The molecular biology of chronic myelogenous leukaemia

Myeloproliferative neoplasms: new translational therapies

The myeloproliferative neoplasms represent a diverse group of hematologic malignancies that have been the subject of intense investigation over the last decade. Although clinical trials of the much anticipated small molecule inhibitors of Janus kinase 2 have shown that these experimental agents are successful in palliating many of the symptoms associated with the myeloproliferative neoplasms, they have not been reported to affect the disease initiating hematopoietic stem cell population or to alter the natural history of these disorders. Investigators remain optimistic that new information about the genetic and cellular origins gained from the efforts of numerous laboratories will ultimately translate in to the identification of new drug targets and more effective therapies. We hypothesize that ultimately, the use of combinations of drugs including chromatin modifying agents, immunomodulatory agents, anti-apoptotic agents, cellular therapies and monoclonal antibodies will be required to effectively treat patients with myeloproliferative neoplasms.

Adult precursor B-ALL with BCR/ABL gene rearrangements displays a unique immunophenotype based on the pattern of CD10, CD34, CD13 and CD38 expresssion

The Philadelphia chromosome (Ph+) reflects a balanced reciprocal translocation between the long arms of chromosomes 9 and 22 [t(9;22)(q34;q11.2] involving the BCR and ABL genes. At present, detection of BCR/ABL gene rearrangements is mandatory in precursor-B-ALL patients at diagnosis for prognostic stratification and treatment decision. In spite of the clinical impact, no screening method, displaying a high sensitive and specificity, is available for the identification of BCR/ABL+ precursor-B-ALL cases. The aim of the present study was to explore the immunophenotypic characteristics of precursor B-ALL cases displaying BCR/ABL gene rearrangements using multiple stainings analyzed by quantitative flow cytometry in order to rapidly (<1 h) identify unique phenotypes associated with this translocation. From the 82 precursor-B-ALL cases included in the study 12 displayed BCR/ABL gene rearragements, all corresponding to adult patients, four of which also displayed DNA aneuploidy. Our results show that BCR/ABL+ precursor B-ALL cases constantly displayed a homogeneous expression of CD10 and CD34 but low and relatively heterogeneous CD38 expression, together with an aberrant reactivity for CD13. In contrast, this unique phenotype was only detected in three out of 70 BCR/ABL cases. Therefore, the combined use of staining patterns for CD34, CD38 and CD13 expression within CD10-positive blast cells is highly suggestive of BCR/ABL gene rearrangements in adults with precursor B-ALL.

Regional cancer cytogenetics: a report on 1,143 diagnostic cases

The results of studies from a regional cancer cytogenetics diagnostic service are reported. In a 10-year period, 1,143 marrow samples from patients with newly diagnosed leukemia and myelodysplastic syndrome were referred. Successful studies were completed on 992 cases (87%). Among all referred cases, the rates of detection of cytogenetically abnormal clones were 95% for chronic myelogenous leukemia (CML), 54% for acute lymphoblastic leukemia (ALL), 51% for acute myeloid leukemia (ANLL), and 43% for myelodysplastic syndrome (MDS). Of 169 cases of CML studied, 90.5% bore the standard Philadelphia chromosome (Ph), 3.55% had an unusual Ph, and 5.33% were Ph-negative. Among the 59 cases of cytogenetically abnormal MDS, common abnormalities observed were trisomy 8 and changes resulting in loss of material from the long arm of chromosomes 5 and 7, and 20q-. Of the 168 abnormal ANLL, there was a strikingly non-random pattern of aneuploidy, with monosomy 7 and trisomy 8 predominating. Common structural changes observed were changes resulting in loss of material from the long arm of chromosomes 5 and 7, trisomy 8, rearrangements of 11q23, t(15;17), t(8;21), rearrangements of 12q13 and 3q, inversion 16, trisomy 11, Ph, trisomy 21, t(6;9) and t(1;22). The differences between adult and pediatric findings were minor, with the exception of chromosome 5 abnormalities, which were common among adults with ANLL but rare in the pediatric cases. There were 273 ALLs with abnormal cytogenetic findings. There was preferential gain of chromosomes 21, X, 14, 6, 4, 18, 17, and 10 (in decreasing order of frequency) in leukemic clones. Of the 193 ALLs with structural changes, many fell into-well-defined categories with established correlations to FAB subtypes. Common changes in ALL were rearrangements of 9p, 12p, 6q, TCR loci, 11q23, Ig loci, and 8q24, and duplication of 1q, Ph, i(17q), t(1;19), i(9q) and dic(9;12). The detailed documentation of the cytogenetic findings in this relatively large, single-institution study will likely facilitate the further characterization of rare, primary cytogenetic changes associated with leukemias and MDS. From a managed health care perspective, regional cancer cytogenetic services may be cost-effective alternatives to single-institution laboratories.

