All-trans-retinoic acid in acute promyelocytic leukemia

Clinical characteristics, prognostic factors and multidrug-resistance related protein expression in 36 adult patients with acute promyelocytic leukemia

We report on a single-center experience about the characteristics and outcome of 36 acute promyelocytic leukemia (APL) patients observed at our Department of Hematology between 1990 and 2002. The expression, of multidrug-resistance (MDR) associated proteins (PGP, LRP, MRP1) was also analyzed. There were 12 males and 24 females (median age 37 yr), 89% (32 of 36) with classic morphology, and 11% (four of 36) with a microgranular variant. Risk class (according to GIMEMA/PETHEMA): 25% (nine of 36) high risk (HR), 53% (nineteen of 36) intermediate risk (IR), 22% (eight of 36) low risk (LR). PGP, LRP, and MRP1 expression at onset and at first relapse was low. CD33 antigen expression was high in all cases. The patients were treated according to GIMEMA protocols (LAP0389 and AIDA) including ATRA in induction in 75% (27 of 36) of cases and 94% (34 of 36) achieved a complete remission (CR) after induction therapy while 6% (two of 36) died early (DDI) of hemorrhage.

OUTCOME

71% (24 of 34) of evaluable patients remain in CR at a median follow-up of 57 months (range 4-158 months) while 29% (10 of 34) relapsed at a median time of 12 months (range 8-43 months) and, of them, eight of 10 died early. The majority of patients that relapsed were in high-risk group. The overall survival (OS) of the whole population at 32 months was 66% and the DFS at 42 months was 62%. A statistically significant difference in terms of DFS was observed between HR and IR/LR patients (P = 0.04 by log-rank). DFS was not affected by age, sex, Hb levels, karyotype, and BCR isoform. At conclusion, our data confirm that despite the high rate of success with ATRA plus chemotherapy as induction (more than 90% of CR), about 30% of APL patients have a relapse (without a long-lasting second remission) and underline the importance of patient stratification in distinct risk groups at diagnosis in order to better adapt the type and intensity of treatment (risk-adapted therapy). Taking into account the high expression of CD33 and the low expression of MDR proteins in APL, new and investigational approaches like gemtuzumab-ozogamicin, with or without ATRA and other new drugs, should be strongly considered expecially in HR APL.

Combined treatment with arsenic trioxide and all-trans-retinoic acid in patients with relapsed acute promyelocytic leukemia

PURPOSE

Arsenic trioxide (ATO) is capable of inducing a high hematologic response rate in patients with relapsed acute promyelocytic leukemia (APL). Preclinical observations have indicated that all-trans-retinoic acid (ATRA) may strongly enhance the response to ATO.

PATIENTS AND METHODS

Between 1998 and 2001, we conducted a randomized study of ATO alone versus ATO plus ATRA in 20 patients with relapsed APL, all previously treated with ATRA-containing chemotherapy. The primary objective was to demonstrate a significant reduction in the time necessary to obtain a complete remission (CR) in the ATO/ATRA group compared with the ATO group. Secondary objectives were safety and molecular response.

RESULTS

The CR rate after one ATO with or without ATRA induction cycle was 80%. Clinical and pharmacokinetic observations indicated that the main mechanism of action of ATO in vivo was the induction of APL cell differentiation. Hematologic and molecular response, time necessary to reach CR, and outcome were comparable in both treatment groups. Of 16 CR patients, three patients who reached a molecular remission after one induction cycle had all received chemotherapy for a treatment-induced hyperleukocytosis. Three additional patients who received further additional ATO with or without ATRA cycles converted later to molecular negativity.

CONCLUSION

ATRA did not seem to significantly improve the response to ATO in patients relapsing from APL. Other potential combinations, including ATO plus chemotherapy, have to be tested.

Chemoprevention of superficial bladder cancer

Patients who have bladder cancer with superficial disease are at high risk for recurrence but low risk for progression to muscle invasive disease and are regularly monitored with cystoscopy to detect recurrent tumors. This clinical setting (high recurrence rate, excellent surveillance, and low risk of progression in stage) provides an ideal setting for secondary chemoprevention. Vitamins, difluoromethylornithine, and cyclooxygenase inhibitors have demonstrated activity in preclinical models of bladder cancer. Limited clinical data suggests that vitamins and their analogs may be useful for decreasing the rate of tumor recurrence in patients with superficial bladder cancer. Ongoing clinical trials are exploring the roles of fenretinide, difluoromethylornithine, and celecoxib in the treatment of patients with a history of superficial bladder cancer.

The molecular pathogenesis of acute promyelocytic leukaemia: implications for the clinical management of the disease

Acute promyelocytic leukaemia (APL) is characterised by chromosomal rearrangements of 17q21, leading to fusion of the gene encoding retinoic acid receptor alpha (RARalpha) to a number of alternative partner genes (X), the most frequent of which are PML (>95%), PLZF (0.8%) and NPM (0.5%). Over the last few years, it has been established that the X-RARalpha fusion proteins play a key role in the pathogenesis of APL through recruitment of co-repressors and the histone deacetylase (HDAC)-complex to repress genes implicated in myeloid differentiation. Paradoxically, the X-RARalpha fusion protein has the potential to mediate myeloid differentiation at pharmacological doses of its ligand (all trans-retinoic acid (ATRA)), which is dependent on the dissociation of the HDAC/co-repressor complex. Arsenic compounds have also been shown to be promising therapeutic agents, leading to differentiation and apoptosis of APL blasts. It is now apparent that the nature of the RARalpha-fusion partner is a critical determinant of response to ATRA and arsenic, underlining the importance of cytogenetic and molecular characterisation of patients with suspected APL to determine the most appropriate treatment approach. Standard protocols involving ATRA combined with anthracycline-based chemotherapy, lead to cure of approximately 70% patients with PML-RARalpha-associated APL. Patients at high risk of relapse can be identified by minimal residual disease monitoring. The challenge for future studies is to improve complete remission rates through reduction of induction deaths, particularly due to haemorrhage, identification of patients at high risk of relapse who would benefit from additional therapy, and identification of a favourable-risk group, for which treatment intensity could be reduced, thereby reducing risks of treatment toxicity and development of secondary leukaemia/myelodysplasia. With the advent of ATRA and arsenic, APL has already provided the first example of successful molecularly targeted therapy; it is hoped that with further understanding of the pathogenesis of the disease, the next decade will yield further improvements in the outlook for these patients.

Treatment of elderly patients (> or =60 years) with newly diagnosed acute promyelocytic leukemia. Results of the Italian multicenter group GIMEMA with ATRA and idarubicin (AIDA) protocols

In all, 134 elderly patients (median age 66 years, range 60-75 years) with newly diagnosed acute promyelocytic leukemia (APL) were enrolled in two successive protocols of the Italian multicenter group GIMEMA. All patients received an identical induction with all-trans retinoic acid and idarubicin; 116 (86%) entered complete remission (CR), two (2%) were resistant and 16 (12%) died during induction. After CR, 106 patients received further therapy whereas 10 did not, because of refusal (n=5) or toxicity (n=5). Consolidation consisted of three chemotherapy courses in the AIDA protocol (AIDA, 67 patients) or, since 1997, of an amended protocol including only the first cycle (amended AIDA, aAIDA, 39 patients). In the AIDA group, 43 patients (64%) completed consolidation, while seven (11%) and 17 (25%) patients were withdrawn after first and second courses, respectively; nine patients (13%) died in CR and 12 (18%) relapsed. In the aAIDA group, all patients received the assigned treatment; two patients (5%) died in CR and six (15%) relapsed. In the AIDA and aAIDA series, the 3-year overall and discase-free survival rates were 81 and 83% (P=NS), 73 and 72% (P=NS), respectively. We highlight here the frequency and severity of complications linked to intensive chemotherapy in this clinical setting and suggest that, in APL of the elderly, less intensive postremission therapy allows significant reduction of severe treatment-related toxicity and may be equally effective.

