Target cell in chronic myeloid leukaemia and its relationship to acute lymphoid leukaemia

CRISPR-Cas9 Technology as a Tool to Target Gene Drivers in Cancer: Proof of Concept and New Opportunities to Treat Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a hematopoietic malignancy produced by a unique oncogenic event involving the constitutively active tyrosine-kinase (TK) BCR/ABL1. TK inhibitors (TKI) changed its prognosis and natural history. Unfortunately, ABL1 remains unaffected by TKIs. Leukemic stem cells (LSCs) remain, and resistant mutations arise during treatment. To address this problem, we have designed a therapeutic CRISPR-Cas9 deletion system targeting BCR/ABL1. The system was efficiently electroporated to cell lines, LSCs from a CML murine model, and LSCs from CML patients at diagnosis, generating a specific ABL1 null mutation at high efficiency and allowing the edited leukemic cells to be detected and tracked. The CRISPR-Cas9 deletion system triggered cell proliferation arrest and apoptosis in murine and human CML cell lines. Patient and murine-derived xenografts with CRISPR-edited LSCs in NOD SCID gamma niches revealed that normal multipotency and repopulation ability of CRISPR edited LSCs were fully restored. Normal hematopoiesis was restored, avoiding myeloid bias. To the best of our knowledge, we show for the first time how a CRISPR-Cas9 deletion system efficiently interrupts BCR/ABL1 oncogene in primary LSCs to bestow a therapeutic benefit. This study is a proof of concept for genome editing in all those diseases, like CML, sustained by a single oncogenic event, opening up new therapeutic opportunities.

Future Approaches for Treating Chronic Myeloid Leukemia: CRISPR Therapy

Simple Summary

In the last two decades, the therapeutic landscape of several tumors have changed profoundly with the introduction of drugs against proteins encoded by oncogenes. Oncogenes play an essential role in human cancer and when their encoded proteins are inhibited by specific drugs, the tumoral process can be reverted or stopped. An example of this is the case of the chronic myeloid leukemia, in which all the pathological features can be attributed by a single oncogene. Most patients with this disease now have a normal life expectancy thanks to a rationality designed inhibitor. However, the drug only blocks the protein, the oncogene continues unaffected and treatment discontinuation is only an option for a small subset of patients. With the advent of genome-editing nucleases and, especially, the CRISPR/Cas9 system, the possibilities to destroy oncogenes now is feasible. A novel therapeutic tool has been developed with unimaginable limits in cancer treatment. Recent studies support that CRISPR/Cas9 system could be a definitive therapeutic option in chronic myeloid leukemia. This work reviews the biology of chronic myeloid leukemia, the emergence of the CRISPR system, and its ability as a specific tool for this disease.

Abstract

The constitutively active tyrosine-kinase BCR/ABL1 oncogene plays a key role in human chronic myeloid leukemia development and disease maintenance, and determines most of the features of this leukemia. For this reason, tyrosine-kinase inhibitors are the first-line treatment, offering most patients a life expectancy like that of an equivalent healthy person. However, since the oncogene stays intact, lifelong oral medication is essential, even though this triggers adverse effects in many patients. Furthermore, leukemic stem cells remain quiescent and resistance is observed in approximately 25% of patients. Thus, new therapeutic alternatives are still needed. In this scenario, the interruption/deletion of the oncogenic sequence might be an effective therapeutic option. The emergence of CRISPR (clustered regularly interspaced short palindromic repeats) technology can offer a definitive treatment based on its capacity to induce a specific DNA double strand break. Besides, it has the advantage of providing complete and permanent oncogene knockout, while tyrosine kinase inhibitors (TKIs) only ensure that BCR-ABL1 oncoprotein is inactivated during treatment. CRISPR/Cas9 cuts DNA in a sequence-specific manner making it possible to turn oncogenes off in a way that was not previously feasible in humans. This review describes chronic myeloid leukemia (CML) disease and the main advances in the genome-editing field by which it may be treated in the future.