Detection of the Mbcr/abl translocation in chronic myeloid leukemia by fluorescence in situ hybridization: comparison with conventional cytogenetics and implications for minimal residual disease detection

The correlation between the detection of the Philadelphia chromosome by conventional cytogenetics and the identification of Mbcr/abl translocation by fluorescence in situ hybridization (FISH) in both metaphase and interphase cells is prospectively analyzed in a group of 21 chronic myeloid leukemia (CML) patients. To gain insight into the sensitivity and specificity of the detection of the bcr/abl translocation by FISH, a group of 10 healthy volunteers was also studied. Our results show that for the detection of bcr/abl translocation in CML patients, FISH is more sensitive than conventional cytogenetics because it detects significantly higher proportions of cells carrying the translocation both in metaphase (P < .0002) and interphase nuclei (P < .003). Moreover, in the metaphases of the controls analyzed, no bcr/abl+ chromosome was detected that makes the colocalization of bcr and abl signals in the CML patients highly specific. Conversely, in control interphase nuclei, a small proportion of cells (ranging between 0% and 3%, mean value of 1.7% +/- 0.9%) displaying colocalization of both signals is usually detected. This limits, at least for the moment, the routine use of FISH for the detection of minimal residual disease in CML patients at levels lower than 10(-1).

A novel translocation involving chromosomes 2, 9, 14, and 22 in chronic myeloid leukemia

A 46-year-old man with chronic myelogenous leukemia was found to have a new complex translocation. In chronic phase, all of the bone marrow cells had a rearrangement of a t(2;9;14;22) (p21;q34;q32;q11). Southern blot analysis of leukocyte DNA revealed rearrangement of the breakpoint cluster region (bcr) within the 5.8-Kb bcr. The patient eventually died in blast crisis 28 months later. The cytogenetic findings of bone marrow cells showed a 46,XY,t(2;9;14;22)(p21;q34;q32;q11),add(1p),del(3q) karyotype in blast crisis.

Immune markers in hematologic malignancies

The precise delineation of biologic traits that distinguish normal hematopoietic cells from their malignant counterparts is of fundamental importance in understanding all aspects of hematologic malignancies. An increasingly sophisticated technologic battery has been utilized to dissect out these differences--primarily utilization of monoclonal antibodies, by immunoperoxidase, immunoalkaline phosphatase and flow cytometric techniques. An even more basic understanding of normal and malignant hematopoietic cells has begun to evolve as molecular biology begins to unravel gene misprogramming by Southern and Northern blot analysis and the polymerase chain reaction. These techniques not only help distinguish a normal cell from a malignant one, but characterize the malignant clone as B-lymphoid, T-lymphoid or myeloid and allow further subcategorization within these broad lineages. These distinctions are vital to the entire spectrum of basic and clinical research involving hematologic malignancies and are assuming an increasingly important role in their diagnosis, prognosis and treatment.

del(15)(q11q15) associated with transformation of chronic myelomonocytic leukemia

Nonrandom cytogenetic abnormalities have been described in a variety of human malignancies including myelodysplastic syndromes (MDS). Acquisition of new chromosomal abnormalities may herald onset of a more aggressive disease. We report a patient with chronic myelomonocytic leukemia (CMMoL) who initially had a normal karyotype, but in whom the clonal interstitial deletion of chromosome 15 (q11-q15) was coincident with development of acute myeloid leukemia (AML) one year later. To date, this chromosomal change has not been reported in CMMoL, AML, or any other human malignancy.

