lymphoid antigen expression

In this review we present our data concerning T-cell receptor (TCR) delta gene rearrangements in acute myeloid leukemia with coexpression of T-lymphoid features (CD2/CD4/CD7; Ly+ AML). We found a correlation between TCR delta gene rearrangements and coexpression of these T-lymphoid features. Ten of 66 Ly+ AML and only one of 44 AML cases without this coexpression exhibited TCR delta gene rearrangements (p = .028). In contrast, no correlation was observed between terminal deoxynucleotidyl transferase (TdT) expression and the occurrence of TCR delta gene rearrangements in AML. Rearrangements were found in two of 25 AML with and seven of 71 AML cases without TdT expression. Interestingly, nucleotide sequencing of junctional sites revealed up to 36 N-nucleotides in cases without or with only weak TdT expression indicating downregulation of TdT expression after the TCR rearrangement took place. Complete V delta 1J delta 1 and incomplete D delta 2J delta 1 gene rearrangements were observed most frequently in Ly+ AML. These recombination patterns were similar to patterns observed in acute T-lymphoblastic leukemia with coexpression of myeloid features (My+ T-ALL) suggesting transformation of a common myeloid/T-lymphoid progenitor cell in these cases.

Adenosine-deaminase-deficient mice die perinatally and exhibit liver-cell degeneration, atelectasis and small intestinal cell death

We report the generation and characterization of mice lacking adenosine deaminase (ADA). In humans, absence of ADA causes severe combined immunodeficiency. In contrast, ADA-deficient mice die perinatally with marked liver-cell degeneration, but lack abnormalities in the thymus. The ADA substrates, adenosine and deoxyadenosine, are increased in ADA-deficient mice. Adenine deoxyribonucleotides are only modestly elevated, whereas S-adenosylhomocysteine hydrolase activity is reduced more than 85%. Consequently, the ratio of S-adenosylhomocysteine (AdoMet) to S-adenosyl homocysteine (AdoHcy) is reduced threefold in liver. We conclude that ADA plays a more critical role in murine than human fetal development. The murine liver pathology may be due to AdoHcy-mediated inhibition of AdoMet-dependent transmethylation reactions.

Lineage determination of CD7+ CD5- CD2- and CD7+ CD5+ CD2- lymphoblasts: studies on phenotype, genotype, and gene expression of myeloperoxidase, CD3 epsilon, and CD3 delta

The gene expression of myeloperoxidase (MPO), CD3 epsilon, and CD3 delta molecules, the gene rearrangement of T-cell receptor (TCR) delta, gamma, and beta and immunoglobulin heavy (IgH) chain, and the expression of cell-surface antigens were investigated in seven cases of CD7+ CD5- CD2- and four cases of CD7+ CD5+ CD2- acute lymphoblastic leukemia or lymphoblastic lymphoma (ALL/LBL) blasts, which were negative for cytochemical myeloperoxidase (cyMPO). More mature T-lineage blasts were also investigated in a comparative manner. In conclusion, the CD7+ CD5- CD2- blasts included four categories: undifferentiated blasts without lineage commitment, T-lineage blasts, T-/myeloid lineage blasts, and cyMPO-negative myeloblasts. The CD7+ CD5+ CD2- blasts included two categories; T-lineage and T-/myeloid lineage blasts. The 11 cases were of the germ-line gene (G) for TCR beta and IgH. Four cases were G for TCR delta and TCR gamma. The others were of the monoclonally rearranged gene (R) for TCR delta and G for TCR gamma or R for both TCR delta and TCR gamma. The expression or in vitro induction of CD13 and/or CD33 antigens correlated with the immaturity of these neoplastic T cells, since it was observed in all 11 CD7+ CD5- CD2- and CD7+ CD5+ CD2-, and some CD7+ CD5+ CD2+ (CD3- CD4- CD8-) cases, but not in CD3 +/- CD4+ CD8+ or CD3+ CD4+ CD8- cases. CD3 epsilon mRNA, but not CD3 delta mRNA, was detected in two CD7+ CD5- CD2- cases, while mRNA of neither of the two CD3 molecules was detected in the other tested CD7+ CD5- CD2- cases. In contrast, mRNA of both CD3 epsilon and CD3 delta were detected in all CD7+ CD5+ CD2- cases, indicating that CD7+ CD5- CD2- blasts at least belong to T-lineage. The blasts of two CD7+ CD5- CD2- cases with entire germ-line genes and without mRNA of the three molecules (MPO, CD3 epsilon, and CD3 delta) were regarded as being at an undifferentiated stage prior to their commitment to either T- or myeloid-lineage. The co-expression of the genes of MPO and CD3 epsilon in a CD7+ CD5- CD2- case MPO, CD3 epsilon, and CD3 delta in a CD7+ CD5+ CD2- case suggested the presence of some overlapping phase for T- and myeloid-lineage commitment during immature stages of differentiation. This helps understand the conversion of some T-ALL/LBL cases to acute myeloblastic leukemia (AML).(ABSTRACT TRUNCATED AT 400 WORDS)

