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Lineage-related sensitivity to apoptosis in human tumor cells undergoing hyperthermia.

In this study the role of hyperthermia as an apoptotic trigger was analyzed in four human tumor cell lines: HL60, U937, DOHH2, and K562. These cell lines were chosen because of their well known and different expression of bcl-2 and bcr-abl genes, the expression of which is known to be an antiapoptotic condition. HL60 and U937 cells were strongly susceptible to heat exposure, while DOHH2 cells were weakly sensitive and K562 cells were resistant, thus suggesting a possible gene involvement in this type of programmed cell death. The mechanisms underlying this apoptosis were investigated by flow cytometry, agarose gel electrophoresis, and light and electron microscopy. A subdiploid peak and DNA laddering, both of which are parameters specifically correlated to programmed cell death, were present in HL60 and U937 and, even if less evident, in DOHH2 cells undergoing hyperthermic treatment, and were absent in K562 cells. In addition, DNA single-strand cleavage was revealed by in situ nick translation, observed by confocal microscopy. Morphological analysis confirmed these results and revealed the typical chromatin changes, followed by the appearance of micronuclei and apoptotic bodies.

Apoptosis↗

Antisense cancer therapy: the state of the science.

Over the last few years, antisense technology has emerged as an exciting and promising strategy in the fight against cancer. The antisense concept is to selectively bind short, modified DNA or RNA molecules to messenger RNA in cells and prevent the synthesis of the encoded protein. As anticancer agents, these molecules can be targeted against a myriad of genes involved in cell transformation, cell survival, metastasis, and angiogenesis. Indeed, the list of possible antisense targets increases as the knowledge of the genetic basis of oncogenesis expands. One aim of this review is to focus on those antisense cancer drugs that have entered human clinical trials. At least four of these compounds are currently in phase II trials, including those targeting protein kinase C-alpha, bcl-2, c-raf, and the R1-alpha subunit of protein kinase A. A new development in antisense chemistry (peptide nucleic acids) is discussed, along with alternative antisense-related strategies (ribozymes and 2-5A-antisense) designed to overcome some of the challenges of this already encouraging technology.

Clinical Trials as Topic↗

What is the contribution of molecular studies to the diagnosis of BCR-ABL-positive disease in adult acute leukemia?

The detection of BCR-ABL transcripts by polymerase chain reaction and hybridization protection assay was investigated in 59 adults with acute leukemia in whom the Philadelphia chromosome (Ph) abnormality was not documented by cytogenetic analysis. These included 35 patients with acute lymphocytic leukemia (ALL) and 24 with acute myelogenous leukemia (AML). Overall, three patients were found to have Ph-related molecular abnormalities; one had p190 and two had p210 disease. All three patients had ALL and were among 16 patients with insufficient metaphases by cytogenetic analysis, yielding an incidence of 19% in the latter category. Based on a 32% incidence of insufficient metaphases in our adult ALL population, we project an additional detection rate of 6% Ph-positive ALL by molecular studies and an overall incidence of 20% (14% + 6%) Ph-positive or BCR-ABL-positive ALL. None of the remaining patients with ALL and none of the 24 patients with AML investigated had BCR-ABL-positive disease. We conclude that molecular studies are useful in detecting BCR-ABL-positive disease in a subset of patients with Ph-positive ALL who are not identified by cytogenetic analysis because of insufficient metaphases.

Acute Disease↗

BCR sequences essential for transformation by the BCR-ABL oncogene bind to the ABL SH2 regulatory domain in a non-phosphotyrosine-dependent manner.

