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PubMed1989

[Onset of Philadelphia chromosome negative chronic myeloid leukemia with symptoms of intrahepatic cholestasis].

The case of a chronic myelogenous leukemia (CML) starting in an unusual form in a young woman is reported. Rapidly progressing icterus was the first and leading symptom of the disease. Simultaneously with the exclusion of the possibility of hepatitis and extrahepatic obstruction of the bile duct the qualitative blood picture roused the suspicion of a myeloproliferative disease. Detailed hematological examinations confirmed Philadelphia chromosome (Ph1) negative CML. Besides the histologically diffuse leukemic infiltration intrahepatic cholostasis could be demonstrated in the background of the icterus. In the chronic and accelerated phase clinical symptoms developing as a consequence of hepatic organic manifestation were dominating. In the authors's case the moderate leukocytosis, initial thrombocytopenia, absence of splenomegaly, early blast-phase and short survival were atypical, characteristic of Ph1 negative CML. The diagnosis and the absence of other associated hepatopathies was supported also by the post-mortem examination. CML beginning with icteric symptoms due to intrahepatic cholostasis is considered as rarity in the literature.

Adult↗

PubMed1997

Apoptosis in chronic myelogenous leukemia: studies of stage-specific differences.

In this study we compared rates of apoptosis, survival and metabolic activity from CML peripheral blood neutrophils with peripheral blood and bone marrow neutrophils from healthy volunteer donors and studied the influence of the disease stage and of cytokines including G-CSF, GM-CSF and IL-1beta on these parameters. Quantification of apoptosis by morphology, diphenylamine DNA fragmentation assay and by gel electrophoresis showed similar rates of apoptosis in chronic phase CML and normal peripheral blood neutrophils when the cells were incubated in RPMI + FCS or in serum-free medium. However, there were lower rates of apoptosis in accelerated and blast phase CML neutrophils (p < .001) and in normal bone marrow neutrophils (p < .001) compared to normal peripheral blood neutrophils (incubated in RPMI + FCS). Survival among neutrophils from chronic phase or accelerated/blast phase CML patients was significantly longer (p < 0.002 and p < 0.001, respectively) than among normal peripheral blood neutrophils but neutrophils purified from normal bone marrow had a survival rate which fell between that of normal peripheral blood and chronic phase CML patients. When the cells were incubated in RPMI + autologous sera, neutrophils from chronic phase CML patients showed markedly lower rates of apoptosis (p < 0.001) and maintained higher metabolic activities (p < 0.002) compared to normal neutrophils. G-CSF and GM-CSF were found to considerably decrease the rate of apoptosis in chronic phase CML neutrophils (p < 0.001 and p = 0.008 respectively) while IL-1beta did not show any antiapoptotic effect. It is suggested that the endogenous production of growth factors may therefore participate in delaying apoptotic cell death, during the progression of CML.

Adult↗

PubMed2004

Results of a phase 1-2 study of clofarabine in combination with cytarabine (ara-C) in relapsed and refractory acute leukemias.

Clofarabine (2-chloro-2'-fluoro-deoxy-9-beta-D-arabinofuranosyladenine) is a second-generation nucleoside analog with activity in acute leukemias. As clofarabine is a potent inhibitor of ribonucleotide reductase (RnR), we hypothesized that clofarabine will modulate ara-c triphosphate accumulation and increase the antileukemic activity of cytarabine (ara-C). We conducted a phase 1-2 study of clofarabine plus ara-C in 32 patients with relapsed acute leukemia (25 acute myeloid leukemia [AML], 2 acute lymphoblastic leukemia [ALL]), 4 high-risk myelodysplastic syndrome (MDS), and 1 blast-phase chronic myeloid leukemia (CML).(1) Clofarabine was given as a 1-hour intravenous infusion for 5 days (days 2 through 6) followed 4 hours later by ara-C at 1 g/m(2) per day as a 2-hour intravenous infusion for 5 days (days 1 through 5). The phase 2 dose of clofarabine was 40 mg/m(2) per day for 5 days. Among all patients, 7 (22%) achieved complete remission (CR), and 5 (16%) achieved CR with incomplete platelet recovery (CRp), for an overall response rate of 38%. No responses occurred in 3 patients with ALL and CML. One patient (3%) died during induction. Adverse events were mainly less than or equal to grade 2, including transient liver test abnormalities, nausea/vomiting, diarrhea, skin rashes, mucositis, and palmoplantar erythrodysesthesias. Plasma clofarabine levels generated clofarabine triphosphate accumulation, which resulted in an increase in ara-CTP in the leukemic blasts. The combination of clofarabine with ara-C is safe and active. Cellular pharmacology data support the biochemical modulation strategy.

