Monitoring Anthracycline Cancer Drug-Nucleosome Interaction by NMR Using a Specific Isotope Labeling Approach for Nucleosomal DNA.

Chromatinized DNA is targeted by proteins and small molecules to regulate chromatin function. For example, anthracycline cancer drugs evict nucleosomes in a mechanism that is still poorly understood. We here developed a flexible method for specific isotope labeling of nucleosomal DNA enabling NMR studies of such nucleosome interactions. We describe the synthesis of segmental one-strand 13C-thymidine labeled 601-DNA, the assignment of the methyl signals, and demonstrate its use to observe site-specific binding to the nucleosome by aclarubicin, an anthracycline cancer drug that intercalates into the DNA minor grooves. Our results highlight intrinsic conformational heterogeneity in the 601 DNA sequence and show that aclarubicin binds an exposed AT-rich region near the DNA end. Overall, our data point to a model where the drug invades the nucleosome from the terminal ends inward, eventually resulting in histone eviction and nucleosome disruption.

Aclarubicin stimulates RNA polymerase II elongation at closely spaced divergent promoters.

Anthracyclines are a class of widely prescribed anticancer drugs that disrupt chromatin by intercalating into DNA and enhancing nucleosome turnover. To understand the molecular consequences of anthracycline-mediated chromatin disruption, we used Cleavage Under Targets and Tagmentation (CUT&Tag) to profile RNA polymerase II during anthracycline treatment in Drosophila cells. We observed that treatment with the anthracycline aclarubicin leads to elevated levels of RNA polymerase II and changes in chromatin accessibility. We found that promoter proximity and orientation affect chromatin changes during aclarubicin treatment, as closely spaced divergent promoter pairs show greater chromatin changes when compared to codirectionally oriented tandem promoters. We also found that aclarubicin treatment changes the distribution of noncanonical DNA G-quadruplex structures both at promoters and at G-rich pericentromeric repeats. Our work suggests that the cancer-killing activity of aclarubicin is driven by the disruption of nucleosomes and RNA polymerase II.

The identification of the anthracycline aclarubicin as an effective cytotoxic agent for pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of cancer, mainly due to its delayed diagnosis and lack of effective therapeutic options. Therefore, it is imperative to find novel treatment options for PDAC. Here, we tested a series of conventional chemotherapeutics together with anthracycline compounds as single agents or in combination, determining their effectivity against established commercial and patient-derived, low-passage PDAC cell lines. Proliferation and colony formation assays were performed to determine the anticancer activity of anthracyclines; aclarubicin and doxorubicin, on commercial and patient-derived, low-passage PDAC cell lines. In addition, the effect of standard-of-care drugs gemcitabine and individual components of FOLFIRINOX were also investigated. To evaluate which mechanisms of cell death were involved in drug response, cleavage of poly(ADP-ribose)polymerase was evaluated by western blot. Aclarubicin showed superior antitumor activity compared to other anthracyclines and standard of care drugs (gemcitabine and individual components of FOLFIRINOX) in a patient-derived, low-passage PDAC cell line and in commercial cell lines. Importantly, the combination of gemcitabine and aclarubicin showed a synergistic effect at a dose range where the single agents by themselves were ineffective. In parallel, evaluation of the antitumor activity of aclarubicin demonstrated an apoptotic effect in all PDAC cell lines. Aclarubicin is cytotoxic for commercial and patient-derived low-passage PDAC cell lines, at doses lower than peak serum concentrations for patient treatment. Our findings support a (re)consideration of aclarubicin as a backbone of new combination regimens for pancreatic cancer patients.

CAG regimen for refractory or relapsed adult T-cell acute lymphoblastic leukemia: A retrospective, multicenter, cohort study.