BCR-ABL is a chimeric oncogene implicated in the pathogenesis of Philadelphia chromosome-positive human leukemias. BCR first exon sequences specifically activate the tyrosine kinase and transforming potential of BCR-ABL. We have tested the hypothesis that activation of BCR-ABL may involve direct interaction between BCR sequences and the tyrosine kinase regulatory domains of ABL. Full-length c-BCR as well as BCR sequences retained in BCR-ABL bind specifically to the SH2 domain of ABL. The binding domain has been localized within the first exon of BCR and consists of at least two SH2-binding sites. This domain is essential for BCR-ABL-mediated transformation. Phosphoserine/phosphothreonine but not phosphotyrosine residues on BCR are required for interaction with the ABL SH2 domain. These findings extend the range of potential SH2-protein interactions in growth control pathways and suggest a function for SH2 domains in the activation of the BCR-ABL oncogene as well as a role for BCR in cellular signaling pathways.

Amino Acid Sequence↗

Chronic myeloid leukaemia and the Philadelphia translocation: do the c-sis oncogene and platelet-derived growth factor provide the link?

The study of cellular oncogenes and of chromosomal abnormalities in human tumours has, in several instances, suggested a link between a specific oncogene translocation and oncogenesis. It was recently suggested that the translocation of the c-abl gene (the human cellular homologue of the transforming sequence of Abelson murine leukaemia virus) from chromosome 9 to 22 in Philadelphia translocation, might have a role in the generation of chronic myeloid leukaemia (CML). We propose an alternative hypothesis and suggest that the translocation of another gene, c-sis, may be more important.

Cell Division↗

Regulation of hematopoietic cell function by protein tyrosine kinase-encoding oncogenes, a review.

Tyrosine phosphorylation of proteins by protein tyrosine kinases (PTKs) is an important mechanism in the regulation of various cellular processes such as proliferation, differentiation, and transformation. Accumulating data implicate PTKs as essential intermediates in the transduction of extracellular signals to the interior of the cell. This review summarizes the mechanism of action of PTKs from the major subclasses and the involvement of PTK-encoding oncogenes in the regulation of hematopoietic cell function.

Cell Differentiation↗

B-lymphoid/myeloid stem cell origin in Ph-positive acute leukemia with myeloid markers.

We report two cases of Philadelphia chromosome (Ph)-positive acute leukemia with definite myeloid markers. Ph was the sole chromosomal abnormality at presentation, and neither eosinophilia, basophilia, thrombocytosis nor hepatosplenomegaly was present. In both cases, Ph+ myeloblasts showed positive stain for myeloperoxidase and naphthol ASD chloroacetate esterase, which fulfilled the FAB criteria of acute myelogenous leukemia (AML). Ph+ myeloblasts co-expressed myeloid and B-lymphoid antigens (CD10, CD13, CD19 and CD33). In case 1, myeloblasts rearranged M-BCR, and the expression of M-BCR/ABL chimeric RNA was demonstrated by using the reverse transcription polymerase chain reaction (RT-PCR). They also clonally rearranged IGH. Ph clone disappeared on cytogenetic analysis in remission, and granulocytes in remission did not have rearranged M-BCR. In case 2, morphocytochemically distinct myeloid and lymphoid blast populations were seen. Myeloblasts and lymphoblasts were enriched > 96% as CD19-/CD33+ and CD19+/CD33- populations, respectively. Both of them possessed the identical rearrangement of IGH and M-BCR, indicating a common leukemic progenitor cell origin. Furthermore, m-BCR/ABL was detected in addition to M-BCR/ABL on RT-PCR. Accordingly, both cases were diagnosed as de novo Ph+ acute leukemia rather than as chronic myelogenous leukemia in blastic crisis. Their mixed B-lymphoid/myeloid characteristics strongly suggest that so-called 'Ph+ AML' is derived from Ph+ myeloid/B-lymphoid stem cells.

Adolescent↗

Capping of bcr-abl antisense oligonucleotides enhances antiproliferative activity against chronic myeloid leukemia cell lines.

