Impact of elevated anti-apoptotic MCL-1 and BCL-2 on the development and treatment of MLL-AF9 AML in mice

Stromal bone marrow fibroblasts and mesenchymal stem cells support acute myeloid leukaemia cells and promote therapy resistance

The bone marrow (BM) is the primary site of adult haematopoiesis, where stromal elements (e.g. fibroblasts and mesenchymal stem cells [MSCs]) work in concert to support blood cell development. However, the establishment of an abnormal clone can lead to a blood malignancy, such as acute myeloid leukaemia (AML). Despite our increased understanding of the pathophysiology of the disease, patient survival remains suboptimal, mainly driven by the development of therapy resistance. In this review, we highlight the importance of bone marrow fibroblasts and MSCs in health and acute myeloid leukaemia and their impact on patient prognosis. We discuss how stromal elements reduce the killing effects of therapies via a combination of contact-dependent (e.g. integrins) and contact-independent (i.e. secreted factors) mechanisms, accompanied by the establishment of an immunosuppressive microenvironment. Importantly, we underline the challenges of therapeutically targeting the bone marrow stroma to improve acute myeloid leukaemia patient outcomes, due to the inherent heterogeneity of stromal cell populations. LINKED ARTICLES: This article is part of a themed issue on Cancer Microenvironment and Pharmacological Interventions. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.2/issuetoc.

A preliminary study on the mechanism of VASH2 in childhood medulloblastoma

To study the differences in VASH2 expression in pediatric medulloblastoma (MB) tumor tissues of different molecular subtypes, to analyze the correlation between VASH2 and the molecular subtypes of medulloblastoma, clinicopathological data, and prognosis, and to explore the specific mechanism of VASH2's role in SHH medulloblastoma cell lines DAOY. We analyzed 47 pediatric medulloblastoma cases admitted to the Department of Pediatric Neurosurgery of the First Affiliated Hospital of Xinjiang Medical University from January 2011 to December 2019, and the expression levels of YAP1 and GAB1 in these tumor tissues were detected by immunohistochemistry (IHC) and molecularly typed (WNT-type, SHH-type, and non-WNT/SHH-type). The correlation between VASH2 and molecular typing of medulloblastoma was analyzed. We also analyzed the medulloblastoma dataset in the GEO database (GSE30074 and GSE202043) to explore the correlation between VASH2 and the prognosis of medulloblastoma patients, as well as performed a comprehensive GO enrichment analysis specifically for the VASH2 gene to reveal the underlying biological pathways of its complex molecular profile. We used vasopressin 2 (VASH2) as a research target and overexpressed and knocked down VASH2 in SHH medulloblastoma cell lines DAOY by lentiviral vectors in vitro, respectively, to investigate its role in SHH medulloblastoma cell lines DAOY cell proliferation, apoptosis, migration, invasion and biological roles in the cell cycle. (1) Among 47 pediatric medulloblastoma cases, 8 were WNT type, 29 were SHH type, and 10 were non-WNT/SHH type. the positive rate of VASH2 was highest in the SHH type with a 68.97% positive rate, followed by non-WNT/SHH and lowest in the WNT type. The results of the multifactorial analysis showed that positive expression of VASH2 was associated with medulloblastoma molecular subtype (SHH type), site of tumor development (four ventricles), and gender (male), P < 0.05. (2) The results of cellular experiments showed that overexpression of VASH2 increased the invasion and migration ability of medulloblast Daoy, while knockdown of VASH2 inhibited the invasion and Overexpression of VASH2 upregulated the expression of Smad2 + 3, Smad4, Mmp2 and the apoptotic indicators Bcl-2 and Caspase3, while knockdown of VASH2 suppressed the expression of Smad2 + 3 and Mmp2, and silenced the expression of Smad4 and the apoptotic indicators Bcl2, Caspase3 expression. Flow cytometric cycle analysis showed that VASH2 overexpression increased the S phase in the Daoy cell cycle, while VASH2 knockdown decreased the S phase in the SHH medulloblastoma cell lines DAOY cell cycle. Bioinformatics analysis showed that there was no statistically significant difference between the expression of VASH2 genes in the GSE30074 and GSE202043 datasets and the prognosis of the patients, but the results of this dataset analysis suggested that we need to continue to expand the sample size of the study in the future. The results of the GO enrichment analysis showed that the angiogenic pathway was the most significantly enriched, and the PPI interactions network of VASH2 was obtained from the STRING database. Using the STRING database, we obtained the PPI interaction network of VASH2, and the KEGG enrichment analysis of VASH2-related genes showed that VASH2-related genes were related to the apoptosis pathway, and therefore it was inferred that VASH2 also affects the development of tumors through apoptosis. We found for the first time that the positive expression rate of VASH2 was closely associated with SHH-type pediatric medulloblastoma and that VASH2 was involved in the invasion, migration, cell cycle, and apoptotic capacity of SHH medulloblastoma cell lines DAOY by affecting downstream indicators of the TGF-β pathway. This suggests that it is involved in the progression of pediatric medulloblastoma, and VASH2 is expected to be a diagnostic and therapeutic target for SHH-type pediatric medulloblastoma.

