Optimal treatment strategies for high-risk acute promyelocytic leukemia:

Differentiation Syndrome in Acute Leukemia: APL and Beyond

Differentiation syndrome (DS) is a frequent and potentially life-threatening clinical syndrome first recognized with the advent of targeted therapeutics for acute promyelocytic leukemia (APL). DS was subsequently observed more broadly with targeted therapeutics for acute myeloid leukemia (AML). DS is typically characterized by fever, dyspnea, hypotension, weight gain, pleural or pericardial effusions, and acute renal failure. The incidence in patients with APL ranges from 2 to 37%, with the wide variation likely attributed to different diagnostic criteria, use of prophylactic treatment, and different treatment regimens. Treatment with corticosteroids +/- cytoreductive therapy should commence as soon as DS is suspected to reduce DS-related morbidity and mortality. The targeted anti-leukemic therapy should be discontinued in patients with severe DS. Here, we discuss the pathogenesis of DS, clinical presentations, diagnostic criteria, management strategies, and implementation of prospective tracking on clinical trials.

A novel network pharmacology approach for leukaemia differentiation therapy using Mogrify®

Acute myeloid leukaemia (AML) is a rapidly fatal blood cancer that is characterised by the accumulation of immature myeloid cells in the blood and bone marrow as a result of blocked differentiation. Methods which identify master transcriptional regulators of AML subtype-specific leukaemia cell states and their combinations could be critical for discovering novel differentiation-inducing therapies. In this proof-of-concept study, we demonstrate a novel utility of the Mogrify® algorithm in identifying combinations of transcription factors (TFs) and drugs, which recapitulate granulocytic differentiation of the NB4 acute promyelocytic leukaemia (APL) cell line, using two different approaches. In the first approach, Connectivity Map (CMAP) analysis of these TFs and their target networks outperformed standard approaches, retrieving ATRA as the top hit. We identify dimaprit and mebendazole as a drug combination which induces myeloid differentiation. In the second approach, we show that genetic manipulation of specific Mogrify®-identified TFs (MYC and IRF1) leads to co-operative induction of APL differentiation, as does pharmacological targeting of these TFs using currently available compounds. We also show that loss of IRF1 blunts ATRA-mediated differentiation, and that MYC represses IRF1 expression through recruitment of PML-RARα, the driver fusion oncoprotein in APL, to the IRF1 promoter. Finally, we demonstrate that these drug combinations can also induce differentiation of primary patient-derived APL cells, and highlight the potential of targeting MYC and IRF1 in high-risk APL. Thus, these results suggest that Mogrify® could be used for drug discovery or repositioning in leukaemia differentiation therapy for other subtypes of leukaemia or cancers.

CUDC-101 overcomes arsenic trioxide resistance via caspase-dependent promyelocytic leukemia-retinoic acid receptor alpha degradation in acute promyelocytic leukemia

Although arsenic trioxide (ATO) treatment has transformed acute promyelocytic leukemia (APL) from the most fatal to the most curable hematological cancer, many high-risk APL patients who fail to achieve a complete molecular remission or relapse become resistant to ATO. Herein, we report that 7-(4-(3-ethynylphenylamino)-7-methoxyquinazolin-6-yloxy)-N-hydroxyheptanamide (CUDC-101) exhibits specific anticancer effects on APL and ATO-resistant APL in vitro and in vivo, while showing negligible cytotoxic effect on the noncancerous cells including normal CD34 cells and bone marrow mesenchymal stem cells from APL patients. Further mechanistic studies show that CUDC-101 triggers caspase-dependent degradation of the promyelocytic leukemia-retinoic acid receptor alpha fusion protein. As a result, APL and ATO-resistant APL cells undergo apoptosis upon CUDC-101 treatment and this apoptosis-inducing effect is even stronger than that of ATO. Finally, using a xenograft mouse model, we demonstrated that CUDC-101 significantly represses leukemia development in vivo. In conclusion, these results suggested that CUDC-101 can serve as a potential candidate drug for APL, particularly for ATO-resistant APL.

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.

DDX5-targeting fully human monoclonal autoantibody inhibits proliferation and promotes differentiation of acute promyelocytic leukemia cells by increasing ROS production

Acute promyelocytic leukemia (APL) therapy involves the compounds cytotoxic to both malignant tumor and normal cells. Relapsed APL is resistant to subsequent chemotherapy. Novel agents are in need to kill APL cells selectively with minimal toxicity. DDX5 has been recognized to be a novel target to suppress acute myeloid leukemia (AML). However, the role of DDX5 remains elusive in APL. Here a DDX5-targeting fully human monoclonal autoantibody named after 2F5 was prepared. It is demonstrated that 2F5 selectively inhibited APL cell proliferation without toxicity to normal neutrophil and tissues. Moreover, 2F5 was confirmed to induce G0/G1 phase arrest in APL cells, and promote APL cell differentiation combined with decreased DDX5 expression and increased reactive oxygen species (ROS) production. Knockdown of DDX5 by siRNA also inhibited proliferation, promoted cell differentiation and enhanced ROS production in APL cells. However, the ROS inhibitor reversed the effects of 2F5 on DDX5 and ROS in APL cells. Thus, we conclude that DDX5-targeting 2F5 inhibits APL cell proliferation, and promotes cell differentiation via induction of ROS. 2F5 showed the therapeutic value of fully human monoclonal autoantibody in APL, which provides a novel and valid approach for treatment of relapse/refractory APL.

