Acute promyelocytic leukemia

Acute renal failure associated with the retinoic acid syndrome in acute promyelocytic leukemia

All-trans-retinoic acid is an effective agent to induce remission in patients with acute promyelocytic leukemia (APL). Unlike conventional chemotherapy, this drug exerts its effect by inducing differentiation of immature leukemic cells. A distinctive clinical syndrome characterized by fever, dyspnea, effusions, weight gain, and organ failure (the "retinoic acid syndrome") can occur during treatment with this drug. Postmortem studies have shown extensive organ infiltration by leukemic cells, and the early administration of corticosteroids can result in prompt resolution of symptoms. We describe a patient with APL in whom acute renal failure developed during treatment with all-trans-retinoic acid. Transient renal enlargement during a period of leukocytosis and a beneficial response to treatment with dexamethasone suggest that renal failure in this patient was probably related to the retinoic acid syndrome.

Stimulation of histamine H2- (and H1)-receptors activates Ca2+ influx in all-trans-retinoic acid-differentiated HL-60 cells independently of phospholipase C or adenylyl cyclase

In human neutrophils, histamine H2-receptors mediate activation of adenylyl cyclase (AC) and inhibition of N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP)-induced superoxide anion (O2-) formation, and in HL-60 promyelocytes, H2-receptors mediate parallel activation of AC, phospholipase C (PLC) and non-selective cation (NSC) channels. As all-trans-retinoic acid (RA) is successfully used in the differentiation therapy of acute promyelocytic leukaemia, we studied signal transduction in RA-differentiated HL-60 cells. Histamine and the H2-receptor agonist, impromidine, induced both rises in cAMP levels and cytosolic Ca2+ ([Ca2+]i). Substances acting at post-receptor sites to increase cAMP did not increase [Ca2+]i. H2- but not H1-receptor antagonists inhibited histamine-induced cAMP accumulation and rises in [Ca2+]i were more effectively inhibited by H2- than by H1-receptor antagonists. Histamine-induced rises in [Ca2+]i were completely dependent on the presence of extracellular Ca2+ and were abolished by the blocker of NSC channels, Gd3+, but were resistant to inhibition by pertussis toxin. Unlike FMLP, histamine did not activate PLC. The effects of FMLP on [Ca2+]i were less sensitive to blockade by Gd3+ than those of histamine, and there was no cross-desensitization between the two stimuli. FMLP, but not histamine, inhibited transiently thapsigargin-induced rises in [Ca2+]. Taken together, our results show that histamine activates AC-mediated cAMP accumulation in RA-differentiated HL-60 cells via H2-receptors and NSC channel-mediated Ca2+ influx via H2- (and H1)-receptors. Histamine-induced NSC channel activation is not the consequence of AC- or PLC stimulation and occurs, directly or indirectly, via pertussis toxin-insensitive guanine nucleotide-binding proteins. FMLP and histamine activate Ca2+ influx by different mechanisms. There are similarities in H2-receptor-mediated signal transduction between RA-differentiated HL-60 cells and HL-60 promyelocytes and differences between the former cells and neutrophils, indicating that RA-differentiated HL-60 cells must be considered as partially immature.

A rapid assay for measuring the metabolism of [3H]-retinoic acid in cell cultures

A simple method was developed to detect the metabolism of [3H]-retinoic acid to polar products using intact tumor cells in culture. Unaltered [3H]-retinoic acid was separated from more polar metabolites using C18-bonded solid phase extraction cartridges. Separation of unaltered retinoic acid and polar metabolites was confirmed by HPLC. The murine mammary carcinoma cell line TA3 Ha used in these studies converted 40% to 50% of added radioactive retinoic acid to polar metabolites released into the culture medium during a 4-hr incubation period. Metabolism of [3H]-retinoic acid by TA3 Ha cells was inhibited by the cytochrome P-450 inhibitors ketoconazole, clotrimazole, and liarozole. The simplicity and rapidity of this assay should make it useful for evaluating compounds as inhibitors of retinoic acid metabolism.

Cerebral infarction in acute promyelocytic leukemia at initial presentation

We report on a 3 year old girl with acute promyelocytic leukemia (APL) with cerebral infarction due to disseminated intravascular coagulation (DIC) at initial presentation. She was hospitalized because of unconsciousness and petechiae on the chest wall and extremities. Cerebral ischemia and infarction were found on computed tomography scan and magnetic resonance imaging. Peripheral blood content was hemoglobin 7.3 g/dL, white blood cells 1.0 x 10(3) cells/microL (31% blasts) and platelet count was 12 x 10(3) cells/microL. Fragmented erythrocytes were frequently observed on May-Giemsa stained blood smears. Bone marrow aspirates showed normal cellularity, with 60.4% blasts, containing faggot cells. The blasts were positive for peroxidase. Therapy was begun; however, the patient died 1 week after admission.

Acute promyelocytic leukemia and pregnancy. A case report

BACKGROUND

Acute promyelocytic leukemia (APL) is an uncommon form of acute myeloid leukemia usually associated with disseminated intravascular coagulation (DIC). Pregnancy in patients with APL requires special consideration to maximize the probability of survival of both mother and fetus.

METHODS

A patient with APL diagnosed during pregnancy who developed DIC is described. Obstetric and oncologic management of this difficult patient is discussed, and a pertinent literature review of pregnancy in APL is presented.

RESULTS

Of 23 pregnancies in patients with APL reported in the literature (including the present patient), 19 yielded live births, including 8 of 12 who received chemotherapy during late pregnancy and all 3 patients who received all-trans-retinoic acid (ATRA) during late pregnancy. Chemotherapy or ATRA induced complete remission in 72% of treated patients.