Infectious complications in patients with acute promyelocytic leukaemia treated with the AIDA regimen

Infections represent a frequent complication of chemotherapy used for acute myeloid leukaemia (AML) and are associated with important toxicity frequently leading to treatment discontinuation. Acute promyelocytic leukaemia (APL) is a unique AML subset requiring tailored therapy including all-trans retinoic acid and anthracycline-based chemotherapy. We analysed in this study the incidence and type of infections complicating the clinical course of 89 consecutive APL patients receiving the AIDA protocol at a single institution. A total of 179 febrile episodes were registered during induction and consolidation, 52% of which were of unknown origin. Infections were clinically and microbiologically documented in 10.6 and 37.4% of cases, respectively. Coagulase-negative staphylococci represented the major cause of septicaemia (28%) and were more frequently isolated during induction, whereas viridans group streptococci, the second pathogen most frequently isolated from blood (27%), represented the principal pathogen detected during consolidation and were significantly associated with mucositis. Gram-negative bacteria accounted for 33.3% of all blood isolates. Fungal infections were only occasionally observed. Bloodstream infections in APL patients were compared with those documented in 271 consecutive patients affected by other subtypes of AML. The incidence of total septicaemia episodes, of staphylococcal bacteraemias and of fungaemias was significantly higher in patients with other AMLs. Empirical antibiotic therapy with ceftriaxone plus amikacin was effective in 73% of APL cases, most of the remaining cases being successfully managed by the addition of teicoplanin. One single death apparently related to infectious complication was recorded. Overall, infections led to antileukaemic treatment withdrawal in six patients, five of whom currently remain in haematologic remission for 13-106 months. These results indicate that a particular pattern of infections is observed in APL patients receiving ATRA plus anthracycline-based chemotherapy and that these appear to be effectively counteracted by standard management.

Pharmacology of all-trans-retinoic acid in children with acute promyelocytic leukemia

BACKGROUND

Due to severe side effects in virtually all children treated with a standard dose of 45 mg/m(2)/day all-trans-retinoic acid (ATRA) for acute promyelocytic leukemia (APL) the AML-BFM study group reduced the dosage to 25 mg/m(2)/day. For the lack of data on the use of ATRA at this dosage in children with APL, the study group further decided to evaluate the pharmacokinetics and metabolism of ATRA in children.

PROCEDURE

Twenty-three pharmacokinetic and metabolic profiles of ATRA were studied in 14 children (aged 0.9-18.4 years) with APL. Eleven plasma samples were collected over a period of 8 hr and analyzed for ATRA and its metabolites by high-performance liquid chromatography.

RESULTS

Peak plasma concentrations of ATRA were characterized by wide interpatient variability (range: 28.6-513.0 nM). Compared to adults the same metabolic pathways were observed in children. Even though peak plasma concentrations were in the lower range of those considered effective in vitro, ATRA side effects, notably neurotoxicity, still required dose reduction, treatment break, or drug withdrawal in eight patients. In this small number of patients, neurotoxicity could not be related to age or any specific level of ATRA or metabolites in the plasma. Plasma concentrations of vitamin A, however, were significantly higher in those patients, who developed signs of neurotoxicity (P = 0.03, Mann-Whitney Rank Sum test).

CONCLUSIONS

Considering the low plasma concentrations and the persistence of toxicity in spite of dose reduction intermittent dosing schedules might be considered as an alternative to further dose reduction of ATRA in the treatment of APL especially in children, who might be at risk of ATRA-induced neurotoxicity.

Retinoic acid inhibits the growth of bone marrow mesenchymal stem cells and induces p27Kip1 and p16INK4A up-regulation

The importance of bone marrow mesenchymal stem cells in hemopoiesis has been definitely demonstrated. Thus, their impairment might cause profound alteration on production and maturation of blood cells. In the present paper, we investigated, for the first time, the effect of retinoic acid, an important antileukemic molecule, on the proliferation of primary cultures of human bone marrow mesenchymal stem cells. We demonstrated that retinoic acid, at a pharmacological concentration, hampers strongly the growth of the cells, without inducing osteoblastic differentiation. The analysis of cell division cycle machinery showed that the antiproliferative effect is associated with (i) the up-regulation of two cyclin-dependent kinase inhibitors, namely p27Kip1 and p16INK4A, and (ii) the down-regulation of cyclin-dependent kinase 2 activity and pRB phosphorylation. The reported findings represent novel insights into the antileukemic effects of the drug and contribute in clarifying the molecular mechanism of its pharmacological activity.

Targeted therapies for the treatment of leukemia

OBJECTIVES

To review novel targeted therapies for the treatment of leukemia.

DATA SOURCES

Professional journals, books, and government publications.

CONCLUSION

Nonspecific cytotoxic chemotherapeutic agents provide marginal therapeutic benefit and significant toxicity when used in the treatment of leukemia. There is a tremendous need for new therapies with increased efficacy and decreased adverse effects. Advances in molecular science, genetics, and immunology, along with improved laboratory technology, have led to the discovery of unique targets integral to the growth and proliferation of malignant cells which are providing the foundation for the development of a new generation of antitumor agents.

IMPLICATIONS FOR NURSING PRACTICE

Nurses must be prepared to educate patients, administer novel therapies, and manage side effects.

Acute promyelocytic leukemia: a case-based review

Retinoid therapy for acute promyelocytic leukemia (APL) is one of the major achievements of leukemia research in the last 15 years. Use of all trans retinoic acid (ATRA) has changed the prognosis of APL from a fatal leukemia to a highly curable disease. This case-based review examines the available clinical and scientific data to form evidence-based decisions in the management of APL. The main aim of this review is to highlight recent progress made in the management of APL and address the role of maintenance therapy, prognostic factors for relapse and treatment of relapsed disease.

Homozygous deletion of the CRABPI gene in AB1 embryonic stem cells results in increased CRABPII gene expression and decreased intracellular retinoic acid concentration

The cellular retinoic acid (RA) binding proteins I and II (CRABPI and CRABPII), intracellular proteins which bind retinoic acid with high affinity, are involved in the actions of RA, though their exact roles are not fully understood. We have generated several genetically engineered AB1 cell lines in which both alleles of the CRABPI gene have been deleted by homologous recombination. We have used these CRABPI knockout cell lines to examine the consequences of functional loss of CRABPI on RA-induced gene expression and RA metabolism in the murine embryonic stem cell line, AB1, which undergoes differentiation in response to RA. Complete lack of CRABPI results in decreased intracellular [3H]RA concentrations under conditions in which external concentrations of [3H]RA are low (1-10nM) and in an altered distribution of [3H] polar metabolites of [3H]RA in the cell and in the medium. Fewer [3H] polar metabolites are retained within the CRABPI(-/-) cells compared to the wild-type cells. These data suggest that CRABPI functions to regulate the intracellular concentrations of retinoic acid and to maintain high levels of oxidized retinoic acid metabolites such as 4-oxoretinoic acid within cells.