Chronic Lymphocytic Leukemia (B-Cell) in the Course of Polycythemia Vera. Description of a Case with an Unusual Chromosomic Anomaly

The present paper describes the case of a patient who developed a B-cell chronic lymphocytic leukemia (B-CLL) 15 months after the diagnosis of polycythemia vera, which had been treated only with phlebotomies. In spite of lymphocytosis and the clinical signs and symptoms of leukemia, the patient exhibited at the same time presumptive elements of polycythemia (high LAP index levels, a high number of neutrophils). Cytogenetic investigations, carried out after the appearance of B-CLL, revealed the presence of an unusual abnormality (18 p+) both in bone marrow not stimulated by mitogens and in PWM-stimulated circulating lymphocytes. This case, which is the ninth of its kind described in the literature, offers some interesting observations about the association between myeloproliferative and lymphoproliferative syndromes.

Stem cell and kinase activity-independent pathway in resistance of leukaemia to BCR-ABL kinase inhibitors

BCR-ABL tyrosine kinase inhibitors, such as imatinib (Gleevec) are highly effective in treating human Philadelphia chromosome-positive (Ph⁺) chronic myeloid leukaemia (CML) in chronic phase but not in terminal acute phase; acquired drug resistance caused mainly by the development of BCR-ABL kinase domain mutations prevents cure of the leukaemia. In addition, imatinib is ineffective in treating Ph⁺ B-cell acute lymphoblastic leukaemia (B-ALL) and CML blast crisis, even in the absence of the kinase domain mutations. This type of drug resistance that is unrelated to BCR-ABL kinase domain mutations is caused by the insensitivity of leukaemic stem cells to kinase inhibitors such as imatinib and dasatinib, and by activation of a newly-identified signalling pathway involving SRC kinases that are independent of BCR-ABL kinase activity for activation. This SRC pathway is essential for leukaemic cells to survive imatinib treatment and for CML transition to lymphoid blast crisis. Apart from BCR-ABL and SRC kinases, stem cell pathways must also be targeted for curative therapy of Ph⁺ leukaemia.

Src kinases as targets for B cell acute lymphoblastic leukaemia therapy

The participation of Src kinases in the induction of BCR-ABL-induced B cell acute lymphoblastic leukaemia (B-ALL), but not chronic myeloid leukaemia (CML), demonstrates cell type-specific signalling in Philadelphia chromosome-positive (Ph+) leukaemias. Different therapeutic strategies are therefore needed for B-ALL and CML. Activation of Src kinases is independent of BCR-ABL kinase activity for activation. Thus, Src kinases provide a mechanism for resistance to the BCR-ABL kinase inhibitors and potential targets for B-ALL therapy. Simultaneous targeting of both BCR-ABL and Src kinases may benefit human B-ALL patients. Leukaemic stem cells may exist in Ph+ B-ALL, and eradication of this group of cells would provide a curative method for this disease.

De novo Ph negative T-cell lymphoblastic leukaemia associated with bcr gene rearrangement

One case of de novo Ph-negative T-cell acute lymphoblastic leukaemia has been found to have a classical breakpoint cluster region (bcr) rearrangement of the type seen in chronic granulocytic leukaemia. There were no haematological features to suggest a previous chronic phase. This case represents the first report of this rearrangement in Ph negative acute T-lymphoblastic leukaemia at presentation. The implications for various therapeutic options in such patients are discussed.

Phenotypic characterization of 'non-T, non-B' acute lymphoblastic leukemia by a new panel (BL) of monoclonal antibodies

