A novel isoflavone, ME-344, targets the cytoskeleton in acute myeloid leukemia

Enhancing anti-AML activity of venetoclax by isoflavone ME-344 through suppression of OXPHOS and/or purine biosynthesis in vitro

Venetoclax (VEN), in combination with low dose cytarabine (AraC) or a hypomethylating agent, is FDA approved to treat acute myeloid leukemia (AML) in patients who are over the age of 75 or cannot tolerate standard chemotherapy. Despite high response rates to these therapies, most patients succumb to the disease due to relapse and/or drug resistance, providing an unmet clinical need for novel therapies to improve AML patient survival. ME-344 is a potent isoflavone with demonstrated inhibitory activity toward oxidative phosphorylation (OXPHOS) and clinical activity in solid tumors. Given that OXPHOS inhibition enhances VEN antileukemic activity against AML, we hypothesized that ME-344 could enhance the anti-AML activity of VEN. Here we report that ME-344 enhanced VEN to target AML cell lines and primary patient samples while sparing normal hematopoietic cells. Cooperative suppression of OXPHOS was detected in a subset of AML cell lines and primary patient samples. Metabolomics analysis revealed a significant reduction of purine biosynthesis metabolites by ME-344. Further, lometrexol, a purine biosynthesis inhibitor, synergistically enhanced VEN-induced apoptosis in AML cell lines. Interestingly, AML cells with acquired AraC resistance showed significantly increased purine biosynthesis metabolites and sensitivities to ME-344. Furthermore, synergy between ME-344 and VEN was preserved in these AraC-resistant AML cells. In vivo studies revealed significantly prolonged survival upon combination therapy of ME-344 and VEN in NSGS mice bearing parental or AraC-resistant MV4-11 leukemia compared to the vehicle control. This study demonstrates that ME-344 enhances VEN antileukemic activity against preclinical models of AML by suppressing OXPHOS and/or purine biosynthesis.

Microtubule-Targeting Combined with HDAC Inhibition Is a Novel Therapeutic Strategy for Diffuse Intrinsic Pontine Gliomas

Diffuse intrinsic pontine gliomas (DIPG) are an incurable childhood brain cancer for which novel treatments are needed. DIPGs are characterized by a mutation in the H3 histone (H3K27M), resulting in loss of H3K27 methylation and global gene dysregulation. TRX-E-009-1 is a novel anticancer agent with preclinical activity demonstrated against a range of cancers. We examined the antitumor activity of TRX-E-009-1 against DIPG neurosphere cultures and observed tumor-specific activity with IC50s ranging from 20 to 100 nmol/L, whereas no activity was observed against normal human astrocyte cells. TRX-E-009-1 exerted its anti-proliferative effect through the induction of apoptotic pathways, with marked increases in cleaved caspase 3 and cleaved PARP levels, while also restoring histone H3K27me3 methylation. Co-administration of TRX-E-009-1 and the histone deacetylase (HDAC) inhibitor SAHA extended survival in DIPG orthotopic animal models. This antitumor effect was further enhanced with irradiation. Our findings indicate that TRX-E-009-1, combined with HDAC inhibition, represents a novel, potent therapy for children with DIPG.

Synthesis and evaluation of benzoylbenzofurans and isoflavone derivatives as sirtuin 1 inhibitors with antiproliferative effects on cancer cells

Isoflavone derivatives were prepared from benzoylbenzofuran precursors. The synthesized compounds were analyzed by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, as well as high-resolution mass spectrometry (HRMS) to confirm their structures. The benzoylbenzofuran and isoflavone analogues were evaluated for inhibition of sirtuin 1 (SIRT1) and cell proliferation in MDA-MB-231 triple-negative breast cancer (TNBC) cells. Several isoflavone and benzoylbenzofuran derivatives exhibited potent antiproliferative effects against the MDA-MB-231 cancer cell line. Most of the isoflavone derivatives attenuated SIRT1 activity to below 50%. The most active compounds were the isoflavone quinones 38, 39, and 40, at IC₅₀ values of 5.58 ± 0.373, 1.62 ± 0.0720, and 7.24 ± 0.823 μM, respectively. Importantly, the most active compound, 6-methoxy-4',6'-dimethylisoflavone-2',5'-quinone (39) displayed SIRT1 inhibitory activity comparable to that of the reference compound, suramin. The in silico docking simulations in the active site of SIRT1 further substantiated the experimental results and explored the binding orientations of potent compounds in the active site of the target.

