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OBJECTIVE: Acute promyelocytic leukemia (APL) is associated with an elevated risk of developing disseminated intravascular coagulation (DIC). The purpose of this study was to assess the outcomes of hospitalizations related to DIC in APL and their impact on healthcare. MATERIALS AND METHODS: This study entailed a cross-sectional and retrospective analysis of the US National Inpatient Sample database. We identified adults with APL and categorized them into groups of patients with and without DIC. Our focus areas included in-hospital mortality, length of stay, charges, and complications associated with DIC. Unadjusted odds ratios/coefficients were computed in univariate analysis, followed by adjusted odds ratios (aOR)/coefficients from multivariate analysis that accounted for confounding factors. RESULTS: Our analysis revealed that APL patients with DIC had a substantially higher aOR for mortality (aOR: 6.68, 95% confidence interval [CI]: 4.76-9.37, p

The objective of this study is to explore the possibility of treating APL patients fully as outpatients. A total of 21 consecutive APL patients were identified over 30 years in the Centro de Hematología y Medicina Interna de Puebla, at Clínica Ruiz, but only 17 were studied, treated as outpatients, and followed for at least 1 month; they were observed for median of 95 months, their median age was 27 years and all were treated with ATRA, prednisone, and adriamycin as outpatients. Treatment was completed on an outpatient basis in 15/17 cases. Molecular remission was achieved in 16/17 patients. The median follow-up was 95 months (IQR 19 - 360). The median OS and LFS were not reached, and the 12-month LFS was 94%. We have confirmed that APL can be treated entirely on an outpatient basis: this observation is of utmost relevance in a resource-limited setting, such as those prevailing in low- and middle-income countries. [ABSTRACT FROM AUTHOR]

Acute myeloid leukemia (AML) with retinoic acid receptor γ (RARG) rearrangement has clinical, morphologic, and immunophenotypic features similar to classic acute promyelocytic leukemia. However, AML with RARG rearrangement is insensitive to alltrans retinoic acid (ATRA) and arsenic trioxide (ATO) and carries a poor prognosis. We initiated a global cooperative study to define the clinicopathological features, genomic and transcriptomic landscape, and outcomes of AML with RARG rearrangements collected from 29 study groups/institutions worldwide. Thirty-four patients with AML with RARG rearrangements were identified. Bleeding or ecchymosis was present in 18 (54.5%) patients. Morphology diagnosed as M3 and M3v accounted for 73.5% and 26.5% of the cases, respectively. Immunophenotyping showed the following characteristics: positive for CD33, CD13, and MPO but negative for CD38, CD11b, CD34, and HLA-DR. Cytogenetics showed normal karyotype in 38% and t(11;12) in 26% of patients. The partner genes of RARG were diverse and included CPSF6, NUP98, HNRNPc, HNRNPm, PML, and NPM1. WT1- and NRAS/KRAS-mutations were common comutations. None of the 34 patients responded to ATRA and/or ATO. Death within 45 days from diagnosis occurred in 10 patients (∼29%). At the last follow-up, 23 patients had died, and the estimated 2-year cumulative incidence of relapse, event-free survival, and overall survival were 68.7%, 26.7%, and 33.5%, respectively. Unsupervised hierarchical clustering using RNA sequencing data from 201 patients with AML showed that 81.8% of the RARG fusion samples clustered together, suggesting a new molecular subtype. RARG rearrangement is a novel entity of AML that confers a poor prognosis. This study is registered with the Chinese Clinical Trial Registry (ChiCTR2200055810).

FIP1L1-RARA-a ssociated neoplasm is a very rare and aggressive disease, with only 3 previously reported cases in the literature. Here, we describe a 9-month-old boy who presented with a FIP1L1-RARA fusion-associated myelodysplastic/myeloproliferative neoplasm-like overlap syndrome, with similarities and distinct features to both acute promyelocytic leukemia and juvenile myelomonocytic leukemia. Using a combined approach of chemotherapy, differentiating agents, and allogeneic hematopoietic stem cell transplant (allo-HCT), this patient remains in remission 20 months after allo-HCT. To our knowledge, this is only the second published pediatric case involving this condition and the only case with a favorable long-term outcome. Given the aggressive disease described in the previously published case report, as well as the successful treatment course described, the combinatorial use of chemotherapy, differentiation therapy, and allo-HCT for treatment of FIP1L1-RARA fusion-associated myeloid neoplasms should be considered.

Multiple Ras proteins, including N-Ras, depend on a palmitoylation/depalmitoylation cycle to regulate their subcellular trafficking and oncogenicity. General lipase inhibitors such as Palmostatin M (Palm M) block N-Ras depalmitoylation, but lack specificity and target several enzymes displaying depalmitoylase activity. Here, we describe ABD957, a potent and selective covalent inhibitor of the ABHD17 family of depalmitoylases, and show that this compound impairs N-Ras depalmitoylation in human acute myeloid leukemia (AML) cells. ABD957 produced partial effects on N-Ras palmitoylation compared with Palm M, but was much more selective across the proteome, reflecting a plasma membrane-delineated action on dynamically palmitoylated proteins. Finally, ABD957 impaired N-Ras signaling and the growth of NRAS-mutant AML cells in a manner that synergizes with MAP kinase kinase (MEK) inhibition. Our findings uncover a surprisingly restricted role for ABHD17 enzymes as regulators of the N-Ras palmitoylation cycle and suggest that ABHD17 inhibitors may have value as targeted therapies for NRAS-mutant cancers.

Acute promyelocytic leukemia (APL) is often associated with activating FLT3 signaling mutations. These are highly related to hyperleukocytosis, a major adverse risk factor with chemotherapy-based regimens. APL is a model for oncogene-targeted therapies: all-trans retinoic acid (ATRA) and arsenic both target and degrade its ProMyelocytic Leukemia/Retinoic Acid Receptor α (PML/RARA) driver. The combined ATRA/arsenic regimen now cures virtually all patients with standard-risk APL. Although FLT3-internal tandem duplication (ITD) was an adverse risk factor for historical ATRA/chemotherapy regimens, the molecular bases for this effect remain unknown. Using mouse APL models, we unexpectedly demonstrate that FLT3-ITD severely blunts ATRA response. Remarkably, although the transcriptional output of initial ATRA response is unaffected, ATRA-induced PML/RARA degradation is blunted, as is PML nuclear body reformation and activation of P53 signaling. Critically, the combination of ATRA and arsenic fully rescues therapeutic response in FLT3-ITD APLs, restoring PML/RARA degradation, PML nuclear body reformation, P53 activation, and APL eradication. Moreover, arsenic targeting of normal PML also contributes to APL response in vivo. These unexpected results explain the less favorable outcome of FLT3-ITD APLs with ATRA-based regimens, and stress the key role of PML nuclear bodies in APL eradication by the ATRA/arsenic combination.