Acute Disease↗

PubMed2002

Clinical development of farnesyltransferase inhibitors in leukemias and myelodysplastic syndrome.

Farnesyltransferase inhibitors (FTIs) target multiple pathways including the Ras pathway implicated in the pathogenesis of some hematologic malignancies. R115777 and BMS-214662, selective FTIs in clinical development, exhibit preclinical activity against cell lines and tumor xenografts with or without ras mutations. Phase I dose-escalating trials at M.D. Anderson Cancer Center have explored the potential of these agents as monotherapy for leukemias and myelodysplastic syndrome (MDS). In 20 patients with MDS, two cycles of oral R115777 for 3 consecutive weeks followed by a 1-week rest produced an overall response rate of 30%, consistent with 29% reported in poor-prognosis acute leukemia or blast-phase chronic myelogenous leukemia (CML). Administration of BMS-214662 as a weekly intravenous infusion produced a decrease in bone marrow blasts of greater than 50% in 23% of patients with acute leukemia or MDS; 18% achieved normalization of blast counts to less than 5%. In both studies, most responding patients did not have ras mutations. The most common side effects at maximum tolerated doses of R115777 (400 mg twice daily) and BMS-214662 (118 mg/m(2) weekly) were myelosuppression and nausea, respectively. Further evaluation of FTIs for hematologic malignancies clearly is warranted. Future research should address whether molecular techniques can identify patients most likely to respond to an FTI, optimal administration schedules for these agents, and the value of incorporating an FTI into combination regimens for difficult-to-treat hematologic malignancies.

Alkyl and Aryl Transferases↗

PubMed1997

Phase I clinical and laboratory evaluation of topotecan and cytarabine in patients with acute leukemia.

PURPOSE: To determine the maximal-tolerated dose (MTD) of topotecan with cytarabine in acute leukemia patients, and to evaluate leukemia cell apoptosis in these patients. PATIENTS AND METHODS: Fifty-three patients with acute leukemia not responsive to standard therapy were treated at eight dose levels of topotecan (2.5 mg/m2/d to 7.75 mg/m2/d). Topotecan was given as a 30-minute infusion daily with cytarabine 1 g/m2/d, both for 5 days. Using a flow-cytometric technique, the percent apoptotic cells in blood and bone marrow samples was determined, and the cell cycle distribution of the leukemic cells studied. RESULTS: Oropharyngeal mucositis was dose-limiting. The MTD of topotecan was 4.75 mg/m2/d for 5 days in high-risk patients and 7.0 mg/m2/d for 5 days in low-risk patients. The mean percent apoptotic cells in the peripheral blood reached a peak of 18.8%, a median of 48 hours following the first dose of topotecan. Patients with higher S-phase fractions, either before treatment or following cytarabine, were more likely to achieve bone marrow aplasia than those with lower S-phase fractions (P = .01 and P < .05, respectively). Clinical responses were seen in four of 39 patients with acute myelogenous leukemia (AML; of whom 32 had received prior high-dose cytarabine), three of six with acute lymphoblastic leukemia (ALL), and one of eight with chronic myelogenous leukemia in blast phase (CML-BP). CONCLUSION: The recommended phase II dose of topotecan with intermediate-dose cytarabine is 4.75 mg/m2/d for high-risk patients and 7.0 mg/m2/d for low-risk patients. The percentage of cells in S phase was important in determining response to treatment.

Adult↗

PubMed2006

Chronic myeloproliferative diseases with the t(5;12)(q33;p13): clonal evolution is associated with blast crisis.

