Retinoic acid and arsenic trioxide in the treatment of acute promyelocytic leukemia: current perspectives

All-trans retinoic acid exhibits anti-proliferative and differentiating activity in Merkel cell carcinoma cells via retinoid pathway modulation

BACKGROUND

The limited therapies available for treating Merkel cell carcinoma (MCC), a highly aggressive skin neoplasm, still pose clinical challenges, and novel treatments are required. Targeting retinoid signalling with retinoids, such as all-trans retinoic acid (ATRA), is a promising and clinically useful antitumor approach. ATRA drives tumour cell differentiation by modulating retinoid signalling, leading to anti-proliferative and pro-apoptotic effects. Although retinoid signalling is dysregulated in MCC, ATRA activity in this tumour is unknown. This study aimed to evaluate the impact of ATRA on the pathological phenotype of MCC cells.

METHODS

The effect of ATRA was tested in various Merkel cell polyomavirus-positive and polyomavirus-negative MCC cell lines in terms of cell proliferation, viability, migration and clonogenic abilities. In addition, cell cycle, apoptosis/cell death and the retinoid gene signature were evaluated upon ATRA treatments.

RESULTS

ATRA efficiently impaired MCC cell proliferation and viability in MCC cells. A strong effect in reducing cell migration and clonogenicity was determined in ATRA-treated cells. Moreover, ATRA resulted as strongly effective in arresting cell cycle and inducing apoptosis/cell death in all tested MCC cells. Enrichment analyses indicated that ATRA was effective in modulating the retinoid gene signature in MCC cells to promote cell differentiation pathways, which led to anti-proliferative and pro-apoptotic/cell death effects.

CONCLUSIONS

These results underline the potential of retinoid-based therapy for MCC management and might open the way to novel experimental approaches with other retinoids and/or combinatorial treatments.

Cardiac glycoside ouabain efficiently targets leukemic stem cell apoptotic machinery independent of cell differentiation status

BACKGROUND

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy characterized by an accumulation of immature leukemic myeloblasts initiating from leukemic stem cells (LSCs)-the subpopulation that is also considered the root cause of chemotherapy resistance. Repurposing cardiac glycosides to treat cancers has gained increasing attention and supporting evidence, but how cardiac glycosides effectively target LSCs, e.g., whether it involves cell differentiation, remains largely unexplored.

METHODS

Digoxin, a user-designed digitoxigenin-α-L-rhamnoside (D6-MA), and ouabain were tested against various human AML-derived cells with different maturation phenotypes. Herein, we established two study models to specifically determine the effects of cardiac glycosides on LSC death and differentiation-one allowed change in dynamics of LSCs and leukemic progenitor cells (LPCs), while another maintained their undifferentiated status. Regulatory mechanisms underlying cardiac glycoside-induced cytotoxicity were investigated and linked to cell cycle distribution and apoptotic machinery.

RESULTS

Primitive AML cells containing CD34+ LSCs/LPCs were very responsive to nanomolar concentrations of cardiac glycosides, with ouabain showing the greatest efficiency. Ouabain preferentially induces caspase-dependent apoptosis in LSCs, independent of its cell differentiation status, as evidenced by (i) the tremendous induction of apoptosis by ouabain in AML cells that acquired less than 15% differentiation and (ii) the higher rate of apoptosis in enriched LSCs than in LPCs. We sorted LSCs and LPCs according to their cell cycle distribution into G0/G1, S, and G2/M cells and revealed that G0/G1 cells in LSCs, which was its major subpopulation, were the top ouabain responders, indicating that the difference in ouabain sensitivity between LSCs and LPCs involved both distinct cell cycle distribution and intrinsic apoptosis regulatory mechanisms. Further, Mcl-1 and c-Myc, which were differentially expressed in LSCs and LPCs, were found to be the key apoptosis mediators that determined ouabain sensitivity in AML cells. Ouabain induces a more rapid loss of Mcl-1 and c-Myc in LSCs than in LPCs via the mechanisms that in part involve an inhibition of Mcl-1 protein synthesis and an induction of c-Myc degradation.

CONCLUSIONS

Our data provide new insight for repurposing cardiac glycosides for the treatment of relapsed/refractory AML through targeting LSCs via distinct cell cycle and apoptosis machinery. Video Abstract.

Tissue factor activates the coagulation cascade in mouse models of acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is associated with a high risk of bleeding and thrombosis. APL patients have an activated coagulation system, hyperfibrinolysis, and thrombocytopenia. APL cells express tissue factor (TF), a receptor and cofactor for factor VII/VIIa. This study had 2 goals. Firstly, we measured biomarkers of coagulation and fibrinolysis activation as well as platelet counts and bleeding in both mouse xenograft and allograft models of APL. Secondly, we determined the effect of inhibiting TF on the activation of coagulation in these models. We observed increased levels of plasma thrombin-antithrombin complexes (TAT), D-dimer, and plasmin-antiplasmin complexes, reduced platelet counts, and increased tail bleeding in both mouse models of APL. Fibrinogen levels decreased in the xenograft model but not in the allograft model. In contrast, the red blood cell count decreased in the allograft model but not in the xenograft model. Inhibition of APL-derived human TF with an anti-human TF monoclonal antibody reduced the level of TAT, increased platelet count, and normalized tail bleeding in a xenograft model. Inhibition of all sources of TF (APL cells and host cells) in the allograft model with a rat anti-mouse TF monoclonal antibody decreased the levels of TAT but did not affect the platelet count. Our study demonstrates that TF plays a central role in the activation of coagulation in both the xenograft and allograft mouse models of APL. These APL mouse models can be used to investigate the mechanisms of coagulopathy and thrombocytopenia in APL.

CD71-mediated liposomal arsenic-nickel complex combined with all-trans retinoic acid for the efficacy of acute promyelocytic leukemia

Clinically, arsenic trioxide (ATO) was applied to the treatment of acute promyelocytic leukemia (APL) as a reliable and effective frontline drug. However, the administration regimen of AsⅢ was limited due to its fast clearance, short therapeutic window and toxicity as well. Based on CD71 overexpressed on APL cells, in present study, a transferrin (Tf)-modified liposome (LP) was established firstly to encapsulate AsⅢ in arsenic-nickel complex by nickel acetate gradient method. The AsⅢ-loaded liposomes (AsLP) exhibited the feature of acid-sensitive release in vitro. Tf-modified AsLP (Tf-AsLP) were specifically taken up by APL cells and the acidic intracellular environment triggered liposome to release AsⅢ which stimulated reactive oxygen species level and caspase-3 activity. Tf-AsLP prolonged half-life of AsⅢ in blood circulation, lowered systemic toxicity, and promoted apoptosis and induced cell differentiation at lesion site in vivo. Considering that ATO combined with RA is usually applied as the first choice in clinic for APL treatment to improve the therapeutic effect, accordingly, a Tf-modified RA liposome (Tf-RALP) was designed to reduce the severe side effects of free RA and assist Tf-AsLP for better efficacy. As expected, the tumor inhibition rate of Tf-AsLP was improved significantly with the combination of Tf-RALP on subcutaneous tumor model. Furthermore, APL orthotopic NOD/SCID mice model was established by 60CO irradiation and HL-60 cells intravenously injection. The effect of co-administration (Tf-AsLP + Tf-RALP) was also confirmed to conspicuous decrease the number of leukemia cells in the circulatory system and prolong the survival time of APL mice by promoting the APL cells' apoptosis and differentiation in peripheral blood and bone marrow. Collectively, Tf-modified acid-sensitive AsLP could greatly reduce the systemic toxicity of free drug. Moreover, Tf-AsLP combined with Tf-RALP could achieve better efficacy. Thus, transferrin-modified AsⅢ liposome would be a novel clinical strategy to improve patient compliance, with promising translation prospects.