Data on childhood acute promyelocytic leukemia (APL) from low-and middle-income countries is limited. Early mortality is a concern and often not highlighted in clinical trials. The retrospective study was conducted on patients (≤12 years) with APL from 2003 to 2021 at a single center in India. Patients were treated with all-trans-retinoic acid (ATRA) and chemotherapy. Induction and three courses of consolidation were followed by maintenance for 2 years. In 2015, the protocol was updated with following modifications: (a) obtaining diagnostic cerebrospinal fluid at end-of-induction rather than at diagnosis, (b) administering intrathecal cytarabine regardless of risk-category, (c) risk-stratified administration of chemotherapy, and (d) inclusion of ATRA in all the cycles of consolidation. Sixty-two patients were diagnosed over the 17 years. The median age was 8 years (range: 0.9–12). Half had high-risk disease. Differentiation syndrome was observed in 32%, none being fatal. Eighteen (29%) patients died due to hemorrhage (83%) or septicemia (17%). Thirteen (21%) had early mortality (≤15 days), all due to hemorrhage. A platelet count <20 × 109/L predicted early mortality (odds ratio: 4.5; 95% CI: 0.9–22, p = 0.06). Treatment abandonment reduced from 23.5% during 2003–2015 to nil during 2015–2021 (p = 0.006). Three (8%) patients relapsed. The 4-year OS of all patients and the patients who survived >15 days was 70.1% and 89.6%, respectively. The 4-year EFS, including abandonment and early mortality, before and following updated protocol, was 61.4% and 65.5%, respectively (p = 0.77). Early mortality continues to be a barrier to an otherwise excellent survival in childhood APL. A significant reduction in treatment abandonment in recent years is gratifying. [ABSTRACT FROM AUTHOR]

Background/Aims We evaluated the feasibility and long-term efficacy of the combination of cytarabine, idarubicin, and all-trans retinoic acid (ATRA) for treating patients with newly diagnosed acute promyelocytic leukemia (APL). Methods We included 87 patients with newly diagnosed acute myeloid leukemia and a t(15;17) or promyelocytic leukemia/retinoic acid receptor alpha (PML-RARα) mutation. Patients received 12 mg/m2/day idarubicin intravenously for 3 days and 100 mg/m2/day cytarabine for 7 days, plus 45 mg/m2/day ATRA. Clinical outcomes included complete remission (CR), relapse-free survival (RFS), overall survival (OS), and the secondary malignancy incidence during a 20-year follow-up. Results The CR, 10-year RFS, and 10-year OS rates were 89.7%, 94.1%, and 73.8%, respectively, for all patients. The 10-year OS rate was 100% for patients that achieved CR. Subjects were classified according to the white blood cell (WBC) count in peripheral blood at diagnosis (low-risk, WBC < 10,000/mm3; high-risk, WBC ≥ 10,000/mm3). The low-risk group had significantly higher RFS and OS rates than the high-risk group, but the outcomes were not superior to the current standard treatment (arsenic trioxide plus ATRA). Toxicities were similar to those observed with anthracycline plus ATRA, and higher than those observed with arsenic trioxide plus ATRA. The secondary malignancy incidence after APL treatment was 2.7%, among the 75 patients that achieved CR, and 5.0% among the 40 patients that survived more than 5 years after the APL diagnosis. Conclusions Adding cytarabine to anthracycline plus ATRA was not inferior to anthracycline plus ATRA alone, but it was not comparable to arsenic trioxide plus ATRA. The probability of secondary malignancy was low.

Although the role of promyelocytic leukemia/retinoic acid receptor α (PML/RARA) fusion protein is well recognized in acute promyelocytic leukemia (APL), its contribution to initiation and maintenance of leukemogenesis is not completely understood. Transcriptome analysis in the murine MRP8-PML/RARA APL model has demonstrated modest alterations in gene expression accompanied by expansion of the promyelocyte compartment. Of particular interest, mice expressing PML/RARA showed downregulation of the transcription factor Irf8 mRNA. Interferon regulatory factor 8 (IRF8) is a known regulator of hematopoiesis. Previous research had implicated IRF8 as a tumor suppressor for myeloid neoplasia, and mice lacking IRF8 develop a well-differentiated myeloproliferative neoplasm characterized by expansion of neutrophilic lineage cells. We hypothesized that PML/RARA-mediated downregulation of Irf8 transcript levels contributes to the initiation of APL. We observed significant downregulation of IRF8 protein levels in highly purified promyelocyte populations of PML/RARA transgenic mice. We also found that loss of IRF8 results in expansion of promyelocytes in vivo, partially phenocopying the impact of PML/RARA expression. Moreover, survival experiments showed that complete loss of IRF8 leads to acceleration of APL onset in our PML/RARA mice. Collectively, these data identify IRF8 downregulation as an important factor in APL initiation and highlight a tumor-suppressor role for IRF8 in this acute leukemia.

Retinoic acid (RA) and arsenic target the t(15;17)(q24;q21) PML/RARA driver of acute promyelocytic leukemia (APL), their combination now curing over 95% patients. We report exome sequencing of 64 matched samples collected from patients at initial diagnosis, during remission, and following relapse after historical combined RA-chemotherapy treatments. A first subgroup presents a high incidence of additional oncogenic mutations disrupting key epigenetic or transcriptional regulators (primarily WT1) or activating MAPK signaling at diagnosis. Relapses retain these cooperating oncogenes and exhibit additional oncogenic alterations and/or mutations impeding therapy response (RARA, NT5C2). The second group primarily exhibits FLT3 activation at diagnosis, which is lost upon relapse together with most other passenger mutations, implying that these relapses derive from ancestral pre-leukemic PML/RARA-expressing cells that survived RA/chemotherapy. Accordingly, clonogenic activity of PML/RARA-immortalized progenitors ex vivo is only transiently affected by RA, but selectively abrogated by arsenic. Our studies stress the role of cooperating oncogenes in direct relapses and suggest that targeting pre-leukemic cells by arsenic contributes to its clinical efficacy.

