Leukemogenesis and therapy of acute promyelocytic leukemia: from the worse to the most favorable subtype of acute myeloid leukemia

The evolution of therapy of acute promyelocytic leukemia (APL) from 1964 to present is reviewed. The paper is focused on the main findings and key studies which formed current and almost standard therapeutic approach to APL. The first important development was the use of anthracyclines for the initial therapy of APL in 1967. Starting 1972, heparin was introduced into a treatment of coagulopathy and the intensity of substitutional transfusion therapy was remarkably enhanced. The main breakthrough was the initiation of differentiation therapy using all-trans retinoic acid (ATRA). The first clinical study which brought information about the effect of ATRA in APL started in China in 1986. A number of the most important subsequent studies focused on pathogenesis and therapy of APL are analyzed and reviewed. The additional considerable finding was the discovery of arsenic trioxide (ATO) therapeutic efficacy in APL and ATO is now in particular used for a therapy of relapsed APL. The publication gives also a recent insight into a leukemogenesis of APL and development of a resistance to ATRA. At the conclusion, the authors emphasize the need of early diagnosis as a one of the main conditions for successful treatment of APL.     

AM580, a stable benzoic derivative of retinoic acid, has powerful and selective cyto-differentiating effects on acute promyelocytic leukemia cells

All-trans retinoic acid (ATRA) is successfully used in the cyto- differentiating treatment of acute promyelocytic leukemia (APL). Paradoxically, APL cells express PML-RAR, an aberrant form of the retinoic acid receptor type alpha (RAR alpha) derived from the leukemia- specific t(15;17) chromosomal translocation. We show here that AM580, a stable retinobenzoic derivative originally synthesized as a RAR alpha agonist, is a powerful inducer of granulocytic maturation in NB4, an APL-derived cell line, and in freshly isolated APL blasts. After treatment of APL cells with AM580 either alone or in combination with granulocyte colony-stimulating factor (G-CSF), the compound induces granulocytic maturation, as assessed by determination of the levels of leukocyte alkaline phosphatase, CD11b, CD33, and G-CSF receptor mRNA, at concentrations that are 10- to 100-fold lower than those of ATRA necessary to produce similar effects. By contrast, AM580 is not effective as ATRA in modulating the expression of these differentiation markers in the HL-60 cell line and in freshly isolated granulocytes obtained from the peripheral blood of chronic myelogenous leukemia patients during the stable phase of the disease. In NB4 cells, two other synthetic nonselective RAR ligands are capable of inducing LAP as much as AM580, whereas RAR beta- or RAR gamma-specific ligands are totally ineffective. These results show that AM580 is more powerful than ATRA in modulating the expression of differentiation antigens only in cells in which PML-RAR is present. Binding experiments, using COS-7 cells transiently transfected with PML-RAR and the normal RAR alpha, show that AM580 has a lower affinity than ATRA for both receptors. However, in the presence of PML-RAR, the synthetic retinoid is a much better transactivator of retinoic acid-responsive element-containing promoters than the natural retinoid, whereas, in the presence of RAR alpha, AM580 and ATRA have similar activity. This may explain the strong cyto-differentiating potential of AM580 in PML-RAR-containing leukemic cells.     

Complete remission through blast cell differentiation in PLZF/RARalpha-positive acute promyelocytic leukemia: in vitro and in vivo studies

Acute leukemia with the t(11;17) expressing the PLZF-RARalpha gene fusion is a rare variant of acute promyelocytic leukemia (APL) that has been associated with poor clinical response to all-trans retinoic acid (ATRA) treatment. However, some recent reports have put into question the absolute refractoriness of this leukemia to ATRA. We describe here a patient with PLZF/RARalpha APL who was treated at relapse with ATRA and low-dose hydroxyurea. Complete hematologic remission was obtained through differentiation of leukemic blasts, as proven by morphologic, immunophenophenotypic, and genetic studies carried out in sequential bone marrow samples. Moreover, in vitro studies indicated that blast differentiation was potentiated by the addition of the histone deacetylase inhibitor tricostatin A, but not of hydroxyurea, to ATRA. Our findings indicate that the maturation block may be overcome and terminal differentiation obtained in this leukemia subset and support the view that sensitivity/refractoriness of this form to ATRA should be revisited.     

