Retinoic acid and proteotoxic stress induce AML cell death overcoming stromal cell protection.

BACKGROUND: Acute myeloid leukemia (AML) patients bearing the ITD mutation in the tyrosine kinase receptor FLT3 (FLT3-ITD) present a poor prognosis and a high risk of relapse. FLT3-ITD is retained in the endoplasmic reticulum (ER) and generates intrinsic proteotoxic stress. We devised a strategy based on proteotoxic stress, generated by the combination of low doses of the differentiating agent retinoic acid (R), the proteasome inhibitor bortezomib (B), and the oxidative stress inducer arsenic trioxide (A). METHODS: We treated FLT3-ITD+ AML cells with low doses of the aforementioned drugs, used alone or in combinations and we investigated the induction of ER and oxidative stress. We then performed the same experiments in an in vitro co-culture system of FLT3-ITD+ AML cells and bone marrow stromal cells (BMSCs) to assess the protective role of the niche on AML blasts. Eventually, we tested the combination of drugs in an orthotopic murine model of human AML. RESULTS: The combination RBA exerts strong cytotoxic activity on FLT3-ITD+ AML cell lines and primary blasts isolated from patients, due to ER homeostasis imbalance and generation of oxidative stress. AML cells become completely resistant to the combination RBA when treated in co-culture with BMSCs. Nonetheless, we could overcome such protective effects by using high doses of ascorbic acid (Vitamin C) as an adjuvant. Importantly, the combination RBA plus ascorbic acid significantly prolongs the life span of a murine model of human FLT3-ITD+ AML without toxic effects. Furthermore, we show for the first time that the cross-talk between AML and BMSCs upon treatment involves disruption of the actin cytoskeleton and the actin cap, increased thickness of the nuclei, and relocalization of the transcriptional co-regulator YAP in the cytosol of the BMSCs. CONCLUSIONS: Our findings strengthen our previous work indicating induction of proteotoxic stress as a possible strategy in FLT3-ITD+ AML therapy and open to the possibility of identifying new therapeutic targets in the crosstalk between AML and BMSCs, involving mechanotransduction and YAP signaling.

ELN2017 risk stratification improves outcome prediction when applied to the prospective GIMEMA AML1310 protocol.

The 2017 version of the European LeukemiaNet (ELN) recommendations, by integrating cytogenetics and mutational status of specific genes, divides patients with acute myeloid leukemia into 3 prognostically distinct risk categories: favorable (ELN2017-FR), intermediate (ELN2017-IR), and adverse (ELN2017-AR). We performed a post hoc analysis of the GIMEMA (Gruppo Italiano Malattie EMatologiche dell'Adulto) AML1310 trial to investigate the applicability of the ELN2017 risk stratification to our study population. In this trial, after induction and consolidation, patients in complete remission were to receive an autologous stem cell transplant (auto-SCT) if categorized as favorable risk or an allogeneic stem cell transplant (allo-SCT) if adverse risk. Intermediate-risk patients were to receive auto-SCT or allo-SCT based on the postconsolidation levels of measurable residual disease as measured by using flow cytometry. Risk categorization was originally conducted according to the 2009 National Comprehensive Cancer Network recommendations. Among 500 patients, 445 (89%) were reclassified according to the ELN2017 criteria: ELN2017-FR, 186 (41.8%) of 455; ELN2017-IR, 179 (40.2%) of 445; and ELN2017-AR, 80 (18%) of 455. In 55 patients (11%), ELN2017 was not applicable. Two-year overall survival (OS) was 68.8%, 51.3%, 45.8%, and 42.8% for the ELN2017-FR, ELN2017-IR, ELN2017-not classifiable, and ELN2017-AR groups, respectively (P < .001). When comparing the 2 different transplant strategies in each ELN2017 risk category, a significant benefit of auto-SCT over allo-SCT was observed among ELN2017-FR patients (2-year OS of 83.3% vs 66.7%; P = .0421). The 2 transplant procedures performed almost equally in the ELN2017-IR group (2-year OS of 73.9% vs 70.8%; P = .5552). This post hoc analysis of the GIMEMA AML1310 trial confirms that the ELN2017 classification is able to accurately discriminate patients with different outcomes and who may benefit from different transplant strategies. This trial was registered as EudraCT number 2010-023809-36 and at www.clinicaltrials.gov as #NCT01452646.

Poly(ADP-Ribose) Polymerase Inhibitors for Arsenic Trioxide-Resistant Acute Promyelocytic Leukemia: Synergistic In Vitro Antitumor Effects with Hypomethylating Agents or High-Dose Vitamin C.