Targeting Mitochondrial Oxidative Phosphorylation Eradicates Acute Myeloid Leukemic Stem Cells

Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy characterized by multiple cytogenetic and molecular abnormalities, with a very poor prognosis. Current treatments for AML often fail to eliminate leukemic stem cells (LSCs), which perpetuate the disease. LSCs exhibit a unique metabolic profile, especially dependent on oxidative phosphorylation (OXPHOS) for energy production. Whereas, normal hematopoietic stem cells (HSCs) and leukemic blasts rely on glycolysis for adenosine triphosphate (ATP) production. Thus, understanding the regulation of OXPHOS in LSCs may offer effective targets for developing clinical therapies in AML. This review summarizes these studies with a focus on the regulation of the electron transport chain (ETC) and tricarboxylic acid (TCA) cycle in OXPHOS and discusses potential therapies for eliminating LSCs.

Biomarker‑driven phase Ib clinical trial of OPB‑111077 in acute myeloid leukemia

OPB-111077 is a novel, highly specific oral signal transducer and activator of transcription 3 inhibitor that has exhibited good efficacy against solid and blood cancers, including acute myeloid leukemia (AML), in preclinical models. In the present study, a phase 1b, two-stage, 3+3 dose-escalation clinical trial [dose level (DL)1 of 200 mg/day and DL2 of 250 mg/day on a once daily dose schedule in 28-day cycles] was conducted to assess the maximum tolerated dose (MTD), safety profile and the preliminary antitumor activity of OPB-111077 in patients with high-risk AML. A preliminary preclinical analysis evaluated the anti-proliferative activity of OPB-111077 in 19 patients with AML with a Vivia Biotech ex vivo PharmaFlow precision medicine test. A total of 12 patients were ultimately enrolled in the trial: 5 patients (42%) were treated with DL1, and 7 (58%) were escalated to DL2 of OPB-111077. Dose-limiting toxicities were not observed and the MTD was not reached. In addition, the most frequently reported treatment-emergent adverse events were nausea, vomiting and fatigue. Finally, clinical activity (overall response) was observed in 3 patients (25%). On the whole, the present study demonstrates that OPB-111077 exhibits a good safety and tolerability profile and an acceptable clinical response in patients with high-risk AML. A biomarker-driven design is useful for selecting the study population upfront.

Mitochondria and Their Relationship with Common Genetic Abnormalities in Hematologic Malignancies

Hematologic malignancies are known to be associated with numerous cytogenetic and molecular genetic changes. In addition to morphology, immunophenotype, cytochemistry and clinical characteristics, these genetic alterations are typically required to diagnose myeloid, lymphoid, and plasma cell neoplasms. According to the current World Health Organization (WHO) Classification of Tumors of Hematopoietic and Lymphoid Tissues, numerous genetic changes are highlighted, often defining a distinct subtype of a disease, or providing prognostic information. This review highlights how these molecular changes can alter mitochondrial bioenergetics, cell death pathways, mitochondrial dynamics and potentially be related to mitochondrial genetic changes. A better understanding of these processes emphasizes potential novel therapies.

Mitochondrial Metabolism in Carcinogenesis and Cancer Therapy

Simple Summary

Reprogramming metabolism is a hallmark of cancer. Warburg’s effect, defined as increased aerobic glycolysis at the expense of mitochondrial respiration in cancer cells, opened new avenues of research in the field of cancer. Later findings, however, have revealed that mitochondria remain functional and that they actively contribute to metabolic plasticity of cancer cells. Understanding the mechanisms by which mitochondrial metabolism controls tumor initiation and progression is necessary to better characterize the onset of carcinogenesis. These studies may ultimately lead to the design of novel anti-cancer strategies targeting mitochondrial functions.