All-trans retinoic acid-induced downregulation of annexin II expression in myeloid leukaemia cell lines is not confined to acute promyelocytic leukaemia

Most acute promyelocytic leukaemia (APL) patients suffer from disordered haemostasis. APL can be treated successfully in most instances by all-trans retinoic acid (ATRA) therapy, which induces endpoint maturation of the leukaemic promyelocytes with the characteristic t(15;17). Annexin II (AnII), a profibrinolytic protein, has been implicated in the bleeding manifestation seen in APL. Our group has shown previously that high levels of AnII are expressed on other acute myeloid leukaemia subtypes that are sometimes associated with disordered haemostasis, albeit less frequently than APL. This study examined the effects of ATRA on AnII expression and cell differentiation, on myeloid leukaemia cell lines to determine whether a regulatory influence on AnII may contribute to the return of haemostatic stability in APL following treatment. The results confirmed that AnII expression in the APL cell line (NB4) was significantly downregulated in response to ATRA (P < 0.01), with associated morphological and immunophenotypical evidence of myeloid differentiation. ATRA also downregulated AnII expression on other myeloid cell lines, albeit to a lesser extent than observed on NB4 cells. The results provide evidence that ATRA may resolve the hyperfibrinolysis in APL by downregulation of AnII expression.     

Acute promyelocytic leukemia and pregnancy

In acute promyelocytic leukemia (APL), the use of all-trans-retinoic acid (ATRA) as a differentiating agent induces complete remission in a high percentage of patients. In pregnancy, however, this drug bears the risk of severe teratogenicity to the child. We report the case of a 23-yr-old woman at 21 weeks' gestation suffering from APL. She was treated with ATRA (45 mg/m2) for 40 d and two courses of standard chemotherapy. The mother achieved complete remission within 22 d of treatment. Fetal development was normal, and a healthy premature girl was born in the 35th week of pregnancy. In a review of the literature we have identified 14 cases of APL in pregnancy treated with ATRA alone or in combination with chemotherapy. ATRA has been used as early as in the 3rd week of gestation and in no case have malformations or other teratogenic effects occurred. Side-effects, however, ranged from fetal cardiac arrhythmias to induction of labour. Although known to exhibit severe teratogenic effects during the first trimester of pregnancy, ATRA seems to be reasonably safe during the second and third trimesters in the treatment of APL. However, careful obstetric follow-up is mandatory regarding fetal cardiac complications.     

A unique case of acute promyelocytic leukemia showing monocytic differentiation after ATRA (all-trans retinoic acid) therapy

Acute promyelocytic leukemia (PML) is characterized by a reciprocal translocation between chromosomes 15 and 17 resulting in a chimeric PML and retinoic acid receptor alpha (RARA) oncogene. The resultant fusion protein (PML/RARA) is thought to block differentiation of bone marrow cells arrested at the promyelocytic stage. In vitro and in vivo studies have shown that the large majority of APL cells undergo granulocytic maturation after ATRA therapy. We report a unique case of a PML/RARA positive APL patient exhibiting extensive monocytic differentiation after ATRA therapy as documented by morphology, flow cytometry, and FISH studies. We discuss potential dual capability for granulocytic/monocytic differentiation of PML/RARA positive APL cells and implications of monocytic differentiation in the management of APL patients treated with ATRA.     

Treatment of acute promyelocytic Leukemia and other hematologic malignancies with arsenic trioxide: Review of clinical and basic studies

Acute promyelocytic leukemia (APL) is now the most potentially curable subtype of acute myeloid leukemia in adults because of the introduction of novel approaches in the management of this disease. All-trans-retinoic acid (ATRA)-based therapy is now the first-choice treatment of patients presenting with de novo APL, and clinical studies have shown that nearly all patients who receive ATRA therapy achieve complete remission. However, approximately 20% to 30% of APL patients eventually have relapses with resistance to further ATRA treatment. Arsenic trioxide (As2O3 [ATO]) has been established as highly effective therapy for patients with APL, even for those with disease refractory to ATRA. Furthermore, results of recent studies have suggested a broad therapeutic potential for ATO in the treatment of hematologic malignancies beyond APL. In this review, we discuss the clinical activity and multiple mechanisms of ATO therapy in the management of APL and other hematologic neoplasms.     

Outcome of pregnancy in women treated with all-trans retinoic acid; a case report and review of literature

All-trans-retinoic acid (ATRA) has been proved to be an effective treatment for acute promyelocytic leukemia (APL), inducing remission in more than 90% of cases. Treatment of APL in pregnancy is controversial as the use of ATRA has been questioned due to the teratogenic effect of retinoids. We report a case of pregnancy in a woman exposed to ATRA during the first trimester. The baby was born healthy, without any anomalies. Review of all reported cases of the use of ATRA in pregnancy revealed no serious adverse outcomes or congenital anomalies although only very few cases had exposure in the first trimester.     