NADPH oxidase mediated oxidative stress signaling in FLT3-ITD acute myeloid leukemia

The internal tandem duplication of the juxtamembrane domain of the FMS-like tyrosine kinase 3 (FLT3-ITD) is the most common genetic change in acute myeloid leukemia (AML), and about 30% of all AMLs harbor a FLT3-ITD mutation. Even though FLT3 inhibitors have displayed encouraging effects in FLT3-ITD-mutated AML, the extent of the clinical response to these compounds is cut short due to the rapid development of drug resistance. Evidence has shown that FLT3-ITD triggered activation of oxidative stress signaling may exert a pivotal role in drug resistance. The downstream pathways of FLT3-ITD, including STAT5, PI3K/AKT, and RAS/MAPK, are considered to be major oxidative stress signaling pathways. These downstream pathways can inhibit apoptosis and promote proliferation and survival by regulating apoptosis-related genes and promoting the generation of reactive oxygen species (ROS) through NADPH oxidase (NOX) or other mechanisms. Appropriate levels of ROS may promote proliferation, but high levels of ROS can lead to oxidative damage to the DNA and increase genomic instability. In addition, post-translational modifications of FLT3-ITD and changes in its subcellular localization can affect downstream signaling which may also be one of the mechanisms leading to drug resistance. In this review, we summarized the research progress on NOX mediated oxidative stress signaling and its relationship with drug resistance in FLT3-ITD AML, and discuss the possible new targets in FLT3-ITD signal blocking to reverse drug resistance in FLT3-ITD-mutated AML.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Dual targeting of BCL-2 and MCL-1 in the presence of BAX breaks venetoclax resistance in human small cell lung cancer

BACKGROUND

No targeted drugs are currently available against small cell lung cancer (SCLC). BCL-2 family members are involved in apoptosis regulation and represent therapeutic targets in many malignancies.

METHODS

Expression of BCL-2 family members in 27 SCLC cell lines representing all known four SCLC molecular subtypes was assessed by qPCR, Western blot and mass spectrometry-based proteomics. BCL-2 and MCL-1 inhibition (venetoclax and S63845, respectively) was assessed by MTT assay and flow cytometry and in mice bearing human SCLC tumours. Drug interactions were calculated using the Combenefit software. Ectopic BAX overexpression was achieved by expression plasmids.

RESULTS

The highest BCL-2 expression levels were detected in ASCL1- and POU2F3-driven SCLC cells. Although sensitivity to venetoclax was reflected by BCL-2 levels, not all cell lines responded consistently despite their high BCL-2 expression. MCL-1 overexpression and low BAX levels were both characteristic for venetoclax resistance in SCLC, whereas the expression of other BCL-2 family members did not affect therapeutic efficacy. Combination of venetoclax and S63845 resulted in significant, synergistic in vitro and in vivo anti-tumour activity and apoptosis induction in double-resistant cells; however, this was seen only in a subset with detectable BAX. In non-responding cells, ectopic BAX overexpression sensitised to venetoclax and S63845 and, furthermore, induced synergistic drug interaction.

CONCLUSIONS

The current study reveals the subtype specificity of BCL-2 expression and sheds light on the mechanism of venetoclax resistance in SCLC. Additionally, we provide preclinical evidence that combined BCL-2 and MCL-1 targeting is an effective approach to overcome venetoclax resistance in high BCL-2-expressing SCLCs with intact BAX.

Olive leaves extract alleviates inflammation and modifies the intrinsic apoptotic signal in the leukemic bone marrow

Introduction

Current anti-leukemic chemotherapies with multiple targets suffer from side effects. Synthetic drugs with huge off-target effects are detrimental to leukemic patients. Therefore, natural plant-based products are being increasingly tested for new anti-leukemic therapy with fewer or no side effects. Herein, we report the effect of ethanolic olive leaves extract (EOLE) on the K562 cell line and on the bone marrow (BM) of N-ethyl-N-nitrosourea (ENU)-induced leukemic mice.

Methods

Using standard methodologies, we assessed viability, chromatin condensation, and induction of apoptosis in EOLE-treated K562 cells in-vitro. The anti-leukemic activity of EOLE was assayed by measuring ROS, levels of various cytokines, expression of iNOS and COX-2 gene, and changes in the level of important apoptosis regulatory and cell signaling proteins in-vivo.

Result

K562 cells underwent apoptotic induction after exposure to EOLE. In the BM of leukemic mice, EOLE therapy decreased the number of blast cells, ROS generation, and expression of NF-κB and ERK1/2. IL-6, IL-1β, TNF-α, iNOS, and COX-2 were among the inflammatory molecules that were down-regulated by EOLE therapy. Additionally, it decreased the expression of anti-apoptotic proteins BCL2A1, BCL-xL, and MCL-1 in the BM of leukemic mice.

Discussion

Chronic inflammation and anomalous apoptotic mechanism both critically contribute to the malignant transformation of cells. Inflammation in the tumor microenvironment promotes the growth, survival, and migration of cancer cells, accelerating the disease. The current investigation showed that EOLE treatment reduces inflammation and alters the expression of apoptosis regulatory protein in the BM of leukemic mice, which may halt the progression of the disease.

Synergistic activity of ABT-263 and ONC201/TIC10 against solid tumor cell lines is associated with suppression of anti-apoptotic Mcl-1, BAG3, pAkt, and upregulation of pro-apoptotic Noxa and Bax cleavage during apoptosis

A major underlying cause of the resistance of solid tumor cells to cancer therapy is the evasion of cell death following anti-cancer drug treatment. We explored the combination of TRAIL-inducing compound ONC201/TIC10 and Bcl-xL/Bcl-2 inhibitor ABT-263 to target the extrinsic and intrinsic apoptotic pathways, respectively, in solid tumor cell lines (N = 13) derived from different tissues (colon, prostate, lung, breast, ovary, bladder). We found an IC50 range of 0.83-20.10 μM for ONC201 and 0.06-14.75 μM for ABT-263 among the 13 cancer cell lines. We show that combination of ONC201 and ABT-263 produces a strong synergistic effect leading to tumor cell death, and that the combination is not toxic to human fibroblast cells. In OVCAR-3 ovarian cancer cells, 2.5 μM ONC201 and 1.25 μM ABT-263 yielded 37% and 27% inhibition of viability, respectively, while the combination of the two agents yielded 92% inhibition of viability, resulting in a high synergy score of 52; conversely, the same combination in the HFF-1 human fibroblast cells yielded 2.45% inhibition of viability and a synergy score of 6.92 (synergy scores were calculated using SynergyFinder; scores greater than 10 are considered synergistic). We also found that the combination of these two agents resulted in synergistic caspase activation and PARP cleavage consistent with induction of apoptosis. Combination therapy-induced cell death correlated with decreased levels of Mcl-1, BAG3, pAkt, and upregulation of Noxa along with Bax cleavage during apoptosis at 48 hours, and ATF4, TRAIL, and DR5 induction at 24 hours. There was some heterogeneity in the cell lines with regard to these responses. Our data provide evidence for synergy from the combination of ONC201 and ABT-263 against human solid tumor cell lines associated with alterations in cell death and pro-survival mediators. The combination of ONC201 and ABT-263 merits further exploration in vivo and in clinical trials against a variety of solid malignancies.