Peripheral blood and/or bone marrow leukemic cell suspensions from 49 patients with 'non-T, non-B' acute lymphoblastic leukemia (ALL) were analysed by flow cytometry using a new panel of four monoclonal antibodies. Anti-BL1 and anti-BL2 originating from NALM-6 and B35M lymphoblastoid cell lines, respectively. These antibodies recognize B-cell differentiation antigens: a heat stable non-immunoprecipitable antigenic determinant, and a 68 000 daltons glycoprotein molecule, respectively. BL5 and BL6 were derived by immunization with the promyelocytic cell line HL-60, recognizing antigens present on early hematopoietic cells: an 85 000 daltons MW glycoprotein (Pro-Im 1) and a heat stable antigen (Pro-Im2), respectively. All ALL patients studied had L1 or L2 morphology by the FAB classification and a blast count exceeding 50 per cent. There were 25 males and 24 females. Median age was 8 years (range 1-67 years). Thirty-nine cases were studied at initial presentation and 10 at relapse. Cells from 46/49 cases expressed BL2 and/or BL1, but were not reactive with BL5 or BL6. Three of 49 cases did not express BL1 or BL2. However, a small percentage of blasts from one case was positive for BL5 (13 per cent) and the other 2 cases were reactive with BL6 (20 per cent and 36 per cent, respectively). These were one adult and 2 pediatric patients that had other ALL markers and achieved a complete remission with appropriate ALL therapy. One of the BL6+ cases relapsed after 19 months with a change in phenotype to BL1+ BL2+ BL5- BL6-. This analysis shows that the majority of 'non-T, non-B' ALL's do express B-cell associated antigens (BL1/BL2) argumentative of their B-cell origin. A small subgroup does not express such antigens and may arise from a more immature cell, since they expressed antigens on early hematopoietic stem cells.

Identification of malignant plasma cell precursors in the bone marrow of multiple myeloma

Precursors of plasma cells were studied in the bone marrow of 28 patients with multiple myeloma, plasma cell leukemia, and benign monoclonal gammopathy. Pre-B and B cell populations were analyzed with anti-B monoclonal antibodies corresponding to the clusters standardized at the Leucocyte Typing Workshops in Paris and Boston (CD9, CD10, CD19-22, CD24). In advanced forms of plasma cell malignancies, such as cases of multiple myeloma in stages II and III and of plasma cell leukemia, some cells of lymphoid morphology expressed common acute lymphoblastic leukemia antigen (CALLA, CD10) and HLA-DR, but contained no detectable terminal deoxynucleotidyl transferase enzyme. These CALLA+ cells were absent in benign monoclonal gammopathies. In multiple myeloma, the CALLA+ cells were negative for surface and cytoplasmic immunoglobulins (Ig), and, unlike CALLA+, terminal deoxynucleotidyl transferase (TdT+) pre-B cells in the normal bone marrow also failed to react with antibodies to B cell-associated antigens such as CD9, CD19, CD22, and CD24. The CALLA+, Ig- cells could be regarded as preplasmacytic since, after having been separated and stimulated with the phorbol ester 12-0-tetradecanoyl-phorbol-13 acetate in vitro, they transformed into plasma cells and synthesized the same heavy and light chains as myeloma cells.

Cell lineage heterogeneity in blast crisis of chronic myeloid leukaemia

Blast cells from 45 patients with chronic myeloid leukaemia in blast crisis (CML-BC) were immunologically phenotyped with a panel of 26 monoclonal antibodies and studied for terminal deoxynucleotidyl transferase (TdT) content. Out of 45 blast-populations, 28 showed a myeloid, 14 a lymphoid, two a mixed and one an unclassifiable marker profile. In contrast to acute myeloid leukaemia (AML), we found frequent involvement of the thrombopoietic and erythropoietic systems in myeloid CML-BC. Furthermore, the marker profile on blast cells in myeloid CML-BC was different from that seen in AML. The blast cells in lymphoid blast crises of CML displayed the same lymphoid marker profile as those in acute lymphoblastic leukaemia. In three of 16 patients who were serially tested, we observed phenotypic changes in the blast cell populations. In one patient the blasts changed from lymphoid to myeloid type while remaining TdT-positive; in another case the blasts switched from granulomonocytic TdT-negative to granulomonocytic TdT-positive. In the third patient erythroid precursor cells appeared as the disease progressed. The results indicate the capacity of blast populations in CML-patients during blast crisis to differentiate along several pathways.

Characterization of extramedullary tumors in a case of Ph-positive chronic myelogenous leukemia: possible involvement of immature T lymphocytes

A 42-year-old male with chronic myelogenous leukemia (CML) developed acute transformation associated with subcutaneous tumors. Histopathologic examinations of the tumors were done on two occasions; the first study revealed reticulum cell sarcoma-like features, and the second suggested a blastoma. Chromosomal analysis showed that the cells of the tumors originated from the CML clone. The cells had a negative reaction for myeloperoxidase by electron microscopy. Furthermore, biochemical and surface marker studies revealed that the tumor cells contained a significant terminal transferase activity. However, they did not express E- or EAC-rosette receptors, Ia-like antigens, or common ALL antigens.