Chronic granulocytic leukemia: reassessment of morphologic and cytogenetic characteristics in Ph1-positive and Ph1-negative cases

33 cases of chronic granulocytic leukemia (CGL) were reassessed to determine if, by strict morphologic criteria. Philadelphia chromosome (Ph1)-negative CGL exists as a diagnostic entity and if Ph1-positive CGL could be distinguished from Ph1-negative CGL. Cases were reassessed using published criteria and, of 11 Ph1-negative cases, only 4 could be reclassified as myelodysplastic syndromes or undifferentiated chronic myeloproliferative disorder. Of the morphologic parameters evaluated, peripheral blood basophilia and bicytopenia proved to be good discriminators between Ph1-positive and Ph1-negative cases. As a group, Ph1-negative cases were more heterogeneous and tended to have lower hemoglobin, WBC, platelet count and absolute eosinophilia. Chromosomal abnormalities other than Ph1 were seen only in the Ph1-positive cases. Based on these findings, we conclude that Ph1-negative CGL constitutes a heterogeneous group, a subgroup of which is morphologically identical with the Ph1-positive CGL. The parameters that best discriminate between Ph1-positive and Ph1-negative cases are peripheral blood absolute basophilia and bicytopenia.

Natural killer cell immunodeficiency in patients with chronic myelogenous leukemia. III. Defective interleukin-2 production by T-helper and natural killer cells

Even though they possess normal to increased numbers of circulating natural killer (NK) cells, patients with chronic myelogenous leukemia (CML) have a functional NK-cell deficiency which is restorable in vitro in the presence of recombinant IL-2. We therefore measured the level of IL-2 production by both T-helper and NK cells from CML patients as compared to normal controls using PHA-stimulated peripheral blood mononuclear cells (PBMs) as well as FACS-sorted CD4+ (OKT4+) lymphoid cells and FACS-sorted CD16+ (B73.1+) lymphoid cells. Peripheral blood mononuclear cells from CML patients demonstrated markedly defective IL-2 production as compared to normal controls (4.0 +/- 1.6 and 5.9 +/- 1.4 units/ml after 24 hr of 5 and 10 micrograms/ml PHA stimulation as compared with 40.7 +/- 10.3 and 69.3 +/- 15.1 units/ml for normal subjects). In addition to the decreased relative percentage of CD4+ (OKT4+) lymphoid cells in CML patients, FACS-sorted CD4+ (OKT4+) cells also demonstrated a significant defect in IL-2 production, (10.8 +/- 3.6 units/ml as compared to 39.0 +/- 5.8 units/ml after 24 hr stimulation with 10 micrograms/ml PHA). FACS-sorted CD16+ (B73.1+) lymphoid cells from CML patients also demonstrated significantly decreased IL-2 production after 24 hr incubation with increasing concentrations of PHA or with the NK-sensitive target K562 as compared to normal controls. Defective IL-2 production by PBMs, CD4+ (OKT4+), and CD16+ (B73.1+) cells from CML patients was also evident after 48 hr of PHA stimulation. Although the percentages of both T4+2H4+ and T4+4B4+ subsets are significantly decreased in CML patients, CML patients have normal ratios of T4+4B4+/T4+2H4+ subsets as compared to normal controls. These and previous results support the hypothesis that decreased IL-2 production by both T-helper and NK cells from CML patients may be mechanistically related to the observed NK-cell immunodeficiency in CML patients.

Two new chromosomal abnormalities in chronic myelogenous leukemia 46,XY,t(9;15;22)(q34;q22;q11) and 46,XY,t(6;9;12;22)(p21;q34;q24;q11)

Two new variant cases of chronic myelogenous leukemia (CML) are presented. The first case is a 19-year-old male with a 46,XY,t(9;15;22)(q34;q22;q11) karyotype. The second case is a 75-year-old man with a 46,XY,t(6;9;12;22)(p21;q34;q24;q11) karyotype. In both cases, the prognosis was no different from those cases of CML with the standard t(9;22) as the only abnormality. We recommend that all unusual translocations be reported.

Laboratory and clinical applications of monoclonal antibodies for leukemias and non-Hodgkin's lymphomas