Clinical trial design for target-based therapy

Anticancer drug discovery has shifted from an empiric random screening directed approach to a more rational and mechanistic, target-based approach, which reflects our rapidly expanding knowledge of the pathogenesis of a variety of forms of cancer at the molecular level, providing new targets for drug discovery and development. The clinical development of target-based anticancer drugs will require fundamental changes to the traditional clinical trial design and end points that have been used for conventional cytotoxic drugs. In the phase I and II settings, traditional end points (toxicity and response) may not be suitable for more selective, cytostatic target-based agents, and these end points may be replaced by biological or pharmacokinetic end points to define the optimal doses and the therapeutic effects of these drugs on their targets. For phase III trials, measurable clinical benefit will continue to be the primary end point. As our understanding of the complex pathways and networks controlling cell signaling, proliferation, and cell death expands, we must learn how and when to use agents to target specific steps in malignant transformation and proliferation, and we must adapt clinical trial design to test the clinical utility of this promising new class of anticancer drugs.

Early onset of chemotherapy can reduce the incidence of ATRA syndrome in newly diagnosed acute promyelocytic leukemia (APL) with low white blood cell counts: results from APL 93 trial

Treatment combining ATRA and chemotherapy (CT) has improved the outcome of APL patients, by comparison with CT alone. ATRA syndrome is a life-threatening complication of ATRA treatment whose prophylaxis remains somewhat controversial. In APL93 trial, newly diagnosed APL patients </=65 years and with initial WBC counts below 5000/mm(3) were randomized between ATRA until CR achievement followed by CT (ATRA --> CT) and ATRA with early addition of CT, on day 3 of ATRA treatment (ATRA + CT). The incidence of ATRA syndrome in the ATRA --> CT arm was 18% (22/122) as compared to 9.2% (17/184) in the ATRA + CT arm (P = 0.035). In the ATRA --> CT arm, three (2.5%) patients died from ATRA syndrome, as compared to one (0.5%) in the ATRA + CT group. Early addition of chemotherapy to ATRA in newly diagnosed APL with low WBC counts significantly reduced the incidence of ATRA syndrome.

Mouse cancer models as a platform for performing preclinical therapeutic trials

Engineering cancer-associated mutations into the mouse germline is an important tool for biological studies of growth control and tumorigenesis. Tractable models of many human cancers now exist in which the initiating genetic lesions have been elucidated and, in some instances, where the cooperating lesions are also known. The urgent need for more effective strategies for treating human cancer has stimulated interest in harnessing these models to test therapeutic agents. Although the ultimate value of genetically engineered mouse models for cancer drug discovery is unknown, several encouraging experiments provide proof of principle.

Cerebrovascular complications in cancer patients

Coagulation disorders are common in cancer patients. In patients with solid tumors, a low-grade activated coagulation can result in systemic and cerebral arterial or venous thrombosis. Cancer treatments may also contribute to this coagulopathy, which usually, but not exclusively, occurs in the setting of advanced malignant disease. There may be TIAs or cerebral infarctions. Because of the widespread distribution of cerebral thromboses, there may be a superimposed encephalopathy; sometimes this is the only sign. Concurrent systemic thrombosis is present in many patients and is a useful clue to the diagnosis. In cerebral venous occlusion, the initial symptom is usually a headache. Except for cerebral intravascular coagulation that is unassociated with NBTE, neuriomaging studies usually demonstrate one or more parenchymal infarctions. MRI or MRV may demonstrate venous thrombosis. The laboratory evidence of coagulopathy is difficult to distinguish from the asymptomatic coagulopathy that often accompanies advanced cancer, and the test results must be interpreted cautiously. NBTE can be diagnosed by transesophageal echocardiography. There is no established treatment for the thrombotic coagulopathy associated with cancer, but anticoagulation should be considered. In leukemia and lymphoma, the coagulopathy is typically acute DIC that can lead to systemic and brain hemorrhages. It is especially common in acute myelogenous leukemias. The clinical signs of cerebral hemorrhage are fulminant and may be fatal. The bleeding usually occurs in the brain or subdural compartment, and rarely in the subarachnoid space. The diagnosis can be suspected by the clinical setting and by systemic thrombosis or hemorrhage. It can be established by examination of the peripheral smear, the platelet count, and tests of coagulation function. Therapy of acute DIC is controversial and should be individualized for the clinical setting. Cerebrovascular disorders can complicate metastatic or primary tumor in the brain, skull, dura, or leptomeninges. The clinical signs of infarction are indistinguishable from other causes of stroke, except that tumor-related venous occlusion will usually first produce signs of increased intracranial pressure. The diagnosis of tumor-related infarction can usually be established by neuroimaging studies that show infarction and may show extracerebral sites of tumor. CSF examination is useful in diagnosing leptomeningeal metastasis. A search for lung or cardiac tumor should be performed when embolic tumor infarction is suspected. Primary or metastatic tumors in the brain or dura may hemorrhage, producing the initial clinical signs of the brain tumor or a change in chronic signs induced by the tumor. There are helpful clues to a neoplastic hemorrhage on brain CT or MRI scans. The brain hemorrhage may require evacuation and the underlying tumor will usually require additional antineoplastic treatment. Hyperleukocytosis (extreme elevation of the cell count) in acute myelogenous leukemia is a less common cause of brain hemorrhage in recent years because of improved methods to lower the cell count. Cerebral arterial or venous thrombosis is sometimes the result of cancer therapy. The attribution of thrombosis to chemotherapy in many published cases is only speculative, because carefully conducted prospective studies that include investigation for other thrombotic causes are not available. The best-known associations with thrombosis are L-asparaginase, which is typically used in the induction therapy of acute lymphocytic leukemia, and combination hormonal therapy and chemotherapy for breast cancer. Radiation to the head and neck, typically administered for head and neck epithelial cancers or lymphoma, may result in delayed carotid atherosclerosis. The distribution of stenosis or occlusion is within the radiation portal and is typically more extensive than is atherosclerosis that develops in the absence of radiation. Small clinical series suggest that surgical treatment is equally effective as in nonirradiated carotid atherosclerosis. In children, the cerebral vessels can be affected by brain radiation resulting in stenosis or occlusion. Brain hemorrhages can result from chemotherapy effects on the hemostatic system or a microangiopathic anemia. Hemorrhages from radiation-induced vascular abnormalities are rare. Opportunistic infections, especially fungal infections, can complicate cancer or its treatment. Septic cerebral emboli may result in focal cerebral signs, seizures, or encephalopathy. Sometimes there is an associated hemorrhagic vasculitis or cerebritis. Rarely, mycotic aneurysms may bleed. A high index of suspicion is needed to diagnose fungal infection because of the difficulty in culturing the organism from the blood or CSF. A clinician can usually establish the cause of stroke in the cancer patient by performing a careful review of the clinical setting--including the type and extent of cancer and the type of antineoplastic therapy--in which the stroke occurred. Systemic thrombosis, embolism, or hemorrhage can be a clue to the cause, and appropriate neuroimaging and coagulation studies to aid in the diagnosis are available. Therapy may ameliorate symptoms or prevent further episodes. The identification of one of these unusual stroke syndromes that leads to the diagnosis of an occult and treatable cancer can be particularly rewarding.

Ham-Wasserman Lecture

Conventional treatment of acute leukemia involves the use of cytotoxic agents (chemotherapy), but other strategies have been explored. All-trans retinoic acid (ATRA) and arsenic have clearly been effective in the treatment of acute promyelocytic leukemia (APL), which creates the possibility that other types of acute leukemia can be conquered by selectively inducing differentiation and/or apoptosis. A great number of investigations have been performed to elucidate the mechanisms and search for effective agents in the treatment of other types of acute leukemia by these new strategies. Progress at the molecular level has been achieved in explaining the mechanisms of action of ATRA and arsenic compounds, and several new agents have emerged, although their clinical effectiveness remains to be confirmed. Mechanism-/gene-based targeted therapy and a combination of different strategies will improve the treatment of acute leukemia.