Discovery of Mcl-1 inhibitors through virtual screening, molecular dynamics simulations and in vitro experiments

As a member of the B-cell lymphoma 2 (Bcl-2) protein family, the myeloid leukemia cell differentiation protein (Mcl-1) can inhibit apoptosis and plays an active role in the process of tumor escape from apoptosis. Therefore, inhibition of Mcl-1 protein can effectively promote the apoptosis of tumor cells and may also reduce tumor cell resistance to drugs targeting other anti-apoptotic proteins. This research is dedicated to the development of Mcl-1 inhibitors, aiming to provide more references for lead compounds with different scaffolds for the development of targeted anticancer drugs. We obtained a series of small molecules with a common core skeleton through molecular docking from Specs database and searched the core structure in ZINC database for more similar small molecules. Collecting these small molecules for preliminary experimental screening, we found a batch of active compounds, and selected two small molecules with the strongest inhibitory activity on B16F10 cells: compound 7 and compound 1. Their IC₅₀s are 7.86 ± 1.25 and 24.72 ± 1.94 μM, respectively. These two compounds were also put into cell scratch test for B16F10 cells and cell viability assay of other cell lines. Furthermore, through molecular dynamics (MD) simulation analysis, we found that compound 7 formed strong binding with the key P2, P3 pocket and ARG 263 of Mcl-1. Finally, ADME results showed that compound 7 performs well in terms of drug similarity. In conclusion, this study provides hits with co-scaffolds that may aid in the design of effective clinical drugs targeting Mcl-1 and the future drug development.

Bone Marrow Microenvironment as a Source of New Drug Targets for the Treatment of Acute Myeloid Leukaemia

Acute myeloid leukaemia (AML) is a heterogeneous disease with one of the worst survival rates of all cancers. The bone marrow microenvironment is increasingly being recognised as an important mediator of AML chemoresistance and relapse, supporting leukaemia stem cell survival through interactions among stromal, haematopoietic progenitor and leukaemic cells. Traditional therapies targeting leukaemic cells have failed to improve long term survival rates, and as such, the bone marrow niche has become a promising new source of potential therapeutic targets, particularly for relapsed and refractory AML. This review briefly discusses the role of the bone marrow microenvironment in AML development and progression, and as a source of novel therapeutic targets for AML. The main focus of this review is on drugs that modulate/target this bone marrow microenvironment and have been examined in in vivo models or clinically.

EIF4A inhibition targets bioenergetic homeostasis in AML MOLM-14 cells in vitro and in vivo and synergizes with cytarabine and venetoclax

BACKGROUND

Acute myeloid leukemia (AML) is an aggressive hematological cancer resulting from uncontrolled proliferation of differentiation-blocked myeloid cells. Seventy percent of AML patients are currently not cured with available treatments, highlighting the need of novel therapeutic strategies. A promising target in AML is the mammalian target of rapamycin complex 1 (mTORC1). Clinical inhibition of mTORC1 is limited by its reactivation through compensatory and regulatory feedback loops. Here, we explored a strategy to curtail these drawbacks through inhibition of an important effector of the mTORC1signaling pathway, the eukaryotic initiation factor 4A (eIF4A).

METHODS

We tested the anti-leukemic effect of a potent and specific eIF4A inhibitor (eIF4Ai), CR-1-31-B, in combination with cytosine arabinoside (araC) or the BCL2 inhibitor venetoclax. We utilized the MOLM-14 human AML cell line to model chemoresistant disease both in vitro and in vivo. In eIF4Ai-treated cells, we assessed for changes in survival, apoptotic priming, de novo protein synthesis, targeted intracellular metabolite content, bioenergetic profile, mitochondrial reactive oxygen species (mtROS) and mitochondrial membrane potential (MMP).

RESULTS

eIF4Ai exhibits anti-leukemia activity in vivo while sparing non-malignant myeloid cells. In vitro, eIF4Ai synergizes with two therapeutic agents in AML, araC and venetoclax. EIF4Ai reduces mitochondrial membrane potential (MMP) and the rate of ATP synthesis from mitochondrial respiration and glycolysis. Furthermore, eIF4i enhanced apoptotic priming while reducing the expression levels of the antiapoptotic factors BCL2, BCL-XL and MCL1. Concomitantly, eIF4Ai decreases intracellular levels of specific metabolic intermediates of the tricarboxylic acid cycle (TCA cycle) and glucose metabolism, while enhancing mtROS. In vitro redox stress contributes to eIF4Ai cytotoxicity, as treatment with a ROS scavenger partially rescued the viability of eIF4A inhibition.

CONCLUSIONS

We discovered that chemoresistant MOLM-14 cells rely on eIF4A-dependent cap translation for survival in vitro and in vivo. EIF4A drives an intrinsic metabolic program sustaining bioenergetic and redox homeostasis and regulates the expression of anti-apoptotic proteins. Overall, our work suggests that eIF4A-dependent cap translation contributes to adaptive processes involved in resistance to relevant therapeutic agents in AML.