Background: Acute promyelocytic leukemia (APL) is a rare subtype of acute myeloid leukemia (AML) and is characterized by a genetic translocation affecting the retinoic acid receptor-alpha gene, leading to blockage in the differentiation of granulocytic cells. The accumulation of promyelocytes in bone marrow leads to cytopenias and life-threatening coagulopathies. Definitive diagnosis is made with bone marrow biopsy. Differentiation of APL from other leukemias is important to appropriately treat with all-trans retinoic acid (ATRA) and arsenic trioxide. Patients with HIV are at a higher risk to develop AML. This article identifies how multiple comorbidities and social factors can contribute to difficulties in diagnosing AML. Case Report: We present a 67-year-old man with a past medical history of hypertension and substance use disorder who presented with progressive exertional dyspnea and was found to have HIV, chronic hepatitis C, and APL with pancytopenia. His bone marrow biopsy confirmed AML. This was a case of co-existing HIV and aleukemic leukemia. Conclusions: APL can present with pancytopenia, weakness, failure to thrive, or bleeding complications, which can be similar to presentations of those diagnosed with HIV. Diagnosis of APL can be differentiated between hypergranular and hypogranular; our patient demonstrated APL with only 52% blasts, which can make for a challenging diagnosis. Given increased mortality of APL, immediate ATRA therapy is warranted. Aleukemic leukemia is a rare presentation typically accompanied by skin manifestations. Our case highlights the importance of having high clinical suspicion for malignancy in patients with comorbidities that can interfere with the classic presentation of leukemia. [ABSTRACT FROM AUTHOR]

A hallmark of acute promyelocytic leukemia (APL) is altered nuclear architecture, with disruption of promyelocytic leukemia (PML) nuclear bodies (NBs) mediated by the PML-retinoic acid receptor α (RARα) oncoprotein. To address whether this phenomenon plays a role in disease pathogenesis, we generated a knock-in mouse model with NB disruption mediated by 2 point mutations (C62A/C65A) in the Pml RING domain. Although no leukemias developed in PmlC62A/C65A mice, these transgenic mice also expressing RARα linked to a dimerization domain (p50-RARα model) exhibited a doubling in the rate of leukemia, with a reduced latency period. Additionally, we found that response to targeted therapy with all-trans retinoic acid in vivo was dependent on NB integrity. PML-RARα is recognized to be insufficient for development of APL, requiring acquisition of cooperating mutations. We therefore investigated whether NB disruption might be mutagenic. Compared with wild-type cells, primary PmlC62A/C65A cells exhibited increased sister-chromatid exchange and chromosome abnormalities. Moreover, functional assays showed impaired homologous recombination (HR) and nonhomologous end-joining (NHEJ) repair pathways, with defective localization of Brca1 and Rad51 to sites of DNA damage. These data directly demonstrate that Pml NBs are critical for DNA damage responses, and suggest that Pml NB disruption is a central contributor to APL pathogenesis.

The co-occurrence of multiple primary cancers with hematological malignancies is uncommon, and acute promyelocytic leukemia (APL) with MPC is even rarer, with only a few cases reported in the literature. Herein, we introduce the diagnosis and treatment of 2 cases of MPC complicated with APL in our hospital and review the relevant literature. Both patients were primary solid tumor patients and were treated with surgery and chemotherapy, and had stable disease (SD). However, more than 1 year after the primary tumor was diagnosed, clinical symptoms were found and APL was diagnosed. Both patients received standard remission-induction therapy, but unfortunately died in the short term due to hemorrhagic complications. In conclusion, treatment of hematological neoplasms, especially acute leukemia combined with multiple primary cancers, is challenging. The prognostic factors and survival analysis of MPC patients with combined APL still need further clinical research and analysis. [ABSTRACT FROM AUTHOR]

Telomere and Telomerase have recently been explored as anti-aging and anti-cancer drug targets with only limited success. Previously we showed that the Chinese herbal medicine Tianshengyuan-1 (TSY-1), an agent used to treat bone marrow deficiency, has a profound effect on stimulating Telomerase activity in hematopoietic cells. Here, the mechanism of TSY-1 on cellular Telomerase activity was further investigated using HL60, a promyelocytic leukemia cell line, normal peripheral blood mononuclear cells, and CD34+ hematopoietic stem cells derived from umbilical cord blood. TSY-1 increases Telomerase activity in normal peripheral blood mononuclear cells and CD34+ hematopoietic stem cells with innately low Telomerase activity but decreases Telomerase activity in HL60 cells with high intrinsic Telomerase activity, both in a dose-response manner. Gene profiling analysis identified Telomerase reverse transcriptase (TERT) as the potential target gene associated with the TSY-1 effect, which was verified by both RT-PCR and western blot analysis. The β-galactosidase reporter staining assay showed that the effect of TSY-1 on Telomerase activity correlates with cell senescence. TSY-1 induced hypomethylation within TERT core promoter in HL60 cells but induced hypermethylation within TERT core promoter in normal peripheral blood mononuclear cells and CD34+ hematopoietic stem cells. TSY-1 appears to affect the Telomerase activity in different cell lines differently and the effect is associated with TERT expression, possibly via the methylation of TERT promoter.

The PML/RARA fusion protein occurs as a result of the t(15;17) translocation in the acute promyelocytic leukemia subtype of human acute myeloid leukemia. Gain of chromosome 8 is the most common chromosomal gain in human acute myeloid leukemia, including acute promyelocytic leukemia. We previously demonstrated that gain of chromosome 8-containing MYC is of central importance in trisomy 8, but the role of the nearby TRIB1 gene has not been experimentally addressed in this context. We have now tested the hypothesis that both MYC and TRIB1 have functional roles underlying leukemogenesis of trisomy 8 by using retroviral vectors to express MYC and TRIB1 in wild-type bone marrow and in marrow that expressed a PML/RARA transgene. Interestingly, although MYC and TRIB1 readily co-operated in leukemogenesis for wild-type bone marrow, TRIB1 provided no selective advantage to cells expressing PML/RARA. We hypothesized that this lack of co-operation between PML/RARA and TRIB1 reflected a common pathway for their effect: both proteins targeting the myeloid transcription factor C/EBPα. In support of this idea, TRIB1 expression abrogated the all-trans retinoic acid response of acute promyelocytic leukemia cells in vitro and in vivo Our data delineate the common and redundant inhibitory effects of TRIB1 and PML/RARA on C/EBPα providing a potential explanation for the lack of selection of TRIB1 in human acute promyelocytic leukemia, and highlighting the key role of C/EBPs in acute promyelocytic leukemia pathogenesis and therapeutic response. In addition, the co-operativity we observed between MYC and TRIB1 in the absence of PML/RARA show that, outside of acute promyelocytic leukemia, gain of both genes may drive selection for trisomy 8.