Chronic myeloproliferative diseases (CMPDs) associated with t(5;12)(q33;p13) are reported to be responsive to imatinib mesylate. We studied 5 cases of CMPD with isolated t(5;12) treated at our hospital between January 1993 and October 2004. All were men with a median age of 55 years (range, 18-68 years). In the peripheral blood, each had marked leukocytosis, with variable eosinophilia (n = 4), monocytosis (n = 3), or basophilia (n = 2). Bone marrow specimens were hypercellular (70%-100%) with marked myeloid hyperplasia in each patient, but only 1 patient had eosinophilia, monocytosis, and basophilia. Follow-up ranged from 23 to 182 months (median, 48 months). Four died 23 to 182 months after initial diagnosis, 3 of blast crisis and 1 of cardiac complications of severe eosinophilia. Additional cytogenetic aberrations were identified at the time of blast crisis. Of 3 patients treated with imatinib, 2 responded, but only 1 had a sustained response. CMPD with t(5;12) commonly transforms to blast phase, and transformation is associated with cytogenetic evidence of clonal evolution.

Adolescent↗

PubMedDate not supplied

Apoptotic and antiproliferative effects of gemcitabine and gemcitabine plus Ara-C on blast cells from patients with blast crisis chronic myeloproliferative disorders.

BACKGROUND: Blast phase of chronic myeloid leukemia (CML) as well as the rare acute transformation of other chronic myeloproliferative disorders constitute forms of leukemia that are particularly refractory, even to aggressive chemotherapy. Many attempts have thus been made to identify new drugs that could be active in these diseases. We wanted to evaluate whether gemcitabine (dFdC), a pyrimidine analogue widely employed in lung cancer chemotherapy, was able to block in vitro proliferation of bcr/abl-positive and bcr/abl-negative blast cells in primary culture. We already showed that gemcitabine is active in inhibiting proliferation and inducing apoptosis of HL60 cells. METHODS: We studied the influence of dFdC on the proliferative potential of blasts by means of tritiated thymidine uptake, colony formation in semisolid medium and cell cycle parameters at flow cytometry. The efficacy of dFdC in inducing apoptosis was evaluated by flow cytometry (A0 peak) and by DNA agarose gel electrophoresis. RESULTS: We demonstrated that dFdC already inhibits tritiated thymidine uptake at doses of 10 microM after 72 hours of culture, and that this effect is dose dependent. The addition of Ara-C 5 microM in the culture medium of dFdC provoked a synergistic inhibitory effect. Consistent results were obtained when cell cycle distribution was studied. In fact, cell incubation in the presence of dFdC resulted in a significant decrease of cells in S phase, although with a certain heterogeneity among cases. The antileukemic activity of dFdC appeared to be specific since it was mediated through apoptosis. We could demonstrate the appearance of the pre-G1 apoptotic peak at cytofluorimetric analysis, and the characteristic DNA fragmentation pattern at agarose electrophoresis in all 10 cases after treatment with different doses of dFdC. Induction of apoptosis was maximal for the highest doses of dFdC (100 mM) and for the combination of dFdC and Ara-C. INTERPRETATION AND CONCLUSIONS: Following incubation with Gemcitabine leukemic blasts from chronic myeloproliferative disorders are induced to accumulate intracytoplasmatic and nuclear Ara-C and undergo apoptosis. These observations suggest that gemcitabine could be considered a candidate drug, capable of being used in polychemotherapy of refractory acute phase chronic myeloproliferative disorders.

Antimetabolites, Antineoplastic↗

PubMed1976

Cell membrane antigens associated with human adult acute leukemia.

Cell membrane antigens associated with the blast phase of human acute leukemia are separable from inhibitory proteins and from histocompatibility antigens also present in the membranes. Since these antigens are not detectable in remission or normal white blood cells, they provide a useful marker for identification of cells undergoing carcinomatous changes. Blast antigens from acute lymphatic leukemia (ALL) are also present on early human fetal thymus cells; antigens from both sources produce cell-mediated immune (CMI) responses and are structurally similar. Blast antigens from acute myelocytic leukemia (AML) are not associated with fetal antigens and do not cross react with ALL antigens. ALL cells possess a larger quantity of CMI inhibitory protein than AML cells. The isolation, purification and idenfication of these blast antigens is a step toward their use in studying cultured and cloned subpopulations of cells thought to be associated with pre-leukemia.

Antigens↗

PubMed1993

[Molecular analysis of transformation into blast crisis in chronic myelogenous leukemia].