CONCLUSIONS

Proper management of pregnant patients with APL usually results in a live birth and complete remission of the mother's leukemia, despite the potentially devastating consequences of DIC, which is present at diagnosis in most patients.

Expression of the leucocyte common antigen (LCA, CD45) isoforms RA and RO in acute haematological malignancies: possible relevance in the definition of new overlap points between normal and leukaemic haemopoiesis

The membrane expression of CD45RA and CD45RO on fresh leukaemic cells taken from 529 cases of acute haemopoietic malignancies, including 117 B-origin acute lymphoblastic leukaemia (B-origin ALL), 37 T-origin acute lymphoblastic leukaemia (T-origin ALL0, 297 de novo acute myeloid leukaemia (AML), 42 refractory anaemia with excess of blasts in transformation (RAEB-T) and 36 myeloid blastic phase of chronic myelogenous leukaemia (CML-BP-my), was analysed. B-origin ALLs were characterized by the lack of the RO isoform along with the consistent presence of RA. Conversely, a differential expression of the two isoforms was detected in different subsets of T-origin ALL, in that T-stem cell leukaemias (T-SCL: CD7+, CD4-, CD8-, CD1-) preferentially expressed CD45RA whereas conventional T-acute lymphoblastic leukaemias (T-ALL: CD7+, CD4+ and/or CD8+ and/or CD1+) were consistently marked by CD45RO. Within myeloid malignancies, most of AMLs displayed CD45RA, while a substantial group of CML-BP-my preferentially exhibited CD45RO. As a general rule, a reciprocal exclusion of the two isoforms was observed in AML as well as in ALL. Nevertheless, a frequent coexpression of CD45RA and CD45RO was observed in CD14+ AML. In vitro treatment with all-trans retinoic acid (ATRA) was able to promote a switch from CD45RA to CD45RO expression in 27 de novo AML, independently from morphological subtyping. To our knowledge, this is the first report on CD45 isoform expression in a large series of patients with acute leukaemia. The knowledge of the differential expression of CD45RA and CD45RO can ameliorate our classificative approach to haematological malignancies, as well as disclose new multiple overlap points between normal and leukaemic cell differentiation.

Unbalanced translocation t(5;17) in an typical acute promyelocytic leukemia

Acute promyelocytic leukemia (APL; M3 in the FAB classification) is specifically associated with the t(15;17)(q23;q12) and the consequent formation of a PML/RARA fusion gene. A few cases of APL with a t(11;17)(q23;q12) and a PLZF/RARA fusion gene have recently been reported. In addition, a new variant, t(5;17)(q32;q12), with a RARA rearrangement was described in a child with atypical APL. We report an unbalanced der(5)t(5;17) in an atypical APL case showing unusual dysgranulopoiesis and some M2 features. The breakpoints were difficult to localize precisely on chromosome 5, because the translocation may have occurred on a previous del(5q). The karyotype also showed del(8q) and multiple double-minutes (dmin). Molecular studies evidenced RARA rearrangement but showed neither PML rearrangement nor PML/RARA fusion. Fluorescence in situ hybridization revealed that the dmin were of chromosome 8 origin and that they accounted for the MYC amplification observed in Southern blots. The patient did very poorly despite chemotherapy and all-trans retinoic acid (ATRA) treatment. Thus, the t(5;17) could represent a second type of variant translocation in APL that, like the disease associated with t(11;17), does not seem to respond to ATRA therapy. Whereas RARA rearrangement appears sufficient for an APL-like phenotype, it seems that the presence of a classical PML/RARA is required for typical APL with response to ATRA.

Tretinoin. A review of its pharmacodynamic and pharmacokinetic properties and use in the management of acute promyelocytic leukaemia

Tretinoin (all-trans retinoic acid), a vitamin A derivative, induces cellular differentiation in several haematological precursor cell lines and cells from patients with acute promyelocytic leukaemia. Drug treatment with tretinoin is associated with morphological and functional maturation of leukaemic promyelocytes and a progressive reduction in the occurrence of the characteristic t(15;17) chromosomal translocation. Recent therapeutic trials indicate that tretinoin induces remission in 64 to 100% of patients with acute promyelocytic leukaemia. In newly diagnosed patients, remission induction treatment with tretinoin followed by intensive chemotherapy resulted in a significant reduction in relapse rate and prolongation of event-free and overall survival compared with chemotherapy alone in 1 comparative trial. Tretinoin alone does not totally eradicate the leukaemic clone and consolidation chemotherapy is recommended as follow-up. The use of reverse transcription polymerase chain reaction (RT-PCR) provides a sensitive and specific technique to assist in prediction and monitoring of a patient's response to treatment and to help detect the presence of residual or recurrent disease. The use of tretinoin is potentially limited by the rapid and almost universal development of drug resistance and occurrence of the often severe retinoic acid syndrome. Useful strategies have been described to manage these effects but current and future efforts must be directed at elucidating the mechanisms involved and determining the optimum therapeutic management. In summary, results to date indicate that the combination of tretinoin and intensive chemotherapy is more effective than chemotherapy alone and appears to improve the prognosis of newly diagnosed patients with acute promyelocytic leukaemia. Further information on the relative efficacy of various induction and post-remission strategies in subsets of patients will help determine optimum use of this promising agent in the management of acute promyelocytic leukaemia.