Adult patients with relapsed or refractory T-cell acute lymphoblastic leukemia (R/R-T-ALL) have extremely poor prognosis, representing an urgent unmet medical need. Finding an optimal salvage regimen to bridge transplantation is a priority. The CAG (cytarabine, aclarubicin, and G-CSF) regimen was initially used by one group in China, showing unexpectedly promising results in 11 R/R-T-ALL patients. Here, we report the multicenter results of 41 patients who received the CAG regimen as salvage therapy. After one cycle of the CAG regimen, complete remission and partial remission were achieved in 33 (80.5%) and two (4.9%) patients, respectively. Failure to respond was observed in six patients (14.6%). Early T-cell precursor (ETP) (n = 26) and non-ETP (n = 15) patients had a similar CR rate (80.8% vs 80.0%, P = .95). Among 41 patients, allo-HSCT was successfully performed in 27 (66%) patients (22 in CR and 5 in non-CR). With a median follow-up time of 12 months, the estimated 2-year overall survival and event-free survival were 68.8% (95% CI, 47.3%-83.0%) and 56.5% (95% CI, 37.1%-71.9%), respectively. The CAG regimen was well-tolerated, and no early death occurred. Our multicenter results show that the CAG regimen is highly effective and safe, representing a novel choice for adult patients with R/R-T-ALL and providing a better bridge to transplantation.

Epigenetic modifier gene mutations-positive AML patients with intermediate-risk karyotypes benefit from decitabine with CAG regimen.

It remains unclear whether there is a relationship between therapeutic effects of hypomethylating agents (HMAs) and epigenetic modifier gene mutations (EMMs) in patients with cytogenetically intermediate-risk acute myeloid leukemia (IR-AML). Based on targeted-capture sequencing, we retrospectively analyzed the correlation between EMMs and prognosis in 83 IR-AML patients treated with decitabine in combination with cytarabine, aclarubicin hydrochloride and granulocyte colony-stimulating factor (DCAG, n = 35) or "7 + 3" induction regimens (n = 48). In the multivariate analyses, EMM (+) patients did not show any statistically significant difference in remission rates from EMM (-) patients in the DCAG group (p > 0.05), but achieved inferior complete remission (CR; p = 0.03) and overall remission rates (ORR; p = 0.04) after the first course of standard induction regimens (p < 0.05). In the EMM (-) cohort, the DCAG group showed the tendency of adverse total CR (p = 0.06). Besides, DCAG group with EMMs achieved the best survival outcome independent of baseline characteristics, whereas it was opposite in EMM (+) patients receiving standard induction regimens (p < 0.05). Additionally, in the EMM (+) cohort, the survival rate of isolated DCAG group was statistically similar to that of the combination of standard chemotherapies and allogeneic hematopoietic stem cell transplantation (allo-HSCT) (p > 0.40), whereas patients who received only standard regimens had the worst survival rate (0.0%, p < 0.01). It can be concluded that the EMMs might be regarded as the potentially predictive biomarkers of better response to DCAG in IR-AML patients.

Directed Biosynthesis of Iso-aclacinomycins with Improved Anticancer Activity.

A four-enzyme catalyzed hydroxy regioisomerization of anthracycline was integrated into the biosynthetic pathway of aclacinomycin A (ALM-A), to generate a series of iso-ALMs via directed combinatorial biosynthesis combined with precursor-directed mutasynthesis. Most of the newly acquired iso-ALMs exhibit obviously (1-5-fold) improved antitumor activity. Therefore, we not only developed iso-ALMs with potential as clinical drugs but also demonstrated the utility of this tailoring tool for modification of anthracycline antibiotics in drug discovery and development.

Emerging role of EPHX1 in chemoresistance of acute myeloid leukemia by regurlating drug-metabolizing enzymes and apoptotic signaling.

Microsomal epoxide hyrolase 1 (EPHX1) is a critical biotransformation enzyme and participants in both the detoxification and activation of potentially genotoxic epoxides. In this study, we firstly aimed to investigate the role of EPHX1 in the chemoresistance of acute myeloid leukemic cells to aclarubicin (ACM) and mitoxantrone (MIT). EPHX1 mRNA expression and prognosis were measured in acute myeloid leukemia (AML) patients, and the function of EPHX1 in leukemic cell viability and apoptosis induced by ACM and MIT was also measured. Our results found that EPHX1 expression is obviously associated with recurrence rate, overall survival and time of obtaining first complete remission in AML patients. EPHX1 silencing promoted ACM and MIT induced decrease in cell viability and cell apoptosis of HL-60, K562, and THP-1 that was inhibited by EPHX1 overexpression. EPHX1 reduced the susceptibility of leukemic cells to ACM and MIT by regulating drug-metabolizing enzymes (CYP1A1, GSTM1, and GSTT1) and apoptotic signaling (Bax, Bcl-2, Caspase-3, Caspase-9, and PARP1). Moreover, Nrf2 overexpression significantly increased EPHX1 expression and leukemic cell viability and decreased leukemic cell apoptosis. Taken together, we summarized the recent findings about the chemoresistance-promoting role of EPHX1, and the potential of targeting EPHX1 was proposed to counteract drug resistance in leukemia treatment.