Acute promyelocytic leukemia (APL) is a subtype of myeloid leukemia characterized by differentiation block at the promyelocyte stage. Besides the presence of chromosomal rearrangement t(15;17), leading to the formation of PML-RARA (promyelocytic leukemia-retinoic acid receptor alpha) fusion, other genetic alterations have also been implicated in APL. Here, we performed comprehensive mutational analysis of primary and relapse APL to identify somatic alterations, which cooperate with PML-RARA in the pathogenesis of APL. We explored the mutational landscape using whole-exome (n=12) and subsequent targeted sequencing of 398 genes in 153 primary and 69 relapse APL. Both primary and relapse APL harbored an average of eight non-silent somatic mutations per exome. We observed recurrent alterations of FLT3, WT1, NRAS and KRAS in the newly diagnosed APL, whereas mutations in other genes commonly mutated in myeloid leukemia were rarely detected. The molecular signature of APL relapse was characterized by emergence of frequent mutations in PML and RARA genes. Our sequencing data also demonstrates incidence of loss-of-function mutations in previously unidentified genes, ARID1B and ARID1A, both of which encode for key components of the SWI/SNF complex. We show that knockdown of ARID1B in APL cell line, NB4, results in large-scale activation of gene expression and reduced in vitro differentiation potential.

Optimal therapy for relapsed APL in pediatric patients is controversial. Allogeneic HSCT is an alternative, with event-free survival of 70-75%. We report a pediatric patient with APL who relapsed 28 months after CBT from her sibling and then was treated with BMT from the same donor. Bone marrow was selected for higher cell dose, donor availability, and partial donor chimerism. Persistent molecular remission was achieved, currently at 65 months after BMT. This case suggests the potential role of GVL activity in APL and illustrates the use of different cell sources from the same donor in allogeneic transplantation for pediatric patients.

Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia (AML) that results from a balanced translocation between chromosomes 15 and 17, which involves the gene encoding the retinoic acid receptor alpha (RARA) on chromosome 17 and the gene for promyelocytic leukemia (PML) on chromosome 15, causing the translocation t (15; 17) PML / RARA. This rearrangement originates the PML / RAR alpha fusion protein, which blocks the differentiation of myeloid stem cells at the promyelocyte stage. APL affects young adults more frequently and carries a high risk of early mortality, especially due to development of severe coagulopathy that, without treatment, is invariably fatal. Early diagnosis, supportive treatment, and the introduction of drugs that promote the terminal differentiation of pathological promyelocytes such as alltrans retinoic acid (ATRA) and arsenic trioxide (ATO), have currently made this a curable disease with high rates of complete remission.

Although arsenic trioxide (arsenite, As(III)) has shown a remarkable efficacy in the treatment of acute promyelocytic leukemia patients, multidrug resistance is still a major concern for its clinical use. Multidrug resistance-associated protein 4 (MRP4), which belongs to the ATP-binding cassette (ABC) superfamily of transporters, is localized to the basolateral membrane of hepatocytes and the apical membrane of renal proximal tubule cells. Due to its characteristic localization, MRP4 is proposed as a candidate in the elimination of arsenic and may contribute to resistance to As(III). To test this hypothesis, stable HEK293 cells overexpressing MRP4 or MRP2 were used to establish the role of these two transporters in As(III) resistance. The IC50 values of As(III) in MRP4 cells were approximately 6-fold higher than those in MRP2 cells, supporting an important role for MRP4 in resistance to As(III). The capacity of MRP4 to confer resistance to As(III) was further confirmed by a dramatic decrease in the IC50 values with the addition of MK571, an MRP4 inhibitor, and cyclosporine A, a well-known broad-spectrum inhibitor of ABC transporters. Surprisingly, the sensitivity of the MRP2 cells to As(III) was similar to that of the parent cells, although insufficient formation of glutathione and/or Se conjugated arsenic compounds in the MRP2 cells might limit transport. Given that MRP4 is a major contributor to arsenic resistance in vitro, further investigation into the correlation between MRP4 expression and treatment outcome of leukemia patients treated with arsenic-based regimens is warranted.

The translocation between chromosomes 15 and 17 t(15;17) at the promyelocytic leukemia (PML) and retinoic acid receptor alpha (RARA) is thought to be specific for acute promyelocytic leukemia (APL). We present a case of acute leukemia with evidence of t(15;17) by banding karyotype, FISH, and PCR, with rare microgranular promyelocytes and significant basophilia detected on marrow aspirate, and an ETV6 missense mutation by molecular diagnostic testing. The patient underwent treatment with isotretinoin (ATRA) and arsenic trioxide (ATO) with attainment of a morphologic remission at the end of induction. There was no evidence of coagulopathy or basophil granule release with therapy. To our knowledge, this is the first report of the co-occurrence of APL with marrow basophilia in conjunction with an ETV6 mutation. The prognostic impact of an ETV6 mutation in this setting is unclear. [ABSTRACT FROM AUTHOR]

BackgroundFindings from clinical trials and population-based studies have differed with regard to whether mortality within 30 days of diagnosis (early death) of acute promyelocytic leukemia (APL) has decreased in the era of all-trans retinoic acid and anthracycline-based chemotherapy.MethodsUsing data from the California Cancer Registry, the authors investigated 7-day and 30-day mortality and survival in 772 patients who were aged birth to 39 years when they were diagnosed with APL during 1988 to 2011. Logistic regression and Cox proportional models were used to examine the association of early death and survival, respectively, with sociodemographic and clinical factors.ResultsThe overall 30-day mortality decreased significantly over time, from 26% (1988-1995) to 14% (2004-2011) (P =.004). On multivariable analysis, the odds of 30-day mortality were 3 times as high during 1988 through 1995 than 2004 through 2011 (P =.001). However, 7-day mortality did not improve over time (P =.229). When patients who died within 7 days of diagnosis were excluded, the 30-day mortality during 1996 to 2011 was 3% to 8%, which is similar to levels reported in clinical trials. Higher early death and lower survival were associated with a lack of health insurance (1996-2011) (early death odds ratio, 2.67; P =.031) and Hispanic race/ethnicity (early death odds ratio, 2.13; P =.014). Early death was not found to be associated with age, sex, socioeconomic status, or hospital type. Black patients also experienced worse survival.ConclusionsThe findings of the current study revealed a decreased 30-day mortality during the all-trans retinoic acid era, but 7-day mortality remained high. Efforts to achieve equal outcomes in young patients with APL should focus on improving access to effective treatment, mainly among uninsured patients and those of Hispanic and black race/ethnicity.