Arsenic trioxide (ATO) is an anticancer agent used for the treatment ofacute promyelocytic leukemia (APL). However, 5%-10% of patients fail to respond or experience disease relapse. Based on poly(ADP-ribose) polymerase (PARP) 1 involvement in the processing of DNA demethylation, here we have tested the in vitro susceptibility of ATO-resistant clones (derived from the human APL cell line NB4) to PARP inhibitors (PARPi) in combination with hypomethylating agents (azacitidine and decitabine) or high-dose vitamin C (ascorbate), which induces 5-hydroxymethylcytosine (5hmC)-mediated DNA demethylation. ATO-sensitive and -resistant APL cell clones were generated and initially analyzed for their susceptibility to five clinically used PARPi (olaparib, niraparib, rucaparib, veliparib, and talazoparib). The obtained PARPi IC50 values were far below (olaparib and niraparib), within the range (talazoparib), or above (rucaparib and veliparib) the C max reported in patients, likely as a result of differences in the mechanisms of their cytotoxic activity. ATO-resistant APL cells were also susceptible to clinically relevant concentrations of azacitidine and decitabine and to high-dose ascorbate. Interestingly, the combination of these agents with olaparib, niraparib, or talazoparib resulted in synergistic antitumor activity. In combination with ascorbate, PARPi increased the ascorbate-mediated induction of 5hmC, which likely resulted in stalled DNA repair and cytotoxicity. Talazoparib was the most effective PARPi in synergizing with ascorbate, in accordance with its marked ability to trap PARP1 at damaged DNA. These findings suggest that ATO and PARPi have nonoverlapping resistance mechanisms and support further investigation on PARPi combination with hypomethylating agents or high-dose ascorbate for relapsed/ATO-refractory APL, especially in frail patients. SIGNIFICANCE STATEMENT: This study found that poly(ADP-ribose) inhibitors (PARPi) show activity as single agents against human acute promyelocytic leukemia cells resistant to arsenic trioxide at clinically relevant concentrations. Furthermore, PARPi enhance the in vitro efficacy of azacitidine, decitabine, and high-dose vitamin C, all agents that alter DNA methylation. In combination with vitamin C, PARPi increase the levels of 5-hydroxymethylcytosine, likely as a result of altered processing of the oxidized intermediates associated with DNA demethylation.

Unraveling the mechanisms behind iron overload and ineffective hematopoiesis in myelodysplastic syndromes.

Myelodysplastic syndromes (MDS) are a group of clonally-acquired blood disorders characterized by ineffective hematopoiesis leading to cytopenias. Red blood cell transfusions are an important component of supportive care in patients with MDS. Prolonged exposure to transfusions can lead to iron overload, which results in iron-induced toxicity caused by the production of reactive oxygen species (ROS). ROS accumulation has detrimental effects also on hematopoietic stem cells and may contribute to MDS progression. The observation that iron chelation improves hematologic parameters and reduces transfusion dependence further indicates that iron overload impairs hematopoiesis. Over the past decade, the mechanisms regulating iron homeostasis and the complex interplay between iron overload and toxicity, ineffective hematopoiesis, and transformation to leukemia have become clearer. In this narrative review, we provide an overview of recent findings pertaining to iron overload in patients with MDS and its effects on hematopoiesis. We also briefly discuss the position of chelation therapy in the context of the new developments.

High-dose ascorbate and arsenic trioxide selectively kill acute myeloid leukemia and acute promyelocytic leukemia blasts in vitro.

The use of high-dose ascorbate (ASC) for the treatment of human cancer has been attempted several decades ago and has been recently revived by several in vitro and in vivo studies in solid tumors. We tested the cytotoxic effects of ASC, alone or in combination with arsenic trioxide (ATO) in acute myeloid leukemia (AML) and acute promyelocytic leukemia (APL). Leukemic cell lines and primary blasts from AML and APL patients were treated with graded concentrations of ASC, alone or in association with standard concentration (1 µM) of ATO. The ASC/ATO combination killed myeloid blasts, including leukemic CD34+ cells, while sparing CD34+ progenitors obtained from normal cord blood and bone marrow. Actually, approximately one-third (11/36) of primary AML cases were highly sensitive to the ASC/ATO combination. The mechanism of cell killing appeared to be related to increased oxidative stress and overproduction of ROS in a non-quantitative fashion, which resulted in induction of apoptosis. These effects were reverted by the addition of the antioxidant N-Acetyl-Cysteine (NAC). In the APL NB4 model, ASC induced direct degradation of the PML and PML/RARA proteins via caspase activation, while the transcriptional repressor DAXX was recruited in re-constituted PML nuclear bodies. Our findings encourage the design of pilot studies to explore the potential clinical benefit of ASC alone or in combination with ATO in advanced AML and APL.

Panobinostat for the treatment of acute myelogenous leukemia.