Uncovering the Heterogeneity and Clinical Relevance of Circulating Tumor-Initiating Cells in Hepatocellular Carcinoma Using an Integrated Immunomagnetic-Microfluidic Platform

Circulating tumor-initiating cells (CTICs) with stem cell-like properties play pivotal roles in tumor metastasis and recurrence. However, little is known about the biology and clinical relevance of CTICs in hepatocellular carcinoma (HCC). Here, we investigated the molecular heterogeneity and clinical relevance of CTICs in HCC using a novel integrated immunomagnetic-microfluidic platform (iMAC). We constructed the iMAC and evaluated its ability to detect CTICs using a series of spiked cell experiments. A four-channel microfluidic chip was applied to investigate the composition of CTICs in patients with primary and recurrent HCC utilizing microbeads labeled with one of four stem-related markers: epithelial cell adhesion molecule (EpCAM), CD133, CD90, and CD24. The dynamic changes of these four CTIC subsets were serially monitored during treatment courses. Finally, single-cell RNA profiling was used to reveal the molecular characteristics of the four CTIC subsets. The iMAC platform detected significantly more EpCAM⁺ CTICs in the blood samples from 33 HCC patients than the FDA-approved CellSearch system (0.92 ± 0.94 vs 0.23 ± 0.36, P < 0.001). The number of EpCAM⁺ CTICs (≥0.75/mL) detected by iMAC was a predictor of early recurrence (P = 0.007). The distinct stem-related markers' expression of CTICs could distinguish primary HCC, recurrent HCC, and TACE-resistant HCC. Single-cell transcriptional profiling proved the heterogeneity among individual CTICs and separated the four CTIC subsets into distinct phenotypes. Dissecting the heterogeneity of CTICs using the iMAC represents a novel and informative method for accurate CTIC detection and characterization. This innovative technology will enable more indepth cancer biology research and clinical cancer management than is currently available.

siRNA Targeting Mcl-1 Potentiates the Anticancer Activity of Andrographolide Nanosuspensions via Apoptosis in Breast Cancer Cells

Breast cancer is the second leading cause of cancer-related death in the US. However, recurrence is frequently found despite adjuvant therapy being available. Combination therapy with cytotoxic drugs and gene therapy is being developed to be a new promising cancer treatment strategy. Introducing substituted dithiocarbamate moieties at the C12 position of andrographolide (3nAG) could improve its anticancer selectivity in the MCF-7 breast cancer cell line. However, its hydrophobicity is one of its main drawbacks. This work successfully prepared 3nAG nanosuspension stabilized with the chitosan derivative NSC (3nAGN-NSC) to increase solubility and pharmacological effectiveness. siRNAs have emerged as a promising therapeutic alternative for interfering with particular mRNA. The 3nAGN-NSC had also induced Mcl-1 mRNA expression in MCF-7 human breast cancer cells at 8, 12, and 24 h. This indicates that, in addition to Mcl-1 silencing by siRNA (siMcl-1) in MCF-7 with substantial Mcl-1 reliance, rationally devised combination treatment may cause the death of cancer cells in breast cancer. The Fa-CI analysis showed that the combination of 3nAGN-NSC and siMcl-1 had a synergistic effect with a combination index (CI) value of 0.75 (CI < 1 indicating synergistic effects) at the fractional inhibition of Fa 0.7. The synergistic effect was validated by flow cytometry, with the induction of apoptosis as the mechanism of reduced cell viability. Our findings suggested the rational use of 3nAGN-NSC in combination with siMcl-1 to kill breast cancer cells.

Gestational exposure to environmental cadmium induces placental apoptosis and fetal growth restriction via Parkin-modulated MCL-1 degradation

Heavy metal cadmium (Cd), a classical environmental pollutant, causes placental apoptosis and fetal growth restriction (FGR), whereby the mechanism remains unclear. Here, our human case-control study firstly showed that there was a positive association of Parkin mitochondrial translocation, MCL-1 reduction, placental apoptosis, and all-cause FGR. Subsequently, Cd was administered to establish in vitro and in vivo models of placental apoptosis or FGR. Our models demonstrated that Parkin mitochondrial translocation was observed in Cd-administrated placental trophoblasts. Meaningfully, Parkin siRNA (siR) dramatically mitigated Cd-triggered apoptosis in placental trophoblasts. Mdivi-1 (M-1), an inhibitor for Parkin mitochondrial translocation, mitigated Cd-induced apoptosis in placental trophoblasts, which further ameliorated the effect of attenuated placental sizes in Cd-exposed mice. Furthermore, the interaction of MCL-1 with Parkin or Ub in Cd-stimulated cells was stronger than that in controls. MG132, an inhibitor for proteasome, abolished MCL-1 degradation in Cd-stimulated cells. Importantly, Parkin siR and M-1 memorably abolished the ubiquitin-dependent degradation of MCL-1 in placental trophoblasts. Interestingly, mito-TEMPO and melatonin, two mitochondria-targeted antioxidants, obviously rescued Cd-caused mitochondrial membrane potential (MMP) decrease, Parkin mitochondrial translocation, MCL-1 degradation, and apoptosis in placental trophoblasts. In conclusion, cadmium induces placental apoptosis and FGR via mtROS-mediated Parkin-modulated degradation of MCL-1.