Aclarubicin in subtoxic doses reduces doxorubicin cytotoxicity in human non-small cell lung adenocarcinoma (A549) and human hepatocellular carcinoma (HepG2) cells by decreasing DNA damage.

In the study, the cytotoxicity and genotoxicity of aclarubicin (ACL) against A549 (human non-small cell lung adenocarcinoma) and HepG2 (human hepatocellular carcinoma) cell lines were evaluated and compared with that of doxorubicin (DOX). The effect of both anthracyclines in combination was also investigated. In order to get a deeper insight into the effectiveness of the drugs and their combination, their effects on the DNA damage and distribution of the cell cycle of A549 and HepG2 cells were investigated. After treatment with investigated compounds, apoptotic and necrotic morphological changes were estimated by double staining cells with orange acridine and ethidium bromide. The results showed that ACL was much more cytotoxic against lung (A549) and liver (HepG2) cancer cell lines than DOX. However, the drugs affected the cell cycle differently. ACL arrested cells in the G1 phase, while DOX arrested them in the G2/M phase. DOX and ACL at high concentrations are able to trigger apoptosis in both A549 and HepG2 cells. When the drugs were used in combination, subtoxic concentrations of ACL antagonized the cytotoxic effects of doxorubicin. Pre-incubation of cells with subtoxic concentrations of ACL reduced the level of DNA damage by DOX but increased DOX genotoxicity in the presence of verapamil.

Upregulated microRNA-146a expression induced by granulocyte colony-stimulating factor enhanced low-dosage chemotherapy response in aged acute myeloid leukemia patients.

The selection of chemotherapy regimen for elderly patients with acute myeloid leukemia (AML) remains challenging. Here, we report that granulocyte colony-stimulating factor (G-CSF) upregulates the expression of microRNA (miR)-146a in a nuclear factor kappaB-dependent manner, leading to direct decreases in the expression of the target proteins CXCR4 and Smad4 in AML cells in vitro. The reduction in CXCR4 expression suppressed the migration abilities of leukemia cells. Downregulation of Smad4 promoted cell cycle entry in leukemia cells. Furthermore, an increase in apoptosis was observed when leukemia cells were treated sequentially with G-CSF and cytosine arabinoside in vitro. These findings suggest that G-CSF treatment may disrupt the protection of bone marrow niches from leukemia cells. In a review of data from 78 cases of primary AML, we found that a high miR-146a expression and/or upregulation of this miRNA during G-CSF priming chemotherapy was predictive of better clinical outcomes. Our findings suggest that miR-146a may be a novel biomarker for evaluating the clinical prognosis and treatment effects of a G-CSF priming protocol in elderly patients with AML.

Role of Chromatin Damage and Chromatin Trapping of FACT in Mediating the Anticancer Cytotoxicity of DNA-Binding Small-Molecule Drugs.

Precisely how DNA-targeting chemotherapeutic drugs trigger cancer cell death remains unclear, as it is difficult to separate direct DNA damage from other effects in cells. Recent work on curaxins, a class of small-molecule drugs with broad anticancer activity, shows that they interfere with histone-DNA interactions and destabilize nucleosomes without causing detectable DNA damage. Chromatin damage caused by curaxins is sensed by the histone chaperone FACT, which binds unfolded nucleosomes becoming trapped in chromatin. In this study, we investigated whether classical DNA-targeting chemotherapeutic drugs also similarly disturbed chromatin to cause chromatin trapping of FACT (c-trapping). Drugs that directly bound DNA induced both chromatin damage and c-trapping. However, chromatin damage occurred irrespective of direct DNA damage and was dependent on how a drug bound DNA, specifically, in the way it bound chromatinized DNA in cells. FACT was sensitive to a plethora of nucleosome perturbations induced by DNA-binding small molecules, including displacement of the linker histone, eviction of core histones, and accumulation of negative supercoiling. Strikingly, we found that the cytotoxicity of DNA-binding small molecules correlated with their ability to cause chromatin damage, not DNA damage. Our results suggest implications for the development of chromatin-damaging agents as selective anticancer drugs.Significance: These provocative results suggest that the anticancer efficacy of traditional DNA-targeting chemotherapeutic drugs may be based in large part on chromatin damage rather than direct DNA damage. Cancer Res; 78(6); 1431-43. ©2018 AACR.