Establishment and characterization of a human leukemic cell line (SR-91) with features suggestive of early hematopoietic progenitor cell origin

The characterization of a cell line (designated SR-91) from a patient with clinical and morphological diagnosis of acute lymphoblastic leukemia (CD3-, CD2+, CD7+, germline TCR genes) who relapsed early after allogeneic bone marrow transplantation, is reported. The line was established from blood cells obtained at diagnosis and placed in suspension culture with medium conditioned by 5637 cells. SR-91 cells are negative for lymphoid surface markers (CD3-, CD2-, CD7-) but positive for markers indicative of myeloid progenitor cells, such as CD33 and CD34. It is likely that the conditioned medium has induced myeloid differentiation from a lymphohematopoietic progenitor cell. After establishment, cells proliferated in response to GM-CSF stimulation but they are not factor-dependent and do not produce GM-CSF. No proliferative response to IL-1, IL-2, IL-3, IL-4, IL-6 or M-CSF was observed. Cells were completely resistant to anti-proliferative effects of tumor necrosis factor-alpha and interferon-alpha or -gamma, and showed no lysis after incubation with freshly isolated natural killer cells or IL-2-activated natural killer cells.

Human thymic epithelial cells: adhesion molecules and cytokine production

The ability to culture human thymic epithelial cells has greatly facilitated studies of direct cell-cell interaction between thymic epithelial cells and T lymphocytes in vitro, as well as cytokine production and regulation of cytokine production. In vitro, human thymic epithelial cells bind to T lymphocytes via two adhesion pathways: CD2-lymphocyte function-associated antigen-3 and lymphocyte function-associated antigen-1-intercellular adhesion molecule-1. Cultured human thymic epithelial cells produce interleukins-1 alpha, -1 beta, -3, -6 and -8, granulocyte colony-stimulating factor, macrophage colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, leukemia inhibitory factor and transforming growth factor-alpha. Production of thymic epithelial cell-derived cytokines is regulated by both adhesion molecules (lymphocyte function-associated antigen-3) and soluble factors via both autocrine (interleukin-1 alpha, transforming growth factor-alpha) and paracrine (interleukin-4, interferon-gamma) pathways. Transforming growth factor-alpha and epidermal growth factor regulate various cytokine mRNA at a post-transcriptional level by increasing cytokine mRNA stability.

CD7+ stem cell leukemia/lymphoma. Features of a subgroup without circulating blast cells

Recent advances in immunology have clarified the cellular origin of hematopoietic neoplasms. Blast cells with a CD7+ CD4- CD8- phenotype are demonstrated to originate from malignant pluripotent hematopoietic stem cells. In this article, the authors describe three rare cases, designated as a lymphoma type of CD7+ stem cell leukemia/lymphoma, with clinical features described below. All three patients were admitted with non-Hodgkin lymphoma with a 2-month to 4-month history of lymphadenopathy. Histologic examination of lymph nodes showed lymphoblastic lymphoma (LBL) in all patients. Bone marrow blast cells had an immunophenotype consistent with CD7+ CD4- CD8- acute leukemia, although abnormal cells were not observed in the peripheral blood during the course of the disease. One patient had a recurrence in the bone marrow, with myeloperoxidase-positive blast cells expressing myeloid differentiation antigens. Chromosomal analysis detected a common abnormal karyotype initially and at relapse. Furthermore, the same T-cell receptor gene rearrangement was found initially and at relapse, suggesting that these blast cells originated from the same pluripotent leukemic clone. Additional studies on more patients are required to determine the clinical significance of this group, including the difference from CD7+ stem cell leukemia/lymphoma with circulating blast cells (leukemic type) or LBL.

