Current management of newly diagnosed acute promyelocytic leukemia.

The management of acute promyelocytic leukemia (APL) has considerably evolved during the past two decades. The advent of all-trans retinoic acid (ATRA) and its inclusion in combinatorial regimens with anthracycline chemotherapy has provided cure rates exceeding 80%; however, this widely adopted approach also conveys significant toxicity including severe myelosuppression and rare occurrence of secondary leukemias. More recently, the advent of arsenic trioxide (ATO) and its use in association with ATRA with or without chemotherapy has further improved patient outcome by allowing to minimize the intensity of chemotherapy, thus reducing serious toxicity while maintaining high anti-leukemic efficacy. The advantage of ATRA-ATO over ATRA chemotherapy has been recently demonstrated in two large randomized trials and this option has now become the new standard of care in low-risk (i.e. non-hyperleukocytic) patients. In light of its rarity, abrupt onset and high risk of early death and due to specific treatment requirements, APL remains a challenging condition that needs to be managed in highly experienced centers. We review here the results of large clinical studies conducted in newly diagnosed APL as well as the recommendations for appropriate diagnosis, prevention and management of the main complications associated with modern treatment of the disease.

A miRNA Signature in Human Cord Blood Stem and Progenitor Cells as Potential Biomarker of Specific Acute Myeloid Leukemia Subtypes.

MicroRNAs (miRNAs) are important regulators of several cellular processes. During hematopoiesis, specific expression signatures have been reported in different blood cell lineages and stages of hematopoietic stem cell (HSC) differentiation. Here we explored the expression of miRNAs in umbilical cord blood stem (HSC) and progenitor cells (HPC) and compared it to unilineage granulocyte and granulo-monocyte differentiation as well as to primary blasts from patients with acute myeloid leukemia (AML). CD34 + CD38- ad CD34 + CD38 + cells were profiled using a global array consisting of about 2000 miRNAs. An approach combining bioinformatic prediction of miRNA targets with mRNA expression profiling was used to search for putative biologically enriched functions and networks. At least 15 miRNAs to be differentially expressed between HSC and HPC cell population, a cluster of 7 miRNAs are located in the q32 region of human chromosome 14 (miR-377-3p, -136-5p, 376a-3p, 495-3p, 654-3p, 376c-3p and 381-3p) whose expression decreased during the early stages of normal myelopoiesis but were markedly increased in a small set of AML. Interestingly, miR-4739 and -4516, two novel microRNA whose function and targets are presently unknown, showed specific and peculiar expression profile during the hematopoietic stem cells differentiation into unilineages and resulted strongly upregulated in almost all AML subsets. miR-181, -126-5p, -29b-3p and -22-3p resulted dis-regulated in specific leukemias phenotypes. This study provides the first evidence of a miRNA signature in human cord blood stem and progenitor cells with a potential role in hematopoietic stemness properties and possibly in leukemogenesis of specific AML subtypes.

PML-RARα kinetics and impact of FLT3-ITD mutations in newly diagnosed acute promyelocytic leukaemia treated with ATRA and ATO or ATRA and chemotherapy.

The APL0406 study showed that arsenic trioxide (ATO) and all-trans retinoic acid (ATRA) are not inferior to standard ATRA and chemotherapy (CHT) in newly diagnosed, low-intermediaterisk acute promyelocytic leukaemia (APL). We analysed the kinetics of promyelocytic leukaemia-retinoic acid receptor-α (PML-RARα) transcripts by real-time quantitative PCR (RQ-PCR) in bone marrow samples from 184 patients and assessed the prognostic impact of fms-related tyrosine kinase 3-internal tandem duplication (FLT3-ITD) in 159 patients enrolled in this trial in Italy. After induction therapy, the reduction of PML-RARα transcripts was significantly greater in patients receiving ATRA-CHT as compared with those treated with ATRA-ATO (3.4 vs 2.9 logs; P=0.0182). Conversely, at the end of consolidation, a greater log reduction of PML-RARα transcripts was detected in the ATRA-ATO as compared with the ATRA-CHT group (6.3 vs 5.3 logs; P=0.0024). FLT3-ITD mutations had no significant impact on either event-free survival (EFS) or cumulative incidence of relapse in patients receiving ATRA-ATO, whereas a trend for inferior EFS was observed in FLT3-ITD-positive patients receiving ATRA-CHT. Our study shows at the molecular level that ATRA-ATO exerts at least equal and probably superior antileukaemic efficacy compared with ATRA-CHT in low-intermediaterisk APL. The data also suggest that ATRA-ATO may abrogate the negative prognostic impact of FLT3-ITD.

Novel strategies in treatment of acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia characterized by t(15;17) and a life-threatening coagulopathy. Once highly fatal, nowadays standard treatment approaches with all-trans retinoic acid (ATRA) along with chemotherapy allows curing up to 80-85% of cases. In the past decade, arsenic trioxide used alone or in combination with ATRA has demonstrated high efficacy in APL, and is currently regarded as the gold standard for treatment of relapsed cases. Chemotherapy-free approaches based on the combination of arsenic trioxide and ATRA are currently being tested against standard ATRA and chemotherapy in randomized clinical trials for frontline therapy of APL.

Comparative molecular analysis of therapy-related and de novo acute promyelocytic leukemia.

Therapy-related acute promyelocytic leukemia (t-APL) has been reported as a late complication of exposure to radiotherapy and/or chemotherapeutic agents targeting DNA topoisomerase II. We have analyzed in t-APL novel gene mutations recently associated with myeloid disorders. Unlike previous reports in acute myeloid leukemia (AML), our results showed neither IDHs nor TET2 mutations in t-APL. However we found an R882H mutation in the DNMT3A gene in a patient with t-APL suggesting a possible role of this alteration in the pathogenesis of t-APL.

Risk of acute promyelocytic leukemia in multiple sclerosis: coding variants of DNA repair genes.

BACKGROUND: Single nucleotide polymorphisms (SNPs) in double-strand break repair genes may alter DNA repair capacity and, in turn, confer predisposition to leukemia. We analyzed polymorphic variants of DNA repair and detoxification genes in patients with multiple sclerosis (MS) who developed secondary acute promyelocytic leukemia (sAPL), in most cases after treatment with mitoxantrone (MTZ). METHODS: Using MassARRAY high-throughput DNA analysis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, we genotyped patients with sAPL (n=20) developed after treatment of MS (18 out 20 treated with MTZ) for the presence of 210 SNPs of 22 genes mostly involved in DNA repair and drug detoxification. Patients with MS who did not develop sAPL including 41 treated with MTZ (n=253 and 41, respectively) and healthy blood donors (n=310) were also genotyped as controls. RESULTS: We observed risk allele frequency between MS and sAPL for BRCA2 (rs1801406): 6% and 26%, p=0.007; XRCC5 (rs207906): 2.5% and 15%, p=0.016; CYP3A4 (rs2740574): 4.5% and 25%, p=0.0035. The association of homozygous variants of BRCA2 and XRCC5 yielded higher risk of sAPL (MS vs sAPL: 0.4% and 18%, p=0.001). We also observed a significant association between a SNP in the promoter region (rs2740574) of CYP3A4, an enzyme involved in the metabolism of chemotherapeutic agents and development of sAPL. CONCLUSIONS: Increased susceptibility to develop sAPL in patients with MS receiving MTZ may be linked to genetic variants in DNA repair and drug-metabolizing enzymes that result in impaired detoxification of chemotherapy or inefficient repair of drug-induced genetic damage.