Aclarubicin, an anthracycline anti-cancer drug, fluorescently contrasts mitochondria and reduces the oxygen consumption rate in living human cells.

Aclarubicin (Acla), an effective anthracycline chemotherapeutic agent for hematologic cancers and solid tumors, is documented to perturb chromatin function via histone eviction and DNA topoisomerase inhibition in the nucleus, but much less attention has been paid to cytotoxic function in the cytoplasm. Here, we showed that Acla emitted fluorescence and that human cervical cancer HeLa cells exposed to Acla exhibited bright fluorescence signals in the cytoplasm when fluorescence microscopy was performed using the red filter (excitation 530-550nm/emission 575nm). Intriguingly, most of the signals appeared to be partitioned and enriched in entangled tubule-like structures; moreover, these signals merged with the mitochondria-specific MitoTracker signals. Notably, analysis of mitochondrial respiratory activity revealed that the oxygen consumption rate was decreased in Acla-treated cells. These findings suggest that Acla accumulates efficiently in the mitochondria of living human cells and leads to mitochondrial dysfunction, implying a previously overlooked cytotoxicity of Acla in the cytoplasm and adding mechanistic insight of the anti-cancer activity, as well as the side effects, of Acla/anthracycline-based chemotherapy.

[Synergistic lethal effect of combined treatment of arsenic trioxide and aclacinomycin on human acute myeloid leukemia cell line KG-1a].

Objective: To investigate the synergistic lethal effect and mechanism of arsenic trioxide (ATO) and aclacinomycin (ACM) on human acute myeloid leukemia cell line KG-1a. Methods: Colony-forming assay was used to detect the proliferation of KG-1a cells treated with different concentration of ATO and ACM. Compusyn software was used to analyze the synergistic effect of ATO and ACM. Flow cytometry and Wright's staining were used to analyze the apoptotic rate of KG-1a cells induced by combined treatment of ATO and ACM. Western blot was used to determine the expression of proteins associated with apoptosis. Results: The cytotoxicity of arsenic trioxide or aclacinomycin alone was in a dose-dependent manner. Flow cytometry analysis showed that the apoptotic rate of KG-1a cells treated with both 0.4 µmol/L ATO and 10 nmol/L ACM was (34.5±3.1)%, significantly higher than (7.6±1.1)% of 0.4 µmol/L ATO treatment or (18.7±2.3) % of 10 nmol/L ACM treatment alone (P<0.05). The apoptotic rate of KG-1a cells treated with both 1.5 µmol/L ATO and 37.5 nmol/L ACM was (52.5±4.7)%, significantly higher than (19.1±3.2)% of 1.5 µmol/L ATO treatment or (27.7±2.2)% of 37.5 nmol/L ACM treatment alone (P<0.05). The apoptotic rate of KG-1a cells treated with both 3.0 µmol/L ATO and 75 nmol/L ACM was (61.3±4.5)%, significantly higher than (29.5±2.5)% of 3.0 µmol/L ATO treatment or (28.6±3.4) % of 75 nmol/L ACM treatment alone (P<0.05). In addition, the result of Wright's staining showed that combined treatment of ATO and ACM induced a more apparent phenotype of apoptosis when compared with single agent treatment. Compusyn software analysis showed that the combination index (CI) value of combined treatment group was less than 1, which indicated the synergistic effect of these two agents. Conclusions: Combined treatment of ATO and ACM shows a synergistic lethal effect on human acute myeloid leukemia cell line KG-1a via activating the apoptotic pathway, which inhibits cell growth and induces apoptosis.