Leukemia due to a chromosomal translocation offers an attractive model for the design and testing of antisense agents because the sequence at the translocation junction is unique to the leukemic cell population. Chronic myeloid leukemia is the most common such translocation-induced leukemia. We have found antisense phosphodiester oligonucleotides directed at the bcr-abl junction to be ineffective in inhibiting the growth of CML cell lines. Therefore, we have investigated the effects produced by certain structural modifications of bcr-abl antisense oligonucleotides. For assay purposes we used K562 cells which have the bcr exon 3/abl exon 2 junction and BV173 cells which have the bcr exon 2/abl exon 2 junction. We have found that 5'-capping with a dimethoxytrityl group and 3'-capping with an amino-2-hydroxypropyl group confer antiproliferative activity. The enhancement of activity by capping appears at least partly attributable to exonuclease resistance since stability in serum-containing medium is increased.

Base Sequence↗

Review of clinical, cytogenetic, and molecular aspects of Ph-negative CML.

Between 1985 and 1989, many cases of Philadelphia (Ph) chromosome negative chronic myelogenous leukemia (CML) were reported. For this review, the following selection criteria were used: the original articles on Ph-negative cases should provide clinical, hematologic, cytogenetic as well as molecular data. In addition, eight unpublished cases of Ph-negative CML are included that were studied in our institute during the last two years. Our purpose was to correlate presence or absence of the Ph rearrangement with the clinical features in an attempt to test whether the entity "Ph-negative CML" really exists and to identify the pathologic characteristics, frequency of occurrence, prognosis for survival, and underlying molecular mechanisms. Data on Ph-negative CML patients were compared with data on Ph-positive CML, atypical CML (aCML), and chronic myelomonocytic leukemia (CMMoL), reported in the same papers as the Ph negative patients. Essential for comparison of data from the different investigators appeared to be a clear description of criteria they used to establish the diagnosis CML, or alternatively a complete presentation of data for all patients reported in the articles. In most cases, Ph-negative CML was distinguishable from CMMoL and aCML, using simple criteria, e.g., differential count of peripheral blood and absence of dysplasia in the bone marrow. Cytogenetic analysis showed normal karyotype in most cases of Ph-negative CML. Interestingly, in cases with abnormal karyotype, chromosome 9 band q34 was relatively frequently involved in translocations with other chromosomes than chromosome 22, suggesting a variant Ph translocation not visible by cytogenetic techniques. This assumption was confirmed by molecular analysis, demonstrating bcr-abl rearrangement in 9 out of 10 of the latter cases. Results of cytogenetic and molecular investigations in 136 cases of Ph-negative CML reviewed in this article clearly indicated that molecular techniques are valuable tools for identification of bcr-abl rearrangements, indicative for the Ph translocation. The different mechanisms responsible for bcr-abl rearrangement in Ph-negative CML patients are discussed. The question remains whether all Ph-negative CML patients will have bcr-abl rearrangements, or whether alternative mechanisms will be identified that are responsible for this disease.

Chromosomes, Human, Pair 22↗

Establishment and characteristics of a T-cell acute lymphoblastic leukemia cell line, JK-T1, with a chromosomal translocation between 8q24 and 14q13.

A human leukemia cell line, JK-T1, was established from the bone marrow of a 10-year-old boy with T-cell acute lymphoblastic leukemia. The origin of the leukemic cell line, JK-T1, was demonstrated by its chromosomal and immunologic similarity to the patient's fresh leukemic cells. Karyotypic analysis revealed 46,XY,del(6)(q?),t(8;14)(q24;q13),der(9)t(9;?)(q34;?). In JK-T1, neither rearrangement nor amplification of the c-myc gene was observed apparently because the breakpoint of chromosome 14 was not q11 but q13. JK-T1 was independent of interleukin 2 (IL-2) because of little production of IL-2, little IL-2 receptor (CD25) on the surface, and no response to exogenous IL-2. JK-T1 had lymphocyte function associated antigen-1 (LFA-1) (CD11a, CD18) on its surface and could adhere to the hematologic stromal layer. These characteristics of JK-T1 cell line are considered to be useful not only for evaluating the role of t(8;14) but also in studying the adhesion molecules of leukemia.