Tocotrienols-enriched Self-nanoemulsifying Drug Delivery System Enhances the Antileukemic Activity of All-trans Retinoic Acid but not Electrocardiogram Alterations Evoked by Its Combination with Arsenic Trioxide

All-trans retinoic acid and arsenic trioxide are the leading choices for the treatment of acute promyelocytic leukemia. Notwithstanding the impressive differentiative properties of all-trans retinoic acid and the apoptotic properties of arsenic trioxide, some problems still occur in acute promyelocytic leukemia treatment. These problems are due to patients' relapses, mainly related to changes in the ligand-binding domain of RARα (retinoic acid receptor α) and the cardiotoxic effects caused by arsenic trioxide. We previously developed a self-nanoemulsifying drug delivery system enriched with tocotrienols to deliver all-trans retinoic acid (SNEDDS-TRF-ATRA). Herein, we have evaluated if tocotrienols can help revert ATRA resistance in an APL cell line (NB4-R2 compared to sensitive NB4 cells) and mitigate the cardiotoxic effects of arsenic trioxide in a murine model. SNEDDS-TRF-ATRA enhanced all-trans retinoic acid cytotoxicity in NB4-R2 (resistant) cells but not in NB4 (sensitive) cells. Moreover, SNEDDS-TRF-ATRA did not significantly change the differentiative properties of all-trans retinoic acid in both NB4 and NB4-R2 cells. Combined administration of SNEDDS-TRF-ATRA and arsenic trioxide could revert QTc interval prolongation caused by ATO but evoked other electrocardiogram alterations in mice, such as T wave flattening. Therefore, SNEDDS-TRF-ATRA may enhance the antileukemic properties of all-trans retinoic acid but may influence ECG changes caused by arsenic trioxide administration. SNEDDS-TRF-ATRA presents cytotoxicity in resistant APL cells (NB4-R2). Combined administration of ATO and SNEDDS-TRF-ATRA in mice prevented the prolongation of the QTc interval caused by ATO but evoked ECG abnormalities such as T wave flattening.

Inhibition of O-GlcNAcase Inhibits Hematopoietic and Leukemic Stem Cell Self-Renewal and Drives Dendritic Cell Differentiation via STAT3/5 Signaling

Myeloid differentiation blockage at immature and self-renewing stages is a common hallmark across all subtypes of acute myeloid leukemia (AML), despite their genetic heterogeneity. Metabolic state is an important regulator of hematopoietic stem cell (HSC) self-renewal and lineage-specific differentiation as well as several aggressive cancers. However, how O-GlcNAcylation, a nutrient-sensitive posttranslational modification of proteins, contributes to both normal myelopoiesis and AML pathogenesis remains largely unknown. Using small molecule inhibitors and the CRISPR/Cas9 system, we reveal for the first time that inhibition of either OGA or OGT, which subsequently caused an increase or decrease in cellular O-GlcNAcylation, inhibits the self-renewal and maintenance of CD34+ hematopoietic stem/progenitor cells (HSPCs) and leukemic stem/progenitor cells and drives normal and malignant myeloid differentiation. We further unveiled the distinct roles of OGA and OGT inhibition in lineage-specific differentiation. While OGT inhibition induces macrophage differentiation, OGA inhibition promotes the differentiation of both CD34+ HSPCs and AML cells into dendritic cells (DCs), in agreement with an upregulation of a multitude of genes involved in DC development and function and their ability to induce T-cell proliferation, via STAT3/5 signaling. Our novel findings provide significant basic knowledge that could be important in understanding AML pathogenesis and overcoming differentiation blockage-agnostic to the genetic background of AML. Additionally, the parallel findings in normal HSPCs may lay the groundwork for future cellular therapy as a means to improve the ex vivo differentiation of normal DCs and macrophages.

The recognition of oral manifestations of haematological disease saves lives: a case report

BACKGROUND

Acute Leukaemias are haematological disorders characterised by the proliferation of immature white blood cells in the bone marrow and/or peripheral blood. Oral manifestations of leukaemia are common and may be the first sign of the disease. The clinical presentation of these Acute Leukaemias may include neutropenic sepsis, hyperviscocity and coagulopathy which confer a potential morbidity and mortality. Clinicians must be able to recognise this pattern of presentation.

CASE REPORT

We report a 34-year-old female who was referred to the Oral and Maxillofacial Surgery department with acute dental pain and pericoronitis. She subsequently had a simple dental extraction but re-presented with a bleeding socket that did not respond to local treatment. Investigation of this led to a diagnosis of Acute Promyelocytic Leukemia (APL). She was admitted under the care of the haematology team for urgent, life-saving, treatment.

CONCLUSIONS

Early diagnosis and treatment of the Acute Leukaemias can be life saving. The oral manifestations of disease are common and may be the first sign. Clinicians must be able to recognise this pattern of presentation and arrange urgent investigation and specialist management.

CLINICAL/CPD RELEVANCE

This case report discusses leukaemia and highlights the important role General Dental Practitioners can play in early diagnosis. We frame a safe approach to managing these patients in a typical case. Whilst this disease subtype is rare, the learning points can be universally applied.

Vitamin D Derivatives in Acute Myeloid Leukemia: The Matter of Selecting the Right Targets

Acute myeloid leukemia (AML) is an aggressive and often fatal hematopoietic malignancy. A very attractive way to treat myeloid leukemia, called “differentiation therapy”, was proposed when in vitro studies showed that some compounds are capable of inducing differentiation of AML cell lines. One of the differentiation-inducing agents, all-trans-retinoic acid (ATRA), which can induce granulocytic differentiation in AML cell lines, has been introduced into clinics to treat patients with acute promyelocytic leukemia (APL) in which a PML-RARA fusion protein is generated by a chromosomal translocation. ATRA has greatly improved the treatment of APL. Since 1,25-dihydroxyvitamin D (1,25D) is capable of inducing monocytic differentiation of leukemic cells, the idea of treating other AMLs with vitamin D analogs was widely accepted. However, early clinical trials in which cancer patients were treated either with 1,25D or with analogs did not lead to conclusive results. Recent results have shown that AML types with certain mutations, such as isocitrate dehydrogenase (IDH) mutations, may be the right targets for differentiation therapy using 1,25D, due to upregulation of vitamin D receptor (VDR) pathway.

Arsenic Trioxide and Venetoclax Synergize against AML Progenitors by ROS Induction and Inhibition of Nrf2 Activation

Venetoclax (VEN) in combination with hypomethylating agents induces disease remission in patients with de novo AML, however, most patients eventually relapse. AML relapse is attributed to the persistence of drug-resistant leukemia stem cells (LSCs). LSCs need to maintain low intracellular levels of reactive oxygen species (ROS). Arsenic trioxide (ATO) induces apoptosis via upregulation of ROS-induced stress to DNA-repair mechanisms. Elevated ROS levels can trigger the Nrf2 antioxidant pathway to counteract the effects of high ROS levels. We hypothesized that ATO and VEN synergize in targeting LSCs through ROS induction by ATO and the known inhibitory effect of VEN on the Nrf2 antioxidant pathway. Using cell fractionation, immunoprecipitation, RNA-knockdown, and fluorescence assays we found that ATO activated nuclear translocation of Nrf2 and increased transcription of antioxidant enzymes, thereby attenuating the induction of ROS by ATO. VEN disrupted ATO-induced Nrf2 translocation and augmented ATO-induced ROS, thus enhancing apoptosis in LSCs. Using metabolic assays and electron microscopy, we found that the ATO+VEN combination decreased mitochondrial membrane potential, mitochondria size, fatty acid oxidation and oxidative phosphorylation, all of which enhanced apoptosis of LSCs derived from both VEN-sensitive and VEN-resistant AML primary cells. Our results indicate that ATO and VEN cooperate in inducing apoptosis of LSCs through potentiation of ROS induction, suggesting ATO+VEN is a promising regimen for treatment of VEN-sensitive and -resistant AML.

CD44-fibrinogen binding promotes bleeding in acute promyelocytic leukemia by in situ fibrin(ogen) deposition

Early haemorrhagic death is still the main obstacle for the successful treatment of acute promyelocytic leukaemia (APL). However, the mechanisms underlying haemostatic perturbations in APL have not been fully elucidated. Here, we report that CD44 on the membrane of APL blasts and NB4 cells ligated bound fibrinogen, resulting in in situ deposition of fibrin and abnormal fibrin distribution. Clots formed by leukaemic cells in response to CD44 and fibrinogen interaction exhibited low permeability and resistance to fibrinolysis. Using flow cytometry and confocal microscopy, we found that CD44 was also involved in platelet and leukaemic cell adhesion. CD44 bound activated platelets but not resting platelets through interaction with P-selectin. APL cell-coated fibrinogen-activated platelets directly induce enhanced procoagulant activity of platelets. In vivo studies revealed that CD44 knockdown shortened bleeding time, increased the level of fibrinogen, and elevated the number of platelets by approximately 2-fold in an APL mouse model. Moreover, CD44 expression on leukaemic cells in an APL mouse model was not only associated with bleeding complications but was also related to the wound healing process and the survival time of APL mice. Collectively, our results suggest that CD44 may be a potential intervention target for preventing bleeding complications in APL.