DNase-active TREX1 frame-shift mutants induce serologic autoimmunity in mice.

TREX1/DNASE III, the most abundant 3'-5' DNA exonuclease in mammalian cells, is tail-anchored on the endoplasmic reticulum (ER). Mutations at the N-terminus affecting TREX1 DNase activity are associated with autoimmune and inflammatory conditions such as Aicardi-Goutières syndrome (AGS). Mutations in the C-terminus of TREX1 cause loss of localization to the ER and dysregulation of oligosaccharyltransferase (OST) activity, and are associated with retinal vasculopathy with cerebral leukodystrophy (RVCL) and in some cases with systemic lupus erythematosus (SLE). Here we investigate mice with conditional expression of the most common RVCL mutation, V235fs, and another mouse expressing a conditional C-terminal mutation, D272fs, associated with a case of human SLE. Mice homozygous for either mutant allele express the encoded human TREX1 truncations without endogenous mouse TREX1, and both remain DNase active in tissues. The two mouse strains are similar phenotypically without major signs of retinal, cerebral or renal disease but exhibit striking elevations of autoantibodies in the serum. The broad range of autoantibodies is primarily against non-nuclear antigens, in sharp contrast to the predominantly DNA-related autoantibodies produced by a TREX1-D18N mouse that specifically lacks DNase activity. We also found that treatment with an OST inhibitor, aclacinomycin, rapidly suppressed autoantibody production in the TREX1 frame-shift mutant mice. Together, our study presents two new mouse models based on TREX1 frame-shift mutations with a unique set of serologic autoimmune-like phenotypes.

Homoharringtonine combined with aclarubicin and cytarabine synergistically induces apoptosis in t(8;21) leukemia cells and triggers caspase-3-mediated cleavage of the AML1-ETO oncoprotein.

Homoharringtonine combined with aclarubicin and cytarabine (HAA) is a highly effective treatment for acute myeloid leukemia (AML), especially for t(8;21) AML. However, the underlying mechanisms by which HAA kills t(8;21) AML cells remain unclear. In this study, SKNO-1 and Kasumi-1 cells with t(8;21) were used. Compared with individual or pairwise administration of homoharringtonine, aclarubicin, or cytarabine, HAA showed the strongest inhibition of growth and induction of apoptosis in SKNO-1 and Kasumi-1 cells. HAA caused cleavage of the AML1-ETO (AE) oncoprotein to form truncated AE (ΔAE). Pretreatment with the caspase-3 inhibitor caspase-3 inhibitor Q-DEVD-OPh (QDO) not only suppressed HAA-induced apoptosis but also abrogated the cleavage of AE and generation of ΔAE. These results suggest that HAA synergistically induces apoptosis in t(8;21) leukemia cells and triggers caspase-3-mediated cleavage of the AML1-ETO oncoprotein, thus providing direct evidence for the strong activity of HAA toward t(8;21) AML.

Cytosolic Nuclease TREX1 Regulates Oligosaccharyltransferase Activity Independent of Nuclease Activity to Suppress Immune Activation.

TREX1 is an endoplasmic reticulum (ER)-associated negative regulator of innate immunity. TREX1 mutations are associated with autoimmune and autoinflammatory diseases. Biallelic mutations abrogating DNase activity cause autoimmunity by allowing immunogenic self-DNA to accumulate, but it is unknown how dominant frameshift (fs) mutations that encode DNase-active but mislocalized proteins cause disease. We found that the TREX1 C terminus suppressed immune activation by interacting with the ER oligosaccharyltransferase (OST) complex and stabilizing its catalytic integrity. C-terminal truncation of TREX1 by fs mutations dysregulated the OST complex, leading to free glycan release from dolichol carriers, as well as immune activation and autoantibody production. A connection between OST dysregulation and immune disorders was demonstrated in Trex1(-/-) mice, TREX1-V235fs patient lymphoblasts, and TREX1-V235fs knock-in mice. Inhibiting OST with aclacinomycin corrects the glycan and immune defects associated with Trex1 deficiency or fs mutation. This function of the TREX1 C terminus suggests a potential therapeutic option for TREX1-fs mutant-associated diseases.