Molecular events associated with the transformation into blast crisis phase in Ph1-positive CML were analyzed in the present study. The 9;22 chromosomal translocation in CML generates the bcr/abl fused gene coding P210bcr/abl that has enhanced tyrosine kinase activity. In 55 CML cases, Southern and RT-PCR analysis revealed that breakpoints of the bcr gene on chromosome 22q11 were clustered in M-bcr, except for one case and no obvious difference was observed between chronic and crisis phases. However, blast crisis cells displayed enhanced the expression of bcr/abl mRNA, when compared with those in chronic phase cells. By DNA transfection and PCR analysis, the point-mutational activation of N-ras oncogene was rarely identified, and no point-mutational activation of fms gene was found in the crisis phase cases. On the other hand, 2 out of 13 crisis cases contained gross alteration of p53 anti-oncogene. Furthermore, all 4 myeloid crisis cases and K562 cells showed disappearance of the P53 transcript, and MC3 cells derived from a myeloid crisis case showed an aberrant transcript, whereas chronic phase cases, Ph1-positive ALL cell lines and lymphoid crisis cases including NALM-1 cells showed normal expression of the P53 gene. At present, the precise mechanism associated with the blastic trans-formation in CML remain to be determined. The present study suggested one possibility that a selective and progressive process of Ph1 clone with high expression of the bcr/abl gene may be involved with the transformation into non-lymphoid crisis phases from chronic phases. In addition, this progression may be accelerated by the alteration of p53 anti-oncogene, or/and rarely by the point-mutational activation of ras oncogene family.

Base Sequence↗

PubMed1991

Treatment with recombinant interferon (alpha-2b) early after bone marrow transplantation in patients at high risk for relapse [corrected].

Relapse continues to be a problem after bone marrow transplantation (BMT) for hematologic malignancies, particularly in recipients of autologous or T-cell-depleted allogeneic grafts and in patients with advanced disease. Interferon (IFN) has shown antiproliferative activity in several malignant hematologic diseases and potentially may be of benefit when administered early after BMT when the number of residual cells is minimal. We tested in a phase I study the maximum tolerated daily dose of recombinant IFN alpha-2b in patients who had received a transplant for a disease at high risk for relapse (acute myeloid leukemia or non-Hodgkin's lymphoma beyond first remission, advanced myelodysplastic syndrome, acute lymphoblastic leukemia at any stage, chronic myeloid leukemia in accelerated or blast phase. Recombinant IFN alpha-2b was started at a dose of 0.5 x 10(6) IU/m2 and escalated by 0.5 x 10(6) IU/m2 in groups of three or four patients. The intention was to administer IFN as soon as stable engraftment after BMT was achieved (defined as an absolute neutrophil count of greater than 2.0 x 10(9)/L and platelet count greater than 100 x 10(9)/L for 5 consecutive days) and continued for 2 months. A total of 14 patients were enrolled after autologous (n = 3) or allogeneic (n = 11) BMT. Dose-limiting toxicity was myelosuppression. Significant (grade 2 to 4) neutropenia and thrombocytopenia led to discontinuation or dose reduction in five of eight patients receiving 1.5 x 10(6) or 2 x 10(6) IU/m2 IFN. Mild to moderate (grade 1 or 2) anorexia, weight loss, and fatigue occurred in the majority of patients independent of the IFN dose. De novo acute GVHD responsive to steroid treatment developed in 3 of 11 allograft recipients. Natural killer (NK) cell function was low before IFN treatment and was not improved with the cytokine. Conversely, interleukin-2-activated NK cells showed normal function even before starting IFN and no change was seen during IFN treatment. Clonogenic hematopoietic progenitor studies showed depression of all progenitor lines (colony-forming unit [CFU]-granulocyte, erythroid, monocyte, megakaryocyte, CFU granulocyte-macrophage, burst-forming unit-erythroid) by IFN at all dose levels except at 0.5 x 10(6) IU/m2. Considering this result and the incidence and severity of marrow depression seen at doses greater than 1.0 x 10(6) IU/m2, we would consider this the maximum dose safely tolerated if IFN alpha-2b is administered in this setting for a prolonged course on a daily basis.