Outcomes of high-risk acute promyelocytic leukemia patients treated with arsenic trioxide (ATO)/all trans retinoic acid (ATRA) based induction and consolidation without maintenance phase: A case Series

Patients with high-risk acute promyelocytic leukemia (APL) have inferior outcomes compared with patients with low-risk APL, predominantly due to higher risk of early mortality related to hemorrhage. The majority of regimens contain prolonged maintenance, but the impact of this phase is not clear in the era of all trans retinoic acid (ATRA) and arsenic trioxide (ATO). We present a retrospective analysis of 10 patients that were treated for high risk APL based on the consolidation treatment phase of APL 0406 study without subsequent maintenance. With a median follow up of 38 months, all patients remain in remission.

Progressive hyperleukocytosis is a relevant predictive marker for differentiation syndrome, early death, and subsequent relapse in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is generally held to have favorable risk, but we have observed a high incidence of early deaths caused by fatal bleeding and differentiation syndrome (DS). We retrospectively analyzed 259 APL patients from 2002 to 2014 who all received all-trans retinoic acid (ATRA) with the support of sufficient transfusions, followed by 4 days of idarubicin. High-risk status was determined as a diagnostic leukocyte count (WBCdx) >10 × 10⁹/L (Sanz criteria). For patients with hyperleukocytosis, we sometimes conducted leukapheresis and also used hydroxyurea and prophylactic dexamethasone. Because we frequently observed patient fatalities from progressive hyperleukocytosis, we also checked the maximum leukocyte count (WBCmax) and stratified patients by their incremental ratios. The 8-week cumulative incidence of early death and DS was 13.5% and 17.8%, respectively. We found that WBCmax correlated better with early death and DS, even in the low-risk group, than WBCdx. Among the patients with WBCdx <10 × 10⁹/L, a WBCmax >43 × 10⁹/L correlated with early death (26.7%) and DS (40.0%). Also, having a WBCdx of 10 to 43 × 10⁹/La that increased to a WBCmax >43 × 10⁹/L correlated with increased early death (33.3%). The multivariate analysis revealed that a WBCmax >43 × 10⁹/L correlated significantly with both early death and DS.

ZYH005, a novel DNA intercalator, overcomes all-trans retinoic acid resistance in acute promyelocytic leukemia

Despite All-trans retinoic acid (ATRA) has transformed acute promyelocytic leukemia (APL) from the most fatal to the most curable hematological cancer, there remains a clinical challenge that many high-risk APL patients who fail to achieve a complete molecular remission or relapse and become resistant to ATRA. Herein, we report that 5-(4-methoxyphenethyl)-[1, 3] dioxolo [4, 5-j] phenanthridin-6(5H)-one (ZYH005) exhibits specific anticancer effects on APL and ATRA-resistant APL in vitro and vivo, while shows negligible cytotoxic effect on non-cancerous cell lines and peripheral blood mononuclear cells from healthy donors. Using single-molecule magnetic tweezers and molecule docking, we demonstrate that ZYH005 is a DNA intercalator. Further mechanistic studies show that ZYH005 triggers DNA damage, and caspase-dependent degradation of the PML-RARa fusion protein. As a result, APL and ATRA-resistant APL cells underwent apoptosis upon ZYH005 treatment and this apoptosis-inducing effect is even stronger than that of arsenic trioxide and anticancer agents including 5-fluorouracil, cisplatin and doxorubicin. Moreover, ZYH005 represses leukemia development in vivo and prolongs the survival of both APL and ATRA-resistant APL mice. To our knowledge, ZYH005 is the first synthetic phenanthridinone derivative, which functions as a DNA intercalator and can serve as a potential candidate drug for APL, particularly for ATRA-resistant APL.