Important insights into leukocyte differentiation and the cellular origins of leukemia and lymphoma have been gained through the use of monoclonal antibodies that define cell surface antigens and molecular probes that identify immunoglobulin and T-cell receptor genes. Results of these studies have been combined with markers such as surface membrane and cytoplasmic immunoglobulin on B lymphocytes, sheep erythrocyte receptors on T lymphocytes, and cytochemical stains. After using all of the aforementioned markers, it is now clear that acute lymphoblastic leukemia (ALL) is heterogeneous. Furthermore, monoclonal antibodies that identify B cells, such as the anti-CD20 and anti-CD19 antibodies in combination with studies of immunoglobulin gene rearrangement, have demonstrated that virtually all cases of non-T-ALL are malignancies of B-cell origin. At least six distinct subgroups of non-T-ALL can now be identified. T-ALL is subdivided by the anti-CD7, anti-CD5, and antibodies that separate T lymphocytes subsets into three primary subgroups. Monoclonal antibodies are also useful in the subclassification of non-Hodgkin's lymphoma, and certain distinct markers can be correlated with morphological classification. Although monoclonal antibodies are useful in distinguishing acute myeloid from acute lymphoid leukemias, they have less certain utility in the subclassification of acute myelogenous leukemia (AML). Attempts to subclassify AML by differentiation-associated antigens rather than by the French-American-British (FAB) classification are underway in order to document the potential prognostic utility of surface markers. Therapeutic trials using monoclonal antibodies in leukemia and lymphoma have been reported. Intravenous infusion of unlabeled antibodies is the most widely used method; transient responses have been demonstrated. Antibodies conjugated to radionuclides have been quite successful in localizing tumors of less than 1 cm in some studies. Therapy trials with antibodies conjugated to isotopes, toxins, and drugs have shown promise. Purging of autologous bone marrow with monoclonal antibodies and complement in vitro has been used in ALL and non-Hodgkin's lymphoma; preliminary data suggest that this approach may be an effective therapy and may circumvent many of the obstacles and toxicities associated with in vivo monoclonal antibody infusion.

Disruption of stromal niches by diffusible factors in the conditioned media of leukemic cell-lines and sera of chronic myelogenous leukemia patients

The bone-marrow microenvironment has a decisive role in maintaining haemopoietic stem cells and regulating their differentiation. In diseases of the haemopoietic system, viz. anaemias and leukemias, the microenvironment has been shown to play a key role. In this paper we show that leukemic cell conditioned medium and sera from CML patients, interact with the in vitro bone-marrow environment and bring about changes which affect the maintenance of normal stem cells.

Primary chromosome abnormalities in human neoplasia

At the cellular level, cancer is a genetic disease; genetic changes in somatic cells are essential events in neoplasia. In a majority of cases these changes involve large enough blocks of genetic material to be visible in the microscope. The chromosome aberrations in neoplastic disorders are probably of three kinds: (1) primary abnormalities, which are essential steps in establishing the tumor; (2) secondary abnormalities, which develop only after the tumor has developed, but which nevertheless may be important in tumor progression; and (3) cytogenetic noise, which is the background level of nonconsequential aberrations. These latter changes are, in contrast to the primary and secondary changes, randomly distributed throughout the genome. The primary abnormalities, of which several dozens have now been identified, are mostly strictly correlated with particular diseases and even with histopathological subtypes within a given disease. This has been evident in the leukemias for some years already, and information now accumulating on solid tumor karyology indicates a similar situation. Clonal chromosome abnormalities are a feature of both benign and malignant neoplasms, although the changes are often less massive in the former. Apart from being clinically useful as a diagnostic technique and an aid in prognostication, tumor cytogenetics also plays a role in identifying those genomic sites which harbor genes essential in the pathogenesis of neoplastic lesions. So far, two functionally different classes of directly cancer-relevant genes have been detected, the oncogenes and antioncogenes. There is every reason to believe that future investigations with cytogenetic and recombinant DNA methods will add to our knowledge of the biology of human neoplasia, in those tumor types where the characteristic genetic change is already partially known, and by identifying hitherto unknown karyotypic abnormalities.

The chromosomal analysis of human solid tumors. A triple challenge

The present review considers the three main issues of the cytogenetic analysis of human solid tumors: the technical limitations, the difficulty in interpreting the available results, and the uncertainty affecting any hypothesis about the role of chromosome changes in tumorigenesis. Information is given on the recent improvements in the field of tumor cell culturing and karyotyping, with a critical discussion of more than 1300 cytogenetic studies from 18 different tumors, and clues for a synthetic understanding of the cytogenetics of malignancy.

Gene probe analysis demonstrates independent clonal evolution of co-existent chronic myeloid and chronic lymphocytic leukaemia

We describe a case of Philadelphia-positive chronic myeloid leukaemia occurring simultaneously with B-cell chronic lymphocytic leukaemia in a 69-yr-old male. Gene probe analysis of DNA from both peripheral blood and bone marrow provided evidence for the independent evolution of 2 clones in this case, with a predominant population showing immunoglobulin heavy chain gene rearrangement and a smaller population showing a rearrangement within the breakpoint cluster region of chromosome 22.