Detection of chromosomal translocations in leukemia-lymphoma cells by polymerase chain reaction

In recent years many chromosomal translocations involved in leukemia and lymphoma have been defined at the molecular level. In addition to advancing the understanding of pathological mechanisms underlying the transformation process, the cloning and sequencing of the genes altered by the translocations have provided new tools for diagnosis and monitoring of patients. In particular, the polymerase chain reaction (PCR) methodology yields rapid, sensitive and accurate diagnostic and prognostic information. As leukemias carrying certain translocations confer a higher risk of treatment failure, it is important to identify accurately all positive cases in order to give appropriate therapy. An important new initiative in the diagnostical setting and anti-leukemic therapy is the early detection of minimal residual disease (MRD). If MRD, implying an increased risk of relapse, is reliably detected during apparent clinical remission, alternative strategies could be applied early while the malignant cell burden is still minimal. The PCR assays are clearly more sensitive than other methods of MRD detection including morphology, immunophenotyping and cytogenetics; treatment failure is first detectable by PCR followed by cytogenetic relapse and finally clinical disease. PCR assays have been most often used in the MRD analysis of follicular lymphoma with t(14;18), chronic myeloid leukemia and acute lymphoblastic leukemia (ALL) with t(9;22), ALL with t(4;11), and acute myeloid leukemia (AML) with t(8;21) or t(15;17). PCR amplification is applicable to any other translocation provided the translocation is highly associated with the malignancy and the breakpoints are sufficiently clustered; a quickly increasing number of such specific molecular markers are now available for PCR assays. PCR still remains an experimental investigation for the detection of covert disease. However, the clinical relevance of MRD detection should be evaluated separately for each type of leukemia as significant prognostic differences between disease entities were found. This review describes the PCR assays available for the detection of leukemia cells with specific chromosomal translocations and summarizes the experience with the application of PCR techniques in monitoring patients during the course of the disease.

Reverse transcription polymerase chain reaction for the diagnosis and molecular monitoring of the PML/RAR alpha fusion gene in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by a specific t(15;17) translocation and a high rate of response to all-trans retinoic acid. The translocation generates a PML/RAR alpha chimeric gene which is transcribed in a fusion PML/RAR alpha mRNA. In this study, by using RT-PCR, we examined 14 APL patients for PML/RAR alpha fusion gene transcripts. Eight patients were studied at diagnosis, 2 at relapse, 1 both at relapse and after reinduction, 1 both at diagnosis and after three cycles of consolidation chemotherapy, and 2 patients were examined for minimal residual disease (MRD) 4 months after completing treatment. A positive result was observed in all 14 cases. Two patients who were in complete hematologic remission had evidence of hematologic relapse soon after the positive test. We conclude that RT-PCR for APL yields important diagnostic and prognostic information for the APL patients.

Leukemia cell lines: in vitro models for the study of acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) serves as a paradigm in clinical and biological leukemia research. Firstly, APL represents a model for the new therapeutic approach of differentiation therapy, taking advantage of the ability of APL cells to respond to retinoic acid treatment by terminal differentiation. Secondly, the 15;17 chromosomal translocation specific for APL leads at the molecular genetic level to a chimeric gene fusing the PML and RAR alpha genes and appears to be an instrumental, if not actually the causative event, in the neoplastic process. These unique characteristics of an otherwise rather rare disease have recently attracted intense research interest. As in other types of leukemia where continuous cell lines are powerful research tools, studies using APL-derived cell lines have contributed a large body of relevant data in efforts to unravel the pathobiology and leukemogenesis of APL. Three cell lines have been reported to be derived from patients with APL: HL-60, NB-4 and PL-21. Both HL-60 and PL-21 lack t(15;17) while NB-4 carries this cytogenetic hallmark pathognomonic for APL. Morphological and immunophenotypical examinations of the cell lines do not permit a clear assignment to any stage of myelomonocytic differentiation. Some additional data, such as expression of myeloperoxidase, monocyte-specific esterase and annexin VIII, together with the cytogenetic and molecular biological information, suggest that NB-4 is the only genuine promyelocytic leukemia cell line, whereas HL-60 may represent a discrete stage of differentiation between the late myeloblasts and the promyelocyte; PL-21 has distinct features associated with monocytic cells. These cell lines provide unique in vitro model systems for studying the cellular and molecular events involved in the proliferation and differentiation of normal and leukemic myelomonocytic cells.

All-trans retinoic acid in the treatment of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a group of hematopoietic disorders characterized by uni- or multilineage maturation defects of the bone marrow. Controversial therapeutic results have been obtained using growth factors or differentiating agents such as 13-cis retinoic acid. In this pilot study we evaluated the effects of all-trans retinoic acid (ATRA) in 10 MDS patients (5 male, 5 female). Six patients had refractory anemia (RA), 1 had refractory anemia with excess of blasts (RAEB), and 3 had refractory anemia with excess of blasts in transformation (RAEB-t). All patients received the same dose of ATRA (45 mg/sqm/day) orally for 6 weeks. A rise in hemoglobin concentration > 1g/dl was observed in 3/10 patients, while 5/10 patients showed an increase in granulocyte count > 0.5 x 10(9)/l without concomitant increase in the percentage of blast cells in the bone marrow. A rise in the platelet count > 50 x 10(9)/l was observed in 1/10 patients. All the effects were transient and maximal responses were obtained by the fourth week of treatment. Thereafter, the peripheral blood counts started to drop again, reaching pre-therapy values by the end of the treatment. This phenomenon could be attributed either to the exhaustion of an ATRA-responding cell pool, the development of cellular resistance to ATRA or to a reduction of plasma ATRA levels after prolonged treatment. According to our results, it seems that ATRA might have therapeutic efficacy in MDS, particularly if its effect could be improved by combinations with other differentiating agents or growth factors.