Acute Myeloid Leukemia and Acute Promyelocytic Leukemia

The therapeutic approach to the patient with acute myeloid leukemia (AML) currently evolves toward new frontiers. This is particularly apparent from the entree of high-throughput diagnostic technologies and the identification of prognostic and therapeutic targets, the introduction of therapies in genetically defined subgroups of AML, as well as the influx of investigational approaches and novel drugs into the pipeline of clinical trials that target pathogenetic mechanisms of the disease.

In Section I, Dr. Bob Löwenberg reviews current issues in the clinical practice of the management of adults with AML, including those of older age. Dr. Löwenberg describes upcoming possibilities for predicting prognosis in defined subsets by molecular markers and reviews experimental strategies to improve remission induction and postinduction treatment.

In Section II, Dr. James Griffin reviews the mechanisms that lead to activation of tyrosine kinases by mutations in AML, the consequences of that activation for the cell, and the opportunities for targeted therapy and discusses some examples of developing novel drugs (tyrosine kinase inhibitors) and their effectiveness in AML (FLT3).

In Section III, Dr. Martin Tallman describes the evaluation and management of patients with acute promyelocytic leukemia, a notable example of therapeutic progress in a molecularly defined entity of leukemia. Dr. Tallman focuses on the molecular genetics of APL, current curative treatment strategies and approaches for patients with relapsed and refractory disease. In addition, areas of controversy regarding treatment are addressed.

Ham-Wasserman Lecture

Conventional treatment of acute leukemia involves the use of cytotoxic agents (chemotherapy), but other strategies have been explored. All-trans retinoic acid (ATRA) and arsenic have clearly been effective in the treatment of acute promyelocytic leukemia (APL), which creates the possibility that other types of acute leukemia can be conquered by selectively inducing differentiation and/or apoptosis. A great number of investigations have been performed to elucidate the mechanisms and search for effective agents in the treatment of other types of acute leukemia by these new strategies. Progress at the molecular level has been achieved in explaining the mechanisms of action of ATRA and arsenic compounds, and several new agents have emerged, although their clinical effectiveness remains to be confirmed. Mechanism-/gene-based targeted therapy and a combination of different strategies will improve the treatment of acute leukemia.

Arsenic trioxide promotes histone H3 phosphoacetylation at the chromatin of CASPASE-10 in acute promyelocytic leukemia cells

Arsenic trioxide (As(2)O(3)) is highly effective for the treatment of acute promyelocytic leukemia, even in patients who are unresponsive to all-trans-retinoic acid therapy. As(2)O(3) is believed to function primarily by promoting apoptosis, but the underlying molecular mechanisms remain largely unknown. In this report, using cDNA arrays, we have examined the changes in gene expression profiles triggered by clinically achievable doses of As(2)O(3) in acute promyelocytic leukemia NB4 cells. CASPASE-10 expression was found to be potently induced by As(2)O(3). Accordingly, caspase-10 activity also substantially increased in response to As(2)O(3) treatment. A selective inhibitor of caspase-10, Z-AEVD-FMK, effectively blocked caspase-3 activation and significantly attenuated As(2)O(3)-triggered apoptosis. Interestingly, the treatment of NB4 cells with As(2)O(3) markedly increased histone H3 phosphorylation at serine 10, an event that is associated with acetylation of the lysine 14 residue. Chromatin immunoprecipitation assays revealed that As(2)O(3) potently enhances histone H3 phosphoacetylation at the CASPASE-10 locus. These results suggest that the effect of As(2)O(3) on histone H3 phosphoacetylation at the CASPASE-10 gene may play an important role in the induction of apoptosis and thus contribute to its therapeutic effects on acute promyelocytic leukemia.

CNS relapses of acute promyelocytic leukemia after all-trans retinoic acid

OBJECTIVE

To review the role of all-trans retinoic acid (ATRA) and arsenic trioxide in central nervous system (CNS) relapses of acute promyelocytic leukemia (APL).

CASE SUMMARY

A 69-year-old white man diagnosed with APL presented with bleeding diathesis. His molecular and cytogenetic studies were positive for promyelocytic leukemia-retinoic acid receptoralpha (PML-RARalpha) and t(15;17) transformation. Complete molecular and cytogenetic remission was achieved with ATRA, daunorubicin, and cytarabine. Within 6 months, the patient was readmitted for investigation of severe global headaches and an ataxic gait. His peripheral blood and cerebral spinal fluid were positive for PML-RARalpha fusion protein. Intrathecal chemotherapy and radiation, as well as ATRA, were the main treatment modalities provided. Molecular and cytogenetic remission was again obtained. Three months later, a second relapse occurred in the CNS and the peripheral blood.

DISCUSSION

APL is typically treated with anthacycline-based chemotherapy and ATRA. Approximately 85-95% of patients achieve complete remission (CR); however, the relapse rate has been reported to be about 30-40%. A thorough literature search (MEDLINE, EMBASE, CANCERLIT, 1966-January 2002) revealed only 54 cases of extramedullary disease, of which 35 involved the CNS.

CONCLUSIONS

The introduction of ATRA has improved patient survival dramatically. APL relapse, in general, has been in part attributable to repetitive or prolonged exposure to ATRA and the possibility of additional chromosomal changes, making the disease more refractory to treat. Given the evidence, one could argue that, with repeated ATRA treatment, CR duration may be shortened. However, limited data are available to guide the appropriate management of APL relapsed to the CNS with either ATRA, chemotherapy, or arsenic trioxide. In our opinion, treatment using arsenic trioxide is an unconventional option worthy of exploring.

Impact of granulocyte colony-stimulating factor use during induction for acute myelogenous leukemia in children: a report from the Children's Cancer Group

PURPOSE

To determine whether granulocyte colony-stimulating factor (G-CSF) administered during acute myelogenous leukemia (AML) induction affects hematopoietic and nonhematopoietic toxicity, length and outcome of induction therapy, event-free survival, overall survival, and prognostic significance of the day 7 bone marrow.

PATIENTS AND METHODS

In Children's Cancer Group study 2891, patients were given intensively timed induction with G-CSF (n = 254) after accrual for the regimen without G-CSF (n = 258) was met.

RESULTS

Time to neutropenic recovery after induction courses 1 and 2 was significantly shorter for patients who received G-CSF. Times to platelet recovery were similar regardless of G-CSF use. Effects on incidence of grades 3 and 4 toxicities, infections, or fatal infections were not observed. Use of G-CSF reduced the median length of induction by 9 days and hospital stay by 6 days. Induction remission rates, overall survival, and event-free survival were similar with and without G-CSF. Day 7 bone marrow was prognostic of better long-term outcome. Patients with hypercellular day 7 marrow who received G-CSF had a higher remission rate and event-free survival than patients who did not receive G-CSF.

CONCLUSIONS

The incidence of severe toxic event and infection, induction remission rate, overall survival, and event-free survival were comparable regardless of G-CSF use. Use of G-CSF decreased neutropenia duration, hospital stay, and length of induction. Patients with hypercellular day 7 bone marrow who received G-CSF had an induction remission rate and event-free survival superior to those of patients who did not receive G-CSF.