Tumor-associated karyotypic lesions coselected with in vitro macrophage differentiation

Several cytogenetic lesions in chromosomes 2, 5, 12, and 16 have been repeatedly coselected with in vitro macrophage differentiation in a clonal murine thymic tumor cell line. Parental-type subclones, which show an extremely immature hemopoietic phenotype, do not carry the aberrations. The frequency of the stable differentiated variants is elevated by 5-azacytidine and bromodeoxyuridine, consistent with chromosome breakage being responsible for the phenotype. The frequency is also raised by dexamethasone. Since variants are 300-3,000-fold more resistant to dexamethasone than parental clones, we interpret this to be largely due to selection. Three of the lesions, on chromosome 2, match those previously described as associated specifically with in vivo-generated murine myeloid tumors, induced by X irradiation and corticosteroid treatment. Several implications follow from these observations. (1) In vitro differentiation in clonal tumor cell lines can be used to select for tumor-associated lesions. This should allow genetic and molecular analysis of the chromosome 2 lesions and of others that may pinpoint genes critical to macrophage differentiation and transformation. (2) Myeloid and lymphoid tumors that occur in response to X irradiation may diverge from a common initiating tumor. (3) The hemopoietic lineage switch phenomenon, previously described by several authors, may be caused by similar or identical chromosome aberrations.

Mapping of the structural gene for S-adenosyl homocysteine hydrolase to mouse chromosome 2, and related sequences to chromosomes 8 and X

Comparative mapping studies in human and mouse have shown that, to date, human Chromosome (Chr) 20 is completely syntenic with distal mouse Chr 2. The structural locus for S-adenosyl-L-homocysteine hydrolase (EC 3.3.1.1) in human, AHCY, maps to 20 qter-->q13.1, and we report here that the homologous locus in the mouse, Ahcy, maps to distal mouse Chr 2 with gene order Pcna-Ahcy-Ada. Analysis of 123 progeny of an interspecific backcross between a laboratory stock, AN, and Mus spretus using a rat cDNA probe revealed the presence of at least two other Ahcy-related sequences segregating independently in the mouse genome. One, Ahcy-rs1, was mapped to Chr 8 in the BXH recombinant inbred strains, and the other, Ahcy-rs2, shows a pattern of inheritance consistent with X-linkage.

Phenotypic and genotypic switch in Philadelphia-positive, BCR-positive blast crisis of chronic myeloid leukemia

We report a case of Ph1-positive, bcr-positive chronic myeloid leukemia blast crisis (CML-BC) which at presentation showed a mixed myeloid/B-lymphoid immunophenotype along with TdT positivity and, at the molecular level, an oligoclonal rearrangement of the immunoglobulin heavy chain (IgH) gene region. After obtaining a successful remission, at the time of relapse the patient underwent a phenotypic and genotypic switch from mixed to myeloid phenotype, characterized by the loss of the lymphoid markers and TdT expression and by a germline configuration of the IgH gene region. The same bcr rearrangement was, however, found in both phases of the disease, supporting the suggestion of a true phenotypic and genotypic conversion. This report confirms that the neoplastic event in CML may take place at an early multipotent stem-cell level, prior to a well-defined phenotypic and genotypic lineage expression. Moreover, it is suggested that different factors (chemotherapy? growth factors?) may have either eradicated the bcr+/IgH+ clone and promoted the growth of bcr+/IgH- leukemic cells or, alternatively, supported the lymphoid differentiation program and induced a myeloid lineage shift.