Genetic and Epigenetic Signatures in Acute Promyelocytic Leukemia Treatment and Molecular Remission

Acute myeloid leukemia (AML) is an aggressive, heterogeneous group of malignancies with different clinical behaviors and different responses to therapy. For many types of cancer, finding cancer early makes it easier to treat. Identifying prognostic molecular markers and understanding their biology are the first steps toward developing novel diagnostic tools or therapies for patients with AML. In this study, we defined proteins and genes that can be used in the prognosis of different acute leukemia cases and found possible uses in diagnostics and therapy. We analyzed newly diagnosed acute leukemia cases positive for t (15; 17) (q22; q21) PML-RAR alpha, acute promyelocytic leukemia (APL). The samples of bone marrow cells were collected from patients at the diagnosis stage, as follow-up samples during standard treatment with all-trans retinoic acid, idarubicin, and mitoxantrone, and at the molecular remission. We determined changes in the expression of genes involved in leukemia cell growth, apoptosis, and differentiation. We observed that WT1, CALR, CAV1, and MYC genes’ expression in all APL patients with no relapse history was downregulated after treatment and could be potential markers associated with the pathology, thereby revealing the potential value of this approach for a better characterization of the prediction of APL outcomes.

Cancer outcomes research - a European challenge Part II: Opportunities and priorities

In Part I of our review of cancer outcome research, we analysed pros and cons of various measures relevant to quantifying the burden of cancer. Based on our recommendations in Part I, we now discuss in Part II opportunities and priorities in four areas of outcome research: primary prevention; early detection screening; treatment; and quality‐of‐life assessment. We recommend the establishment of an infrastructure that facilitates high‐quality research in these areas: (a) progress in primary prevention can be assessed most directly by monitoring cancer incidence although the interpretation of temporal trends is notoriously confounded by numerous factors that complicate causal inference. (b) preventive screening, with the aim to prevent advanced disease, appears to work well in in some tumours but not in others. It will require randomized control trials (RCTs) to quantify benefits and harms although conclusive studies are increasingly difficult to undertake. We therefore propose learning screening programmes (randomization at the time of rolling out population‐based programmes) as the most feasible approach. (c) New therapeutic interventions tailored to the individual patient often require assessment in RCTs with rather complex and dynamic structure, making their design and analyses increasingly challenging but also more suited to be executed as academic, PI‐initiated trials. (d) We next discuss assessment of quality‐of‐life aspects. Quality of life is a neglected component in outcome research with an urgent need for development, validation and standardization. We finally recommend four initiatives that would pave the way for a valid and informative assessment of the goals for improved cancer control in Europe as defined by the European Academy of Cancer Sciences.

The multifaceted roles of mitochondria at the crossroads of cell life and death in cancer

Mitochondria are the cytoplasmic organelles mostly known as the "electric engine" of the cells; however, they also play pivotal roles in different biological processes, such as cell growth/apoptosis, Ca²⁺ and redox homeostasis, and cell stemness. In cancer cells, mitochondria undergo peculiar functional and structural dynamics involved in the survival/death fate of the cell. Cancer cells use glycolysis to support macromolecular biosynthesis and energy production ("Warburg effect"); however, mitochondrial OXPHOS has been shown to be still active during carcinogenesis and even exacerbated in drug-resistant and stem cancer cells. This metabolic rewiring is associated with mutations in genes encoding mitochondrial metabolic enzymes ("oncometabolites"), alterations of ROS production and redox biology, and a fine-tuned balance between anti-/proapoptotic proteins. In cancer cells, mitochondria also experience dynamic alterations from the structural point of view undergoing coordinated cycles of biogenesis, fusion/fission and mitophagy, and physically communicating with the endoplasmic reticulum (ER), through the Ca²⁺ flux, at the MAM (mitochondria-associated membranes) levels. This review addresses the peculiar mitochondrial metabolic and structural dynamics occurring in cancer cells and their role in coordinating the balance between cell survival and death. The role of mitochondrial dynamics as effective biomarkers of tumor progression and promising targets for anticancer strategies is also discussed.

Liposome nano-formulation with cationic polar lipid DOTAP and cholesterol as a suitable pH-responsive carrier for molecular therapeutic drug (all-trans retinoic acid) delivery to lung cancer cells

The molecular targeted drug ATRA demands a suitable carrier that delivers to the cancer site due to its poor bioavailability and drug resistance. ATRA, being a lipid with carboxylic acid, has been nano‐formulated as a cationic lipo‐ATRA with DOTAP:cholesterol:ATRA (5:4:1) and its pH‐responsive release, intracellular drug accumulation, and anticancer effect on human lung cancer (A549) cell line analysed. The analysis of the physicochemical characteristics of the developed lipo‐ATRA (0.8 µmol) revealed that the size of 231 ± 2.35 d.nm had a zeta potential of 6.4 ± 1.19 and an encapsulation efficiency of 93.7 ± 3.6%. The ATRA release from lipo‐ATRA in vitro was significantly (p ≤ 0.05) higher at acidic pH 6 compared to pH 7.5. The intracellular uptake of ATRA into lipo‐ATRA‐treated A549 cells was seven‐fold higher (0.007 ± 0.001 mg/ml) while only three‐fold uptake was observed in free ATRA treatment (0.003 ± 0.002 mg/ml). The lipo‐ATRA treatment caused a highly significant (p ≤ 0.001) decrease in percent cell viability at 48 h when compared with the free ATRA treatment. Overall, the results proved that the developed lipo‐ATRA has suitable physicochemical properties with enhanced ATRA release at acidic pH, while maintaining stability at physiologic pH and temperature. This resulted in an increased ATRA uptake by lung cancer cells with enhanced treatment efficiency. Hence, it is concluded that DOTAP lipo‐ATRA is a suitable carrier for ATRA delivery to solid cancer cells.

G2/M cell cycle arrest and apoptosis induced by COH-203 in human promyelocytic leukemia HL-60 cells

The combretastatin A-4/oltipraz hybrid (COH), 5-(3-amino-4-methoxyphenyl)-4-(3,4,5-trimethoxyphenyl)-3H-1,2-dithiole-3-one (COH-203) is one of the COH compounds synthesized by our previous study, which has been reported to affect a number of cancer cell lines, such as SGC-7901, KB, HT-1080, HepG2, SMMC-7721 and BEL-7402. The sensitivity of human acute leukemia cell lines to COH-203, and the mechanism underlying its anti-proliferative effects remain unknown, which was investigated in the present study. In the present study, it was demonstrated that COH-203 had notable time- and dose-dependent antiproliferative effects on the human acute promyelocytic leukemia HL-60 cell line. Furthermore, COH-203 treatment resulted in cell cycle arrest at G₂/M phase in a dose-dependent manner, and subsequently induced apoptosis. Western blot analysis revealed that upregulation of cyclin B was associated with G₂/M arrest. In addition, treatment with COH-203 resulted in downregulated expression of Bcl-2. This result revealed that COH-203-induced apoptosis in HL-60 cells may occur via the mitochondrial pathway in a caspase-dependent manner.

Genomic Abnormalities as Biomarkers and Therapeutic Targets in Acute Myeloid Leukemia

Simple Summary

AML is a heterogenous malignancy with a variety of underlying genomic abnormalities. Some of the genetic aberrations in AML have led to the development of specific inhibitors which were approved by the Food and Drug Administration (FDA) and are currently used to treat eligible patients. In this review, we describe five gene mutations for which approved inhibitors have been developed, the response of AML patients to these inhibitors, and the known mechanism(s) of resistance. This review also highlights the significance of developing function-based screens for target discovery in the era of personalized medicine.

Abstract

Acute myeloid leukemia (AML) is a highly heterogeneous malignancy characterized by the clonal expansion of myeloid stem and progenitor cells in the bone marrow, peripheral blood, and other tissues. AML results from the acquisition of gene mutations or chromosomal abnormalities that induce proliferation or block differentiation of hematopoietic progenitors. A combination of cytogenetic profiling and gene mutation analyses are essential for the proper diagnosis, classification, prognosis, and treatment of AML. In the present review, we provide a summary of genomic abnormalities in AML that have emerged as both markers of disease and therapeutic targets. We discuss the abnormalities of RARA, FLT3, BCL2, IDH1, and IDH2, their significance as therapeutic targets in AML, and how various mechanisms cause resistance to the currently FDA-approved inhibitors. We also discuss the limitations of current genomic approaches for producing a comprehensive picture of the activated signaling pathways at diagnosis or at relapse in AML patients, and how innovative technologies combining genomic and functional methods will improve the discovery of novel therapeutic targets in AML. The ultimate goal is to optimize a personalized medicine approach for AML patients and possibly those with other types of cancers.