Co-Delivery of Paclitaxel and shMCL-1 by Folic Acid-Modified Nonviral Vector to Overcome Cancer Chemotherapy Resistance

Acquired chemoresistance presents a major clinical impediment, which is an urgent problem to be solved. Interestingly, myeloma cell leukemia-1 (MCL-1) and folate receptor expression levels are higher in chemotherapy-resistant patients than in pretreatment patients. In this study, a multifunctional folic acid (FA)-targeting core-shell structure is presented for simultaneous delivery of shMCL-1 and paclitaxel (PTX). The transfection efficiency of shMCL-1 with the FA-targeting delivery system is higher than with a nontargeting delivery system in Skov3 and A2780T cells. The FA-targeting system significantly inhibits cell growth, blocks cell cycles, and promotes apoptosis of cancer cells in vitro. The mechanisms involved in inhibiting growth are related to Bcl-2/Bax and cdc2/Cyclin B1 pathways. An analysis of RNA sequencing suggests that shMCL-1 reverses chemoresistance through regulating genes such as regulator of chromosome condensation 2 (RCC2). The synergetic effect of shMCL-1 and PTX effectively inhibits tumor growth in both PTX-resistant and normal cancer models by inducing tumor apoptosis, inhibiting proliferation, and limiting tumor angiogenesis. The study results indicate that a FA-targeting delivery system combining shMCL-1 with PTX can simultaneously target tumor sites and restore the sensitivity of chemotherapy-resistant cancer to PTX. These findings have important implications for patients with normal or PTX-resistant cancer.

Emerging roles of the HECT-type E3 ubiquitin ligases in hematological malignancies

Ubiquitination-mediated proteolysis or regulation of proteins, ultimately executed by E3 ubiquitin ligases, control a wide array of cellular processes, including transcription, cell cycle, autophagy and apoptotic cell death. HECT-type E3 ubiquitin ligases can be distinguished from other subfamilies of E3 ubiquitin ligases because they have a C-terminal HECT domain that directly catalyzes the covalent attachment of ubiquitin to their substrate proteins. Deregulation of HECT-type E3-mediated ubiquitination plays a prominent role in cancer development and chemoresistance. Several members of this subfamily are indeed frequently deregulated in human cancers as a result of genetic mutations and altered expression or activity. HECT-type E3s contribute to tumorigenesis by regulating the ubiquitination rate of substrates that function as either tumour suppressors or oncogenes. While the pathological roles of the HECT family members in solid tumors are quite well established, their contribution to the pathogenesis of hematological malignancies has only recently emerged. This review aims to provide a comprehensive overview of the involvement of the HECT-type E3s in leukemogenesis.

MYC: a multipurpose oncogene with prognostic and therapeutic implications in blood malignancies

MYC oncogene is a transcription factor with a wide array of functions affecting cellular activities such as cell cycle, apoptosis, DNA damage response, and hematopoiesis. Due to the multi-functionality of MYC, its expression is regulated at multiple levels. Deregulation of this oncogene can give rise to a variety of cancers. In this review, MYC regulation and the mechanisms by which MYC adjusts cellular functions and its implication in hematologic malignancies are summarized. Further, we also discuss potential inhibitors of MYC that could be beneficial for treating hematologic malignancies.

Celecoxib Analogues for Cancer Treatment: An Update on OSU-03012 and 2,5-Dimethyl-Celecoxib

Cyclooxygenase-2 (COX-2) is an important enzyme involved in prostaglandins biosynthesis from arachidonic acid. COX-2 is frequently overexpressed in human cancers and plays a major tumor promoting function. Accordingly, many efforts have been devoted to efficiently target the catalytic site of this enzyme in cancer cells, by using COX-2 specific inhibitors such as celecoxib. However, despite their potent anti-tumor properties, the myriad of detrimental effects associated to the chronic inhibition of COX-2 in healthy tissues, has considerably limited their use in clinic. In addition, increasing evidence indicate that these anti-cancerous properties are not strictly dependent on the inhibition of the catalytic site. These findings have led to the development of non-active COX-2 inhibitors analogues aiming at preserving the antitumor effects of COX-2 inhibitors without their side effects. Among them, two celecoxib derivatives, 2,5-Dimethyl-Celecoxib and OSU-03012, have been developed and suggested for the treatment of viral (e.g., recently SARS-CoV-2), inflammatory, metabolic diseases and cancers. These molecules display stronger anti-tumor properties than celecoxib and thus may represent promising anti-cancer molecules. In this review, we discuss the impact of these two analogues on cancerous processes but also their potential for cancer treatment alone or in combination with existing approaches.

Pimozide and Imipramine Blue Exploit Mitochondrial Vulnerabilities and Reactive Oxygen Species to Cooperatively Target High Risk Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogeneous disease with a high relapse rate. Cytokine receptor targeted therapies are therapeutically attractive but are subject to resistance-conferring mutations. Likewise, targeting downstream signaling pathways has been difficult. Recent success in the development of synergistic combinations has provided new hope for refractory AML patients. While generally not efficacious as monotherapy, BH3 mimetics are very effective in combination with chemotherapy agents. With this in mind, we further explored novel BH3 mimetic drug combinations and showed that pimozide cooperates with mTOR inhibitors and BH3 mimetics in AML cells. The three-drug combination was able to reach cells that were not as responsive to single or double drug combinations. In Flt3-internal tandem duplication (ITD)-positive cells, we previously showed pimozide to be highly effective when combined with imipramine blue (IB). Here, we show that Flt3-ITD⁺ cells are sensitive to an IB-induced dynamin 1-like (Drp1)-p38-ROS pathway. Pimozide contributes important calcium channel blocker activity converging with IB on mitochondrial oxidative metabolism. Overall, these data support the concept that antioxidants are a double-edged sword. Rationally designed combination therapies have significant promise for further pre-clinical development and may ultimately lead to improved responses.