Acute promyelocytic leukemia is an aggressive malignancy characterized by the accumulation of promyelocytes in the bone marrow. PML/RARA is the primary abnormality implicated in this pathology, but the mechanisms by which this chimeric fusion protein initiates disease are incompletely understood. Identifying PML/RARA targets in vivo is critical for comprehending the road to pathogenesis. Utilizing a novel sorting strategy, we isolated highly purified promyelocyte populations from normal and young preleukemic animals, carried out microarray and methylation profiling analyses, and compared the results from the two groups of animals. Surprisingly, in the absence of secondary lesions, PML/RARA had an overall limited impact on both the transcriptome and methylome. Of interest, we did identify down-regulation of secondary and tertiary granule genes as the first step engaging the myeloid maturation block. Although initially not sufficient to arrest terminal granulopoiesis in vivo, such alterations set the stage for the later, complete differentiation block seen in leukemia. Further, gene set enrichment analysis revealed that PML/RARA promyelocytes exhibit a subtle increase in expression of cell cycle genes, and we show that this leads to both increased proliferation of these cells and expansion of the promyelocyte compartment. Importantly, this proliferation signature was absent from the poorly leukemogenic p50/RARA fusion model, implying a critical role for PML in the altered cell-cycle kinetics and ability to initiate leukemia. Thus, our findings challenge the predominant model in the field and we propose that PML/RARA initiates leukemia by subtly shifting cell fate decisions within the promyelocyte compartment.

Flow cytometry is a ubiquitous, multiparametric method for characterizing cellular populations. However, this method can grow increasingly complex with the number of proteins that need to be screened simultaneously: spectral emission overlap of fluorophores and the subsequent need for compensation, lengthy sample preparation, and multiple control tests that need to be performed separately must all be considered. These factors lead to increased costs, and consequently, flow cytometry is performed in core facilities with a dedicated technician operating the instrument. Here, we describe a low-cost, label-free microfluidic method that can determine the phenotypic profiles of single cells. Our method employs Node-Pore Sensing to measure the transit times of cells as they interact with a series of different antibodies, each corresponding to a specific cell-surface antigen, that have been functionalized in a single microfluidic channel. We demonstrate the capabilities of our method not only by screening two acute promyelocytic leukemia human cells lines (NB4 and AP-1060) for myeloid antigens, CD13, CD14, CD15, and CD33, simultaneously, but also by distinguishing a mixture of cells of similar size—AP-1060 and NALM-1—based on surface markers CD13 and HLA-DR. Furthermore, we show that our method can screen complex subpopulations in clinical samples: we successfully identified the blast population in primary human bone marrow samples from patients with acute myeloid leukemia and screened these cells for CD13, CD34, and HLA-DR. We show that our label-free method is an affordable, highly sensitive, and user-friendly technology that has the potential to transform cellular screening at the benchside.

The clinical characteristics, treatment options and outcomes in patients with acute promyelocytic leukaemia (APL) and hyperleucocytosis remain poorly defined. This study reviewed 242 consecutive patients with APL; 29 patients (12%) had a white blood cell count (WBC) ≥ 50 × 10(9) /l at presentation (median WBC 85·5 × 10(9) /l). Patients with hyperleucocytosis had inferior complete remission (CR) rates (69% vs. 88%; P = 0·004) and higher 4-week mortality (24% vs. 9%; P = 0·018) compared to patients without hyperleucocytosis. We noted a trend towards inferior 3-year disease-free survival (DFS) (69% vs. 80%; P = 0·057) and inferior 3-year overall survival (OS) (74% vs. 92%; P = 0·2) for patients with hyperleucocytosis. Leukapheresis was performed in 11 (38%) of the 29 patients with hyperleucocytosis. CR rate and 3-year OS were not significantly improved in patients who received leukapheresis. CR rate and 3-year OS for the 15 patients with hyperleucocytosis treated with all-trans retinoic acid (ATRA) plus arsenic trioxide (ATO) plus cytotoxic therapy (idarubicin or gemtuzumab ozogamicin) combinations were 100% and 100% vs. 57% and 35% for the 14 patients treated with non-ATRA/ATO combinations (P = 0·004 and P = 0·002). Leukapheresis does not improve the outcomes in patients with APL presenting with hyperleucocytosis. ATRA/ATO-based combinations are superior to other regimens in these patients.

Acute promyelocytic leukemia (APL) comprises approximately 5-10% of childhood acute myeloid leukemia (AML) cases in the US. While variation in this percentage among other populations was noted previously, global patterns of childhood APL have not been thoroughly characterized. In this comprehensive review of childhood APL, we examined its geographic pattern and the potential contribution of environmental factors to observed variation. In 142 studies (spanning >60 countries) identified, variation was apparent-de novo APL represented from 2% (Switzerland) to >50% (Nicaragua) of childhood AML in different geographic regions. Because a limited number of previous studies addressed specific environmental exposures that potentially underlie childhood APL development, we gathered 28 childhood cases of therapy-related APL, which exemplified associations between prior exposures to chemotherapeutic drugs/radiation and APL diagnosis. Future population-based studies examining childhood APL patterns and the potential association with specific environmental exposures and other risk factors are needed.

Dengue is predominantly a self-limiting illness. The association of dengue with new onset of leukemia has been rarely reported. We describe herein a series of three patients diagnosed with acute lymphoblastic leukemia, chronic myeloid leukemia, and acute promyelocytic leukemia who presented with concurrent dengue infection at a tertiary care institute in the southwestern coastal region of India. In spite of the different types of leukemias, we observed similar trends in their blood parameters, which were comparable with those of nonleukemic dengue patients. The transfusion profile of each of these patients is described. We could conclude that even in the presence of leukemia, dengue tends to be self-limited. No such comparative case reports have been published so far, and with an increasing incidence of dengue in the world, the occurrence of the two might not remain a remote possibility.

These NCCN Guidelines Insights summarize several key updates to the NCCN Guidelines for Acute Myeloid Leukemia and discuss the clinical evidence that support the recommendations. The updates described in this article focus on the acute promyelocytic leukemia (APL) section, featuring recommendations for additional induction/consolidation regimens in patients with low- or intermediate-risk APL, and providing guidance on maintenance strategies for APL.