Safety and efficacy of different doses of anthracyclines combined with arsenic trioxide and all-trans retinoic acid in the treatment of de novo acute promyelocytic leukemia

OBJECTIVES

The purpose of this study was to evaluate the efficacy and safety of different doses of anthracyclines combined with arsenic trioxide (ATO) and all-trans retinoic acid (ATRA) for induction in newly diagnosed acute promyelocytic leukemia (APL).

METHODS

One hundred and forty patients were included between January 2011 and December 2017. Seventy patients received low dose anthracycline, ATO and ATRA for induction chemotherapy; and other seventy patients received standard dose anthracycline, ATO and ATRA for induction chemotherapy.

RESULTS

The outcomes of both groups were similar: low dose group versus standard dose group: early mortality 5.7% vs. 10.0% (P = 0.532), disease-free survival (DFS), probabilities of overall-survival (OS) at 2 years 94.6% vs. 95.1% (P = 0.657), 92.8% vs. 88.2% (P = 0.951), respectively. However, the standard-dose group was associated with a longer duration of neutropenia (p < 0.001) and thrombocytopenia (p < 0.001), more volumes of platelets (p = 0.037) and red blood cell transfusions (p < 0.001), and a higher rate of infections (p = 0.042).

CONCLUSION

Low-dose group achieves outcomes similar to those of standard dose group for APL patients, but the low-dose group may be even safer than standard-dose group. So the low-dose anthracycline may be a better choice for newly diagnosed APL patients.

Arsenicals, the Integrated Stress Response, and Epstein-Barr Virus Lytic Gene Expression

Following our observation that clofoctol led to Epstein–Barr virus (EBV) lytic gene expression upon activation of the integrated stress response (ISR), we decided to investigate the impact of As₂O₃ on viral lytic gene expression. As₂O₃ has also been reported to activate the ISR pathway by its activation of the heme-regulated inhibitor (HRI). Our investigations show that As₂O₃ treatment leads to eIF2α phosphorylation, upregulation of ATF4 and TRB3 expression, and an increase of EBV Zta gene expression in lymphoid tumor cell lines as well as in naturally infected epithelial cancer cell lines. However, late lytic gene expression and virion production were blocked after arsenic treatment. In comparison, a small molecule HRI activator also led to increased Zta expression but did not block late lytic gene expression, suggesting that As₂O₃ effects on EBV gene expression are also mediated through other pathways.

Characteristics and clinical influence factors of arsenic species in plasma and their role of arsenic species as predictors for clinical efficacy in acute promyelocytic leukemia (APL) patients treated with arsenic trioxide

Background: Arsenic trioxide (ATO) is successfully applied to treat acute promyelocytic leukemia (APL). Arsenic species levels in blood are critical to reveal metabolic mechanism and relationship between arsenic species and clinical response. Characteristics and influence factors of arsenic species in APL patients have not been studied.Methods: 305 plasma samples from APL patients treated with ATO were analyzed using HPLC-HG-AFS. Trough concentration (C_trough), distribution, methylation levels of arsenic species were evaluated. The influence factors on arsenic species levels of plasma and association between arsenic concentrations and clinical efficacy were explored.Results: C_trough of arsenic in effective treatment groups provide basis for defining the target range of arsenic plasma concentrations in APL patients treated with ATO. Distribution trends: DMA^V > As^III, MMA^V> As^V (p < 0.0001) for continuous slow-rate (CS) infusion and DMA^V > MMA^V > As^III > As^V (p < 0.0001) for conventional infusion. Infusion methods and combined medication may affect arsenic metabolism. There was a weak correlation between ATO dose and plasma C_trough of arsenic species. C_trough of plasma arsenic species had predictive value for treatment efficacy.Conclusion: Arsenic concentration monitoring in APL patients treated with ATO is required. These findings are critical to optimize treatment outcomes of ATO therapy.

Drug Combination in Cancer Treatment-From Cocktails to Conjugated Combinations

It is well recognized today that anticancer drugs often are most effective when used in combination. However, the establishment of chemotherapy as key modality in clinical oncology began with sporadic discoveries of chemicals that showed antiproliferative properties and which as a first attempt were used as single agents. In this review we describe the development of chemotherapy from its origins as a single drug treatment with cytotoxic agents to polydrug therapy that includes targeted drugs. We discuss the limitations of the first chemotherapeutic drugs as a motivation for the establishment of combined drug treatment as standard practice in spite of concerns about frequent severe, dose limiting toxicities. Next, we introduce the development of targeted treatment as a concept for advancement within the broader field of small-molecule drug combination therapy in cancer and its accelerating progress that was boosted by recent scientific and technological progresses. Finally, we describe an alternative strategy of drug combinations using drug-conjugates for selective delivery of cytotoxic drugs to tumor cells that potentiates future improvement of drug combinations in cancer treatment. Overall, in this review we outline the development of chemotherapy from a pharmacological perspective, from its early stages to modern concepts of using targeted therapies for combinational treatment.

Microfluidic-Based Detection of AML-Specific Biomarkers Using the Example of Promyelocyte Leukemia

A microfluidic assay for the detection of promyelocytic leukemia (PML)-retinoic acid receptor α (RARα) fusion protein was developed. This microfluidic-based system can be used for rapid personalized differential diagnosis of acute promyelocyte leukemia (APL) with the aim of early initiation of individualized therapy. The fusion protein PML-RARα occurs in 95% of acute promyelocytic leukemia cases and is considered as diagnostically relevant. The fusion protein is formed as a result of translocation t(15,17) and is detected in the laboratory by fluorescence in situ hybridization (FISH) or reverse transcriptase polymerase chain reaction (RT-PCR). Diagnostic methods require many laboratory steps with specialized staff. The developed microfluidic assay includes a sandwich enzyme-linked immunosorbent assay (ELISA) system for PML-RARα on surface of magnetic microparticles in a microfluidic chip. A rapid detection of PML-RARα in cell lysates is achieved in less than one hour. A biotinylated PML-antibody on the surface of magnetic streptavidin coated microparticles is used as capture antibody. The bound translocation product is detected by a RARα antibody conjugated with horseradish peroxidase and the substrate QuantaRed. The analysis is performed in microfluidic channels which involves automated liquid processing with stringent washing and short incubation times. The results of the developed assay show that cell lysates of PML-RARα-positive cells (NB-4) can be clearly distinguished from PML-RARα-negative cells (HL-60, MV4-11).

The History of the Chemo-Free Model in the Treatment of Acute Promyelocytic Leukemia

Acute promyelocytic leukemia (APL) has become a highly curable disease after four decades of endeavors. Thanks to the efforts of investigators throughout the world, the chemo-free concept has become a reality for both low- and high-risk patients. All-trans retinoic acid (ATRA) plus arsenic trioxide (ATO) without chemotherapy has become a first-line treatment for newly diagnosed APL and has been adopted in guidelines or expert recommendations from the NCCN and ELN and in China. Though the regimen has achieved great success, challenges still exist. The rate of early death still has not diminished significantly and is a major obstacle to curing all patients. Leukocytosis is the most important factor for ED, and completely abandoning chemotherapy is dangerous for certain patients in practice. To narrow the gap between guidelines and practice, this review aims to examine the history of the chemo-free model for the treatment of APL in the arsenic-alone era (1974–2002) and the arsenic plus ATRA era (2002–present) and provide practical considerations regarding early death.

Role of cofilin‑1 in arsenic trioxide‑induced apoptosis of NB4‑R1 cells

All-trans retinoic acid (ATRA) and arsenic trioxide (As₂O₃) are currently first-line treatments for acute promyelocytic leukemia (APL). However, a number of patients with APL are resistant to ATRA but still sensitive to As₂O₃, and the underlying mechanisms of this remain unclear. In the present study, two-dimensional gel electrophoresis, mass spectrometry and other proteomic methods were applied to screen and identify the differentially expressed proteins between the retinoic acid-sensitive cell lines and drug-resistant cell lines. The results demonstrated that in retinoic acid-resistant NB4-R1 cells, the protein expression of cofilin-1 was markedly increased compared with that in the drug-sensitive NB4 cells. Subsequently, the effects of cofilin-1 on As₂O₃-induced apoptosis in NB4-R1 cells were further investigated. The results revealed that cell viability was markedly suppressed and apoptosis was increased in the As₂O₃-treated NB4-R1 cells, with increased expression levels of cleaved-poly (ADP-ribose) polymerase and cleaved-caspase 12. Cofilin-1 expression was significantly decreased at both the mRNA and protein levels in the As₂O₃-treated group compared with the control. Western blotting further revealed that As₂O₃ treatment decreased the cytoplasmic cofilin-1 level but increased its expression in the mitochondrion. However, the opposite effects of As₂O₃ on the cytochrome C distribution were found in NB4-R1 cells. This suggested that As₂O₃ can induce the transfer of cofilin-1 from the cytoplasm to mitochondria and trigger the release of mitochondrial cytochrome C in NB4-R1 cells. Moreover, cofilin-1 knockdown by its specific short hairpin RNA significantly suppressed As₂O₃-induced NB4-R1 cell apoptosis and inhibited the release of mitochondrial cytochrome C. Whereas, overexpression of cofilin-1 using a plasmid vector carrying cofilin-1 increased the release of cytochrome C into the cytoplasm from the mitochondria in As₂O₃-treated NB4-R1 cells. In conclusion, cofilin-1 played a role in As₂O₃-induced NB4-R1 cell apoptosis and it might be a novel target for APL treatment.