INTRODUCTION: Therapeutic strategies in patients with acute myeloid leukemia (AML) have not changed significantly over the last decades. Appropriate strategies are ultimately driven by the assessment of patients' fitness to define suitability for intensive induction chemotherapy, which produces high initial remission rates but, increased likelihood of relapse. Old/unfit AML patients still represent an urgent and unmet therapeutic need. Epigenetic deregulation represents a strategic characteristic of AML pathophysiology whereby aberrant gene transcription provides an advantage to leukemic cell survival. Efforts to re-establish impaired epigenetic regulation include hypomethylating agents and histone deacetylase inhibitors (HDACi). AREAS COVERED: The review discusses the underlying mechanisms leading to disruption of lysine acetyltransferases (KAT or HAT)/deacetylase (KDAC or HDAC) balance and the rationale for using the HDACi panobinostat (LBH-589) in AML. EXPERT OPINION: Although panobinostat has produced significant results in myeloma, its efficacy remains limited in AML. Panobinostat exerts pleiotropic activity and lack of specificity, which likely contributes to its inadequate safety in elderly AML patients. Phase I-II trials, utilizing panobinostat associated with well-known chemotherapeutic agents are ongoing and combinations with other druggable targets may likely be evaluated in future trials. The clinical use of this HDACi in AML the near future does not appearing promising.

Health-related quality of life in transfusion-dependent patients with myelodysplastic syndromes: a prospective study to assess the impact of iron chelation therapy.

OBJECTIVE: The primary objective of this study was to evaluate the health-related quality of life (HRQOL) in lower-risk, transfusion-dependent patients with myelodysplastic syndromes (MDS) treated with deferasirox. A secondary objective was to investigate the relationship between HRQOL, serum ferritin levels and transfusion dependency. PATIENTS AND METHODS: This was a prospective multicentre study enrolling 159 patients, of whom 152 received at least one dose of deferasirox. HRQOL was assessed with the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30) at baseline and then at 3, 6, 9 and 12 months. Primary analysis was performed estimating mean HRQOL scores over time by a linear mixed model on selected scales. RESULTS: The median age of treated patients was 72 years (range 24-87 years). No statistically significant changes over time were found in mean scores for global health status/quality of life (p=0.564), physical functioning (p=0.409) and fatigue (p=0.471) scales. Also, no significant changes were found for constipation (p=0.292), diarrhoea (p=0.815) and nausea and vomiting (p=0.643). Serum ferritin levels were not associated with HRQOL outcomes. A higher patient-reported baseline pain severity was an independent predictive factor of an earlier achievement of transfusion independence with a HR of 1.032 (99% CI 1.004 to 1.060; p=0.003). CONCLUSIONS: HRQOL of transfusion-dependent patients with MDS receiving deferasirox therapy remains stable over time. HRQOL assessment might also provide important predictive information on treatment outcomes. TRIAL REGISTRATION NUMBER: NCT00469560.

An increase in hemoglobin, platelets and white blood cells levels by iron chelation as single treatment in multitransfused patients with myelodysplastic syndromes: clinical evidences and possible biological mechanisms.

Iron chelation therapy can improve hematopoiesis in myelodysplastic syndromes. Only few studies showed hematologic improvement with deferoxamine, and the erythroid responses were correlated with good compliance to long-term treatment. Indeed, single-case reports and data from clinical trials testing the efficacy of deferasirox reported hematologic improvements with varying rates of response in different lineages. Overall, about 760 myelodysplastic syndrome (MDS) patients with iron overload receiving deferasirox were included in six different studies, and an increase in hemoglobin level was reported to range from 6 to 44.5%, an increase in platelet count from 13 to 61%, and in neutrophil count from 3 to 76%. In all the published studies, hematologic improvements were not related to serum ferritin or to non-total binding iron changes; indeed, other pathways were indicated as possible pathogenetic mechanisms, such as decreased NF-kB activity, modulation of mTOR signalling, and reduced reactive oxygen species. The aims of this review are to provide all available information relating clinical and hematologic changes after chelation therapy and to discuss potential mechanisms involved in such responses.

Deferasirox chelation therapy in patients with transfusion-dependent MDS: a 'real-world' report from two regional Italian registries: Gruppo Romano Mielodisplasie and Registro Basilicata.