Important insights into nuclear function would arise if gene loci physically interacting with particular subnuclear domains could be readily identified. Immunofluorescence microscopy combined with fluorescence in situ hybridization (immuno-FISH), the method that would typically be used in such a study, is limited by spatial resolution and requires prior assumptions for selecting genes to probe. Our new technique, immuno-TRAP, overcomes these limitations. Using promyelocytic leukemia nuclear bodies (PML NBs) as a model, we used immuno-TRAP to determine if specific genes localize within molecular dimensions with these bodies. Although we confirmed a TP53 gene-PML NB association, immuno-TRAP allowed us to uncover novel locus-PML NB associations, including the ABCA7 and TFF1 loci and, most surprisingly, the PML locus itself. These associations were cell type specific and reflected the cell's physiological state. Combined with microarrays or deep sequencing, immuno-TRAP provides powerful opportunities for identifying gene locus associations with potentially any nuclear subcompartment.

While all-trans retinoic acid (ATRA) treatment in acute promyelocytic leukemia (APL) has been the paradigm of targeted therapy for oncogenic transcription factors, the underlying mechanisms remain largely unknown, and a significant number of patients still relapse and become ATRA resistant. We identified the histone demethylase PHF8 as a coactivator that is specifically recruited by RARα fusions to activate expression of their downstream targets upon ATRA treatment. Forced expression of PHF8 resensitizes ATRA-resistant APL cells, whereas its downregulation confers resistance. ATRA sensitivity depends on the enzymatic activity and phosphorylation status of PHF8, which can be pharmacologically manipulated to resurrect ATRA sensitivity to resistant cells. These findings provide important molecular insights into ATRA response and a promising avenue for overcoming ATRA resistance.

Differentiation therapy for acute myeloid leukemia uses transcriptional modulators to reprogram cancer cells. The most relevant clinical example is acute promyelocytic leukemia (APL), which responds dramatically to either retinoic acid (RA) or arsenic trioxide (As(2)O(3)). In many myeloid leukemia cell lines, cyclic adenosine monophosphate (cAMP) triggers growth arrest, cell death, or differentiation, often in synergy with RA. Nevertheless, the toxicity of cAMP derivatives and lack of suitable models has hampered trials designed to assess the in vivo relevance of theses observations. We show that, in an APL cell line, cAMP analogs blocked cell growth and unraveled As(2)O(3)-triggered differentiation. Similarly, in RA-sensitive or RA-resistant mouse models of APL, continuous infusions of 8-chloro-cyclic adenosine monophosphate (8-Cl-cAMP) triggered major growth arrest, greatly enhanced both spontaneous and RA- or As(2)O(3)-induced differentiation and accelerated the restoration of normal hematopoiesis. Theophylline, a well-tolerated phosphodiesterase inhibitor which stabilizes endogenous cAMP, also impaired APL growth and enhanced spontaneous or As(2)O(3)-triggered cell differentiation in vivo. Accordingly, in an APL patient resistant to combined RA-As(2)O(3) therapy, theophylline induced blast clearance and restored normal hematopoiesis. Taken together, these results demonstrate that in vivo activation of cAMP signaling contributes to APL clearance, independently of its RA-sensitivity, thus raising hopes that other myeloid leukemias may benefit from this therapeutic approach.

Pro-myelocytic acute leukemia (APL) is characterized by the proliferation of cells blocked at promyelocytic stage and ATRA is the choice of initial treatment because of the APL sensitivity to this compound. In this case study we report a 28-year-old man who presented to the Emergency Department with epistaxis, petechial rash, and fever. Laboratory tests revealed the presence of high white blood cell count with 60% blasts and evidence of coagulopathy. The diagnosis was confirmed later as APL. Because of the delayed transfer to the reference center and unavailability of ATRA initial treatment, the patient received isotretinoin, a related compound. The treatment was successfully implemented in the initial management of acute pro-myelocytic leukemia as patient condition improved. isotretinoin could be used as an alternative therapy for ATRA whenever the latter is not available. further research is needed to establish the appropriate doses and to assess the potential risk of differentiation syndromes.

The promyelocytic leukemia retinoic acid receptor alpha (PMLRARalpha) chimeric protein is associated with acute promyelocytic leukemia (APL). PMLRARalpha transgenic mice develop leukemia only after several months, suggesting that PMLRARalpha does not by itself confer a fully malignant phenotype. Suppression of apoptosis can have a central role in tumorigenesis; therefore, we assessed whether BCL-2 influenced the ability of PMLRARalpha to initiate leukemia. Evaluation of preleukemic animals showed that whereas PMLRARalpha alone modestly altered neutrophil maturation, the combination of PMLRARalpha and BCL-2 caused a marked accumulation of immature myeloid cells in bone marrow. Leukemias developed more rapidly in mice coexpressing PMLRARalpha and BCL-2 than in mice expressing PMLRARalpha alone, and all mice expressing both transgenes succumbed to leukemia by 7 mo. Although both preleukemic, doubly transgenic mice and leukemic animals had abundant promyelocytes in the bone marrow, only leukemic mice exhibited thrombocytopenia and dissemination of immature cells. Recurrent gain of chromosomes 7, 8, 10, and 15 and recurrent loss of chromosome 2 were identified in the leukemias. These chromosomal changes may be responsible for the suppression of normal hematopoiesis and dissemination characteristic of the acute leukemias. Our results indicate that genetic changes that inhibit apoptosis can cooperate with PMLRARalpha to initiate APL.

The promyelocytic leukemia retinoic acid receptor alpha (PMLRARalpha) chimeric protein is associated with acute promyelocytic leukemia (APL). PMLRARalpha transgenic mice develop leukemia only after several months, suggesting that PMLRARalpha does not by itself confer a fully malignant phenotype. Suppression of apoptosis can have a central role in tumorigenesis; therefore, we assessed whether BCL-2 influenced the ability of PMLRARalpha to initiate leukemia. Evaluation of preleukemic animals showed that whereas PMLRARalpha alone modestly altered neutrophil maturation, the combination of PMLRARalpha and BCL-2 caused a marked accumulation of immature myeloid cells in bone marrow. Leukemias developed more rapidly in mice coexpressing PMLRARalpha and BCL-2 than in mice expressing PMLRARalpha alone, and all mice expressing both transgenes succumbed to leukemia by 7 mo. Although both preleukemic, doubly transgenic mice and leukemic animals had abundant promyelocytes in the bone marrow, only leukemic mice exhibited thrombocytopenia and dissemination of immature cells. Recurrent gain of chromosomes 7, 8, 10, and 15 and recurrent loss of chromosome 2 were identified in the leukemias. These chromosomal changes may be responsible for the suppression of normal hematopoiesis and dissemination characteristic of the acute leukemias. Our results indicate that genetic changes that inhibit apoptosis can cooperate with PMLRARalpha to initiate APL.