Adolescent↗

PubMed2000

A prospective randomized study of alpha-2b interferon plus hydroxyurea or cytarabine for patients with early chronic phase chronic myelogenous leukemia: the International Oncology Study Group CML1 study.

A prospective randomized international study of 143 patients showed no apparent early survival advantage conferred by combining cytarabine, rather than hydroxyurea, with INF as first-line CML therapy. Combinations of alpha-interferon (INF) and chemotherapeutic agents are currently first-line therapy for the majority of patients with chronic myeloid leukemia (CML). The International Oncology Study Group conducted a prospective randomized study comparing INF combined with hydroxyurea or cytarabine. The primary study aim was to compare the survival durations in these patient cohorts. Patients with early chronic phase CML were randomized to receive INF 5 million units (Mu) given five times per week subcutaneously plus hydroxyurea or cytarabine as required to achieve a complete hematologic response and to maintain a WBC count between 2x10(9)/L and 10x10(9)/L and a platelet count between 75x10(9)/L and 100x10(9)/L. Therapy continued as tolerated unless progressive or blast phase disease occurred. At 36 months, the actuarial survival rate was equivalent in both groups: HI group (79 patients) survival was 85% (95% CI, 68-100%), as compared to 95% (95% CI, 79-100%) in the CI group (64 patients). In conclusion if seems that there is no apparent early survival advantage conferred by combining cytarabine, rather than hydroxyurea, with INF as first-line CML therapy.

Adolescent↗

PubMed1992

Phase I study of busulfan, cyclophosphamide, and timed sequential escalating doses of cytarabine followed by bone marrow transplantation.

In both animal models and human studies in leukemia, residual disease on day 8 following myelosuppressive therapy is in a proliferative phase and therefore may be sensitive to the S-phase specific drug cytarabine. Based on this concept, 17 patients with refractory or relapsed leukemia or lymphoma undergoing either autologous or allogeneic bone marrow transplantation (BMT) were treated on a Phase I protocol using high doses of busulfan (16 mg/kg, days -10, -9, -8, -7) and cyclophosphamide (120 mg/kg, days -6, -5) followed by escalating doses of a 48-h continuous infusion of cytarabine (starting dose 1000 mg/m2/48 h, days -3, -2). Ten patients received autologous transplants (two with Hodgkin's disease, seven with non-Hodgkin's lymphoma, one with chronic myelogenous leukemia (CML) in blast phase). Seven received allogeneic BMT (two with refractory acute myelocytic leukemia (AML), one with refractory acute lymphoblastic leukemia (ALL) undergoing a second BMT, one with Burkitt's-type leukemia, one with ALL in fifth relapse and two with CML in accelerated/blast phase). Two of these patients received a T cell-depleted haploidentical transplant. The maximum tolerated dose of cytarabine was 1500 mg/m2/48 h; a pulmonary syndrome including dyspnea, hypoxemia, and interstitial infiltrates which responded to aggressive diuresis was the dose limiting toxicity. Of the 10 patients who received cytarabine doses of 2000 or 2500 mg/m2/48 h, five patients developed adult respiratory distress syndrome (ARDS) with three patients requiring intubation; two recovered. Of the nine patients with lymphoma, seven responded with complete tumor clearance (CTC) with two patients tumor-free 13 and 15 months post-BMT, one remained refractory and one died too early to evaluate (TETE).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1998

c-Cbl tyrosine phosphorylation and subcellular localization in human primary leukemic cells.