Mitochondrial metabolism as a target for acute myeloid leukemia treatment

Acute myeloid leukemias (AML) are a group of aggressive hematologic malignancies resulting from acquired genetic mutations in hematopoietic stem cells that affect patients of all ages. Despite decades of research, standard chemotherapy still remains ineffective for some AML subtypes and is often inappropriate for older patients or those with comorbidities. Recently, a number of studies have identified unique mitochondrial alterations that lead to metabolic vulnerabilities in AML cells that may present viable treatment targets. These include mtDNA, dependency on oxidative phosphorylation, mitochondrial metabolism, and pro-survival signaling, as well as reactive oxygen species generation and mitochondrial dynamics. Moreover, some mitochondria-targeting chemotherapeutics and their combinations with other compounds have been FDA-approved for AML treatment. Here, we review recent studies that illuminate the effects of drugs and synergistic drug combinations that target diverse biomolecules and metabolic pathways related to mitochondria and their promise in experimental studies, clinical trials, and existing chemotherapeutic regimens.

Tumor-targeted nanoparticles improve the therapeutic index of BCL2 and MCL1 dual inhibition

Cancer and normal cells use multiple antiapoptotic BCL2 proteins to prevent cell death. Therapeutic targeting of multiple BCL2 family proteins enhances tumor killing but is also associated with increased systemic toxicity. Here, we demonstrate that the dual targeting of MCL1 and BCL2 proteins using the small molecules S63845 and venetoclax induces durable remissions in mice that harbor human diffuse large B-cell lymphoma (DLBCL) tumors but is accompanied by hematologic toxicity and weight loss. To mitigate these toxicities, we encapsulated S63845 or venetoclax into nanoparticles that target P-selectin, which is enriched in tumor endothelial cells. In vivo and ex vivo imaging demonstrated preferential targeting of the nanoparticles to lymphoma tumors over vital organs. Mass spectrometry analyses after administration of nanoparticle drugs confirmed tumor enrichment of the drug while reducing plasma levels. Furthermore, nanoparticle encapsulation allowed 3.5- to 6.5-fold reduction in drug dose, induced sustained remissions, and minimized toxicity. Our results support the development of nanoparticles to deliver BH3 mimetic combinations in lymphoma and in general for toxic drugs in cancer therapy.

BH3 Mimetics in AML Therapy: Death and Beyond?

B cell lymphoma 2 (BCL2) homology domain 3 (BH3) mimetics are targeted therapeutic agents that allow response prediction and patient stratification. BH3 mimetics are prototypical activators of the mitochondrial death program in cancer. They emerged as important modulators of cellular mechanisms contributing to poor therapeutic responses, including cancer cell stemness, cancer-specific metabolic routes, paracrine signaling to the tumor microenvironment, and immune modulation. We present an overview of the antagonism between BH3 mimetics and antiapoptotic BCL2 proteins. We focus on acute myeloid leukemia (AML), a cancer with reduced therapeutic options that have recently been improved by BH3 mimetics.

Ubiquitination and deubiquitination of MCL1 in cancer: deciphering chemoresistance mechanisms and providing potential therapeutic options

MCL1 is an important antiapoptotic member of the BCL-2 family that is distinguishable from other family members based on its relatively short half-life. Emerging studies have revealed the crucial role of MCL1 in the chemoresistance of cancer cells. The antiapoptotic function of MCL1 makes it a popular therapeutic target, although specific inhibitors have begun to emerge only recently. Notably, emerging studies have reported that several E3 ligases and deubiquitinases modulate MCL1 stability, providing an alternate means of targeting MCL1 activity. In addition, the emergence and development of proteolysis-targeting chimeras, the function of which is based on ubiquitination-mediated degradation, has shown great potential. In this review, we provide an overview of the studies investigating the ubiquitination and deubiquitination of MCL1, summarize the latest evidence regarding the development of therapeutic strategies targeting MCL1 in cancer treatment, and discuss the promising future of targeting MCL1 via the ubiquitin–proteasome system in clinical practice.

Abivertinib synergistically strengthens the anti-leukemia activity of venetoclax in acute myeloid leukemia in a BTK-dependent manner

B‐cell lymphoma 2 (BCL‐2), a crucial member of the anti‐apoptotic BCL‐2 family, is frequently dysregulated in cancer and plays an important role in acute myeloid leukemia (AML). Venetoclax is a highly selective BCL‐2 inhibitor that has been approved by the FDA for treating elderly AML patients. However, the emergence of resistance after long‐term treatment emphasizes the need for a deeper understanding of the potential mechanisms of resistance and effective rescue methods. By using RNA‐seq analysis in two human AML cohorts made up of three patients with complete remission and three patients without remission after venetoclax treatment, we identified that upregulation of BTK enabled AML blast resistance to venetoclax. Interestingly, we found that abivertinib, an oral BTK inhibitor, could synergize with venetoclax to inhibit the proliferation of primary AML cells and cell lines. It is worth noting that the combination of the two effectively enhanced the sensitivity of two AML patients (AML#3 and AML#12) to venetoclax. In this study, we demonstrated that combined use of the two drugs can synergistically inhibit the colony‐forming capacity of AML cells, arrest the AML cell cycle in the G0/G1 phase, and inhibit the BCL‐2 anti‐apoptotic family protein, activating the caspase family to induce apoptosis. Mechanistically, knockdown of BTK in AML cell lines impaired the synergistic effect of the two drugs. In vivo study showed similar results as those seen in vitro. Abivertinib in combination with venetoclax could significantly prolong the survival time and reduce the tumor burden of MV4‐11‐NSG mice compared with those of control and single‐agent groups. Our in vitro and in vivo studies have shown that the combination of abivertinib and venetoclax may benefit AML patients, especially in patients resistant to venetoclax or those that relapse. New clinical trials will be planned.

WT1 facilitates the self-renewal of leukemia-initiating cells through the upregulation of BCL2L2: WT1-BCL2L2 axis as a new acute myeloid leukemia therapy target

Background

Overexpression of Wilms’ tumor-1 (WT1) transcription factor facilitates proliferation in acute myeloid leukemia (AML). However, whether WT1 is enriched in the leukemia-initiating cells (LICs) and leukemia stem cells (LSCs) and facilitates the self-renewal of LSCs remains poorly understood.