Introduction. The accurate diagnosis of acute promyelocytic leukemia (APL), not only on the morphological and clinical, but also on the molecular level, is very important for application of targeted therapies. Case report. A 62- year-old woman presented with APL. By using conventional cytogenetic analysis as well as applying the fluorescence in situ hybridization (FISH) analysis it has not been possible to confirm the presence of t(15;17) in the presented patient. Using reverse transcriptase polymerase chain reaction (RT-PCR) two atypical promyelotic leukemia/retinoic acid receptor alpha (PML/RAR-α) fusion transcripts were identified. Both detected transcripts were isoforms. The larger transcript was in-frame, coding for functional aberrant PML/RAR-α protein, while the shorter transcript was an out-of-frame. Conclusion. Our study highlights the need for the application of molecular methodology in daily clinical practice. Precise characterization of PML/RAR-α fusion transcript creates a basis for identifying rare individual cases that require special caution when treating such patients. To our knowledge this is only the fifth case of atypical PML/RAR-α transcript containing full PML exon 7a, and among them the only one that was cytogenetically cryptic and FISH negative. All of the herein presented cases had lethal outcome. Therefore, our findings with the additional review of the literature, emphasizes the importance of detailed identification of atypical PML/RAR-α fusions, not only for the purpose of knowing their role in leukemogenesis, but also for the assessment of the impact that they can have on the outcome of the treatment. [ABSTRACT FROM AUTHOR]

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Patients with acute promyelocytic leukemia (APL) usually relapse after all-trans retinoic acid (RA) treatment because this therapy fails to eradicate the malignant clone. Our data showed that KH 1060 and other 20-epi vitamin D3 analogs alone were potent inhibitors of clonal growth of NB4 cells, an APL cell line (ED50, approximately 5 x 10(-11) M). The combination of KH 1060 and 9-cis-RA synergistically and irreversibly enhanced this effect. Neither KH 1060 nor 9-cis-RA (10(-6) M, 3 d) were strong inducers of differentiation of NB4 cells. However, 98% of the cells underwent differentiation to a mature phenotype with features of both granulocytes and monocytes after exposure to a combination of both compounds. Apoptosis only increased after incubation of NB4 cells with 9-cis-RA alone (28%) or with a combination of 9-cis-RA plus KH1060 (32%). Immunohistochemistry showed that the bcl-2 protein decreased from nearly 100% of the wild-type NB4 cells to 2% after incubation with a combination of KH 1060 and 9-cis-RA, and the bax protein increased from 50% of wild-type NB4 cells to 92% after culture with both analogs (5 x 10(-7) M, 3 d). Western blot analysis paralleled these results. Studies of APL cells from one untreated individual paralleled our results with NB4 cells. Taken together, the data demonstrated that nearly all of the NB4 cells can be irreversibly induced to differentiate terminally when exposed to the combination of KH 1060 and 9-cis-RA.

We used specific antisera and immunohistochemical methods to investigate the subcellular localization and expression of Bcr, Abl, and Bcr-Abl proteins in leukemic cell lines and in fresh human leukemic and normal samples at various stages of myeloid differentiation. Earlier studies of the subcellular localization of transfected murine type IV c-Abl protein in fibroblasts have shown that this molecule resides largely in the nucleus, whereas transforming deletion variants are localized exclusively in the cytoplasm. Here, we demonstrate that the murine type IV c-Abl protein is also found in the nucleus when overexpressed in a mouse hematopoietic cell line. However, in both normal and leukemic human hematopoietic cells, c-Abl is discerned predominantly in the cytoplasm, with nuclear staining present, albeit at a lower level. In contrast, normal endogenous Bcr protein, as well as the aberrant p210BCR-ABL and p190BCR-ABL proteins consistently localize to the cytoplasm in both cell lines and fresh cells. The results with p210BCR-ABL were confirmed in a unique Ph1-positive chronic myelogenous leukemia (CML) cell line, KBM5, which lacks the normal chromosome 9 and hence the normal c-Abl product. Because the p210BCR-ABL protein appears cytoplasmic in both chronic phase and blast crisis CML cells, as does the p190BCR-ABL in Ph1-positive acute leukemia, a change in subcellular location of Bcr-Abl proteins between cytoplasm and nucleus cannot explain the different spectrum of leukemias associated with p210 and p190, nor the transition from the chronic to the acute leukemia phenotype seen in CML. Further analysis of fresh CML and normal hematopoietic bone marrow cells reveals that p210BCR-ABL, as well as the normal Bcr and Abl proteins, are expressed primarily in the early stages of myeloid maturation, and that levels of expression are reduced significantly as the cells mature to polymorphonuclear leukocytes. Similarly, a decrease in Bcr and Abl levels occurs in HL-60 cells induced by DMSO to undergo granulocytic differentiation. The action of p210BCR-ABL and its normal counterparts may, therefore, take place during the earlier stages of myeloid development.

Most human cells express two TNF and lymphotoxin (LT) membrane receptors (TNF-R), of 55 and 75 kDa. The regulatory effect of these two receptors on intercellular adhesion molecules (ICAM-1) expression was examined in various human cell lines in vitro, including human lymphokine-activated killer T cells (T-LAK) cells and HL-60 cells. Rabbit antihuman TNF-R antisera specific for each receptor were employed as probes to selectively stimulate 55- and 75-kDa TNF/LT membrane receptor production. These antisera compete with TNF/LT binding to each specific cell membrane receptor and have been found to bind to specific membrane receptors on various human cell lines in vitro. In the present study, we demonstrated biologic activity for anti-55-kDa TNF-R antiserum. For example, antibodies that bind to the 55-kDa TNF-R caused cytolysis of HeLa and ME-180 human cervical cancer cells and induced proliferation of MRC-5 human fibroblasts. In contrast, however, anti-75-kDa TNF-R antiserum demonstrated no bioactivity in these assays. In addition, no synergy or costimulation was observed when a combination of both anti-55- and anti-75-kDa TNF-R antisera were tested in these assay systems. Anti-55-kDa TNF-R antiserum up-regulated ICAM-1 expression on human HL-60, T-LAK, and THP-1 cells, whereas anti-75-kDa TNF-R antiserum had no effect. Unexpectedly, however, ICAM-1 expression was greatly enhanced by the addition of anti-75-kDa TNF-R to the anti-55-kDa TNF-R containing culture. This enhancing effect was also observed with human T-LAK cells and THP-1 monocytic leukemia cell, in vitro.