Acute promyelocytic leukemia: a model for the role of molecular diagnosis and residual disease monitoring in directing treatment approach in acute myeloid leukemia

Acute promyelocytic leukemia (APL) is characterized by a number of features that underpin the need for rapid and accurate diagnosis and demand a highly specific treatment approach. These include the potentially devastating coagulopathy, sensitivity to anthracycline-based chemotherapy regimens, as well as unique responses to all-trans retinoic acid and arsenic trioxide that have revolutionized therapy over the last decade. The chromosomal translocation t(15;17) which generates the PML-RARalpha fusion gene has long been considered the diagnostic hallmark of APL; however, this abnormality is not detected in approximately 10% cases with successful karyotype analysis. In the majority of these cases, the PML-RARalpha fusion gene is still formed, resulting from insertion events or more complex rearrangements. These cases share the beneficial response to retinoids and favorable prognosis of those with documented t(15;17), underscoring the clinical relevance of molecular analyses in diagnostic refinement. In other cases of t(15;17) negative APL, various chromosomal rearrangements involving 17q21 have been documented leading to fusion of RARalpha to alternative partners, namely PLZF, NPM, NuMA and STAT5b. The nature of the fusion partner has a significant bearing upon disease characteristics, including sensitivity to retinoids and arsenic trioxide. APL has provided an exciting treatment model for other forms of AML whereby therapeutic approach is directed towards cytogenetically and molecularly defined subgroups and further modified according to response as determined by minimal residual disease (MRD) monitoring. Recent studies suggest that rigorous MRD monitoring, coupled with pre-emptive therapy at the point of molecular relapse improves survival in the relatively small subgroup of PML-RARalpha positive patients with 'poor risk' disease. Advent of 'real-time' quantitative RT-PCR technology seems set to yield further improvements in the predictive value of MRD assessment, achieve more rapid sample throughput and facilitate inter- and intra-laboratory standardization, thereby enabling more reliable comparison of data between international trial groups.

Retinoic acid resistance in acute promyelocytic leukemia

Primary resistance of PML-RARalpha-positive acute promyelocytic leukemia (APL) to the induction of clinical remission (CR) by all-trans retinoic acid (ATRA) is rare but markedly increases in frequency after > or =2 relapses from chemotherapy-induced CRs. Nevertheless, even in de novo cases, the primary response of ATRA-naive cases is variable by several measures, suggesting involvement of heterogeneous molecular elements. Secondary, acquired ATRA resistance occurs in most patients treated with ATRA alone and in many patients who relapse from combination ATRA chemotherapy regimens despite limited ATRA exposure. Although early studies suggested that an adaptive hypercatabolic response to pharmacological ATRA levels is the principal mechanism of ATRA resistance, recent studies suggest that molecular disturbances in APL cells have a predominant role, particularly if disease relapse occurs a few months after discontinuing ATRA therapy. This review summarizes the systemic and APL cellular elements that have been linked to clinical ATRA resistance with emphasis on identifying areas of deficient information and important topics for further investigation. Overall, the subject review strongly supports the hypothesis that, although APL is an infrequent and nearly cured disease, much can be gained by understanding the complex relationship of ATRA resistance to the progression and relapse of APL, which has important implications for other leukemias and malignancies.

Neoadjuvant and adjuvant therapy for resectable hepatocellular carcinoma: review of the randomised clinical trials

Hepatocellular carcinoma (HCC) is common worldwide, and its incidence is increasing. Liver resection or transplantation is potentially curative, although subsequent recurrence and death are common. We reviewed randomised trials on the role of adjuvant therapy in resectable HCC. We identified 13 randomised trials with recurrence or survival endpoints reported at 3 years or longer. Three studies involved predominantly systemic adjuvant chemotherapy; four involved predominantly hepatic-artery-based chemotherapy or embolisation; and six used other therapeutic modalities including immunological, radiation, and differentiation agents. A therapeutic benefit in terms of disease-free or overall survival was noted in six trials, five of which involved modalities other than systemic or hepatic-artery chemotherapy or embolisation. We conclude that systemic and hepatic-artery chemotherapy or chemoembolisation have not been shown to improve overall or disease-free survival after resection of HCC, although there has been no definitive trial comparing adjuvant systemic chemotherapy with no treatment. Other adjuvant modalities (mostly tested in small, preliminary settings) may confer benefit after potentially curative resection of HCC.

The World Health Organization (WHO) classification of the myeloid neoplasms

A World Health Organization (WHO) classification of hematopoietic and lymphoid neoplasms has recently been published. This classification was developed through the collaborative efforts of the Society for Hematopathology, the European Association of Hematopathologists, and more than 100 clinical hematologists and scientists who are internationally recognized for their expertise in hematopoietic neoplasms. For the lymphoid neoplasms, this classification provides a refinement of the entities described in the Revised European-American Lymphoma (REAL) Classification-a system that is now used worldwide. To date, however, there has been no published explanation or rationale given for the WHO classification of the myeloid neoplasms. The purpose of this communication is to outline briefly the WHO classification of malignant myeloid diseases, to draw attention to major differences between it and antecedent classification schemes, and to provide the rationale for those differences.

The role of retinoids and retinoic acid receptors in normal hematopoiesis

The dramatic therapeutic activity of all-trans retinoic acid (ATRA) in inducing terminal granulocytic differentiation of the malignant promyelocytes that characterize human acute promyelocytic leukemia (APL) has led to numerous studies assessing the role of retinoids and the retinoic acid receptors (RARs) in the regulation of normal hematopoiesis. Studies with knock out mice indicate that retinoic acid receptor activity is not essential for normal hematopoiesis, but both in vitro and in vivo studies indicate that these receptors may be important modifiers/regulators of different myeloid precursors/ progenitors including the primitive transplantable stem cell. A number of target genes have been identified that are either directly or indirectly regulated by RA receptors and which likely play important roles in the retinoid-mediated regulation of myelopoiesis. Several in vitro models of hematopoiesis suggest that the transcriptional activity of RA receptors is developmentally regulated during different stages of myelopoiesis. This regulation might involve non-ligand mediated molecular events that alter the interaction of RA receptors with transcriptional corepressor complexes. Moreover, the interaction of RA receptors with other families of transcription factors expressed in different hematopoietic lineages might also account for differential RA receptor activity at different stages of myelopoiesis.

Advances in the management of acute promyelocytic leukemia and other hematologic malignancies with arsenic trioxide

Acute promyelocytic leukemia (APL), once considered the most devastating subtype of acute myeloid leukemia, is now the most treatable of all subtypes as a result of intensive research into its molecular pathogenesis. This research has led to a rational approach to treatment in which the use of the differentiating agent all-trans-retinoic acid (ATRA) has proven to be effective first-line treatment for inducing complete remission. Arsenic trioxide (ATO) is currently used to treat relapsed disease, further enhancing survival rates in a patient population for which limited salvage options exist. This review discusses the molecular mechanisms responsible for development of APL and the evolution of treatment options over the last three decades, including the major advances using ATRA and ATO in the last 12 years. The mechanism of action of ATO is also described in view of this agent's potential for broader therapeutic application in a variety of hematologic malignancies.

Management of acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) has become the most potentially curable subtype of acute myeloid leukemia (AML) in adults. With current treatment strategies that incorporate all-trans retinoic acid (ATRA), long-term disease-free survival and potential cure rates of 70% to 80% can be expected. Such progress reflects what can be accomplished with insights into the molecular pathogenesis of leukemia, identification of a molecular target, and rapid accrual to a series of clinical trials. The leukemic promyelocytes from patients with APL are uniquely susceptible to a variety of novel agents in addition to ATRA, including arsenic trioxide, and in preliminary studies, gemtuzumab ozogamicin, the immunoconjugate comprised of an anti-CD33 monoclonal antibody linked to the potent cytotoxic agent calicheamicin. Incorporation of such agents into the treatment of patients with high-risk disease may be an important future direction to pursue.