Significant reduction of medical costs by differentiation therapy with all-trans retinoic acid during remission induction of newly diagnosed patients with acute promyelocytic leukemia. The Japan Adult Leukemia Study Group

BACKGROUND

Differentiation therapy with all-trans retinoic acid (RA) induces more than 80% complete remission with the least complications in patients with acute promyelocytic leukemia (APL). The authors studied the cost-benefit of this new treatment modality compared with conventional chemotherapy in newly diagnosed patients with APL.

METHODS

Costs were calculated retrospectively through the monthly bills of each patient to national health insurance and were compared between 36 patients treated with conventional chemotherapy in the AML-87 or AML-89 studies and 40 patients treated with all-trans RA alone or with all-trans RA plus low dose chemotherapy in the AML-92 study of the Japan Adult Leukemia Study Group who were treated at 22 university and cancer hospitals in Japan.

RESULTS

Average medical costs except for antileukemic drugs during 2 months after admission were 4,164,026 yen (approximately US$46,300) in the chemotherapy group and 2,906,825 yen (approximately US$32,300) in the all-trans RA group (P < 0.0001). The difference resulted mainly from the costs of antibiotics and of platelet and erythrocyte transfusions. Average costs of antibiotics were 650,494 yen (approximately US$7,200) and 349,138 yen (approximately US$3,900), respectively (P < 0.0002), and those of platelet and erythrocyte transfusions were 1,016,190 yen (approximately US$11,300) and 633,444 yen (approximately US$7,000), respectively (P < 0.0020).

CONCLUSION

During the remission induction therapy of newly diagnosed APL, all-trans RA significantly reduced medical costs. all-trans RA should be incorporated into the front-line therapy of patients with APL for medical and economic reasons.

The effects of retinoid status on TGF beta expression during mouse embryogenesis

In a previous study we investigated the effects of RA excess on TGF beta protein localization in early postimplantation stages of mouse development. Here we extend this investigation by comparing the effects of retinoid deficiency with those of excess, and by comparing the effects of altered retinoid status on TGF beta protein and RNA transcript distribution. In vitamin A-deficient embryos, TGF beta 1 RNA and protein distribution were both unaltered compared with controls; conversely, TGF beta 2 protein levels were reduced while RNA levels remained normal. In RA-treated embryos, the previous study showed that intracellular TGF beta 1 levels were decreased, while those of extracellular TFG beta 1 were initially decreased but subsequently increased; here we found that TGF beta 1 RNA transcript levels were reduced following exposure to RA excess. TGF beta 2 showed a clear disparity between the effects of RA excess on protein and RNA transcript levels: RNA transcript distribution was unchanged or showed a slight increase in RA-treated embryos, whereas the previous results showed greatly reduced protein levels. The new results provide further evidence for interaction between retinoids and TGF beta s during mouse development, and indicate that retinoids are capable of differentially regulating TGF beta isoforms through mechanisms involving different stages in the process of TGF beta synthesis and secretion. The long-term nature of the effects of transient exposure to RA excess suggests that the mechanisms of RA-TGF beta interaction may be indirect.

Assessment of minimal residual disease in acute promyelocytic leukaemia with t(15;17) by chromosome painting

To detect the minimal residual disease (MRD) in acute promyelocytic leukaemia patients treated with all-trans retinoic acid, we compared the sensitivity of metaphase fluorescence in situ hybridization (FISH) with conventional analysis of G-banded metaphases. 5 out of 6 patients studied at diagnosis showed the t(15;17) translocation. 4 out of 5 patients carrying t(15;17) achieved complete remission and conventional cytogenetic conversion. In 3 cases the whole chromosome painting (WCP) probe 17 discovered one normal chromosome 17 and two fragments indicative of t(15;17) persistence. The FISH-WCP technique seems to be highly sensitive and recommendable in monitoring leukaemias with specific chromosome rearrangements.

Successful treatment of retinoic acid syndrome with high-dose dexamethasone pulse therapy in a child with acute promyelocytic leukemia treated with ATRA

A 5 year old female developed femoral pain, fever, and hemorrhagic tendency. She was diagnosed as having acute promyelocytic leukemia (APL). Approximately 2 weeks after the administration of all-trans retinoic acid (ATRA), she developed a high fever, edema, and respiratory distress which met the criteria for retinoic acid syndrome. At first, we tried to treat the patient with oral corticosteroid, however, this approach was unsuccessful. Considering the worsening of her condition, we then chose to administer a large dose of intravenous dexamethasone therapy for 3 days. Immediately after this therapy, she became afebrile, respiratory distress and edema disappeared, and there was a general improvement of the symptoms. All-trans retinoic acid at the reduced dose of 25 mg/m2, was continued for an additional 6 weeks and then discontinued. Since the cessation of dexamethasone and ATRA, there has been no relapse of APL in this patient. Although based on only one case, we recommend the intravenous high-dose dexamethasone pulse therapy (13 mg/m2 per day, for 3 days) for treating retinoic acid syndrome which develops in pediatric APL patients treated with ATRA.