Cell surface markers in leukemia: biological and clinical correlations

Recent advances in analysis of leukemic cell phenotypes using cell surface markers have provided important insights into leukocyte differentiation and the cellular origin of leukemia. In addition to the traditional cell surface markers, i.e., surface membrane immunoglobulin and receptors for sheep erythrocytes that define B and T lymphocytes, highly specific monoclonal antibodies have been developed that discriminate various stages of human lymphocyte and granulocyte differentiation. Explorations of the detailed phenotypes of leukemic cells in relation to normal hemopoietic differentiation reveal that consistent, composite phenotypes of different subclasses of lymphoid malignancies closely mimic those of corresponding normal cells at equivalent levels of maturation. This is exemplified in lymphoma cells (chronic lymphocytic leukemia of B or T type, Sezary Syndrome, immunocytoma) that resemble mature and immunocompetent T and B cells, in T cell acute lymphoblastic leukemia (T-ALL) (equivalent to thymus cells) and in non-T ALL (corresponding to lymphoid progenitor cells in the bone marrow). The major phenotypes documented in different leukemias represent the level of maturation arrest imposed on the dominant subclone; this is determined by, but not necessarily synonymous with, the target cell and associated clonogenic cell population in the leukemia. The clinical significance of immunodiagnosis of leukemia cell types becomes best evidenced in acute leukemias. Besides the improvement of diagnosis by using objective criteria, clinically useful subclassifications became evident: five major subtypes of ALL are now recognized, including unclassified or null ALL, common ALL, pre-B-ALL, B-ALL and pre-T/T-ALL. In addition to disclosing that ALL is an heterogeneous disease, such classifications have proved to be prognostically significant. This is exemplified in 248 children and 145 adults with ALL which were analysed for cell type and clinical data. In addition to their utility in leukemia classification, monoclonal antibodies that identify leukemia associated antigens are becoming used therapeutically, e.g., to lyse residual leukemia cells from remission bone marrows removed from leukemia patients before reinfusion. New approaches to the treatment of leukemia in which the objective is to encourage maturation of leukemia cells rather than to achieve leukemia eradication, can be monitored by phenotyping the alterations of the cell surface, and cell markers may hopefully be useful in identifying cell types that can be induced to differentiate.

Ia+T10+ blast cells in acute lymphoblastic leukaemia are precursors of T+ and B+ cells

Leukaemic blasts isolated from peripheral blood of two patients with non-T, non-B ALL were cultivated for 10-13 days and cell markers were assayed on day 0 and during culture period. Using a panel of cell markers it was demonstrated that the populations of ALL blasts of both patients were composed of T10+Ia+ and "null" blasts. These blasts in the culture differentiated into three cell lines: T and B lymphocytes and myelomonocytic cells. The results thus obtained suggested that within the population of ALL blasts of these two patients there are progenitors of lymphoid and myelomonocytic cells ("null" blasts) and common precursors of T and B lymphocytes (T10+Ia+ blasts). In vitro differentiation of ALL blasts was not affected by LPS and CTPE.

Chronic myeloproliferative disorders (CMPD)