Oncogenes in human leukemias

Eukaryotic cells contain a family of genes termed cellular oncogenes or proto-oncogenes thought to regulate normal cell growth and development. In some abnormal circumstances, such as following transduction by retroviruses, activation of these genes causes leukemias in animals. Possible mechanisms of activation of cellular oncogenes include: point mutation, deletion, or insertion; amplification; activation by internal rearrangement, chromosomal translocation, or promoter insertion; recombinatorial events resulting in the formation of novel chimeric genes; among others. In this review, we consider data implicating activation of cellular oncogenes in the pathogenesis of leukemia in humans. We discuss possible mechanisms whereby oncogene activation may induce leukemias, as well as potential diagnostic and therapeutic implications.

Use of the X-chromosome linked hypoxanthine phosphoribosyl transferase gene as a marker of cell monoclonality in hemopoietic malignancies

The X-chromosome linked gene encoding hypoxanthine phosphoribosyl transferase (HPRT) has been reported to provide a novel approach to the investigation of cell monoclonality in females based on non-random methylation-sensitive restriction enzyme cleavage of the active vs inactive HPRT alleles and a polymorphic Bam HI restriction site to distinguish the maternal and paternal gene copies. In a survey of 80 females, which included 65 cases of hemopoietic malignancy and 15 normal individuals, we found only nine (11.3%) to be heterozygous (informative) for the Bam HI polymorphism. Monoclonality was demonstrable by HPRT gene analysis in five of six informative cases of leukemia, the exception being a case of acute myeloid leukemia which displayed anomalous methylation of the HPRT gene. Our studies suggest that the applicability of the HPRT gene probe strategy may be limited by (1) the low frequency of informative cases and (2) potential inappropriate methylation of the HPRT gene in a proportion of cases.

Oncogenes in chronic lymphocytic leukemia

Oncogenes, in the context of retroviruses, are a common cause of leukemia in animals. Recently, activation of cellular oncogenes has been shown to be associated with leukemia in humans. Relatively few studies of oncogene activation in chronic lymphocytic leukemia (CLL) have been reported. In most instances, rearrangement of oncogenes has not been detected. Exceptions include the bcl-1 oncogene in B-cell prolymphocytic leukemia, the tcl-1 oncogene in T-cell CLL, the Hu-ets-1 and Hu-ets-2 oncogenes in small cell lymphocytic lymphoma and c-myc in a Sezary cell leukemia cell/line. Overall, it appears that oncogene abnormalities are less common in CLL than in other leukemias. The reason for it is uncertain and may relate to the relatively few cases evaluated. Alternatively, novel mechanisms of oncogene involvement or gene other than oncogenes may be important in the etiology or pathogenesis of CLL.

Possible prognostic value of plasma activity augmenting polymorphonuclear neutrophils (PMN) adherence estimations in untreated patients with chronic myeloid leukemia

Plasma activity augmenting polymorphonuclear neutrophils adherence was evaluated in 30 untreated patients with chronic myeloid leukemia. The estimations were done by the use of cells isolated from healthy persons. The plasma of some patients with CML induced the intensive adherence of PMN to plastic surface. Further observations suggested, that these patients were characterized by earlier blast crisis occurrence and poorer prognosis.

Oncogenes and human leukemias

Eukaryotic cells contain a family of genes termed "cellular oncogenes" or "proto-oncogenes," thought to regulate normal cell growth and development. In some circumstances, such as following transduction by retroviruses, activation of these genes causes tumors and leukemias in animals. Possible mechanisms of cellular oncogene activation include: 1) DNA point mutation, deletion or insertion, 2) gene amplification, 3) gene activation by internal rearrangement, chromosomal translocation or promoter insertion, 4) recombinative events resulting in the formation of novel chimeric genes, and others. In this review, we consider data which implicates cellular oncogene activation in the pathogenesis of leukemia in humans. We discuss possible mechanisms by which oncogene activation may induce leukemias, as well as potential diagnostic and therapeutic implications.