Formulation parameters determining the physicochemical characteristics of solid lipid nanoparticles loaded with all-trans retinoic acid

Solid lipid nanoparticles (SLNs) have gained attention as a colloidal drug carrier, particularly for drugs with limited solubility. The poor aqueous solubility of all-trans retinoic acid (ATRA) has been a limiting factor in its clinical use. This study was undertaken to overcome the solubility limitation of ATRA by loading in SLNs. The physicochemical characteristics of ATRA-loaded SLNs were investigated by particle size analysis, zeta potential measurement, thermal analysis and HPLC determination of ATRA content. The mean particle size of ATRA-loaded SLNs could be reduced (1) by mixing EggPC and Tween 80 as a surfactant and (2) by increasing the total surfactant amount. The smallest mean particle size of SLNs was obtained with 50 mg/g surfactant mixture composed of 54:46% (w/w) EggPC:Tween 80 (154.9 nm). The zeta potential of SLNs could be increased by mixing EggPC, Tween 80 and DSPE-PEG in the surfactant mixture. The zeta potential of SLNs prepared with 50 mg/g surfactant mixture composed of 48:6:46% (w/w) of EggPC:DSPE-PEG:Tween 80 was -38.18 mV. ATRA could be loaded at 2.4% (percentage of lipid matrix) on these SLNs without impairing their physical stability. After freeze-drying, the mean particle size and polydispersity index of ATRA-loaded SLNs were only slightly increased (181.8 vs. 265.2 nm, 0.173 vs. 0.200). Furthermore, no significant change was observed in the SLN-loaded concentration of ATRA and the zeta potential of SLNs after freeze-drying. Taken together, SLN formulation of ATRA with similar characteristics to those of parenteral emulsions could be obtained even after freeze-drying.

Phosphatidylinositol 3-kinases are involved in the all-trans retinoic acid-induced upregulation of CD38 antigen on human haematopoietic cells

All-trans retinoic acid (ATRA) is a specific inducer of CD38 antigen on marrow CD34+ cells as well as on blast cells in acute promyelocytic and myeloblastic leukaemia. The CD38 antigen contributes to the control of blast cell proliferation, and the upregulation of CD38 might constitute an element in the pathogenesis of retinoic acid syndrome. The aim of this study was to determine whether phosphoinositide 3-kinase (PI3-K) is involved in the modification of CD38 antigen expression on myeloid cells, as PI3-K plays a major role in the ATRA-induced granulocytic differentiation of HL-60 cells. We evaluated the effects of PI3-K inhibitors (wortmannin and LY294002) on the levels of CD38 antigen and mRNA in HL-60 and normal marrow CD34+ cells exposed to ATRA (1 micromol/l). The inhibitors prevented increase in CD38 mRNA expression and the overexpression of membrane CD38 antigen, without modification of the cytoplasmic level of this antigen. Interestingly, PI3-K activity was also necessary for CD38 expression on normal marrow CD34+ cells and for the ATRA-induced upregulation of CD157, a CD38-related antigen. In conclusion, PI3-K activity plays an essential role in the regulation of CD38 expression on human haematopoietic cells, and might constitute an interesting therapeutic target in haematological disorders involving CD38 overexpression.

The value of allogeneic bone marrow transplant in patients with acute myeloid leukaemia at differing risk of relapse: results of the UK MRC AML 10 trial

Patients under 55 years in the United Kingdom Medical Research Council Acute Myeloid Leukaemia 10 trial who entered complete remission were tissue typed (n = 1063). Four hundred and nineteen had a matched sibling donor and 644 had no match. When compared on a donor versus no donor basis the relapse risk was reduced in the donor arm (36%vs 52%; P = 0.001) and the disease-free survival (DFS) improved (50%vs 42%; P = 0.01), but overall survival (OS) was not different (55%vs 50%; P = 0.1). Sixty-one per cent of patients with a donor underwent transplantation. When patients were subdivided into risk groups based on cytogenetics alone or with the addition of blast response to course 1, a reduction in relapse risk was seen in all risk groups and in three age cohorts (0-14, 15-34 and 35+ years). Significant benefit in DFS was only seen in the intermediate-risk cytogenetic group (50%vs 39%; P = 0.004). The OS benefit was only seen in intermediate-risk patients (55%vs 44%; P = 0.02). The reduction in relapse risk in good-risk patients was attributable to patients with t(15;17) and not to patients with t(8;21) or inv(16). Allogeneic transplantation given after intensive chemotherapy was able to reduce relapse in all risk and age groups. However, due to the competing effects of procedural mortality and an inferior response to chemotherapy if relapse does occur, there was a survival advantage only in patients of intermediate risk. This trial found no survival advantage in children, patients over 35 years or good-risk disease.

Combination of 22-oxa-1,25-dihydroxyvitamin D(3), a vitamin D(3) derivative, with vitamin K(2) (VK2) synergistically enhances cell differentiation but suppresses VK2-inducing apoptosis in HL-60 cells

We originally reported that vitamin K(2) (VK2) effectively induces apoptosis in various types of primary cultured leukemia cells and leukemia cell lines in vitro. In addition, VK2 was shown to induce differentiation of leukemia cells when the cells were resistant against VK2-inducing apoptosis. A novel synthetic vitamin D(3)derivative, 22-oxa-1,25-dihydroxyvitamin D(3) (OCT: oxacarcitriol) shows a more potent differentiation-inducing ability among myeloid leukemia cells in vitro with much lesser extent of the induction of hypercalcemia in vivo as compared to the effects of 1alpha,25(OH)(2)D(3). In the present study, we focused on the effects of a combination of OCT plus VK2 on leukemia cells. Treatment of HL-60 cells with OCT for 72 h induces monocytic differentiation. A combination of OCT plus VK2 dramatically enhances monocytic differentiation as assessed by morphologic features, positivity for non-specific esterase staining, and cell surface antigen expressions. This combined effect far exceeds the maximum differentiation induction ability at the optimal concentrations of either OCT or VK2 alone. In addition, pronounced accumulation of the cells in the G0/G1 phase is observed by combined treatment with OCT plus VK2 as compared with each vitamin alone. In contrast to cell differentiation, caspase-3 activation and apoptosis induction in response to VK2 are significantly suppressed in the presence of OCT in HL-60 cells. These data suggest that monocytic differentiation and apoptosis induction of HL-60 cells are inversely regulated. Furthermore, pronounced induction of differentiation by combined treatment with VK2 plus OCT was also observed in four out of six cases of primary cultured acute myeloid leukemia cells in vitro, suggesting that VK2 plus OCT might be a potent combination for the differentiation-based therapy for acute myeloid leukemias.

New advances in the treatment of acute promyelocytic leukemia

OBJECTIVE

Describe the treatment options of newly diagnosed and relapsed APL.

INDUCTION

The fusion PML/RAR gene provided the rationale for using all-trans retinoic acid (ATRA) as differentiation therapy. The standard approach is antracycline + ATRA and no ARA-C.

CONSOLIDATION

Anthracycline based chemotherapy, no high dose ARA-C and perhaps no ARA-C. Maintenance seems to be important. Cure with ATRA + chemotherapy increased to 75% from 35% with chemotherapy alone.

POOR PROGNOSIS FACTORS

WBC >10,000, age >55, platelets <40,000 and CD 56 expression. Achieving and maintaining a molecular remission (MCR) i.e. RT-PCR (-) for PML/RAR alpha expression, is the best predictor for cure. Conversion to PCR (+) will eventually result in relapse. PCR monitoring in the first 2 years and intervention during molecular relapse would be safer than treatment in clinical relapse. Molecular relapses have been treated successfully by ATRA plus BMT. Arsenic trioxide (ATO) or gentuzumab (mylotarg) are also being studied.