Chemical profiling of the genome with anti-cancer drugs defines target specificities.

Many anticancer drugs induce DNA breaks to eliminate tumor cells. The anthracycline topoisomerase II inhibitors additionally cause histone eviction. Here, we performed genome-wide high-resolution mapping of chemotherapeutic effects of various topoisomerase I and II (TopoI and II) inhibitors and integrated this mapping with established maps of genomic or epigenomic features to show their activities in different genomic regions. The TopoI inhibitor topotecan and the TopoII inhibitor etoposide are similar in inducing DNA damage at transcriptionally active genomic regions. The anthracycline daunorubicin induces DNA breaks and evicts histones from active chromatin, thus quenching local DNA damage responses. Another anthracycline, aclarubicin, has a different genomic specificity and evicts histones from H3K27me3-marked heterochromatin, with consequences for diffuse large B-cell lymphoma cells with elevated levels of H3K27me3. Modifying anthracycline structures may yield compounds with selectivity for different genomic regions and activity for different tumor types.

Low-dose arsenic trioxide combined with aclacinomycin A synergistically enhances the cytotoxic effect on human acute myelogenous leukemia cell lines by induction of apoptosis.

Acute myeloid leukemia (AML) is a common disorder in the elderly. Although remarkable progress has been made over recent decades, the outcome remains poor. Thus, the development of a more effective method to overcome this problem is necessary. In this study, we aimed to investigate the synergistic cytotoxic effect of low-dose arsenic trioxide (As2O3) combined with aclacinomycin A (ACM) on the human AML cell lines KG-1a and HL-60, and to clarify the underlying mechanism. Results showed that As2O3 combined with ACM exerted a synergistic cytotoxic effect by activation of the apoptosis pathway. Additionally, we found that the combination treatment decreased Bcl-2, c-IAP and XIAP expression but increased SMAC and caspase-3 expression more significantly than the single drug treatments. Furthermore, combination index (CI) values were < 1 in all matched combination groups. Additional evaluation of As2O3 combined with ACM as a potential therapeutic benefit for AML seems warranted.

Redox-regulated pathway of tyrosine phosphorylation underlies NF-κB induction by an atypical pathway independent of the 26S proteasome.

Alternative redox stimuli such as pervanadate or hypoxia/reoxygenation, induce transcription factor NF-κB by phospho-tyrosine-dependent and proteasome-independent mechanisms. While considerable attention has been paid to the absence of proteasomal regulation of tyrosine phosphorylated IκBα, there is a paucity of information regarding proteasomal regulation of signaling events distinct from tyrosine phosphorylation of IκBα. To delineate roles for the ubiquitin-proteasome pathway in the phospho-tyrosine dependent mechanism of NF-κB induction, we employed the proteasome inhibitor, Aclacinomycin, and the phosphotyrosine phosphatase inhibitor, pervanadate (PV). Results from these studies demonstrate that phospho-IκBα (Tyr-42) is not subject to proteasomal degradation in a murine stromal epithelial cell line, confirming results previously reported. Correspondingly, proteasome inhibition had no discernable effect on the key signaling intermediaries, Src and ERK1/2, involved in the phospho-tyrosine mechanisms regulating PV-mediated activation of NF-κB. Consistent with previous reports, a significant redox imbalance leading to the activation of tyrosine kinases, as occurs with pervanadate, is required for the induction of NF-κB. Strikingly, our studies demonstrate that proteasome inhibition can potentiate oxidative stress associated with PV-stimulation without impacting kinase activation, however, other cellular implications for this increase in intracellular oxidation remain to be fully delineated.

ß-Catenin and AKT are promising targets for combination therapy in acute myeloid leukemia.

In this study, we confirmed that combining HHT with ACR can result in synergistic cytotoxicity to AML cells in vitro and in vivo. Combining HHT and ACR simultaneously inhibited PI3K/AKT and WNT/ß-catenin signaling in AML cells. Significant increases in growth inhibition and apoptosis were induced by an AKT inhibitor when the WNT3A gene of THP-1 cells was silenced. HHT+ACR could synergistically induce the apoptosis of CD34(+)/CD38(-) primary AML cells. These results highlight ß-catenin and AKT are promising targets for combination therapy for AML.