Bone Marrow Cells↗

The application of fluorescent in situ hybridization to detect Mbcr/abl fusion in variant Ph chromosomes in CML and ALL.

We investigated the usefulness of fluorescent in situ hybridization with different-colored major breakpoint cluster region (Mbcr) and Abelson oncogene (abl) probes in clinical practice. In standard Ph chromosomes with a Mbcr breakpoint, these probes produced a fusion of Mbcr and abl signals that was visible in interphase and metaphase cells. The normal range for apparent Mbcr/abl fusion signals in interphase nuclei was established in bone marrow from 25 normal controls. We tested the probes on 35 bone marrow specimens from five normal subjects and 29 patients with various kinds of Ph chromosomes and chronic myelogenous leukemia or acute lymphocytic leukemia. This method produced Mbcr/abl fusion signals in patients with a standard Ph chromosome, simple or complex variants of Ph chromosomes, and "Ph-negative chronic myelogenous leukemia." In metaphase cells of patients with acute lymphocytic leukemia, this method established Ph chromosomes with minor bcr (mbcr) breakpoints. Fluorescent in situ hybridization is a relatively inexpensive and rapid method. When this method is used in conjunction with conventional chromosome analysis, the cytogeneticist can combine the power of complete karyotype studies and the resolution of molecular techniques for patients suspected of having a Ph chromosome.

Bone Marrow Cells↗

Reversed BCR/ABL rearrangement detected by FISH in Philadelphia negative chronic myelocytic leukemia.

We investigated leukemic cells from a patient with chronic myelocytic leukemia (CML) and a normal 46,XX karyotype. Molecular studies revealed rearrangement of the M-bcr region and formation of BCR/ABL fusion mRNA with b3a2 configuration. Fluorescence in situ hybridization (FISH) using the abl probe showed signal on both chromosomes 9 band q34, while the bcr probe hybridized to one chromosome 22 and to one chromosome 9. In this case, as in three other cases recently described (Hagemeijer et al. and Nachava et al.), the bcr/abl rearrangement is shown to be on 9q34, instead of the usual location on 22q11.

Chromosomes, Human, Pair 9↗

A mapped set of genetic markers for human chromosome 9.

A genetic map of markers for human chromosome 9, spanning a genetic distance of 147 cM in males and 231 cM in females, has been constructed from linkage studies with 19 loci in a large panel of reference families. The markers included four classical systems previously assigned to chromosome 9, and restriction fragment length polymorphisms of two cloned genes, ABL oncogene and argininosuccinase synthetase pseudogene 3 (ASSP3). The remaining 13 marker loci, with an average heterozygosity of 42%, were defined by arbitrary DNA probes newly ascertained from genomic libraries; seven of them were variable number of tandem repeat (VNTR) loci. A subset of 7 of the 19 linked markers is proposed for a primary map that could detect linkage with a genetic defect within the covered region of chromosome 9, provided that at least 45 phase-known meioses were available for study in an affected family.

Cell Line↗

Comparison of baculovirus-expressed c-Abl and BCR/ABL protein tyrosine kinases.

Mouse c-Abl type IV and human BCR/ABL proteins have been expressed in insect cells using the baculovirus system. The proteins were expressed as full-length polypeptides as judged by electrophoresis in denaturing gels. They were identified by immunoprecipitation and immunoblotting with antibodies against ABL peptides and, for BCR/ABL, against a BCR peptide. In these immunoprecipitates both proteins gave autophosphorylation principally on tyrosine. Both proteins were active tyrosine kinases, phosphorylating a variety of tyrosine-containing substrates. In fresh extracts both proteins contained phosphotyrosine as shown by Western blots with antiphosphotyrosine antibodies. Partial purification could be achieved readily using ion exchange columns, and the BCR/ABL protein, p210BCR/ABL, could be further purified to near-homogeneity using an antiphosphotyrosine column. Both enzymes required a divalent metal ion for activity. At low concentrations of ATP (2 microM) and with angiotensin II as substrate both enzymes were activated by Mn2+ or by Mg2+. No major differences in catalytic properties were found between the two isolated enzymes in solution. The oncogenic properties of p210BCR/ABL may be due to its different subcellular location, or to the presence of an intracellular inhibitor of c-Abl that does not inhibit BCR/ABL, or to altered substrate-specificity such that it can phosphorylate a unique substrate which is not recognised by c-Abl.