Several studies indicate that a number of signal-transducing molecules involved in the proliferation, differentiation, and functional activation of normal hemopoietic cells may be constitutively activated in primary leukemic cells and play a role in the outcome or in the progression of these neoplastic disorders. In this study we show that the product of the proto-oncogene c-Cbl, whose function is still unknown, is constitutively tyrosine phosphorylated not only in cells from chronic myelogenous leukemias (CMLs) in the blast phase, but also in cells from acute myeloblastic leukemias (AMLs), Ph-negative acute T-lymphoblastic leukemias (T-ALLs), and Ph-negative pre-B lymphoblastic leukemias (pre-B ALL). Moreover, in acute leukemia cells, c-Cbl was not stably complexed with the tyrosine-phosphorylated adaptor protein CrkL. The analysis of Grb2/c-Cbl interaction demonstrated that, in both acute leukemia and CML blasts, c-Cbl was stably complexed with the N-terminal Src homology (SH) 3 domain of Grb2 and, in blasts from ALL patients, with the Grb2 SH2 domain. The analysis of c-Cbl subcellular distribution showed that in all cases of leukemia tested, as well as in growth factor-stimulated M-07e cells, c-Cbl was present in the cytosolic, in the membrane, and in the detergent-insoluble fractions. Finally, in polymorphonuclear neutrophils (PMNs) from CML patients, c-Cbl was found stably associated with the detergent-insoluble fraction, whereas in PMNs from normal donors, it was detected only in the cytosolic fraction. Our findings that c-Cbl is constitutively tyrosine phosphorylated and associated with the detergent-insoluble fraction in AML and ALL blasts and in PMNs from CML patients suggest that this event represents a common step in the neoplastic transformation of both myeloid and lymphoid progenitor cells.

Adaptor Proteins, Signal Transducing↗

PubMed1995

Chronic myeloid leukemia: correlation between purine metabolism enzyme activities and membrane immunophenotype.

Peripheral blood or bone marrow of 24 patients with chronic myeloid leukemia (CML) were characterized for their surface membrane marker profiles using flow cytometry and fluorescence microscopy. Purine metabolism enzyme activities were compared with membrane immunophenotype and cytochemical stains. CML subtypes were correlated with the expression of surface membrane antigens detected by the monoclonal antibodies. On the basis of immunophenotyping we found the following characteristic marker profiles: In stable phase of CML (CML-SP)-CD15, CD11b, CDw65, CD13, in accelerated phase of CML (CML-AP)-CD15, CDw65, CD11b, CD13 and CD33, in myeloid blastic phase of CML(CML-BP-M)-CD13, CD33, HLA-DR, CD11b, CD15, CDw65, in myeloid and lymphoid (mixed) blastic phase of CML (CML-BP-M+L)-CD13, CD33, CD34, HLA-DR, CD11b, CD10 and in chronic myelomonocytic leukemia (CMML)-CD14, CDw65, CD11b, CD33 and HLA-DR. Analysis of purine metabolism enzyme activities showed that there was a correlation between the values of adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) and various types of CML. ADA levels in CML-SP, CML-AP and CMML were comparable with those in normal cells. In CML-BP-M, which represents proliferation of less mature myeloid cells (similar to less mature AML subtypes), ADA activity increased and PNP activity decreased. ADA activity was significantly different between control group and CML-BP-M (p < 0.01), between CML-SP and CML-BP-M (p < 0.05). The values of PNP activity were the highest in stable phase of CML (125 pkat. 10(-6) cells) and the lowest (23 pkat.10(-6) cells) in CML-BP-M+L. PNP activity in the other groups corresponded to control values. High ADA/PNP ratio was found in CML-BP-M and CML-BP-M+L (0.7 and 2.0, respectively) in comparison to CML-SP (0.2). It follows from our results that ADA/PNP ratio enables to discriminate between stable and blast phases of CML (p < 0.01). The level of the cytochemical enzymes (CHAE, MPO, SBB, ANAE and 5' NT) varied and reflected the degree of cell differentiation and maturation. CHAE and MPO were characteristic enzymes for CML, ANBE for CMML and 5' NT for CML-BP-lymphoid.

Adenosine Deaminase↗

PubMed2004

Evidence of ABL-kinase domain mutations in highly purified primitive stem cell populations of patients with chronic myelogenous leukemia.

To study the hierarchical levels of stem cell targets for ABL-kinase domain mutations in CML, highly purified CD34+CD38- and CD34+CD38+ cell populations and their LTC-IC-derived progeny were analyzed in four patients at diagnosis (n=1) or in advanced phases (n=3) of their disease. In the single patient with early phase CML who later developed an Imatinib Mesylate-resistance and a Y253H mutation, no mutation was detectable in purified cell fractions analyzed at diagnosis nor in their LTC-IC-derived progeny. In contrast, in three patients in advanced phase CML, ABL-kinase mutations demonstrated in peripheral blood cells by sequencing (Q252E and M351T) were detectable in the FACS-sorted cells and became amplified in the LTC-IC-derived progeny of the primitive cells. These findings demonstrate that in late CP or advanced CML, ABL-kinase mutations occur as an intraclonal event in the primitive Ph1+ stem cell compartments with progression of this clone towards IM-resistant blast phase.