The BCR/ABL hybrid gene

A DNA region on chromosome 22, designated M-BCR, contains the chromosomal breakpoint of the Philadelphia (Ph) translocation in all Ph positive CML patients studied to date. M-BCR is part of a gene, BCR, oriented with its 5' end towards the centromere of chromosome 22. All of the CML DNAs analysed have a breakpoint within introns of the BCR gene. As a consequence of the Ph translocation the 3' end of the BCR gene has been translocated to chromosome 9, while the 5' part remains on the Ph chromosome. The remaining BCR sequences act as an acceptor for a chromosome 9 gene, the ABL oncogene: the ABL oncogene is fused in a head-to-tail fashion to the chromosome 22 sequences. This genomic configuration results in the transcription of a novel chimeric mRNA consisting of 5' BCR sequences and 3' ABL oncogene sequences. In K562, a cell line derived from a CML patient, and in five CML patients such chimeric BCR/ABL transcripts have been demonstrated. An abnormally sized ABL protein has been detected in the cell line K562 and in leukaemic cells from patients. This protein represents the translational product of the chimeric mRNA. The role of the BCR part of the fusion protein is unknown; it is possible that the BCR moiety could alter the structure of the ABL protein and unmask its tyrosine kinase activity. By analogy with the gag/v-abl polyprotein, the CML-specific BCR/ABL protein might have transforming activity and could play an essential role in the generation and/or maintenance of CML.

Ph-negative chronic myeloid leukaemia

An analysis of five patients with Philadelphia chromosome (Ph) negative chronic myeloid leukaemia (CML) revealed that two were clinically and haematologically identical to Ph-positive CML whereas three should be reclassified as chronic myelomonocytic leukaemia (CMML). At a molecular level the first two patients showed the same juxtaposition of c-abl and bcr genes as is seen in Ph-positive CML. These genomic changes were not seen in the other three patients. Observations on these five patients suggest that the clinical course and prognosis of the rare patient who carries the Ph 'molecular defect' but lacks the Philadelphia chromosome is no different from Ph-positive CML.

DNA changes during blastic transformation in chronic granulocytic leukemia

Immunoglobulin and T cell receptor gene mapping were undertaken in 10 patients during both chronic and blastic phases of chronic granulocytic leukemia. Twenty percent were shown to undergo lymphoblastic transformation. DNA changes did not predict blastic transformation or those who would respond favourably to treatment with vincristine and prednisone.

The cytogenetics of solid tumors. Relation to diagnosis, classification and pathology

This overview discusses the chromosome changes in solid tumors and how recent advancements in techniques have yielded results which at least qualitatively are similar to those obtained in the leukemias, i.e., that consistent and recurrent chromosome changes characterize most tumors adequately examined and that tumor entities consist of cytogenetically defined and unique subsets. Thus, the findings point to a similar application of the chromosome changes in tumors in their classification, diagnosis and causation.

Effect of platelet-derived growth factor on enriched populations of haemopoietic progenitors from patients with chronic myeloid leukaemia

The effect of pure platelet-derived growth factor and fresh serum on the in-vitro growth of purified haemopoietic progenitors from the peripheral blood of 12 patients with CML was studied. Purified haemopoietic progenitors were prepared using Percoll separation followed by cell sorting with the monoclonal antibody BI.3C5. Both pure PDGF at a concentration of 20 ng/ml and fresh serum significantly increased the numbers of BFU-E (p less than 0.01) and CFU-GEMM (p less than 0.014), but not the CFU-GM. That the PDGF effect was not mediated to any significant extent via prostaglandins, was shown by the lack of inhibitory effect of indomethacin on the growth of purified progenitor cells in the presence of fresh serum. Increased amounts of pure PDGF were required to give maximal stimulation of purified CML peripheral blood progenitors compared to normal bone marrow progenitors. These results show that CML progenitors are capable of responding to PDGF. Whether the quantitative difference in response is due to a reduced proportion of mesenchymal cells in CML peripheral blood compared to normal marrow, or whether CML progenitors are most likely already stimulated by autocrime PDGF or other growth factors remains to be elucidated.