RELAPSE (INDUCTION)

Patients after ATRA in first CR are less likely to respond to ATRA reinduction regardless of the time off ATRA and rarely achieve a molecular remission. Single-agent ATO induced in 52 relapsed patients CR of 87% (75% MCR) with low toxicity and no treatment related deaths (U.S. pivotal trial), confirmed in a NCI trial. Induction of relapsing patients with single agent ATO is preferable than ATRA + chemotherapy because the high molecular remission and lower toxicity.

RELAPSE (POST REMISSION)

No standard approach and the role of chemotherapy is unknown. ATO alone: in the pivotal trial, 9/21 patients had long remissions without other therapy. BMT: Not indicated in 1st MCR. In young patients auto BMT with PCR (-) harvests could be done in subsequent CR. Allo BMT has a higher death rate without overall better results. In the pivotal trial 12 patients were transplanted in CR after ATO alone (9 allo BMT) and 11 still without disease. Possibly allo BMT is safer after a less toxic ATO induction.

OTHER

ATO plus ATRA +/- AntiCD33 conjugated with toxin (gentuzumab) or 131I; Synthetic retinoid (Am80); histone deacetylase inhibitors; oral tetra-arsenic tetra-sulfide and various combinations.

Acute myeloid leukemia

Through the hard work of a large number of investigators, the biology of acute myeloid leukemia (AML) is becoming increasingly well understood, and as a consequence, new therapeutic targets have been identified and new model systems have been developed for testing novel therapies. How these new therapies can be most effectively studied in the clinic and whether they will ultimately improve cure rates are questions of enormous importance. In this article, Dr. Jacob Rowe presents a summary of the current state-of-the-art therapy for adult AML. His contribution emphasizes the fact that AML is not a single disease, but a number of related diseases each distinguished by unique cytogenetic markers which in turn help determine the most appropriate treatment. Dr. Jerald Radich continues on this theme, emphasizing how these cytogenetic abnormalities, as well as other mutations, give rise to abnormal signal transduction and how these abnormal pathways may represent ideal targets for the development of new therapeutics. A third contribution by Dr. Frederick Appelbaum describes how AML might be made the target of immunologic attack. Specifically, strategies using antibody-based or cell-based immunotherapies are described including the use of unmodified antibodies, drug conjugates, radioimmunoconjugates, non-ablative allogeneic transplantation, T cell adoptive immunotherapy and AML vaccines. Finally, Dr. John Dick provides a review of the development of the NOD/SCID mouse model of human AML emphasizing both what it has taught us about the biology of the disease as well as how it can be used to test new therapies. Taken together, these reviews are meant to help us understand more about where we are in the treatment of AML, where we can go and how we might get there.

Adaptive immunity cooperates with liposomal all-trans-retinoic acid (ATRA) to facilitate long-term molecular remissions in mice with acute promyelocytic leukemia

We previously developed a murine model of acute promyelocytic leukemia (APL) by using human cathepsin G gene regulatory elements to direct the expression of promyelocytic leukemia (PML)/retinoic acid receptor alpha (RAR alpha) and RAR alpha/PML fusion cDNAs to the early myeloid compartment of transgenic mice. To study the efficacy of noncytotoxic therapy in this animal model, cohorts of naive immunocompetent mice were inoculated with primary murine APL cells from a frozen tumor bank. Arsenic trioxide and liposomally encapsulated all-trans-retinoic acid (Lipo ATRA), alone or in combination, were administered for 21 days by i.p. injection using doses that yielded plasma levels similar to those observed in human APL patients treated with these agents. Lipo ATRA was highly effective in inducing durable molecular remissions in immunocompetent mice [C57BL/6 x C3H F(1) (B6C3HF1)]; arsenic therapy was much less effective, and did not clearly synergize with Lipo ATRA to increase the remission rate in immunocompetent mice. The survival of Lipo ATRA-treated severe combined immunodeficient (SCID) animals (lacking functional T and B cells) was inferior to that of immunocompetent B6C3HF1 recipients (40% vs. 88% survival at 1 y, P < 0.001). These data suggest that adaptive immunity cooperates with pharmacologic therapy to induce or maintain remissions in murine APL. It also implies that immunosuppressive anti-leukemia therapies could paradoxically blunt effective anti-leukemia immune responses that are important for clearing small numbers of residual tumor cells after chemotherapy-mediated cytoreduction.

Antigen expression patterns reflecting genotype of acute leukemias

Multi-parameter flow cytometry, molecular genetics, and cytogenetic studies have all contributed to new classification of leukemia. In this review we discuss immunophenotypic characteristics of major genotypic leukemia categories. We describe immunophenotype of: B-lineage ALL with MLL rearrangements, TEL/AML1, BCR/ABL, E2A/PBX1 translocations, hyperdiploidy, and myc fusion genes; T-ALL with SCL gene aberrations and t(5;14) translocation; and AML with AML1/ETO, PML/RARalpha, OTT/MAL and CBFbeta/MYH11 translocations, trisomies 8 or 11 and aberrations of chromosomes 7 and 5. Whereas some genotypes associate with certain immunophenotypic features, others can present with variable immunophenotype. Single molecules (as NG2, CBFbeta/SMMHC and PML/RARalpha proteins) associated with or derived from specific translocations have been described. More often, complex immunophenotype patterns have been related to the genotype categories. Most known associations between immunophenotype and genotype have been defined empirically. Therefore, these associations should be validated in independent patient cohorts before they can be widely used for prescreening of leukemia. Progress in our knowledge on leukemia will show how the molecular-genetic changes modulate the immunophenotype as well as how the expressed protein molecules further modulate cell behavior.

Ear involvement in acute promyelocytic leukemia at relapse: a disease-associated 'sanctuary'?

Extramedullary (EM) involvement occurs infrequently in acute promyelocytic leukemia (APL) and usually involves skin and CNS. We describe seven patients (four observed at a single institution) who relapsed in various sites of the auditory apparatus, including the external canal and middle ear (temporal bone). Front-line treatment included ATRA and chemotherapy (six patients) or chemotherapy alone (one patient). Three patients had concomitant hematologic relapse, two had molecular relapse and two were in hematologic and molecular remission when ear localization was documented. Local symptoms that stimulated further diagnostic studies included ear bleeding/discharge in the first patient, but were mild in the others (hypoacusia, five patients; earache, two patients). Ear involvement by leukemia was documented by histological and/or molecular studies after local surgery in five cases, and by CT scan or NMR in the remaining patients. We suggest that the ear might represent a specific sanctuary for disease involvement in APL.

Variant-type PML-RAR(alpha) fusion transcript in acute promyelocytic leukemia: use of a cryptic coding sequence from intron 2 of the RAR(alpha) gene and identification of a new clinical subtype resistant to retinoic acid therapy

The physiologic actions of retinoic acids (RAs) are mediated through RA receptors (RARs) and retinoid X receptors (RXRs). The RAR(alpha) gene has drawn particular attention because it is the common target in all chromosomal translocations in acute promyelocytic leukemia (APL), a unique model in cancer research that responds to the effect of RA. In the great majority of patients with APL, RAR(alpha) is fused to the PML gene as a result of the t(15;17) translocation. Three distinct types of PML-RAR(alpha) transcripts, long (L), short (S), and variant (V), were identified. The V-type is characterized by truncation of exon 6 of PML and in some cases by the insertion of a variable "spacer" sequence between the truncated PML and RAR(alpha) mRNA fusion partners, although the precise mechanisms underlying formation of the V-type transcript remain unclear. To get further insights into the molecular basis of the t(15;17), we sequenced the entire genomic DNA region of RAR(alpha). Of note, all previously reported "spacer" sequences in V-type transcripts were found in intron 2 of the RAR(alpha) gene and most of these sequences were flanked by gt splice donor sites. In most cases, these "cryptic" coding sequences maintained the ORF of the chimeric transcript. Interestingly, two cases with a relatively long spacer sequence showed APL cellular and clinical resistance to RA treatment. In these cases, the aberrant V-type PML-RAR(alpha) protein displayed increased affinity to the nuclear corepressor protein SMRT, providing further evidence that RA exerts the therapeutic effect on APL through modulation of the RAR-corepressor interaction. Finally, among patients with the L- or S-type PML-RAR(alpha) fusion transcript, some consensus motifs were identified at the hotspots of the chromosome 17q breakpoints within intron 2 of RAR(alpha), strengthening the importance of this intron in the molecular pathogenesis of APL.