Comparison of gene regulatory networks to identify pathogenic genes for lymphoma

Lymphoma is the most complicated cancer that can be divided into several tens of subtypes. It may occur in any part of body that has lymphocytes, and is closely correlated with diverse environmental factors such as the ionizing radiation, chemocarcinogenesis, and virus infection. All the environmental factors affect the lymphoma through genes. Identifying pathogenic genes for lymphoma is consequently an essential task to understand its complexity in a unified framework. In this paper, we propose a new method to expose high-confident edges in gene regulatory networks (GRNs) for a total of 32 organs, called Filtered GRNs (f-GRNs), comparison of which gives us a proper reference for the Lymphoma, i.e. the B-lymphocytes cells, whose f-GRN is closest with that for the Lymphoma. By using the Gene Ontology and Biological Process analysis we display the differences of the two networks' hubs in biological functions. Matching with the Genecards shows that most of the hubs take part in the genetic information transmission and expression, except a specific gene of Retinoic Acid Receptor Alpha (RARA) that encodes the retinoic acid receptor. In the lymphoma, the genes in the RARA ego-network are involved in two cancer pathways, and the RARA is present only in these cancer pathways. For the lymphoid B cells, however, the genes in the RARA ego-network do not participate in cancer-related pathways.

Retrospective analysis of data from 73 patients with childhood acute promyelocytic leukaemia receiving modified chemotherapy: a single-centre study

PURPOSE

Early death (ED) and treatment-related toxicity emerge as two major barriers for curing paediatric acute promyelocytic leukaemia (APL) patients. This study aims to investigate the effect of idarubicin on controlling hyperleukocytosis in induction therapy and the efficacy and safety of a risk-adapted attenuated consolidation chemotherapy.

METHODS

We summarised the characteristics and long-term outcomes of 73 paediatric APL patients treated at our institution from February 2002 to October 2018, during which treatment protocols evolved over three periods and were defined as protocol A, B and C chronologically. All of the patients received an all-trans retinoic acid (ATRA)-arsenic trioxide (ATO) combination remission induction therapy, with hydroxyurea (group A) or idarubicin (group B and C) to control hyperleukocytosis. Consolidation chemotherapy was modified with risk-adapted attenuated intensity and minimised cumulative doses of anthracyclines for group C (144 mg/m² and 288 mg/m² of daunorubicin equivalents for standard- and high-risk patients, respectively).

RESULTS

The median initial WBC, platelet count, and fibrinogen were 2.9 × 10⁹/L (range 0.9-158.3 × 10⁹/L), 32 × 10⁹/L (range 4-226 × 10⁹/L), and 160 mg/dL (range 53-549 mg/dL), respectively. High-risk and standard-risk were seen in 20.5% and 79.5% of patients, respectively. Three patients (4.1%) suffered early haemorrhagic death. At the end of induction therapy, 68 (93.2%) patients achieved haematologic complete remission (HCR). At a median follow-up of 91.97 months, the estimated 5-year overall survival (OS) and event-free survival (EFS) rates for the whole cohort were 95.9 ± 2.3% and 88.7 ± 3.8%, respectively. A comparison of HCR rates and documented instances of toxicity between groups A and B + C showed no significant differences. However, idarubicin significantly reduced the peak WBC count (Z = - 3.292, P = 0.001) and duration of hyperleukocytosis (Z = - 2.827, P = 0.005). Estimated 3-year EFS (91.7 ± 8.0%) and OS (100%) rates for group C were not significantly different from those for group B, whereas the risk of treatment-related infections was significantly reduced (χ² = 5.515, P = 0.019).

CONCLUSIONS

Idarubicin (8-10 mg/m²/day for 2 days) for hyperleukocytosis control in induction therapy is safe and effective for paediatric APL. Risk-adapted attenuated consolidation chemotherapy is advocated.

Docosahexaenoic Acid Reverted the All-trans Retinoic Acid-Induced Cellular Proliferation of T24 Bladder Cancer Cell Line

The treatment of solid cancers with pharmacological all-trans retinoic acid (ATRA) concentrations, even if it is a gold standard therapy for the acute promyelocytic leukaemia (APL), is not always effective due to some resistance mechanisms. Here the resistance to ATRA treatment of T24 cell line, bladder cancer, was investigated. T24 was not only resistant to cell death when treated at concentrations up to 20 µM of ATRA, but it was also able to stimulate the cellular proliferation. An over-expression of the fatty acid binding protein 5 (FABP5) in conjunction with the cellular retinol-binding protein-II (CRABP-II) down-expression was found. However, the direct inhibition of the peroxisome proliferator-activated receptor β/δ (PPARβ/δ) did not abolish T24 proliferation, but rather potentiated it. Moreover, considering the ability of the long-chain fatty acids (LCFAs) to displace ATRA from FABP5, the actions of the saturated palmitic acid (PA), unsaturated omega-6 linoleic acid (LA) and omega-3 docosahexaenoic acid (DHA) were evaluated to counteract ATRA-related proliferation. ATRA-PA co-treatment induces cellular growth inhibition, while ATRA-LA co-treatment induces cellular growth enhancement. However, even if DHA is unsaturated LCFA as LA, it was able to reverse the ATRA-induced cellular proliferation of T24, bringing the viability percentages at the levels of the control.

The prognostic value of CD2, CD4, and HLA-DR expression and FLT3-ITD mutation in adult acute promyelocytic leukemia

In order to explore the prognostic value of CD2, CD4, and human leucocyte antigen-DR (HLA-DR) expression and Fms-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) mutation in leukemia cells in the bone marrow of patients with acute promyelocytic leukemia (APL), we retrospectively collected and analyzed the immunophenotype, molecular features and clinical characteristics of 219 newly diagnosed adult patients with APL in Henan Provincial People's Hospital from January 2010 to December 2019. It turned out that the relapse rates of patients with CD2, CD4, or HLA-DR expression and the early mortality rates of patients with CD2 expression, HLA-DR expression, or FLT3-ITD mutation were higher than those of their counterparts. Moreover, reduced overall survival was found for patients who showed CD2 expression, HLA-DR expression or FLT3-ITD mutation. Therefore, CD2 expression, HLA-DR expression and FLT3-ITD mutation were adverse prognostic factors in adults with APL.

Arsenic represses airway epithelial mucin expression by affecting retinoic acid signaling pathway

Arsenic is a ubiquitous environmental toxicant, found in high concentrations worldwide. Although abundant research has dealt with arsenic-induced cancers, studies on mechanisms of non-malignant lung diseases have not been complete. In addition, decades of research have mostly concentrated on high-dose arsenic exposure, which has very limited use in modeling the biological effects of today's low-dose exposures. Indeed, accumulated evidence has shown that low-dose arsenic exposure (i.e. ≤100 ppb) may also alter lung homeostasis by causing host susceptibility to viral infection. However, the underlying mechanism of this alteration is unknown. In this study, we found that low-dose sodium arsenite (As (III)) repressed major airway mucins-MUC5AC and MUC5B at both mRNA and protein levels. We further demonstrated that this repression was not caused by cellular toxicity or mediated by the reduction of a common mucin-inducing pathway-EGFR. Other established mucin activators- dsRNA, IL1β or IL17 were not able to override As (III)-induced mucin repression. Interestingly, the suppressing effect of As (III) appeared to be partially reversible, and supplementation of all trans retinoic acid (t-RA) doses dependently restored mucin gene expression. Further analyses indicated that As (III) treatment significantly reduced the protein level of retinoic acid receptors (RARα, γ and RXRα) as well as RARE promoter reporter activity. Therefore, our study fills in an important knowledge gap in the field of low-dose arsenic exposure. The interference of RA signaling, and mucin gene expression may be important pathogenic factors in low-dose arsenic induced lung toxicity.