Clinical and prognostic features of Philadelphia chromosome-negative chronic myelogenous leukemia

Between 1965 and 1982, 105 patients with a diagnosis of Philadelphia chromosome-negative chronic myelogenous leukemia were referred to our institution with minimal or no prior therapy. The median age was 63 years and 64% were males. The overall median survival from time of referral was 14 months; 53% of patients survived 1 year and only 10% survived beyond 5 years. At the time of analysis, 92 patients (88%) were dead, 56% of deaths being preceded by a blastic crisis. Compared with Philadelphia chromosome-positive disease, patients with Philadelphia chromosome-negative chronic myelogenous leukemia were older and had a significantly higher incidence of anemia, thrombocytopenia, monocytosis, marrow blasts, decreased marrow megakaryocytes and a lower incidence of basophilia and thrombocytosis. Chromosomal abnormalities occurred in 33% of patients and consisted most frequently of trisomy 8, or an additional chromosome C, loss of the Y chromosome, or abnormalities in chromosomes #5 and #7. Of nine pretreatment characteristics significantly associated with poor survival, a multivariate analysis identified four to have independent additive prognostic significance: severe thrombocytopenia, hemoglobin levels less than 10 g/dl, increasing peripheral blasts and promyelocytes, and age 60 years or older. Monocytosis was not of prognostic significance. The derived prognostic model divided patients into three risk groups, low, intermediate, and high, with median survivals of 36, 16, and 3 months, respectively. The authors conclude that Philadelphia chromosome-negative chronic myelogenous leukemia is a distinct entity among the myeloproliferative syndromes with characteristic clinical and laboratory features and a poor prognosis. Prognostic factors and related risk categories were demonstrated within this disease entity.

Uracil-DNA glycosylase in benign and malignant maturing human hematopoietic cells

The expression of uracil-DNA glycosylase was studied in human normal hematopoietic bone marrow cells and in malignant counterparts obtained from patients with chronic granulocytic leukemia. We observed that the expression of the enzyme was highest in the proliferating granulocytic compartment (myeloblasts through myelocytes) and that it was diminished in more mature cells. Furthermore, we demonstrated that uracil-DNA glycosylase activity was higher in immature red blood cells or reticulocytes than in more mature red cells. The same tendency was also demonstrated in human malignant monoblasts, which were induced to terminal maturation by phorbol ester. It can be concluded from these results that uracil-DNA glycosylase expression is equal in benign and malignant hematopoietic progenitor cells; no selectivity towards malignant vs. benign progenitors can be expected in possible chemotherapeutic approaches relying on uracil-DNA glycosylase.

Philadelphia-positive metaphases in the marrow after bone marrow transplantation for chronic granulocytic leukemia

A 28-year-old man with Ph-positive chronic granulocytic leukemia (CGL) was treated by high-dose chemoradiotherapy and transplantation of marrow cells harvested from his HLA-identical brother. One year after bone marrow transplantation (BMT) examination of his marrow showed a minority population of Ph-positive cells; their proportion subsequently fell such that 2 years after transplant analysis of marrow cells showed only cytogenetically normal cells. The patient remains clinically normal with a persisting mild lymphocytosis but without hematological evidence of leukemia. We cannot in this patient distinguish between persisting leukemia that later could no longer be recognized and relapse of leukemia that is now suppressed, perhaps only temporarily. This case emphasizes the need for caution in interpreting chromosomal finding after BMT for CGL.

Chromosomal changes in secondary leukemias of childhood and young adulthood

The increasing success of antineoplastic therapy has resulted in a growing number of long-term survivors. These people are at risk for complications of the therapy itself. Among these induced acute nonlymphoid leukemia (ANLL) has been both common and often lethal. We reviewed 72 recently reported patients under 30 years of age at the time of initial diagnosis who developed a secondary, karyotypically defined leukemia. Fifty-eight patients contracted ANLL a mean of 4 1/2 years from the initial diagnosis. In 25 patients, this was preceded by a preleukemic phase characterized by a hypercellular bone marrow with abnormal precursors, often accompanied by peripheral pancytopenia, that lasted a mean of 6 months. Three additional patients died in this preleukemic phase. In all 61, the most common chromosomal abnormalities were numerical errors. Twenty-four patients had a hypodiploid karyotype, most often in those in whom the primary diagnosis was lymphoma (22 of 43). The most common chromosomes missing in whole or in part were number 7 (18 patients), number 5 (8 patients), number 17 (5 patients), and number 21 (4 patients). The anomalies were frequently multiple and complex. Monosomy 7 figured particularly strongly and may be similar to a karyotypically identical myeloproliferative disorder characterized by micromegakaryocytes, giant platelets, and abnormal granulocyte function arising de novo in children. These findings are similar to those in older patients with ANLL induced by environmental carcinogens or antineoplastic therapy. They are different from the karyotypic changes seen in de novo ANLL in children and young adults, suggesting a different etiology. Also, they reinforce the need to find less leukemogenic treatment programs.