Myeloid sarcoma is a rare presentation of acute leukemia as a solid tumor at various extramedullary sites. It may present concurrently, before or after the onset of systemic bone marrow leukemia. Unusual clinical localization may lead to misdiagnosis, or delayed diagnosis and treatment. We describe the first case, to our knowledge, of de novo myeloid sarcoma of the breast confirmed as acute promyelocytic leukemia. Immunohistochemical analysis, flow cytometry, fluorescent in situ hybridization analysis and molecular analysis using RQ-PCR of tissue samples should be routine in determining the correct diagnosis in this setting. [ABSTRACT FROM AUTHOR]

Background: Acute promyelocytic leukemia (APL) is a rare form of acute myelogenous leukemia (AML). Survival rates exceed 80% in developed countries. Successful treatments rely on all-trans retinoic acid with anthracycline-based chemotherapy. Availability of modern care and public knowledge play important roles in pediatric APL survival. Method: A cytogenetic diagnosis of APL was confirmed in 30 (14.5%) out of 207 children consecutively diagnosed with de novo AML between January 2005 and December 2012 at nine cancer care centers in Saudi Arabia. Patients were treated based on the standard protocol used by the center following the PETHEMA or the C9710 treatment protocols. We modeled 5-year overall survival (OS), event-free survival (EFS) and cumulative incidence of relapse (CIR) vs. treatment and potential covariates of age at diagnosis, involvement of central nervous system (CNS), and white blood cell (WBC) levels. Results: The median age was 10.4 years with a male:female ratio of 1.9. WBC was 10 × 109/l or greater in 57% and CNS involvement was confirmed in 13%. OS, EFS, and CIR were 74 ± 12%, 55 ± 19%, and, 36 ± 17% respectively. No significant difference was found by treatment protocol. WBC levels were significantly prognostic for all negative events, but treatment with C9710 significantly ameliorated negative WBC effects. Overall outcomes were comparable to those reported in developed countries. Conclusions: Access to modern care is likely to be a critical factor in successful and comparable outcomes of childhood APL across the globe. In the present study, utilizing a cytarabine-containing protocol improved outcome of high-risk pediatric patients with APL. [ABSTRACT FROM AUTHOR]

A case study of 62-year-old man is presented with pancytopenia and underwent a bone marrow aspiration and biopsy. Topics include examines there were several percentage immature myeloid cells and atypical promyelocyte-like cells in the bone marrow aspirate, many with bilobed nuclei and cytoplasmic granules.

The aim of our study was to evaluate the impact of oral arsenic (the realgar-indigo naturalis formula, RIF) and all-trans retinoic acid (ATRA) on coagulopathy in acute promyelocytic leukemia (APL) compared with intravenous arsenic trioxide (ATO) and ATRA during induction. Mitoxantrone was added to all the patients at a dose of 1.4 mg/m 2 per day for 5–7 days. D-dimer levels, prothrombin time (PT), fibrinogen (Fbg) levels and the platelet count were comparably analyzed among 83 newly diagnosed APL patients treated with RIF (n = 45) or with ATO (n = 38). Since induction therapy with RIF and ATRA, the median levels of Fbg, PT and platelets were recovered to the normal range within 4 days, 10 days and 28 days, respectively. The last day of platelet and plasma transfusion was day 12 (range: 0–24 days) and day 3 (range: 0–27 days), respectively. Among the 42 patients with a disseminated intravascular coagulation (DIC) score = 4, the consumption of transfused platelets was less in the RIF group than that in the ATO group ( P = 0.037). In the 17 patients with a DIC score <4, prompt recovery of Fbg levels ( P = 0.028) was observed in the RIF group compared with that in the ATO group ( P = 0.401). RIF and ATO showed similar effects on the recovery of coagulopathy in APL patients. RIF had a potential beneficial effect in accelerating the recovery of thrombocytopenia and hypofibrinogenemia for subclinical DIC patients. [ABSTRACT FROM AUTHOR]

El objetivo fue describir la frecuencia de los subtipos moleculares de PML/RARα en pacientes con leucemia promielocítica aguda (LPA) y su distribución según grupo de riesgo de recaída y citomorfología. Se realizó una serie de casos que incluyó a cincuenta pacientes registrados en el Instituto Nacional de Enfermedades Neoplásicas (INEN), durante el periodo 2010-2012, con diagnóstico molecular de LPA PML/RARα y subtipos bcr1, bcr2 y bcr3 por reacción en cadena de la polimerasa con transcriptasa reversa (RT-PCR). El subtipo bcr1 fue el más frecuente (62%). Los pacientes con riesgo de recaída intermedio y morfología hipergranular fueron, en su mayoría, bcr1 (70%) y todos los que poseían riesgo de recaída alto y morfología hipogranular fueron bcr3. Se concluye que en la población estudiada hay un predomino del subtipo bcr1 y que existen diferencias en la distribución de los subtipos bcr1 y bcr3 según el grupo de riesgo de recaída y citomorfologíaThe objective was to describe the frequency of molecular subtypes of PML/RARα in patients with acute promyelocytic leukemia (APL) and their distribution according to risk of recurrence and cytomorphology. A case series was carried out, including fifty patients registered at the National Institute of Neoplastic Diseases (INEN) during 2010-2012, with molecular diagnosis of APL PML/RARα and bcr1, bcr2 and bcr3 subtypes by reverse-transcription polymerase chain reaction (RT-PCR). Bcr1 subtype was the most frequent (62%). Most patients with an intermediate risk of recurrence and hypergranular morphology were bcr1 (70%), while all patients with high risk of recurrence and hypogranular morphology were bcr3. A predominance of bcr1 subtype among the population studied can therefore be concluded, as well as the fact that there are differences in the distribution of bcr1 and bcr3 subtypes according to recurrence risk group and cytomorphology

The article discusses recommendations from the North American Children's Oncology Group (COG) and the International Berlin-Frankfurt-Münster-Study Group (I-BFM) SG) on the management of relapsed and refractory childhood acute promyelocytic leukemia (APL). Topics covered include relapsed APL with translocation, the controversy over the definition of early and late relapse, and prognostic factors in relapsed APL.