Drug-Related Carcinogenesis: Risk Factors and Approaches for Its Prevention

The review summarizes the data on the role of metabolic and repair systems in the mechanisms of therapy-related carcinogenesis and the effect of their polymorphism on the cancer development risk. The carcinogenic activity of different types of drugs, from the anticancer agents to analgesics, antipyretics, immunomodulators, hormones, natural remedies, and non-cancer drugs, is described. Possible approaches for the prevention of drug-related cancer induction at the initiation and promotion stages are discussed.

Feasibility and clinical utility of a pan-solid tumor targeted RNA fusion panel: A single center experience

Gene fusions are caused by chromosomal rearrangements and encode fusion proteins that can act as oncogenic drivers in cancers. Traditional methods for detecting oncogenic fusion transcripts include fluorescence in situ hybridization (FISH), reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). However, these methods are limited in scalability and pose significant technical and interpretational challenges. Next-generation sequencing (NGS) is a high-throughput method for detecting genetic abnormalities and providing prognostic and therapeutic information for cancer patients. We present our experience with the validation of a custom-designed Archer Anchored Multiplex PCR (AMP™) technology-based NGS technology, "NYU FUSION-SEQer" using RNA sequencing. We examine both analytical performance and clinical utility of the panel using 75 retrospective validation samples and 84 prospective clinical samples of solid tumors. Our panel showed robust sequencing performance with strong enrichment for target regions. The lower limit of detection was 12.5% tumor fraction at 125 ng of RNA input. The panel demonstrated excellent analytic accuracy, with 100% sensitivity, 100% specificity and 100% reproducibility on validation samples. Finally, in the prospective cohort, the panel detected fusions in 61% cases (n = 51), out of which 41% (n = 21) enabling diagnosis and 59% (n = 30) enabling treatment and prognosis. We demonstrate that the fusion panel can accurately, efficiently and cost-effectively detect the majority of known fusion genes, novel clinically relevant fusions and provides an excellent tool for discovery of new fusion genes in solid tumors.

(-)-Epigallocatechin-3-gallate encapsulated realgar nanoparticles exhibit enhanced anticancer therapeutic efficacy against acute promyelocytic leukemia

Realgar and (-)-Epigallocatechin-3-gallate (EGCG) are natural medicines that inhibit cancer cell growth, resulting in inhibition of formation and development of tumors. The anticancer effects of realgar and EGCG were greatly improved following formulation as nanoparticles. EGCG has received increased attention as a drug carrier. The aim of this study was to prepare a new nanomedicine, (EGCG-RNPs), in which encapsulated nano-realgar. EGCG-RNPs were prepared by coprecipitation and characterized by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), particle size and zeta potential, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and in vitro release. Furthermore, we evaluated the antiproliferative effects of EGCG-RNPs on HL-60 cells in vitro, antitumor effect by intratumoral injection of EGCG-RNPs into solid tumors derived from APL HL-60 cells in vivo. Possible mechanisms were evaluated using uptake and efflux experiments in HL-60 cells. The results showed that the average particle size and zeta potentials of EGCG-RNPs was 200.3 ± 1.23 nm and −46.8 ± 1.31 mV. Controlled release of EGCG-RNPs was sustained and continued up to 72 h in vitro. Compared with nano-realgar and EGCG + RNPs (EGCG and nano-realgar physical mixing), EGCG-RNPs significantly inhibited growth of HL-60 cells. In a solid tumor model, EGCG-RNPs decreased tumor volumes, with an inhibitory rate of 60.18% at a dose of 70 mg · kg⁻¹. The mechanisms of antitumor improvement may correlate with the increased uptake of realgar and prolonged the retention time of realgar in HL-60 cells due to EGCG as a carrier. EGCG-RNPs could enhance anticancer therapeutic efficacy for acute promyelocytic leukemia.

Chemogenomics analysis of drug targets for the treatment of acute promyelocytic leukemia

The main challenges in treating acute promyelocytic leukemia (APL) are currently early mortality, relapse, refractory disease after induction therapy, and drug resistance to ATRA and ATO. In this study, a computational chemogenomics approach was used to identify new molecular targets and drugs for APL treatment. The transcriptional profiles induced by APL were compared with those induced by genetic or chemical perturbations. The genes that can reverse the transcriptional profiles induced by APL when perturbed were considered to be potential therapeutic targets for APL. Drugs targeting these genes or proteins are predicted to be able to treat APL if they can reverse the APL-induced transcriptional profiles. To improve the target identification accuracy of the above correlation method, we plotted the functional protein association networks of the predicted targets by STRING. The results determined PML, RARA, SPI1, HDAC3, CEBPA, NPM1, ABL1, BCR, PTEN, FOS, PDGFRB, FGFR1, NUP98, AFF1, and MEIS1 to be top candidates. Interestingly, the functions of PML, RARA, HDAC3, CEBPA, NPM1, ABL, and BCR in APL have been previously reported in the literature. This is the first chemogenomics analysis predicting potential APL drug targets, and the findings could be used to guide the design of new drugs targeting refractory and recurrent APL.

Development and Clinical Validation of a Large Fusion Gene Panel for Pediatric Cancers

Gene fusions are one of the most common genomic alterations in pediatric cancer. Many fusions encode oncogenic drivers and play important roles in cancer diagnosis, risk stratification, and treatment selection. We report the development and clinical validation of a large custom-designed RNA sequencing panel, CHOP Fusion panel, using anchored multiplex PCR technology. The panel interrogates 106 cancer genes known to be involved in nearly 600 different fusions reported in hematological malignancies and solid tumors. The panel works well with different types of samples, including formalin-fixed, paraffin-embedded samples. The panel demonstrated excellent analytic accuracy, with 100% sensitivity and specificity on 60 pediatric tumor validation samples. In addition to identifying all known fusions in the validation samples, three unrecognized, yet clinically significant, fusions were also detected. A total of 276 clinical cases were analyzed after the validation, and 51 different fusions were identified in 104 cases. Of these fusions, 16 were not previously reported at the time of discovery. These fusions provided genomic information useful for clinical management. Our experience demonstrates that CHOP Fusion panel can detect the vast majority of known and certain novel clinically relevant fusion genes in pediatric cancers accurately, efficiently, and cost-effectively; and the panel provides an excellent tool for new fusion gene discovery.

An Atypical PML-RARA Rearrangement Resulting from Submicroscopic Insertion of the RARA Gene at the PML Locus with Novel Breakpoints within PML Exon 7b and RARA Exon 3

The diagnostic hallmark of acute promyelocytic leukemia (APL) is the reciprocal translocation t(15;17), resulting in the characteristic PML-RARA fusion; however, patients occasionally have masked PML-RARArearrangements. We report an APL case with no evidence of t(15;17) or PML-RARA rearrangement by karyotype or commercial reverse transcription polymerase chain reaction analyses. Fluorescence in situ hybridization detected a small RARA insertion signal within PML. mRNA sequencing identified a novel PML-RARA transcript generated from the juxtaposition of PMLIIa (exons 1-4, 6, and 7ab) and RARA exons (3-9), with novel breakpoints in PML exon 7b and RARA exon 3. The patient achieved molecular remission after the second consolidation chemotherapy and remains in complete remission 22 months after initial presentation. This is the first report of an APL case presenting with submicroscopic ins(15;17) and simultaneous novel breakpoints in both PML and RARA. This case highlights the importance of sequence analysis to confirm APL diagnosis and for subsequent monitoring of minimal residual disease.