How I treat children and adolescents with acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APL) is a rare subtype of acute myeloid leukaemia. The outcome of paediatric APL has improved substantially over the past 20 years; cure rates above 80% are expected when all‐trans retinoic acid (ATRA) is given with anthracycline‐based regimens. The presenting features of paediatric APL may include severe bleeding and thrombotic complications, which contribute to the high early death rate. The incidence of leucocytosis and the microgranular subtype is greater in paediatric than adult APL, and children experience greater ATRA‐related toxicity. It is crucial to begin ATRA therapy and intensive platelet and fibrinogen replacement on first suspicion of APL. Recent risk‐adapted therapeutic trials have shown that patients at greater risk of relapse benefit from the introduction of high‐dose cytarabine during consolidation. Combination therapy with ATRA and arsenic trioxide provides very effective frontline treatment and may reduce the need for subsequent anthracycline therapy.     

Sivelestat relieves respiratory distress refractory to dexamethasone in all-trans retinoic acid syndrome: a report of two cases

Treatment with all-trans retinoic acid (ATRA) improves the prognosis of patients with acute promyelocytic leukemia (APL), but ATRA syndrome may occur as a possible fatal side effect, especially in cases refractory to medication or involving pulmonary hemorrhage. We describe two patients with APL who suffered from intracranial hemorrhage. The first patient was a 16-yr-old girl who was treated with ATRA and then developed respiratory distress refractory to treatment with dexamethasone combined with anthracycline-cytarabine cytoreduction therapy. Treatment with Sivelestat, a small molecule inhibitor of neutrophil elastase, achieved rapid improvement in oxygenation and chest radiograph findings, and the patient has been in complete remission for 24 months. The second patient was a 10-yr-old boy in whom pulmonary hemorrhage developed following administration of ATRA, dexamethasone and cytoreduction therapy. Aspiration and administration of Sivelestat improved oxygenation and he remained stable. Hematological improvement was also achieved, but the patient died of brain dysfunction because of cerebral edema accompanied by intracranial bleeding. The two cases suggest that Sivelestat may be effective as an additional agent in the treatment of refractory ATRA syndrome, and, therefore, prospective randomized studies of treatment protocols are warranted.     

Acute promyelocytic leukemia: evolving therapeutic strategies.

Acute promyelocytic leukemia (APL) is now the most curable subtype of acute myeloid leukemia in adults. All-trans retinoic acid (ATRA), which induces differentiation of the leukemic cells into mature granulocytes, represents the important advance. The incorporation of ATRA in induction results in a high complete remission rate, leads to rapid resolution of the characteristic life-threatening coagulopathy, and, most importantly, decreases the relapse rate compared with treatment with chemotherapy alone. However, ATRA is associated with unique toxicities not observed with conventional cytotoxic chemotherapy. A number of clinical trials have been performed to define the optimal role of ATRA in the treatment of patients. The therapeutic strategies have rapidly evolved as a result of both single institution and large cooperative group trials. Arsenic trioxide and stem cell transplantation are effective treatments for patients with APL who relapse after or are refractory to ATRA-based therapy. As experience with ATRA and arsenic trioxide in patients with APL accumulates, a number of important questions arise that need to be addressed.     

低剂量全反式维甲酸治疗急性早幼粒细胞白血病的疗效

为了评价低剂量全反式维甲酸（ＡＴＲＡ）治疗急性早幼粒细胞白血病（ＡＰＬ）的临床效果，分别比较了正常个体单次口服１５ｍｇ／ｍ２和４５ｍｇ／ｍ２ＡＴＲＡ的药代动力学。结果显示：口服低剂量的最大峰浓度（Ｃｍａｘ）虽低于口服高剂量组，仍足以诱导ＡＰＬ细胞分化。于是，应用１５～２０ｍｇｍ－２ｄ－１ＡＴＲＡ连续治疗２７例ＡＰＬ初发病人。在临床评价的２６例中，２４例在治疗１３～６７天内达完全缓解（ＣＲ）。无任何病人发生维甲酸综合征和ＤＩＣ。在检测的３例病人中，ＣＲ时和首次服药时的药代动力学比较发现，２例Ｃｍａｘ明显下降而１例相似。尤其重要的是，和过去一组相对匹配的高剂量ＡＴＲＡ治疗病人比较，本组结果显示低剂量ＡＴＲＡ的疗效与高剂量相似，并且可能有利于降低高白细胞血症的程度及其他一些副反应。     

全反式维甲酸治疗急性早幼粒细胞性白血病致Sweet综合征--病例报告及文献复习

目的:提高对全反式维甲酸(ATRA)治疗急性早幼粒细胞性白血病(APL)少见副作用的认识。方法:报告1例ATRA治疗APL致Sweet综合征的病例及治疗过程,并对相关文献进行复习总结。结果:ATRA治疗APL可以导致Sweet's综合征,采用糖皮质激素治疗有效。结论:Sweet综合征是维甲酸的少见副作用,临床上应提高对该综合征的早期诊断。     

Differentiation syndrome in acute promyelocytic leukaemia

Acute promyelocytic leukaemia differentiation syndrome (APL DS) is seen when patients with APL are treated with all-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO). Presenting symptoms are varied but frequently include dyspnoea, unexplained fever, weight gain >5 kg, unexplained hypotension, acute renal failure and a chest radiograph demonstrating pulmonary infiltrates or pleural or pericardial effusion. Immediate treatment with steroids at the first clinical suspicion is recommended and ATRA/ATO should be stopped in severe cases or if there is no response to treatment. The utility of steroid prophylaxis in order to prevent APL DS is less certain. Here we provide a detailed review of the pathogenesis, clinical signs and symptoms as well as management and prophylaxis strategies of APL DS.     