Differentiation induction of human leukemia cells (HL60) by a combination of 1,25-dihydroxyvitamin D3 and retinoic acid (all trans or 9-cis)

1,25(OH)2D3 and two stereoisomers of retinoic acid, all trans and 9-cis retinoic acid, are regulators of cell proliferation and differentiation. The aim of this study was to evaluate the effects of a combination of 1,25(OH)2D3 and retinoic acid (all trans or 9-cis) on proliferation and cell differentiation of the human promyelocytic leukemia cell line HL60, and to test the reversibility of the induced differentiation. Cell proliferation was inhibited as expected by 1,25(OH)2D3 and all trans retinoic acid alone (IC50 of cell survival was 4 x 10(-7) M, 9 x 10(-6) M and 9 x 10(-7) M for 1,25(OH)2D3, all trans and 9-cis retinoic acid, respectively). Combination of 1,25(OH)2D3 and either form of retinoic acid resulted in a partially additive decrease in cell proliferation. 1,25(OH)2D3 induced a monocytic differentiation (100% CD14+ cells with 10(-7) M 1,25(OH)2D3), while retinoic acid led to a predominantly granulocytic differentiation (36 and 42% CD67+ cells with 10(-6) M all trans and 9-cis retinoic acid, respectively). Additive effects on differentiation were observed upon combination of subtherapeutical doses of the drugs, achieving a mainly monocytic population, demonstrating the dominant role of 1,25(OH)2D3 in determining the direction of differentiation. The effects on proliferation and differentiation of the solitary drugs were reversible, while the proliferation arrest and differentiation induced by the combination persisted and even progressed after withdrawal of the drugs. We conclude that 1,25(OH)2D3 and retinoic acid (all trans or 9-cis) exert additive effects on inhibition of proliferation and induction of cell differentiation of HL60 cells, leading to a persistent differentiation, even after drug withdrawal.

The N-terminal part of TIF1, a putative mediator of the ligand-dependent activation function (AF-2) of nuclear receptors, is fused to B-raf in the oncogenic protein T18

Nuclear receptors (NRs) bound to response elements mediate the effects of cognate ligands on gene expression. Their ligand-dependent activation function, AF-2, presumably acts on the basal transcription machinery through intermediary proteins/mediators. We have isolated a mouse nuclear protein, TIF1, which enhances RXR and RAR AF-2 in yeast and interacts in a ligand-dependent manner with several NRs in yeast and mammalian cells, as well as in vitro. Remarkably, these interactions require the amino acids constituting the AF-2 activating domain conserved in all active NRs. Moreover, the oestrogen receptor (ER) AF-2 antagonist hydroxytamoxifen cannot promote ER-TIF1 interaction. We propose that TIF1, which contains several conserved domains found in transcriptional regulatory proteins, is a mediator of ligand-dependent AF-2. Interestingly, the TIF1 N-terminal moiety is fused to B-raf in the mouse oncoprotein T18.

Acute promyelocytic leukaemia with hypogranular bone marrow blasts in a 16-year-old girl: diagnostic value of different genetic methods

We report a 16-year-old girl who presented with anaemia, thrombocytopenia, leukocytosis and disseminated intravascular coagulation. Bone marrow analysis showed promyelocyte-like myeloblasts with rare Auer rods and very few granula. CD2 antigen was not expressed in bone marrow blasts. Karyotype analysis revealed a complex pattern of chromosomal aberrations without the promyelocytic leukaemia (PML) specific translocation t(15;17) (q22;q21). Southern blot analysis revealed a rearrangement of the retinoic acid receptor alpha (RAR alpha) locus. Reverse transcribed polymerase chain reaction assay confirmed the initial diagnosis of PML by amplification of the PML-specific PML/RAR alpha fusion transcript.

CONCLUSION

This case report confirms that a characteristic translocation t(15;17) is not always detectable in PML blasts by karyotype analysis despite presence of specific PML/RAR alpha-transcripts. Together with careful morphological analysis of bone marrow blasts this assay apparently is the most specific and sensitive method to confirm the diagnosis.

A variant t(14;17) in acute promyelocytic leukemia. Positive response to retinoic acid treatment

We present a case of acute promyelocytic leukemia (APL) carrying an atypical translocation involving chromosomes 14 and 17. This translocation could be considered a variant of the APL-specific t(15;17). Positive response to retinoic acid treatment suggests molecular rearrangement of retinoic acid receptor alpha.

Detection of PML-RAR alpha fusion transcript in Ph positive leukemia with acute promyelocytic phenotype lacking the t(15;17) cytogenetic abnormality

A 39-year-old woman was diagnosed with acute promyelocytic leukemia (APL) with disseminated intravascular coagulation syndrome. The hematologic examination showed a morphologic, cytochemical, and immunophenotypic picture typical of an APL, with a marked leukocytosis and a mixed population of hypergranular and microgranular promyelocytes. The cytogenetic analysis showed a 46,XX,t(9;22) karyotype, without any alterations of chromosomes 15 and 17. The t(15;17) translocation was not evident in FISH experiments, while a molecular analysis revealed the presence of a PML-RAR alpha chimera.

Pharmacokinetics of all-trans retinoic acid in pediatric patients with leukemia

Since all-trans retinoic acid (ATRA) induces complete remission in a high proportion of patients with acute promyelocytic leukemia (APL), and its effectiveness appears to be related to the plasma or serum level, a pharmacokinetic study of ATRA was undertaken in nine patients with various leukemias. After oral administration at a dose of 30 mg/m2, the time required to reach the peak plasma level of ATRA (20-1198 ng/ml) was between 120 and 240 min and the apparent plasma elimination half life was 21-51 min. In addition, 13-cis retinoic acid was detected in the plasma of seven patients, indicating the occurrence of ATRA isomerization in vivo. ATRA therapy did not induce complete remission in all patients, even when high plasma levels were achieved. Among the six APL patients given ATRA therapy, one who failed to respond had a very low plasma ATRA level. These findings suggest that it may be useful to monitor plasma levels during oral ATRA therapy in order to achieve an appropriate treatment regimen.