Combination of enzastaurin and ATRA exerts dose-dependent dual effects on ATRA-resistant acute promyelocytic leukemia cells

All-trans retinoic acid (ATRA) resistance continues to be a critical problem in acute promyelocytic leukemia (APL)-relapsed patients. In this study, a clinically achievable concentration of enzastaurin synergized with ATRA to induce differentiation and apoptosis in ATRA-resistant APL cell lines, NB4-R1 and NB4-R2. Mechanistically, although enzastaurin is a protein kinase Cβ (PKCβ) inhibitor, PKCβ may not be required since the activity of PKCβ was not suppressed by enzastaurin-ATRA (enz-ATRA) co-treatment, and another PKCβ-selective inhibitor did not mimic the effects of enzastaurin. An MEK inhibitor but not a RAF-1 inhibitor suppressed enz-ATRA treatment-triggered differentiation, activation of MEK/ERK and up-regulation of CCAAT/enhancer binding protein β (C/EBPβ) and/or PU.1. Therefore, RAF-1-independent MEK/ERK signaling was required for enz-ATRA treatment-induced differentiation via modulation of the protein levels of C/EBPβ and/or PU.1. Enz-ATRA treatment collapsed mitochondrial transmembrane potential without the activation of caspase-3, -6 and -7. Moreover, caspase-3/7- and caspase-6-specific inhibitors had no inhibitory effect on enz-ATRA treatment-triggered apoptosis. Therefore, enz-ATRA treatment-induced apoptosis was mitochondria-dependent but caspase-independent. Enz-ATRA treatment degraded PML-RARα, which may be involved in enz-ATRA treatment-induced dual effects and may also be beneficial for APL eradication. These findings may provide a potential therapy for ATRA-resistant APL patients.

The combination of UCN-01 and ATRA triggers differentiation in ATRA resistant acute promyelocytic leukemia cell lines via RAF-1 independent activation of MEK/ERK

With the introduction of arsenic trioxide and all-trans retinoic acid, the prognosis of acute promyelocytic leukemia has greatly improved. However, all-trans retinoic acid resistance is still unresolved in acute promyelocytic leukemia relapsed patients. In this study, the clinical achievable concentration of 7-hydroxystaurosporine synergized with all-trans retinoic acid to induce terminal differentiation in all-trans retinoic acid resistant acute promyelocytic leukemia cell lines. Though 7-hydroxystaurosporine is a PKC inhibitor, PKC might not be involved in the combination-induced differentiation since other PKC selective inhibitors, Gö 6976 and rottlerin failed to cooperate with all-trans retinoic acid to trigger differentiation. The combination significantly enhanced the protein level of CCAAT/enhancer binding protein β and/or PU.1 as well as activated MEK/ERK. U0126 (MEK specific inhibitor) not only suppressed the combination-induced differentiation but also restored the protein level of CCAAT/enhancer binding protein β and/or PU.1. However, RAF-1 inhibitor had no inhibitory effect on MEK activation and the combination-induced differentiation. Therefore, the combination overcame differentiation block via RAF-1 independent MEK/ERK modulation of the protein level of CCAAT/enhancer binding protein β and/or PU.1. These findings may provide a preclinical rationale for the potential role of this combination in the treatment of all-trans retinoic acid resistant acute promyelocytic leukemia patients.

Protective role of all-trans retinoic acid (ATRA) against hypoxia-induced malignant potential of non-invasive breast tumor derived cells

Background

The presence of hypoxic areas is common in all breast lesions but no data clearly correlate low oxygenation with the acquisition of malignant features by non-invasive cells, particularly by cells from ductal carcinoma in situ (DCIS), the most frequently diagnosed tumor in women.

Methods

By using a DCIS-derived cell line, we evaluated the effects of low oxygen availability on malignant features of non-invasive breast tumor cells and the possible role of all-trans retinoic acid (ATRA), a well-known anti-leukemic drug, in counteracting the effects of hypoxia. The involvement of the β2 isoform of PI-PLC (PLC-β2), an ATRA target in myeloid leukemia cells, was also investigated by specific modulation of the protein expression.

Results

We demonstrated that moderate hypoxia is sufficient to induce, in DCIS-derived cells, motility, epithelial-to-mesenchymal transition (EMT) and expression of the stem cell marker CD133, indicative of their increased malignant potential.

Administration of ATRA supports the epithelial-like phenotype of DCIS-derived cells cultured under hypoxia and keeps down the number of CD133 positive cells, abrogating almost completely the effects of poor oxygenation. We also found that the mechanisms triggered by ATRA in non-invasive breast tumor cells cultured under hypoxia is in part mediated by PLC-β2, responsible to counteract the effects of low oxygen availability on CD133 levels.

Conclusions

Overall, we assigned to hypoxia a role in increasing the malignant potential of DCIS-derived cells and we identified in ATRA, currently used in treatment of acute promyelocytic leukemia (APL), an agonist potentially useful in preventing malignant progression of non-invasive breast lesions showing hypoxic areas.

Long-term effect of all-trans retinoic acid and arsenic trioxide sequential maintenance in patients with acute promyelocytic leukemia

The specific prognostic factors and the long-term effects of different treatment options in APL remain unclear. In this retrospective study, 70 APL patients were treated with ATRA + DNR/DA or ATRA + ATO regimens for induction therapy and DA or ATRA + ATO for consolidation and maintenance therapy. The prognostic factors and treatment effects on outcome were analyzed. Results showed that the 5-year OS in low-intermediate risk and high risk groups were 95.63% and 100%, and the 5-year RFS were 95.34% and 100%, respectively, the early mortality rate was 4.28%. No significant difference was found on OS and RFS with different regimens, but side-effects and treatment-related mortality rates were lower in ATRA + ATO group. CD34 expression, FLT3-ITD mutation and PML-RARA isoform had no significance on OS and RFS. In conclusion, cytogenetic and molecular abnormalities had no influence on effect of APL patients; ATRA + ATO sequential maintenance may alleviate complications, treatment-related mortality, and the previously high risk factors.

Cyclooxygenase-1 (COX-1) and COX-1 Inhibitors in Cancer: A Review of Oncology and Medicinal Chemistry Literature

Prostaglandins and thromboxane are lipid signaling molecules deriving from arachidonic acid by the action of the cyclooxygenase isoenzymes COX-1 and COX-2. The role of cyclooxygenases (particularly COX-2) and prostaglandins (particularly PGE₂) in cancer-related inflammation has been extensively investigated. In contrast, COX-1 has received less attention, although its expression increases in several human cancers and a pathogenetic role emerges from experimental models. COX-1 and COX-2 isoforms seem to operate in a coordinate manner in cancer pathophysiology, especially in the tumorigenesis process. However, in some cases, exemplified by the serous ovarian carcinoma, COX-1 plays a pivotal role, suggesting that other histopathological and molecular subtypes of cancer disease could share this feature. Importantly, the analysis of functional implications of COX-1-signaling, as well as of pharmacological action of COX-1-selective inhibitors, should not be restricted to the COX pathway and to the effects of prostaglandins already known for their ability of affecting the tumor phenotype. A knowledge-based choice of the most appropriate tumor cell models, and a major effort in investigating the COX-1 issue in the more general context of arachidonic acid metabolic network by using the systems biology approaches, should be strongly encouraged.

The success and the challenge of all-trans retinoic acid in the treatment of cancer

All-trans retinoic acid (ATRA), an active metabolite of vitamin A, plays important roles in cell proliferation, cell differentiation, apoptosis, and embryonic development. The effects of ATRA are mediated by nuclear retinoid receptors as well as non-genomic signal pathway, such as MAPK and PKA. The great success of differentiation therapy with ATRA in acute promyelocytic leukemia (APL) not only improved the prognosis of APL but also spurred the studies of ATRA in the treatment of other tumors. Since the genetic and physiopathological simplicity of APL is not common in human malignancies, the combination of ATRA with other agents (chemotherapy, epigenetic modifiers, and arsenic trioxide, etc) had been extensively investigated in a variety of tumors. In this review, we will discuss in details about ATRA and its role in cancer treatment.

Rhein augments ATRA-induced differentiation of acute promyelocytic leukemia cells

BACKGROUND

Rhein (4, 5-dihydroxyanthraquinone-2-carboxylic acid), a natural anthraquinone derivative, is a traditional Chinese herb that has been used as a medication in many Asian countries. It has been used as a laxative and stomach drug for a long time in both China and Korea. It is well-known to have many pharmacological activities, such as anti-cancer, anti-bacterial, anti-fungal, anti-oxidant, anti-atherogenic, anti-angiogenic, anti-fibrosis, anti-inflammatory, hepatoprotective, and nephroprotective properties. However, little is known about how rhein may affect the differentiation activities in acute promyelocytic leukemia (APL) cells.

PURPOSE

The present study was designed to examine the anti-leukemic effects of rhein against APL cells and to explore the underlying mechanism.

METHODS

Cell viability was investigated by MTS assay. To examine the differentiation activities in APL cells, the cell surface molecules (CD11b, CD14, CCR1 and CCR2), phagocytosis, reactive oxygen species (ROS) were determined by flow cytometry. Also, induction of caspase-3 activity and reduction of mitochondrial membrane potential (MMP) were determined by flow cytometry. RNA and protein expressions were determined by qRT-PCR and western blotting, respectively.