The wide clinical range of CMPD can be understood as leukaemia of pluripotent stem cells according to the pathogenic concepts reviewed above. Blastic metamorphoses of CMPD are regressions to a more primitive level of cellular differentiation. The predominant proliferative cell line characterizes the classical entities of PV, PT and CML, and their different prognoses. Pure erythrocytic and megakaryocytic proliferations are more compatible with sustained physiologic bone marrow functions than granulocytic proliferations. The combinations of granulocytic and megakaryocytic growth are especially prone to develop MF/OMS, in which participation of immune reactions, of granulocytic and of platelet factors is probable. An etiologic role for ineffective thrombocytopoiesis is supported by experimental as well as by histologic evidence. Myelofibrosis and osteomyelosclerosis may have similar causes, but develop independently. The prevalence of the female sex among thrombocythaemic patients was proven statistically also for the increase of giant type megakaryocytes in the form of clusters in the bone marrow, and for longer median survival of females in CMPD, especially when there is megakaryocytosis in the bone marrow. It is assumed that females may be better protected against the detrimentous effects of abnormal platelet production. An arbitrary classification according to haematologic and histologic criteria was applied to PV, PT and CML, and groups with typical and atypical haematologic and histologic signs were distinguished. The latter cannot be separated from each other by their various haematologic manifestations, but by histology and their different propensity to progress into more immature and/or fibrotic stages. Three major groups are characterized by histology: mixed granulocytic-megakaryocytic myelosis with giant megakaryocytic clusters, a similar variant with diffuse distribution of giant megakaryocytes, and immature and/or pleomorphic megakaryocytic myelosis. Transitions from each of these groups have been observed as well as transitions from each of the typical CMPD-entities into these less typical forms. CML, frequently accompanied by dwarf-megakaryocytes, often develops into pleomorphic megakaryocytic or blastic myelosis. Blastic dedifferentiation and myelofibrosis manifest themselves as closely related end stages, to which principally all groups proceed after a longer or shorter period of time, modified by the proliferating cell lines in each group. Clinical, experimental and histologic evidence of this natural history has been reviewed, with special emphasis on the re-evaluation of technically optimal bone marrow biopsies of untreated patients.(ABSTRACT TRUNCATED AT 400 WORDS)

T-cell acute lymphoblastic leukaemia with late developing Philadelphia chromosome

A case of childhood T-cell acute lymphoblastic leukaemia (ALL) is presented in which the only chromosome abnormality at diagnosis was a deletion of part of the short arm of one chromosome 9 (9p-). Cytogenetic studies at relapse showed, in addition to 9p-, a partial deletion of the long arm of one chromosome 6 (6q-) and the Philadelphia chromosome (Ph1) produced as a result of the classical translocation t(9q+;22q-). All metaphases from haemopoietic colonies grown from a cryopreserved specimen of this patient's marrow at relapse were normal, in contrast to haemopoietic colonies cultured from patients with chronic myelogenous leukaemia (CML) which contained the Ph1. A hypothesis which incorporates T-cell ALL with late development of the Ph1 into the overall family of Ph1 positive diseases is suggested.

Second neoplasms in acute lymphoblastic leukemia

The authors reviewed 61 reported cases of second neoplasms in acute lymphoblastic leukemia (ALL), including 17 patients with ALL followed by another type of acute leukemia, 12 patients with ALL followed by chronic myelocytic leukemia, 19 patients with ALL followed by lymphoma, and 13 patients with ALL followed by other solid tumors. From a review of the literature, it is believed that there is no firm evidence yet that patients with ALL, intensively treated with chemotherapy and/or radiotherapy, are at increased risk of developing therapy-related second neoplasms. Because the number of cases reported is small, there is even insufficient data to firmly suggest that acute myeloblastic leukemia, following intensive therapy for ALL, occurs in a higher-than-expected frequency.

Ph1-positive acute myelocytic leukemia with high TdT levels

The authors have determined TdT levels in a case of Ph1-positive AML. Peripheral blood cells and bone marrow cells taken during the various phases of the disease were examined. Liquor cells were analyzed when symptomatic central nervous system involvement occurred. High TdT levels were found in all of the phases of the disease including the liquor. TdT eluted at various isoelectric points indicating a shifting of the activity to greater molarity during progress of the disease. Two different forms of TdT were present in the liquor. The authors speculate about the existence of a relation between TdT levels and Ph1-positive leukemia. They point out the importance of TdT levels as functional criterion of remission in acute leukemia. Finally, the existence of different forms of TdT could be the expression of a clonal selection caused by therapy or of a spontaneous clonal competition.