Antineoplastic Agents↗

PubMed1988

Absence of alternative splicing in bcr-abl mRNA in chronic myeloid leukemia cell lines.

The major consequence of the Philadelphia (Ph) translocation in chronic myeloid leukemia (CML) is the formation of a bcr-abl hybrid oncogene encoding a tumor cell-specific protein P210bcr-abl. In contrast to this, in Ph chromosome-positive acute lymphoblastic leukemia (Ph + ALL), a P190bcr-abl can be observed. This P190bcr-abl has been implicated in acute rather than chronic leukemogenesis. Therefore, it can be hypothesized that the transition from chronic to blast phase in CML is accompanied by an alternative splice in the bcr-abl mRNA, which results in a switch of the production of P210bcr-abl into P190bcr-abl. Initial S1 nuclease protection mapping supported this theory. However, this result appears to be based on an artifact in the S1 analysis. By using the polymerase chain reaction we provide evidence for the absence of alternative splicing in bcr-abl mRNA in two CML blast crisis cell lines.

Blast Crisis↗

PubMed1999

The TGF-beta type II receptor in chronic myeloid leukemia: analysis of microsatellite regions and gene expression.

Genomic instability is one mechanism proposed to play a role in the disease progression of chronic myeloid leukemia (CML). Microsatellite regions in the type II transforming growth factor-beta receptor (TGF-beta RII) gene appear to be targets for mutation in some cancers displaying microsatellite instability (replication error phenotype, RER+). Furthermore, TGF-beta RII mutations in RER+ tumors have been associated with decreased TGF-beta RII mRNA levels. As TGF-beta is a potent negative growth regulator of hematopoietic cells, investigations were undertaken to determine whether inactivation of the receptor by microsatellite alteration might be involved in the progression of CML. Analysis of TGF-beta RII mRNA expression by RNase protection, with comparison of cells from the chronic, accelerated and blast phases of CML, showed no change in TGF-beta RII transcript levels during disease progression. However, during each phase of the disease, low levels of TGF-beta RII were detected when compared with the hematopoietic cells of normal donors. Furthermore, this decreased expression was also observed in the other myeloproliferative disorders, polycythemia rubra vera (PRV) and essential thrombocythemia (ET). The leukemia cell lines K562 and HL-60 had no detectable TGF-beta RII mRNA. Two microsatellite regions found altered in RER+ colon cancers were analyzed to establish if these sequences were aberrant in CML. No alteration was detected in either of these regions in any phase of the disease. These results suggest that alterations of the microsatellite regions in the TGF-beta RII gene are not involved in the progression of CML. Decreased expression of TGF-beta RII in CML cells and leukemia cell lines raises the possibility that altered expression of the receptor may play a role in the initiation and/or maintenance of the disease state.

Base Pair Mismatch↗

PubMed1988

Origin of near-haploidy in malignant hematopoietic cells.

Hyperdiploidy is common in neoplastic diseases but severe hypodiploidy or near-haploidy is extremely rare. Acute lymphocytic leukemia (ALL) and blast phase of chronic myelocytic leukemia (BC/CML) are the two most common leukemias where metaphases with as low as 23 chromosomes have been reported. Recent studies have indicated that during the course of malignant development, cells undergo numerous changes, however, it is still not known whether malignant transformation proceeds or results from the near-haploid state. Retrospectively, we have examined 100 metaphases with chromosome counts of 23 to 35 in patients with CML who have not yet progressed to the blastic phase, to see whether such metaphases share any common characteristics with published cases. The unusual behavior of chromosomes 8, 17 and the presence of Ph-chromosomes in 85% of the cells are highly unique features in our study. These observations are compatible with those found in BC/CML patients reported earlier. Therefore, it is hypothesized that selective chromosome loss is a gradual phenomenon and one of these near-haploid clones may replace a diploid clone as the dominant component of the population during blast transformation. Several hypotheses are proposed as to the origin of such clones in malignant hematopoietic stem cells.

Chromosome Aberrations↗