Methods

MLL-AF9-induced murine leukemia model was used to evaluate the effect of knockdown of wt1 on the self-renewal ability of LSC. RNA sequencing was performed on WT1-overexpressing cells to select WT1 targets. Apoptosis and colony formation assays were used to assess the anti-leukemic potential of a deubiquitinase inhibitor WP1130. Furthermore, NOD/SCID-IL2Rγ (NSG) AML xenotransplantation and MLL-AF9-induced murine leukemia models were used to evaluate the anti-leukemogenic potential of WP1130 in vivo.

Results

We found that wt1 is highly expressed in LICs and LSCs and facilitates the maintenance of leukemia in a murine MLL-AF9-induced model of AML. WT1 enhanced the self-renewal of LSC by increasing the expression of BCL2L2, a member of B cell lymphoma 2 (BCL2) family, by direct binding to its promoter region. Loss of WT1 impaired self-renewal ability in LSC and delayed the progression of leukemia. WP1130 was found to modify the WT1-BCL2L2 axis, and WP1130-induced anti-leukemic activity was mediated by ubiquitin proteasome-mediated destruction of WT1 protein. WP1130 induced apoptosis and decreased colony formation abilities of leukemia cells and prolonged the overall survival in the THP1-based xenograft NSG mouse model. WP1130 also decreased the frequency of LSC and prolonged the overall survival in MLL-AF9-induced murine leukemia model. Mechanistically, WP1130 induced the degradation of WT1 by positively affecting the ubiquitination of WT1 protein.

Conclusions

Our results indicate that WT1 is required for the development of AML. WP1130 exhibits anti-leukemic activity by inhibiting the WT1-BCL2L2 axis, which may represent a new acute myeloid leukemia therapy target.

Targeting Bim via a lncRNA Morrbid Regulates the Survival of Preleukemic and Leukemic Cells

Inhibition of anti-apoptotic proteins BCL-2 and MCL-1 to release pro-apoptotic protein BIM and reactivate cell death could potentially be an efficient strategy for the treatment of leukemia. Here, we show that a lncRNA, MORRBID, a selective transcriptional repressor of BIM, is overexpressed in human acute myeloid leukemia (AML), which is associated with poor overall survival. In both human and animal models, MORRBID hyperactivation correlates with two recurrent AML drivers, TET2 and FLT3ITD. Mice with individual mutations of Tet2 or Flt3ITD develop features of chronic myelomonocytic leukemia (CMML) and myeloproliferative neoplasm (MPN), respectively, and combined presence results in AML. We observe increased levels of Morrbid in murine models of CMML, MPN, and AML. Functionally, loss of Morrbid in these models induces increased expression of Bim and cell death in immature and mature myeloid cells, which results in reduced infiltration of leukemic cells in tissues and prolongs the survival of AML mice.

Targeting MCL-1 in hematologic malignancies: Rationale and progress

Myeloid cell leukemia sequence 1 (MCL-1) is an antiapoptotic protein that plays a key role in promoting cell survival in multiple myeloma (MM), acute myeloid leukemia (AML), and non-Hodgkin lymphoma (NHL). Overexpression of MCL-1 is associated with treatment resistance and poor prognosis; thus, MCL-1 inhibitors are rational therapeutic options for malignancies depending on MCL-1. Several MCL-1 inhibitors have entered clinical trials, including AZD5991, S64315, AMG 176, and AMG 397. A key area of investigation is whether MCL-1 inhibitors will complement the activity of BCL-2 inhibitors, such as venetoclax, and synergistically enhance anti-tumor efficacy when given in combination with other anti-cancer drugs. Another important question is whether a safe therapeutic window can be found for this new class of inhibitors. In summary, inhibition of MCL-1 shows potential as a treatment for hematologic malignancies and clinical evaluation of MCL-1 inhibitors is currently underway.

Impact of BH3-mimetics on Human and Mouse Blood Leukocytes: A Comparative Study

BH3-mimetics are small molecule inhibitors that neutralize the function of anti-apoptotic BCL-2 family members. BH3-mimetics have recently gained a lot of popularity in oncology because of their success in cancer treatment. However, BH3-mimetics might have a broader clinical application. Here, we established an ex vivo flow cytometric assay allowing the comparison of the impact of BH3-mimetics (ABT-199, ABT-263, WEHI-539, and S63845) on leukocyte populations of both, healthy human subjects and C57BL/6 J wild type mice. BH3-mimetics were added to freshly drawn blood that was diluted 1/2 in cell medium, and BH3-mimetics-mediated impact on leukocyte count was assessed by flow cytometry. Our results demonstrate that responses towards 1μM of BH3-mimetics can be identical as well as considerably different in leukocytes of humans and mice. For instance, the inhibition of BCL-2 by ABT-199 caused cell death in all types of lymphocytes in mice but was exclusively specific for B cells in humans. Moreover, inhibition of BCL-X_L by WEHI-539 affected solely mouse leukocytes while targeting MCL-1 by S63845 resulted in efficient induction of cell death in human neutrophils but not in their mouse counterparts. Our ex vivo assay enables initial identification of analogies and differences between human and mouse leukocytes in response towards BH3-mimetics.