Establishment of a Ph1 chromosome-positive cell line from chronic myelogenous leukemia in blast crisis

A new hematopoietic cell line, designated KCL-22, was established in vitro by cultivation of pleural effusion cells obtained from a woman with chronic myelogenous leukemia in blast crisis. KCL-22 grew in suspension culture with a doubling time of 24 h and consisted of immature undifferentiated cells which were positive for periodic acid-Schiff and acid phosphatase staining. Chromosome analysis of the KCL-22 line showed a female karyotype with double Ph1 chromosomes and additional chromosome abnormalities. Its representative karyotype was 52,XX, + 1p-,+6,+8,+8,+8, t(9q+;22q-), +22q-. This cell line possessed receptors for the Fc portion of IgG, but lacked lymphoid cell characteristics and the Epstein-Barr virus-associated nuclear antigen. These results indicate that the KCL-22 cells were derived from chronic myelogenous leukemia cells. This cell line should prove useful for research involving various aspects of chronic myelogenous leukemia.

Philadelphia chromosome-positive blastic leukaemia: ultrastructural and ultracytochemical evidence of basophil and mast cell differentiation

Ultrastructural, ultracytochemical, immunologic and biochemical studies were performed on leukaemic cells from 41 patients with Philadelphia chromosome-positive blastic leukaemia; 28 patients were in blast transformation of chronic myelogenous leukaemia and 13 patients presented with 'acute' leukaemia. The patients were divided into two morphologic groups, lymphoid (16 cases) and myeloid (25 cases), on the basis of light microscopy and cytochemistry. All lymphoid cases studied for the presence of CALLA (10 patients) and TdT (11 patients) were positive. Two of 13 myeloid cases studied were TdT positive. The blasts from 10 of 16 lymphoid cases contained immature basophil/mast cell granules on ultrastructural examination. Peroxidase-positive 'lymphoid' blasts were noted in three of seven patients studied by ultracytochemical techniques. The reactivity was primarily confined to granular structures. Of the 25 cases in the myeloid group, blasts from 14 cases showed basophil/mast cell differentiation, nine cases showed neutrophil/monocyte features, and two cases were megakaryoblastic. Distinct patterns of ultrastructural peroxidase positivity were seen in the seven myeloid cases studied. In basophil/mast cell precursors the reactivity was primarily confined to granules; neutrophil precursors showed reactivity in the nuclear envelope, rough endoplasmic reticulum (RER), golgi and granules; in megakaryoblasts, only the nuclear envelope and RER were positive while the granules were consistently negative.

Mixed myeloid-Lymphoid colonies in a patient with polycythemia vera

Peripheral blood mononuclear cells from a patient with polycythemia vera were cultured in a methylcellulose system employing human serum. Electron microscopy documented the appearance of mixed colonies containing lymphocytes, granulocytes, megakaryocytes, and erythrocytes. In vitro culture characteristics were similar to those seen for other patients with polycythemia ver, ie, colonies grew in the absence of added erythropoietin or other pathway-specific regulators. Plating efficiency was linearly related to the number of cells plated, which supports the concept that each colony arose from a single cell. The appearance of mixed myeloid-lymphoid colonies points to the existence of a primitive stem cell capable of giving rise to multiple hematopoietic cell lines.

Sialyltransferase activity in leukemia

Sialyltransferase activity in blasts from acute lymphoblastic leukemia (ALL) was markedly lower (1.68 +/- 1.23 pmol/mg protein) than those (6.18 +/- 2.22 pmol/mg protein) of lymphocytes from normal volunteers (t less than 0.001). On the contrary, enzyme activity was significantly increased in blasts (1.21 +/- 0.38 pmol/mg protein) from acute non-lymphoblastic leukemia, compared to the level (0.53 +/- 0.32 pmol/mg protein) of mature granulocytes (t less than 0.001). In TdT-negative CML in blast crisis, sialytransferase activity (2.11 +/- 0.88 pmol/mg protein) was significantly higher than those of mature granulocytes (t less than 0.001), whereas no significant difference in the enzyme activity was noted between the blasts from TdT-positive CML in blast crisis and from ALL. In TdT-positive ALL cases, there was an inverse relationship (r = -0.85, t less than 0.01) between sialytransferase activity and terminal deoxynucleotidyl transferase (TdT) activity of the blasts. Therefore, sialytransferase in leukocytes may be a unique enzyme in which changes in activity relate to the differentiation or malignant transformation of leukocytes.