Amino Acid Sequence↗

Classification of chronic myeloid disorders: from Dameshek towards a semi-molecular system.

Hematological malignancies are phenotypically organized into lymphoid and myeloid disorders, although such a distinction might not be precise from the standpoint of lineage clonality. In turn, myeloid malignancies are broadly categorized into either acute myeloid leukemia (AML) or chronic myeloid disorder (CMD), depending on the presence or absence, respectively, of AML-defining cytomorphologic and cytogenetic features. The CMD are traditionally classified by their morphologic appearances into discrete clinicopathologic entities based primarily on subjective technologies. It has now become evident that most CMD represent clonal stem cell processes where the primary oncogenic event has been characterized in certain instances; Bcr/Abl in chronic myeloid leukemia, FIP1L1-PDGFRA or c-kit(D816V) in systemic mastocytosis, rearrangements of PDGFRB in chronic eosinophilic leukemia, and rearrangements of FGFR1 in stem cell leukemia/lymphoma syndrome. In addition, Bcr/Abl-negative classic myeloproliferative disorders are characterized by recurrent JAK2(V617F) mutations, whereas other mutations affecting the RAS signaling pathway molecules have been associated with juvenile myelomonocytic leukemia. Such progress is paving the way for a transition from a histologic to a semi-molecular classification system that preserves conventional terminology, while incorporating new information on molecular pathogenesis.

Fusion Proteins, bcr-abl↗

3'CBFbeta deletion associated with inv(16) in acute myeloid leukemia.

Recent reports have shown that concomitant submicroscopic deletions can occur in association with chromosomal translocations/inversions in several leukemia subtypes. Detectable by fluorescence in situ hybridization (FISH), these losses of sequence include deletion of the 5' region of the ABL gene and the 3' region of BCR in chronic myeloid leukemia (CML) and acute lymphoblastic leukemia (ALL), as well as the 5' region of ETO in acute myeloid leukemia (AML) French-American-British type M2 associated with t(8;21), 3'MLL in AML and ALL, and 3' core-binding factor beta (CBFbeta) in AML associated with inv(16). While it has been widely reported that submicroscopic deletions of the derivative 9 in CML have an adverse prognostic impact, the clinical significance, if any, of deletions associated with t(8;21), inv(16)/t(16;16), or MLL rearrangement is yet to be determined. We analyzed a series of 39 patients diagnosed with AML who had cytogenetically detectable inv(16)/t(16;16) by using a FISH probe for the CBFbeta region to determine the incidence of the 3'CBFbeta deletion. Deletions were detected in three patients (8%), all associated with inv(16), bringing the number of cases reported so far to seven. The prognostic significance of this finding remains unclear.

Acute Disease↗

Mechanisms of transformation by the BCR-ABL oncogene: new perspectives in the post-imatinib era.

Since its introduction less than 3 years ago, imatinib mesylate (STI571) has altered the entire approach to the therapy of patients with chronic myeloid leukemia (CML). In addition to its impact on clinical practice, imatinib has also increased the focus of basic and translational CML research on enhancing the cellular effects of imatinib and preventing and overcoming resistance to the drug. Here, I summarize some recent advances in our understanding of the regulatory and signaling mechanisms of Bcr-Abl, with an emphasis on therapeutic implications.

Benzamides↗