Outcome of pregnancy in women treated with all-trans retinoic acid; A case report and review of literature

Abstract

All-trans-retinoic acid (ATRA) has been proved to be an effective treatment for acute promyelocytic leukemia (APL), inducing remission in more than 90% of cases. Treatment of APL in pregnancy is controversial as the use of ATRA has been questioned due to the teratogenic effect of retinoids. We report a case of pregnancy in a woman exposed to ATRA during the first trimester. The baby was born healthy, without any anomalies. Review of all reported cases of the use of ATRA in pregnancy revealed no serious adverse outcomes or congenital anomalies although only very few cases had exposure in the first trimester.     

Successful All-<Emphasis Type="Italic">trans</Emphasis> Retinoic Acid Treatment of Acute Promyelocytic Leukemia in a Patient with <Emphasis Type="Italic">NPM/RAR</Emphasis> Fusion

Acute promyelocytic leukemia (APL) is characterized by a reciprocal chromosomal translocation involving the gene for retinoic acid receptor alpha(RAR). Most APL patients have a t(15;17) translocation that generates the PML-RAR fusion gene, and such patients respond well to treatment with all-trans retinoic acid (ATRA). Some APL cases also involve rearrangements that fuse RAR to partner genes other than PML, including nucleophosmin (NPM), promyelocytic leukemia zinc finger (PLZF), nuclear mitotic apparatus (NUMA), and Stat5b, but the clinical characteristics of APL without PML-RAR have not been fully clarified. We describe a 64-year-old man with NPM-RAR-positive APL who was receiving hemodialysis therapy for chronic uremia. Complete remission was achieved with ATRA monotherapy and was maintained for 18 months with consolidation chemotherapy. These findings suggest that ATRA can be used to treat APL patients with NPM/RAR as well as APL with PML/RAR.     

Successful treatment of acute promyelocytic leukaemia during pregnancy

A case is reported of a pregnant 16-year-old-woman diagnosed with Acute promyelocytic leukaemia (APL) at 25 weeks gestation and treated with all-trans retinoic acid (ATRA) (45 mg/m2) for 25 days in combination with chemotherapy. She achieved a complete cytogenetic and molecular remission. Clinical course was complicated, with an intracerebral bleed, respiratory failure requiring ventilation and prolonged pancytopenia following initial chemotherapy. A live female infant was born at 28 weeks gestation who survived to discharge with significant pulmonary complications. She remains oxygen dependent at 6 months of age. ATRA has been used from the 3rd week of gestation, but fetal malformations are common during the first trimester. In contrast it seems to be safe in the second and third trimesters with regard to teratogenesis but can cause other side-effects. Most successful outcomes in treatment of APL during pregnancy are seen after treatment with ATRA and delivery of the baby at as late a stage as possible. Pregnancies terminated before remission has been obtained or those treated in the first trimester have a poor maternal outcome.     

All-trans retinoic acid and chemotherapy in the treatment of acute promyelocytic leukemia

All-trans retinoic acid (ATRA) can induce complete remission (CR) in most patients with acute promyelocytic leukemia (APL) through in vivo differentiation of APL-blasts. However, it cannot eliminate the leukemic clone and must be used in combination with anthracycline-based chemotherapy. Experience accumulated over the last 10 years has clearly shown that the combination of ATRA and chemotherapy gave better survival than chemotherapy alone in newly diagnosed APL because of fewer relapses and a slightly higher CR rate. It is also strongly suggested that maintenance treatment with ATRA, and possibly with low-dose chemotherapy, can further reduce the incidence of relapse. Overall, more than 90% of patients with newly diagnosed APL can achieved CR, and about 75% can be cured by the combination of ATRA and chemotherapy. ATRA syndrome remains the major side effect of ATRA treatment, which should be prevented by addition of chemotherapy and/or dexamethasone in case of increasing white blood cell (WBC) counts. Current issues in the treatment of newly diagnosed APL include the role of early addition of chemotherapy to ATRA, whether or not ara-C is useful in combination with anthracycline, and a possible interest of arsenic trioxide during consolidation in patients remaining at relatively high risk of relapse.