Improved chemotherapy modeling with RAG-based immune deficient mice

We have previously characterized an acute myeloid leukemia (AML) chemotherapy model for SCID-based immune deficient mice (NSG and NSGS), consisting of 5 days of cytarabine (AraC) and 3 days of anthracycline (doxorubicin), to simulate the standard 7+3 chemotherapy regimen many AML patients receive. While this model remains tractable, there are several limitations, presumably due to the constitutional Pkrdc^scid (SCID, severe combined immune deficiency) mutation which affects DNA repair in all tissues of the mouse. These include the inability to combine preconditioning with subsequent chemotherapy, the inability to repeat chemotherapy cycles, and the increased sensitivity of the host hematopoietic cells to genotoxic stress. Here we attempt to address these drawbacks through the use of alternative strains with RAG-based immune deficiency (NRG and NRGS). We find that RAG-based mice tolerate a busulfan preconditioning regimen in combination with either AML or 4-drug acute lymphoid leukemia (ALL) chemotherapy, expanding the number of samples that can be studied. RAG-based mice also tolerate multiple cycles of therapy, thereby allowing for more aggressive, realistic modeling. Furthermore, standard AML therapy in RAG mice was 3.8-fold more specific for AML cells, relative to SCID mice, demonstrating an improved therapeutic window for genotoxic agents. We conclude that RAG-based mice should be the new standard for preclinical evaluation of therapeutic strategies involving genotoxic agents.

The multiple-kinase inhibitor lenvatinib inhibits the proliferation of acute myeloid leukemia cells

BACKGROUND

Current chemotherapy for acute myeloid leukemia (AML) mainly involves cytotoxic agents such as doxorubicin (DNR), mitoxantrone (Mito) or 2-aminopurine-6-thiol (6-TG). However, because these agents are relatively ineffective, discovering other more effective drugs for AML treatment would be valuable.

METHODS

The in vitro antitumor effect of lenvatinib on AML cells was examined using the colorimetric MTT assay for assessing cell metabolic activity. AML cells mixed with Poloxamer 407 were injected into nude mice to form subcutaneous tumors. Tumor-bearing mice received lenvatinib by oral administration. The antitumor effect of lenvatinib was established by measuring tumor volumes and weights.

RESULTS

Lenvatinib inhibited the growth of AML cells in a dose-dependent manner. We used AML cells to establish subcutaneous tumor tissues by mixing the cell suspension with Poloxamer 407. Poloxamer 407 alone did not influence the subcutaneous growth of AML cells. Treatment of lenvatinib inhibited in vivo tumor growth of AML cells.

CONCLUSION

The multiple-kinase inhibitor lenvatinib inhibits the in vitro proliferation of AML cells, and restricts the in vivo growth of AML tumors.

A personalized approach to acute myeloid leukemia therapy: current options

Therapeutic options for acute myeloid leukemia (AML) have remained unchanged for nearly the past 5 decades, with cytarabine and anthracyclines and use of hypomethylating agents for less intensive therapy. Implementation of large-scale genomic studies in the past decade has unraveled the genetic landscape and molecular etiology of AML. The approval of several novel drugs for targeted therapy, including midostaurin, enasidenib, ivosidenib, gemtuzumab–ozogamicin, and CPX351 by the US Food and Drug Administration has widened the treatment options for clinicians treating AML. This review focuses on some of these novel therapies and other promising agents under development, along with key clinical trial findings in AML.

Leukemic IL-17RB signaling regulates leukemic survival and chemoresistance

Secreted proteins provide crucial signals that have been implicated in the development of acute myeloid leukemia (AML) in the bone marrow microenvironment. Here we identify aberrant expressions of inflammatory IL-17B and its receptor (IL-17RB) in human and mouse mixed lineage leukemia-rearranged AML cells, which were further increased after exposure to chemotherapy. Interestingly, silencing of IL-17B or IL-17RB led to significant suppression of leukemic cell survival and disease progression in vivo. Moreover, the IL-17B-IL-17RB axis protected leukemic cells from chemotherapeutic agent-induced apoptotic effects. Mechanistic studies revealed that IL-17B promoted AML cell survival by enhancing ERK, NF-κB phosphorylation, and the expression of antiapoptotic protein B-cell lymphoma 2, which were reversed by small-molecule inhibitors. Thus, the inhibition of the IL-17B-IL-17RB axis may be a valid strategy to enhance sensitivity and therapeutic benefit of AML chemotherapy.-Guo, H.-Z., Niu, L.-T., Qiang, W.-T., Chen, J., Wang, J., Yang, H., Zhang, W., Zhu, J., Yu, S.-H. Leukemic IL-17RB signaling regulates leukemic survival and chemoresistance.

Emerging Therapies for Acute Myelogenus Leukemia Patients Targeting Apoptosis and Mitochondrial Metabolism

Acute Myelogenous Leukemia (AML) is a malignant disease of the hematopoietic cells, characterized by impaired differentiation and uncontrolled clonal expansion of myeloid progenitors/precursors, resulting in bone marrow failure and impaired normal hematopoiesis. AML comprises a heterogeneous group of malignancies, characterized by a combination of different somatic genetic abnormalities, some of which act as events driving leukemic development. Studies carried out in the last years have shown that AML cells invariably have abnormalities in one or more apoptotic pathways and have identified some components of the apoptotic pathway that can be targeted by specific drugs. Clinical results deriving from studies using B-cell lymphoma 2 (BCL-2) inhibitors in combination with standard AML agents, such as azacytidine, decitabine, low-dose cytarabine, provided promising results and strongly support the use of these agents in the treatment of AML patients, particularly of elderly patients. TNF-related apoptosis-inducing ligand (TRAIL) and its receptors are frequently deregulated in AML patients and their targeting may represent a promising strategy for development of new treatments. Altered mitochondrial metabolism is a common feature of AML cells, as supported through the discovery of mutations in the isocitrate dehydrogenase gene and in mitochondrial electron transport chain and of numerous abnormalities of oxidative metabolism existing in AML subgroups. Overall, these observations strongly support the view that the targeting of mitochondrial apoptotic or metabolic machinery is an appealing new therapeutic perspective in AML.