"Target" cells, cellular phenotypes, and lineage fidelity in human leukaemia

A detailed analysis of lymphoid leukaemia cells with a panel of monoclonal antibodies plus other markers indicates a striking conservation of phenotype that closely mimics that of normal lymphoid precursor or progenitor cells and reflects the imposition of maturation arrest. The composite phenotypes detected show some minimal deviations or asynchronies (with respect to maturation "stages") but are faithful with respect to cell lineage. These observations are suggested to shed light on the available "target" populations for lymphoid malignancy in humans and challenge the view that dedifferentiation or qualitatively aberrant gene expression is common and important in malignancy. They are further taken to support the view that normal gene products that regulate or couple proliferation and maturation are critically involved in the successive clonal selection events underlying the evolution of leukaemia. No qualitatively unique and consistent leukaemia "markers" may exist or be required. The only exception to this rule are the nonrandom chromosome changes, which, it is suggested, involve genetic loci critical to the regulation of growth and maturation in particular normal cell types.

Terminal transferase expression in relapsed acute myeloid leukaemia

In three cases of acute myeloid leukaemia marked increases in expression of the nuclear enzyme, terminal deoxynucleotidyl transferase (TdT), were observed during disease relapse. The first case was heterogeneous at diagnosis, consisting of subpopulations of large TdT- myeloblasts and small TDT+ blasts; however, at relapse there was complete replacement by TdT+ lymphoblasts. The other cases at diagnosis were both typical acute myeloid leukaemia, TdT-; at relapse, one showed a mixture of TdT- myeloblasts and TdT+ lymphoblasts, while in the other, TdT was demonstrated on a subpopulation of myeloblasts. No chromosomal abnormalities were found. It is suggested that in the first two cases these phenomena may have been due to leukaemic involvement of a pluripotential stem cell, or that sub-clones with different properties may have coexisted. In the third case at relapse, TdT was expressed aberrantly by malignant myeloid cells.

9;22;15 complex translocation in Ph1 chromosome positive CML revealed by Giemsa-11 procedure in apparent lymphoid cells of blastic crisis

A Ph1 chromosome positive chronic myeloid leukemia patient whose chronic phase lasted 7.5 years experienced a blastic transformation originating in the spleen. The spleen was infiltrated with undifferentiated blast cells that on cytogenetic analysis had a hyperdiploid karyotype and were Ph1 chromosome positive. The blast cells were negative for PAS, peroxidase. Sudan black and esterase stains. They were non-T, non-B with TdT activity. Remission was achieved in response to prednisone, vincristine, and adriamycin. Ph1 positive cells were present with cells responding to PHA stimulation throughout the course of the disease. A Giemsa-11 staining procedure male possible the ascertainment of a No. 9 translocation chromosome in blastic crisis cells that had also been present in Ph1 chromosome positive cells early in the disease. The presence of this translocation initially in myeloid cells and subsequently in apparent lymphoid cell types suggests the origin of this patient's leukemia as a pluripotential stem cell.

Sideroblastic anemia associated wtih hairy cell leukemia

A patient with leukemic reticuloendotheliosis ("hairy cell" leukemia) with sideroblastic anemia and an epinephrine-induced platelet-aggregation abnormality is presented. Immunologic membrane marker studies supported a B-lymphocyte origin of the hairy cells. It is hypothesized that a defect in the pluripotent marrow stem cell may be responsible for the hairy cell leukemia and for the intrinsic abnormalities in erythrocytes and platelets.

An antigen expressed by cells of the myelo-monocytic lineage

We describe an antigen(s) characterized by a heteroantiserum raised in rabbits against mature human granulocytes. This antigen was found on neutrophils, monocytes, platelets, acute and chronic myelocytic leukemia cells and on granulocyte-macrophage progenitor cells grown in agar. It was not found on lymphocytes, eosinophils, erythrocytes, or erythroid progenitor cells. On the basis of tissue distribution and absorption studies, the antigen (tentatively designated the "myelo-monocytic" antigen) is distinct from antigens previously identified on human neutrophils. Restriction of the "myelo-monocytic" antigen to normal and malignant cells of the myelo-monocytic series suggests that it may represent a normal differentiation antigen of the myelo-monocytic lineage.