Retinoic acid inhibition of ex vivo human immunodeficiency virus-associated apoptosis of peripheral blood cells

T cells from human immunodeficiency virus (HIV)-infected individuals undergo spontaneous and activation-induced ex vivo apoptosis. Here we report that peripheral blood mononuclear cells (PBMCs) obtained from six HIV-infected individuals exhibited reduced ex vivo DNA fragmentation and cell death after ingestion of all-trans-retinoic acid (tRA). These effects were attenuated with continued daily RA administration, which correlated with a > 5-fold decrease in serum peak RA concentrations. Incubation of PBMCs from HIV+ individuals with tRA in vitro resulted in decreased DNA fragmentation in a subset of patients, especially those having < 500 CD4+ T cells per mm3. tRA also inhibited apoptosis of preactivated normal PBMCs induced to die by restimulation, which raises the possibility of a common mechanism between activation-induced apoptosis of activated normal PBMCs and apoptosis associated with HIV infection. Whether HIV-associated apoptosis of PBMCs, and its prevention by RA, has an impact on T-cell survival or the course of disease in patients infected with HIV will require further evaluation.

Expression of the zinc-finger gene PLZF at rhombomere boundaries in the vertebrate hindbrain

To investigate the potential biological role(s) of the PLZF gene, discovered as a fusion with the RARA locus in a patient with acute promyelocytic leukemia harboring a t(11;17) chromosomal translocation, we have isolated its murine homologue (mPLZF) and studied its patterns of developmental expression. The levels of mPLZF mRNAs increased perinatally in the liver, heart, and kidney, but with the exception of the heart, they were either absent or very low in the adult tissues. In situ analysis of mPLZF expression in mouse embryos between 7.0 and 10.5 days of development revealed that mPLZF mRNAs and proteins were coexpressed in spatially restricted and temporally dynamic patterns in the central nervous system. In the hindbrain region, a segmental pattern of expression correlated with the development of the rhombomeres. From 9.0 days of development, starting first in rhombomeres 3 and 5, there was an ordered down-regulation of expression in the center of each rhombomere, so that 1 day later elevated levels of mPLZF mRNAs and proteins were restricted to cells surrounding the rhombomeric boundaries. The chicken homologue of the PLZF gene, which we have also cloned, demonstrated a similar segmental pattern of expression in the hindbrain. To date, PLZF represents the only example of a transcription factor with elevated expression at rhombomeric boundaries. The high degree of evolutionary conservation between the patterns of PLZF expression during mammalian and avian central nervous system development suggests that it has an important functional role in the regionalization of the vertebrate hindbrain, potentially regulating boundary cell interactions.

A 7-base-pair sequence protects DNA from exonucleolytic degradation in Lactococcus lactis

Linear DNA molecules are subject to degradation by various exonucleases in vivo unless their ends are protected. It has been demonstrated that a specific 8-bp sequence, 5'-GCTGGTGG-3', named Chi, can protect linear double-stranded DNA from the major Escherichia coli exonuclease RecBCD. Chi protects linear replication products of rolling-circle plasmids from RecBCD degradation in vivo, in agreement with observations in vitro. A unique 7-bp sequence, 5'-GCGCGTG-3', is shown to protect similar replication products from degradation in Lactococcus lactis strains but not in more distantly related Gram-positive bacteria. The properties of this sequence in L. lactis correspond to those of a Chi site. Linear plasmid replication products have been detected in numerous prokaryotes, suggesting the widespread existence of short species-specific sequences that preserve linear DNA from extensive degradation by host cell exonucleases.

A retinoic acid resistant HL-60 cell clone sensitive to N-(4-hydroxyphenyl) retinamide-mediated clonal growth inhibition

Among the Retinoic Acid (RA) derivatives, retinamides, and in particular N-(4-hydroxyphenyl) retinamide (4-HPR), are currently being investigated in selected cases of cancer chemoprevention. The cellular target range, however, seems to be limited, as cells of hemopoietic origin are virtually incapable of terminal differentiation upon addition of the compound. We have reconsidered the effect of 4-HPR on HL-60 cells by taking advantage of a mutant clone, generated in our laboratory, unresponsive to RA but highly responsive to dimethylsulfoxide (DMSO). We show here that this clone, upon addition of 4-HPR, although unable of undergoing full differentiation, shows considerable reduction of clonal growth. Moreover, the combination of 4-HPR and RA resulted in a much greater effect than the administration of 4-HPR alone. We suggest that 4-HPR and RA, at least in terms of mediating growth inhibition, may follow different metabolic pathways.

Treatment of acute promyelocytic leukemia in patients presenting at Vancouver General Hospital from 1983 to 1992

Between 6/83 and 8/92, 23 of 361 patients (6.4%) presenting at Vancouver General Hospital with acute myelogenous leukemia had acute promyelocytic leukemia (APL). Treatment plan was: 1) induction with high-dose cytosine arabinoside and an intercalator; and 2) consolidation with allogeneic bone marrow transplantation (BMT) for those aged < or = 50 years with a sibling donor or repeat of induction for the the others. Complete remission (CR) was achieved in 20 patients (87%). Eleven patients in CR were eligible for allogeneic BMT; 4 were considered unsuitable, 2 refused, and 5 underwent this treatment--1 died of acute graft-versus-host disease, 1 relapsed and 3 are leukemia-free and well 1.6, 3.3 and 3.9 years after diagnosis. Fifteen patients did not undergo allogeneic BMT in CR; 4 received no further treatment and all died, 2 relapsed before consolidation therapy and both died, 1 underwent autologous BMT and died of complications, and 8 received consolidation treatment as planned--1 died of sepsis, 2 relapsed and 5 are leukemia-free and well 1.0, 3.8, 4.5, 4.9 and 8.5 years after diagnosis. The actuarial overall survival for all 23 patients was 38% (95% confidence interval [CI] 18-57%). The actuarial 2-year leukemia-free survival was 60% (95% CI 20-85%) for the 8 patients who underwent consolidation chemotherapy as planned and 53% (95% CI 68-86%) for the 5 patients who underwent allogeneic BMT in CR. These results suggest that patients with APL who are able to undergo consolidation chemotherapy have a relatively good prognosis and allogeneic BMT may reasonably be held in reserve for salvage therapy.