RESULTS

In this study we assessed the role of rhein in treating APL. Interestingly, rhein potentiated all-trans retinoic acid (ATRA)-induced macrophage differentiation in NB4 cells by inducing changes in morphology, expression of the differentiation markers CD11b and CD14, ROS production, phagocytic activity, and expression of CCR1 and CCR2. Signaling through CD11b was found to be dependent on ERK activation. Additionally, rhein induced APL cell death by activating apoptosis and suppressing the mTOR pathway.

CONCLUSION

Therefore, we suggest that a combination of rhein and ATRA carries strong therapeutic potential through the beneficial differentiation of APL cells. Moreover, rhein causes cell death via the activation of apoptosis and suppression of survival signals in APL cells. In combination with the ability of rhein to promote functional macrophage differentiation in APL, these properties suggest that a combined treatment of rhein and ATRA has great potential as an anti-leukemic therapy for APL.

RACK1 deficiency synergizes with all-trans retinoic acid to induce apoptosis in human acute promyelocytic leukemia cells

As a classic differentiation agent, all-trans retinoic acid (ATRA) has been widely used in the treatment of acute promyelocytic leukemia (APL). However, the clinical application of ATRA has strict limitations, for its severe side effects due to the accumulation of peripheral blood leukocytes. The scaffold protein RACK1 (Receptor for activated C kinase 1), which regulates multiple signaling pathways, has been proposed to contribute to the survival of leukemic progenitors. But it remains unclear whether it is also involved in the oncogenic growth of APL. In the present study, we demonstrate that silencing of endogenous RACK1 expression synergized with ATRA to promote the death of NB4 and HL-60 APL cells without effect on cell differentiation induced by ATRA. Interestingly, RACK1 knockdown combined with ATRA treatment mainly induces apoptosis. It is distinct to the necrotic cell death induced by idarubicin in combination with ATRA, a regimen extensively used in the clinic to prevent neutrophil accumulation. Further exploration revealed that the lysosome-autophagy pathway is likely to be responsible for the anti-apoptotic role of RACK1. Taken together, our findings indicate that RACK1 is essential in maintaining the malignant features of APL, and targeting RACK1 may have promising therapeutic implications in the treatment of APL.

ATPR-induced G0 /G1 phase arrest in gastric cancer cells by regulating the binding of 14-3-3ε and filamin A

4‐amino‐2‐trifluoromethyl‐phenyl retinate (ATPR) was able to induce the G₀/G₁ phase arrest in gastric cancer SGC‐7901 cells by downregulating 14‐3‐3ε. However, the mechanisms underlying this effect have not been fully elucidated. Because 14‐3‐3ε functions as a molecular chaperone on cell cycle regulation, the interaction between 14‐3‐3ε and the target proteins is worth an in‐depth study. In this study, the use of targeting proteomics identified 352 14‐3‐3ε‐binding proteins in SGC‐7901 cells. Analysis of gene ontology (GO) was performed using PANTHER to annotate the biological processes, protein classes, and pathways of these proteins. In 25 cell cycle‐related proteins, filamin A was reduced following ATPR treatment, and this change was validated by immunoprecipitation. The cell cycle was arrested at the G₀/G₁ phase following ATPR treatment or filamin A silencing in SGC‐7901 cells. Furthermore, subcellular expression analysis showed that 14‐3‐3ε and filamin A were transferred from the cytoplasm to the nucleus after ATPR treatment. On the other hand, overexpression of 14‐3‐3ε, in SGC‐7901 cells, resulted in an increase in the total cellular level of filamin A and an increase in the subcellular localization of filamin A in the cytoplasm. ATPR treatment of the 14‐3‐3ε overexpression cells decreased the total level of filamin A and redistributed filamin A protein from the cytoplasm to the nucleus. Immunohistochemical analysis showed that the expression levels of 14‐3‐3ε and filamin A in gastric cancer tissues were significantly higher, with a predominant localization in the cytoplasm, compared to the levels in matched tissues. Taken together, our results suggest that ATPR can induce nuclear localization of filamin A by reducing the binding of 14‐3‐3ε and filamin A, which may be the mechanism of ATPR‐induced G₀/G₁ phase arrest.

Toxic effects of arsenic trioxide on Echinococcus granulosus protoscoleces through ROS production, and Ca2+-ER stress-dependent apoptosis

Cystic echinococcosis is a severe parasitic disease that commonly affects the liver and causes abscesses or rupture into the surrounding tissues, leading to multiple complications, such as shock, severe abdominal pain, and post-treatment abscess recurrence. Currently, there are no efficient measures to prevent these complications. We previously confirmed that arsenic trioxide (As2O3) exhibited in vitro cytotoxicity against Echinococcus granulosus protoscoleces. In the present study, we aimed to explore the mechanism of As2O3-induced E. granulosus protoscoleces apoptosis. After exposing E. granulosus protoscoleces to 0, 4, 6, and 8 μM As2O3, reactive oxygen species (ROS) level was detected by fluorescence microscopy; superoxide dismutase (SOD), and caspase-3 activities were measured; intracellular Ca2+ was detected by flow cytometry; GRP-78 and caspase-12 protein levels were measured by western blot analysis. Our results showed that the expression of caspase-3 was gradually increased and the expression of SOD was gradually decreased in As2O3-treated groups of protoscoleces. Simultaneously, fluorescence microscopy and flow cytometry showed that the ROS level and the intracellular Ca2+ level were increased in a time- and dose-dependent manner. Western blot analysis showed that the expressions of GRP-78 and caspase-12 were higher in As2O3-treated groups than in the control group. These results suggest that As2O3-induced apoptosis in E. granulosus protoscoleces is related to elevation of ROS level, disruption of intracellular Ca2+ homeostasis, and endoplasmic reticulum stress. These mechanisms can be targeted in the future by safer and more effective drugs to prevent recurrence of cystic echinococcosis.

Cell dynamics during differentiation therapy with all-trans retinoic acid in acute promyelocytic leukemia

The introduction of all-trans retinoic acid (ATRA) has made acute promyelocytic leukemia (APL) a curable disease; however, early death prior to the completion of treatment remains a problem. In quantitative evaluation of response to ATRA treatment, lymphocytes must be excluded as they do not originally have t(15;17). We categorized peripheral blood leukocytes by nuclear morphology into polymorphonuclear cells (PMNs) comprising segmented granulocytes, and non-polymorphonuclear cells (NPMs) which includes lymphocytes, monocytes, band cells, and immature myeloid cells. We consecutively evaluated the ratio of t(15;17)-positive cells using fluorescence in situ hybridization in eight newly diagnosed patients with APL. We confirmed the differentiation of APL cells until cytogenetic complete remission; the association of a decrease of t(15;17)-positive NPMs and an increase of t(15;17)-positive PMNs was followed by a decrease of t(15;17)-positive PMNs. The kinetic pattern of t(15;17)-positive NPMs and PMNs was consistent in most patients, irrespective of leukocyte counts at diagnosis, additional chromosomal changes, and ATRA with or without chemotherapies. Kinetic analysis enables us to evaluate treatment response and the recovery of normal hematopoiesis in individuals.

Hyperfibrinolysis Is an Important Cause of Early Hemorrhage in Patients with Acute Promyelocytic Leukemia

Background

The objective of the current study was to guide the early clinical treatment strategies by assessing the recovery of abnormal coagulation in acute promyelocytic leukemia (APL) patients during induction therapy.

Material/Methods

Retrospective analysis was performed in 112 newly-diagnosed patients with APL during induction treatment.

Results

The early death (ED) rate in our study was 5.36% and the main cause was fetal hemorrhage. The presence of bleeding symptoms was significantly correlated with low platelet and fibrinogen levels. The values of white blood cell (WBC), lactate dehydrogenase (LDH), prothrombin time (PT), fibrinogen, and bone marrow leukemic promyelocyte in the high-risk group were significantly different from those in the low/intermediate-risk groups. Coagulation variables significantly improved after dual induction therapy. No significant difference was found in changes of platelet (PLT), prothrombin time (PT), activated partial thromboplastin time (APTT), D-dimers, and fibrinogen among different risk groups after induction therapy. D-dimer levels were initially high and remained well above normal after 4 weeks of induction therapy.

Conclusions

Aggressive prophylactic transfusion to maintain high platelet and fibrinogen transfusion thresholds could reduce hemorrhage in APL patients. Immediately starting induction therapy effectively alleviated coagulopathy in APL patients. Hyperfibrinolysis was a more important event in the APL hemorrhagic diathesis.