Myeloproliferative and lymphoproliferative disorders in the same patient

A 67-year-old man developed a Philadelphia-negative myeloproliferative disorder which initially manifested as marked thrombocytosis, followed two years later by marked leucocytosis. He subsequently developed an IgG lambda plasma cell dyscrasia together with a monoclonal proliferation of circulating lymphocytes with IgM kappa surface immunoglobulin. The lymphoid neoplasm was associated with a rapidly progressive and fatal course.

Insulin receptors in acute and chronic lymphoid leukaemias

Normal lymphocytes lack insulin receptors. The binding of this hormone was studied in twelve patients with acute lymphoblastic leukaemia (ALL) and fourteen patients with chronic lymphocytic leukaemia (CLL). Lymphoblasts from ALL have been found to possess hormone receptors with properties identical to those of the known target cells for insulin: specificity, pH and temperature dependence, and ligand-induced increase in dissociation rate. All patients with ALL displayed insulin receptors on their lymphoblasts. The null-type cells possessed higher numbers of binding sites than the T-type cells, without overlapping of the values. In the fourteen patients with CLL, eight had low levels of insulin receptors on their lymphocytes while six showed a complete lack of such binding sites. Our results suggest that measurement of insulin binding might be a useful non-immunological marker for the classification of human leukaemias.

Localized blastoma preceding blastic transformation in Ph1-positive chronic myelogenous leukaemia: morphological and cultural studies of the transformation event

In a patient with Ph1-positive chronic myelogenous leukaemia (CML), the development of a localized blastoma preceding generalized blastic transformation was accompanied by a reduction of granulocyte-macrophage (GM) colony forming capacity in agar of bone marrow cells as well as an increase in peripheral neutrophil alkaline phosphatase (NAP) scores. Successful transplantation of the blastoma cells into nude mice enabled extensive studies of the cell properties. The blastoma cells were double Ph1-positive cells which did not respond to human granulocyte-macrophage colony-stimulating factor (GM-CSF), and were similar to cells demonstrated in spleen and bone marrow at the terminal stage of the patient's illness. These observations clearly support the case for sequential studies of colony formation in vitro as a useful test for the early detection of disturbances in marrow function that may occur before generalized blastic transformation. Studies of the properties of the blastoma cells also provide some insight into possible mechanisms for the transformation event.

Lymphoblastic leukemic transformation (lymphoblastic crisis) in myelofibrosis and myeloid metaplasia

Acute lymphoblastic leukemia (ALL) developing in myelofibrosis (MF) and myeloid metaplasia (MM) is reported in two patients. In both cases, the clinical course of the "blastic crisis" was rapidly progressive with little response to chemotherapy. The circulating cells were readily identified as lymphoblasts on the basis of cytology, cytochemistry, immunologic studies, and ultrastructure. In one of the cases, 40% of cells had T-cell markers and all cells contained paranuclear acid phosphatase. In the second case, cells had a "Burkitt-like appearance, contained multiple cytoplasmic vacuoles positive for oil red O, and one-third of them had B-cell markers. The development of lymphoblastic crisis in MF and MM occurs rarely, is analogous to blastic transformation in chronic granulocytic leukemia, and supports the hypothesis that myeloproliferative disorders originate from pluripotent hematopoietic stem cells.

Agranulocytosis associated with carbamazepine, and a positive reaction with anti-lymphoid leukaemia antiserum during recovery

Carbamazepine is a valuable drug in the treatment of trigeminal neuralgia and temporal lobe epilepsy. Rarely agranulocytosis has been described associated with its use but in this further non-fatal case a new finding of a positive reaction with anti-lymphoid leukaemia anti-serum was seen during the recovery phase. A brief review of 18 cases in the literature is provided and it is noted that 94% of reported cases are over the age of 45 years. The significance of the haematological finding is discussed.