MicroRNA-204 Potentiates the Sensitivity of Acute Myeloid Leukemia Cells to Arsenic Trioxide

Although arsenic trioxide (ATO) is a well-known antileukemic drug used for acute promyelocytic leukemia treatment, the development of ATO resistance is still a big challenge. We previously reported that microRNA-204 (miR-204) was involved in the regulation of acute myeloid leukemia (AML) cell apoptosis, but its role in chemoresistance is poorly understood. In the present study, we showed that miR-204 was significantly increased in AML cells after ATO treatment. Interestingly, the increased miR-204 level that was negatively correlated with ATO induced the decrease in cell viability and baculoviral inhibition of apoptosis protein repeat-containing 6 (BIRC6) expression. Overexpression of miR-204 potentiated ATO-induced AML cell growth inhibition and apoptosis. Furthermore, miR-204 directly targets to the 3′-UTR of BIRC6. Upregulation of miR-204 decreased BIRC6 luciferase activity and expression, which subsequently enhanced the expression of p53. Restoration of BIRC6 markedly reversed the effect of miR-204 on the regulation of AML cell sensitivity to ATO. Taken together, our study demonstrates that miR-204 decreases ATO chemoresistance in AML cells at least partially via promoting BIRC6/p53-mediated apoptosis. miR-204 represents a novel target of ATO, and upregulation of miR-204 may be a useful strategy to improve the efficacy of ATO in AML treatment.

Multi-omics profiling reveals a distinctive epigenome signature for high-risk acute promyelocytic leukemia

Epigenomic alterations have been associated with both pathogenesis and progression of cancer. Here, we analyzed the epigenome of two high-risk APL (hrAPL) patients and compared it to non-high-risk APL cases. Despite the lack of common genetic signatures, we found that human hrAPL blasts from patients with extremely poor prognosis display specific patterns of histone H3 acetylation, specifically hyperacetylation at a common set of enhancer regions. In addition, unique profiles of the repressive marks H3K27me3 and DNA methylation were exposed in high-risk APLs. Epigenetic comparison with low/intermediate-risk APLs and AMLs revealed hrAPL-specific patterns of histone acetylation and DNA methylation, suggesting these could be further developed into markers for clinical identification. The epigenetic drug MC2884, a newly generated general HAT/EZH2 inhibitor, induces apoptosis of high-risk APL blasts and reshapes their epigenomes by targeting both active and repressive marks. Together, our analysis uncovers distinctive epigenome signatures of hrAPL patients, and provides proof of concept for use of epigenome profiling coupled to epigenetic drugs to ‘personalize’ precision medicine.

Biological effects and epidemiological consequences of arsenic exposure, and reagents that can ameliorate arsenic damage in vivo

Through contaminated diet, water, and other forms of environmental exposure, arsenic affects human health. There are many U.S. and worldwide "hot spots" where the arsenic level in public water exceeds the maximum exposure limit. The biological effects of chronic arsenic exposure include generation of reactive oxygen species (ROS), leading to oxidative stress and DNA damage, epigenetic DNA modification, induction of genomic instability, and inflammation and immunomodulation, all of which can initiate carcinogenesis. High arsenic exposure is epidemiologically associated with skin, lung, bladder, liver, kidney and pancreatic cancer, and cardiovascular, neuronal, and other diseases. This review briefly summarizes the biological effects of arsenic exposure and epidemiological cancer studies worldwide, and provides an overview for emerging rodent-based studies of reagents that can ameliorate the effects of arsenic exposure in vivo. These reagents may be translated to human populations for disease prevention. We propose the importance of developing a biomarker-based precision prevention approach for the health issues associated with arsenic exposure that affects millions of people worldwide.

Role of Vitamin A/Retinoic Acid in Regulation of Embryonic and Adult Hematopoiesis

Vitamin A is an essential micronutrient throughout life. Its physiologically active metabolite retinoic acid (RA), acting through nuclear retinoic acid receptors (RARs), is a potent regulator of patterning during embryonic development, as well as being necessary for adult tissue homeostasis. Vitamin A deficiency during pregnancy increases risk of maternal night blindness and anemia and may be a cause of congenital malformations. Childhood Vitamin A deficiency can cause xerophthalmia, lower resistance to infection and increased risk of mortality. RA signaling appears to be essential for expression of genes involved in developmental hematopoiesis, regulating the endothelial/blood cells balance in the yolk sac, promoting the hemogenic program in the aorta-gonad-mesonephros area and stimulating eryrthropoiesis in fetal liver by activating the expression of erythropoietin. In adults, RA signaling regulates differentiation of granulocytes and enhances erythropoiesis. Vitamin A may facilitate iron absorption and metabolism to prevent anemia and plays a key role in mucosal immune responses, modulating the function of regulatory T cells. Furthermore, defective RA/RARα signaling is involved in the pathogenesis of acute promyelocytic leukemia due to a failure in differentiation of promyelocytes. This review focuses on the different roles played by vitamin A/RA signaling in physiological and pathological mouse hematopoiesis duddurring both, embryonic and adult life, and the consequences of vitamin A deficiency for the blood system.