Deferasirox (DFX) is an orally administered iron chelator approved for use in patients with transfusion-dependent iron overload due to myelodysplastic syndromes (MDS). The safety and efficacy of DFX has been explored in clinical trial settings, but there is little data on unselected patients with MDS. The aim of this study was to retrospectively evaluate the safety, compliance, efficacy and effect on haematopoiesis of DFX in a large 'real-world' MDS population. One hundred and eighteen patients with transfusion-dependent MDS were treated with DFX across 11 centres in Italy. Serum ferritin levels, haematological response, dosing, adverse events and transfusion dependence were recorded at baseline, 3, 6, 12 and 24 months following initiation of treatment. DFX reduced mean serum ferritin levels from 1790 to 1140 ng/mL (P < 0.001), with 7.1% of patients achieving transfusion independence. Significant haematological improvement was seen in erythroid (17.6%), platelet (5.9%) and neutrophil counts (7.1%). Adverse events were reported in 47.5% of patients, including gastrointestinal and renal toxicity. Regression analysis showed that higher starting doses of DFX are associated with transfusion independence at 24 months. DFX is a safe, effective treatment for transfusion-dependent MDS that can lead to transfusion independence and haematological improvement in a subset of patients.

Deferasirox for transfusion-dependent patients with myelodysplastic syndromes: safety, efficacy, and beyond (GIMEMA MDS0306 Trial).

BACKGROUND: In the absence of randomized, controlled trial data to support iron chelation therapy in transfusion-dependent patients with myelodysplastic syndromes (MDS), continued evidence from large prospective clinical trials evaluating the efficacy and safety of iron chelation therapy in this patient population is warranted. METHODS: The safety and efficacy of deferasirox was examined in a prospective, open-label, single-arm, multicenter trial of transfusion-dependent patients with International Prognostic Scoring System low- or intermediate-1-risk MDS and evidence of transfusion-related iron overload. The effects of deferasirox therapy on hematological response and disease progression were also examined. RESULTS: Of 159 participants enrolled from 37 Italian centers, 152 received ≥1 dose of deferasirox (initiated at 10-20 mg/kg/day and titrated as appropriate), and 68 completed the study. Of 84 patients who discontinued deferasirox therapy, 22 died during the trial, and 28 withdrew due to an adverse event (AE). Fourteen treatment-related grade 3 AEs occurred in 11 patients, whereas no grade 4 or 5 drug-related AEs were reported. Significant risks for dropout were a higher serum ferritin level at baseline, a higher MDS-Specific Comorbidity Index, and a shorter diagnosis-enrollment interval. Median serum ferritin level fell from 1966 ng/mL to 1475 ng/mL (P < 0.0001). The cumulative incidence of transfusion independence, adjusted for death and disease progression, was 2.6%, 12.3%, and 15.5% after 6, 9, and 12 months, respectively. CONCLUSIONS: Deferasirox therapy in transfusion-dependent patients with MDS was moderately well tolerated and effectively lowered serum ferritin levels. Positive hematological responses were observed, and a subset of patients achieved transfusion independence.

Iron in Hodgkin's lymphoma.

Anemia is a frequent finding of Hodgkin's lymphoma (HL) diagnosis. It is usually mild, with hemoglobin levels between 10 and 12 g/dl; it is rarely (<10% of cases) a result of bone marrow infiltration; and it displays the characteristics of the anemia of chronic disease due to abnormalities in iron metabolism. The inflammatory cytokine IL-6 is frequently up-regulated in Hodgkin's lymphoma, and IL-6 levels are strongly associated with hepcidin, the main regulator of iron metabolism. Elevated hepcidin levels result in iron restriction and signs of anemia of chronic disease. In addition, the abundant microenvironment surrounding the neoplastic Hodgkin's and Reed-Sternberg cells may contribute to alterations in iron metabolism. Tumor-infiltrating macrophages can sequester iron using scavenger receptors. Iron-restricted anemia at HL diagnosis can be aggravated by intensive chemotherapy, and iron overload may become clinically relevant in heavily treated patients with relapsed or refractory disease undergoing high-dose chemotherapy and stem cell transplantation.

New treatments for myelodysplastic syndromes.

In the last decade, significant advances have been made in the treatment of patients with Myelodysplastic Syndromes (MDS). Although best supportive care continues to have an important role in the management of MDS, to date the therapeutic approach is diversified according to the IPSS risk group, karyotype, patient's age, comorbidities, and compliance. Hematopoietic growth factors play a major role in lower risk MDS patients, and include high dose erithropoiesis stimulating agents and thrombopoietic receptor agonists. Standard supportive care should also include iron chelating therapy to reduce organ damage related to iron overload in transfusion-dependent patients. Biologic therapies have been introduced in MDS, as lenalidomide, which has been shown to induce transfusion independence in most lower risk MDS patients with del5q. Hypomethylating agents have shown efficacy in INT-2/high risk MDS patients, reducing the risk of leukemic transformation and increasing survival. Other agents under development for the treatment of MDS include histone deacetylase inhibitors, farnesyltransferase inhibitors, clofarabine and ezatiostat.