Targeted disruption of retinoic acid receptor alpha (RAR alpha) and RAR gamma results in receptor-specific alterations in retinoic acid-mediated differentiation and retinoic acid metabolism

F9 embryonic teratocarcinoma stem cells differentiate into an epithelial cell type called extraembryonic endoderm when treated with retinoic acid (RA), a derivative of retinol (vitamin A). This differentiation is presumably mediated through the actions of retinoid receptors, the RARs and RXRs. To delineate the functions of each of the different retinoid receptors in this model system, we have generated F9 cell lines in which both copies of either the RAR alpha gene or the RAR gamma gene are disrupted by homologous recombination. The absence of RAR alpha is associated with a reduction in the RA-induced expression of both the CRABP-II and Hoxb-1 (formerly 2.9) genes. The absence of RAR gamma is associated with a loss of the RA-inducible expression of the Hoxa-1 (formerly Hox-1.6), Hoxa-3 (formerly Hox-1.5), laminin B1, collagen IV (alpha 1), GATA-4, and BMP-2 genes. Furthermore, the loss of RAR gamma is associated with a reduction in the metabolism of all-trans-RA to more polar derivatives, while the loss of RAR alpha is associated with an increase in metabolism of RA relative to wild-type F9 cells. Thus, each of these RARs exhibits some specificity with respect to the regulation of differentiation-specific gene expression. These results provide an explanation for the expression of multiple RAR types within one cell type and suggest that each RAR has specific functions.

Acute myeloid leukemias M2 potentially misdiagnosed as M3 variant French-American-Britain (FAB) subtype: a transitional form?

From 1990 to 1994, 3 patients with de novo acute myeloid leukemia (AML) in whom light microscopy and cytochemistry suggested a FAB subtype M3 variant were observed at our Institute. Immunophenotype showed HLA-DR-, CD13+, CD33+, CD2+, CD9+; promyelocytic features were also detected by electron microscopy. However, leukemic cells lacked both translocation t(15;17) and RAR alpha/PML genes rearrangement. These cases were considered to be 'M2 atypical' subtypes and they contribute to point out how cytogenetics and molecular biology are mandatory for a correct diagnosis of acute promyelocytic leukemia (APL) particularly because therapy with all trans retinoic acid (ATRA) is now the best treatment for APL. Nevertheless these 3 cases indicate that the atypical M2 subtype may be confused with the M3v if only cytochemistry, immunophenotype and electron microscopy are used in the defining the FAB subtypes.

Acute promyelocytic leukaemia (M3): relapse with acute myeloblastic leukaemia (M2) and dic(5;17) (q11;p11)

Secondary leukaemia following treatment of M3 acute promyelocytic leukaemia (APL) is a rare event. We describe a patient in remission following chemotherapy for APL who relapsed with M2 acute non-lymphoblastic leukaemia (ANLL). The original t(15;17) (q22;q21) chromosome translocation was lost and replaced by a clone containing a dic(5;17) (q11;p11) abnormality. Southern genomic analysis demonstrated re-arrangements of the retinoic acid receptor varies; is directly proportional to (RAR varies; is directly proportional to) and PML genes in the APL blasts at presentation but not in the M2 ANLL marrow at relapse. The significance of unbalanced 5;17 translocations as markers for therapy-related secondary leukaemia is discussed.

Acute promyelocytic leukemia: from clinic to molecular biology

Acute promyelocytic leukemia (APL) is a good model for studying the human malignancies in that up to 90% of APL patients can achieve complete remission (CR) with a differentiation inducer, all-trans retinoic acid (ATRA). APL is also associated with a specific chromosomal translocation t(15;17) which fuses the retinoic acid receptor alpha (RAR alpha) gene with a chromosome 15q locus, PML. Recently the RAR alpha and the PML gene structural alterations in t(15;17) have been characterized. The heterogeneity of the PML rearrangements juxtaposes different PML gene portions to the same set of RAR alpha exons, producing two major PML-RAR alpha fusion mRNA isoforms. A retrotranscriptase/polymerase chain reaction (RT-PCR) analysis of the fusion transcripts has been developed which allows the detection of minimal residual disease during the clinical remission of APL. Molecular study showed PML-RAR alpha can form heterodimers with wild-type PML and RXR. Recently, PML has been shown to be one of the components of a nuclear body, POD. In APL, the normal organization of POD is disrupted by PML-RAR alpha, whereas ATRA treatment in vivo and in vitro can induce a reorganization of this organelle. Cytogenetic and molecular study allowed a variant translocation t(11;17) being recently discovered in a small subset of APL. This time RAR alpha is fused to a new gene, PLZF, on chromosome 11q23. It has been shown that the PLZF-RAR alpha, like PML-RAR alpha, has a "dominant negative" effect on the wild-type RAR-RXR. Clinical data obtained from a group of t(11;17) APL patients showed that these respond poorly to ATRA and could be grouped in a special clinical syndrome within APL. The comparison of the biological activities mediated by PML-RAR alpha and PLZF-RAR alpha may give new insights into the pathogenesis as well as the mechanisms of ATRA-induced differentiation in APL.