Modelling haematopoietic malignancies in the mouse and therapeutical implications

Modelling human disease in the mouse has become an essential activity in biomedical research in order to unravel molecular mechanisms underlying pathological conditions as well as to determine in vivo the consequences of aberrant gene function. The mouse is by far the most accessible mammalian system physiologically similar to humans. Furthermore, the development of novel techniques for manipulating the murine genome, which allow the in vivo modification of virtually any genomic region in a time and/or tissue specific manner, renders the mouse an ideal model system to study human pathological conditions. Modelling human diseases in mice has reached an even greater relevance in the field of haematological malignancies, due to the already advanced characterization of the molecular basis of many haematological disorders. In this review, we describe the most important technological developments that made it possible to reproduce in the mouse the genetic lesions that characterize human haematological malignancies, thus often generating faithful mouse models of the human condition. We provide specific examples of the advantages and limitations of the various genetic approaches utilized to model leukaemia and lymphoma in the mouse. Finally, we discuss the power of mouse modelling in developing and testing novel therapeutic modalities in pre-clinical studies.

Tetra-arsenic tetra-sulfide for the treatment of acute promyelocytic leukemia: a pilot report

In the past 6 years, we treated 129 patients who had acute promyelocytic leukemia (APL) with a new arsenic agent, oral tetra-arsenic tetra-sulfide (As(4)S(4)). Nineteen of the patients had newly diagnosed APL, 7 had first relapse, and 103 had hematologic complete remission (HCR). HCR was achieved in all patients with newly diagnosed APL and in all those with hematologic relapse. Of 16 patients with newly diagnosed disease and available cytogenetic and molecular analyses, 14 had cytogenetic and molecular complete remission (CR). Cytogenetic and molecular CR was also obtained in 5 of the 7 patients with hematologic relapse. In the HCR group, 35 of 44 patients positive for PML-RARalpha at baseline became negative. In the newly diagnosed group, estimated disease-free survival (DFS) rates for 1 and 3 years were 86.1% and 76.6%, respectively, with a median follow-up time of 13.5 months (range, 2-40 months). In the HCR group, DFS rates for 1 and 6 years were 96.7% and 87.4%, respectively, with a median follow-up of 23 months (range, 2-71 months). Treatment with As(4)S(4) was well tolerated, with only moderate side effects, including asymptomatic prolongation of corrected QT interval, transient elevation in liver enzyme levels, rash, and mild gastrointestinal discomfort; neither myelosuppression nor appreciable long-term side effects occurred. Degeneration or apoptosis of APL promyelocytes was observed during As(4)S(4) therapy. Pharmacokinetic studies showed that the agent was absorbed rapidly. Most urinary arsenic excretion occurred within the first 24 hours. Both blood and urinary arsenic levels declined after discontinuation of As(4)S(4). Our results show, for the first time, that As(4)S(4) treatment alone is highly effective and safe in both remission induction and maintenance therapy in patients with APL, regardless of disease stage.

Advances in the treatment of relapsed acute promyelocytic leukemia

The presence of the characteristic fusion transcript gene, promyelocytic leukemia-retinoic acid receptor-alpha (PML-RARalpha), provided hematologists with a rationale for the use of all-trans retinoic acid (ATRA) for differentiation therapy for acute promyelocytic leukemia (APL). Multiple studies have established that combination of ATRA and chemotherapy in newly diagnosed patients has increased the cure rate to 70% from 35% in patients treated with chemotherapy alone. However, still about 30% of the patients relapse and are often resistant to ATRA retreatment. Consequently, a number of novel agents that include several differentiation agents and monoclonal antibodies have been studied to provide improved outcomes for patients with APL who have relapsed. In particular, arsenic trioxide has shown great promise for the induction, consolidation, and maintenance of complete remission in relapsed patients with APL. The unique mechanisms of action by which arsenic trioxide exerts its effects are complementary to those of ATRA, potentially allowing for combination therapies with additive or even synergistic results. Within this context autologous or allogeneic bone marrow transplantations are also considered in second or subsequent relapse, especially after arsenic trioxide-induced complete remission in relapsing patients. Furthermore, molecular monitoring for the PML-RARalpha fusion protein permits prompt intervention for early molecular relapse of APL before clinical relapse, ultimately improving chances of prolonged remission.

Spatial distribution patterns of interphase centromeres during retinoic acid-induced differentiation of promyelocytic leukemia cells

BACKGROUND

The pericentromeric heterochromatin is an important element for the regulation of gene silencing. Its spatial distribution during interphase appears to be cell-type specific. This study analyzes three-dimensional (3D) centromere distribution patterns during cellular differentiation along the neutrophil pathway.

METHODS

Differentiation of the promyelocytic leukemia cell line NB4 was induced by retinoic acid. Centromeres in interphase nuclei were visualized by immunofluorescence staining of centromere-associated proteins with CREST serum. 3D images of nuclei were obtained by confocal microscopy. Automated methods for the segmentation of point-like objects in 3D images were implemented to detect the position of centromeres. Features of centromere localization patterns were determined by constructing the minimal spanning tree of the centromere distribution.

RESULTS

In differentiated NB4 cells, the number of centromere conglomerates (chromocenters) was decreased and the distance between chromocenters was increased as compared with untreated controls. The nuclear volume did not differ between the two groups.

CONCLUSIONS

The measured rearrangement of centromeres indicates a progressive clustering of heterochromatin and a global remodeling of interphase chromosome territories during differentiation of NB4 cells. The developed methods for the analysis of 3D centromere distribution patterns provide the opportunity for a fast and objective analysis of heterochromatin remodeling.

Established practice in the treatment of patients with acute promyleocytic leukemia and the introduction of arsenic trioxide as a novel therapy

First-line therapy for patients with newly diagnosed acute promyelocytic leukemia (APL) has been established in a series of randomized clinical trials. Remission induction and consolidation are based on the differentiation agent, all-trans retinoic acid (ATRA), and anthracycline-based chemotherapy. Maintenance therapy is also based on ATRA and may involve additional chemotherapy. Established protocols are associated with a high rate of complete responses (CRs) (87% to 97%), and long-term follow-up has indicated a 4-year disease-free survival of greater than 60%. Therapy for patients who relapse or are refractory to ATRA-based regimens is not standardized and there is a need for new approaches. Arsenic trioxide (ATO) has recently been licensed for use in patients with relapsed/refractory APL. Controlled clinical trials have indicated that ATO is associated with a CR rate of 87% in this population. This agent has a manageable toxicity profile and presents a welcome option for patients with relapsed disease for whom other, more debilitating therapies are unsuitable. Several prognostic factors have been defined in patients with APL, and it is possible that novel treatments such as ATO should be differentially applied to specific prognostic groups.