Vitamin A, differentiation and cancer

Retinoids, which are derivatives of vitamin A, have a variety of effects on normal cellular differentiation and on the process of carcinogenesis. A number of novel endogenous retinol metabolites have been identified recently. The response of many cell types to retinoid treatment is mediated by retinoid receptors, and involves changes in gene expression, cell growth and cell differentiation. The gene encoding one of the retinoic acid receptors is disrupted by the chromosome translocations associated with acute promyelocytic leukemia, and the expression of another is altered in epithelial tumors; both of these findings have important implications for the use of retinoids as anti-carcinogenic agents. It has been demonstrated recently that certain homeobox genes are regulated by retinoids; these genes may also prove to be useful agents for anti-carcinogenic therapies.

Inhibition of nitric oxide synthesis in vascular smooth muscle by retinoids

1. These studies examine the effect of retinoids on interleukin 1 beta (IL-1 beta)-induced nitric oxide synthase (NOS) activity in cultured rat aortic vascular smooth muscle (VSM) cells and isolated rat aortic rings. 2. All-trans-retinoic acid (all-trans-RA, 0.1-10 microM) and its active analogues produced concentration-dependent inhibition of IL-1 beta (0.1-10 ng ml-1)-induced nitrite production in cultured VSM cells. In contrast, the inactive retinoid, Ro 14-6113 (0.1-10 microM), had no effect on IL-1 beta-induced nitrite production. 3. Since some of the actions of retinoids are mediated by induction of transforming growth factor beta (TGF-beta), its effect on inducible NOS activity in VSM cells was examined. TGF-beta produced concentration-dependent (0.1-10 ng ml-1) inhibition of IL-1 beta-induced nitrite production and the maximum effect (approximately 90% inhibition) was significantly greater than that seen with all-trans-RA (approximately 70% with 10 microM). However, an anti-TGF-beta antibody (50 micrograms ml-1) which blocked the effect of exogenous TGF-beta (5 ng ml-1) did not significantly reverse the inhibitory action of all-trans-RA (10 microM). 4. In addition to inhibiting IL-1 beta-induced nitrite production, all-trans-RA (10 microM) reduced substantially inducible NOS mRNA and protein levels in IL-1 beta-induced VSM cells (P < 0.01). 5. Incubation of isolated rat aortic rings with IL-1 beta (10 ng ml-1) caused a progressive resistance of the rings to the vasoconstrictor action of phenylephrine (10 nM to 10 microM). This effect was abolished by the addition of the nitric oxide synthase inhibitor L-NG-monomethyl-L-arginine (L-NMMA, 1 mM). All trans-RA (10 micro M) also markedly and significantly reversed this IL-1p-induced vascular hyporeactivity(P<0.01).6. These data show that all-trans-RA and other active retinoids are able to block cytokine-stimulated expression of inducible NOS in cultured VSM cells and isolated aortic rings.

Myeloperoxidase gene expression in normal granulopoiesis and acute leukemias

Myeloperoxidase (MPO) is an abundant heme protein found in granulocytes and monocytes, which plays an important role in host defense against infection. MPO enzyme activity as determined by light microscopic cytochemistry has long been an important marker used in the diagnosis of acute leukemias and other hematopoietic disorders. Recently, MPO expression has been studied at the electron microscopic level, and monoclonal antibodies (mAbs) against MPO protein have been developed. Furthermore, techniques and probes for analysing MPO expression at the RNA level are now available. This has made possible more extensive studies of MPO expression in a wide range of neoplastic and preneoplastic blood disorders. This review will discuss the fundamental biology of MPO as well as recent developments in our understanding of MPO expression in leukemic cells and cell lines of various lineages.

PML-RAR alpha PCR positivity in the bone marrow of patients with APL precedes haematological relapse by 2-3 months

We report the results of serial tests in three patients with hyperleucocytotic AML M3 by haematological methods, coagulation assays and PCR analyses following treatment with ATRA and chemotherapy. All three patients became PCR negative in bone marrow and peripheral blood (sensitivity level 1 in 10(5) cells) after one cycle of ATRA + chemotherapy. However, they relapsed haematologically 6-9 months after achieving complete haematological remission. The haematological relapse was preceded by PCR positivity in the bone marrow by 3 months. Platelet counts decreased already during CHR, but dropped below normal levels only at the time of relapse. Coagulation parameters were not helpful for early prediction of relapse. Our results demonstrate that PCR analysis in the bone marrow is the best way to monitor patients with APL. However, in hyperleucocytotic patients, PCR negativity does not seem to indicate long-term remission.

Advantage of induction therapy with all trans retinoic acid in acute promyelocytic leukaemia in a country with limited transfusion resources: a Malaysian experience

Induction of remission of acute promyelocytic leukaemia (APL) needs intensive blood support (16) to prevent bleeding attributed to disseminated intravascular coagulation. Between 1989 and 1991, at the University Hospital in Kuala Lumpur, Malaysia, the remission rate of APL was only 27% with conventional chemotherapy as a result of inadequate transfusion resources. The use of all trans retinoic acid in induction therapy followed by consolidation and maintenance chemotherapy has improved the situation dramatically. Twelve patients entered the study. Ten patients achieved remission (83%), indicating how ATRA had significantly improved the results (p = 0.003). Blood component transfusions were also significantly reduced (p = 0.003). Two ethnic Chinese patients developed pulmonary leucostasis. Published Chinese (2, 6) and Japanese (11) studies have not reported this serious adverse effect. We can now state that leucostasis is not a phenomenon limited to the Western population. ATRA has proved to be extremely beneficial for patients at this centre. Early analysis also suggests that consolidation and maintenance chemotherapy has prolonged remission duration. ATRA should be made available for the treatment of APL in all countries where there are inadequate transfusion services.