Abstract

Carcinogenesis is a multi-step process that refers to transformation of a normal cell into a tumoral neoplastic cell. The mechanisms that promote tumor initiation, promotion and progression are varied, complex and remain to be understood. Studies have highlighted the involvement of oncogenic mutations, genomic instability and epigenetic alterations as well as metabolic reprogramming, in different processes of oncogenesis. However, the underlying mechanisms still have to be clarified. Mitochondria are central organelles at the crossroad of various energetic metabolisms. In addition to their pivotal roles in bioenergetic metabolism, they control redox homeostasis, biosynthesis of macromolecules and apoptotic signals, all of which are linked to carcinogenesis. In the present review, we discuss how mitochondria contribute to the initiation of carcinogenesis through gene mutations and production of oncometabolites, and how they promote tumor progression through the control of metabolic reprogramming and mitochondrial dynamics. Finally, we present mitochondrial metabolism as a promising target for the development of novel therapeutic strategies.

Combating TKI resistance in CML by inhibiting the PI3K/Akt/mTOR pathway in combination with TKIs: a review

Chronic myeloid leukemia (CML), a myeloproliferative hematopoietic cancer, is caused by a genetic translocation between chromosomes 9 and 22. This translocation produces a small Philadelphia chromosome, which contains the Bcr-Abl oncogene. The Bcr-Abl oncogene encodes the BCR-ABL protein, upregulates various signaling pathways (JAK-STAT, MAPK/ERK, and PI3K/Akt/mTOR), and out of which the specifically highly active pathway is the PI3K/Akt/mTOR pathway. Among early treatments for CML, tyrosine kinase inhibitors (TKIs) were found to be the most effective, but drug resistance against kinase inhibitors led to the discovery of novel alternative therapies. At this point, the PI3K/Akt/mTOR pathway components became new targets due to stimulation of this pathway in TKIs-resistant CML patients. The current review article deals with reviewing the scientific literature on the PI3K/Akt/mTOR pathway inhibitors listed in the National Cancer Institute (NCI) drug dictionary and proved effective against multiple cancers. And out of those enlisted inhibitors, the US FDA has also approved some PI3K inhibitors (Idelalisib, Copanlisib, and Duvelisib) and mTOR inhibitors (Everolimus, Sirolimus, and Temsirolimus) for cancer therapy. So far, several inhibitors have been tested, and further investigations are still ongoing. Even in Imatinib, Nilotinib, and Ponatinib-resistant CML cells, a dual PI3K/mTOR inhibitor, BEZ235, showed antiproliferative activity. Therefore, by considering the literature data of these reviews and further examining some of the reported inhibitors, which proved effective against the PI3K/Akt/mTOR signaling pathway in multiple cancers, may improve the therapeutic approaches towards TKI-resistant CML cells where the respective signaling pathway gets upregulated.

Targeting multiple signaling pathways: the new approach to acute myeloid leukemia therapy

Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults and the second most common form of acute leukemia in children. Despite this, very little improvement in survival rates has been achieved over the past few decades. This is partially due to the heterogeneity of AML and the need for more targeted therapeutics than the traditional cytotoxic chemotherapies that have been a mainstay in therapy for the past 50 years. In the past 20 years, research has been diversifying the approach to treating AML by investigating molecular pathways uniquely relevant to AML cell proliferation and survival. Here we review the development of novel therapeutics in targeting apoptosis, receptor tyrosine kinase (RTK) signaling, hedgehog (HH) pathway, mitochondrial function, DNA repair, and c-Myc signaling. There has been an impressive effort into better understanding the diversity of AML cell characteristics and here we highlight important preclinical studies that have supported therapeutic development and continue to promote new ways to target AML cells. In addition, we describe clinical investigations that have led to FDA approval of new targeted AML therapies and ongoing clinical trials of novel therapies targeting AML survival pathways. We also describe the complexity of targeting leukemia stem cells (LSCs) as an approach to addressing relapse and remission in AML and targetable pathways that are unique to LSC survival. This comprehensive review details what we currently understand about the signaling pathways that support AML cell survival and the exceptional ways in which we disrupt them.

Targeting mitochondrial respiration for the treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous disease with variable presentation, molecular phenotype, and cytogenetic abnormalities and has seen very little improvement in patient survival over the last few decades. This heterogeneity supports poor prognosis partially through the variability in response to the standard chemotherapy. Further understanding of molecular heterogeneity has promoted the development of novel treatments, some of which target mitochondrial metabolism and function. This review discusses the relative dependency that AML cells have on mitochondrial function, and the ability to pivot this reliance to target important subsets of AML cells, including leukemia stem cells (LSCs). LSCs are tumor-initiating cells that are resistant to standard chemotherapy and promote the persistence and relapse of AML. Historically, LSCs have been targeted based on immunophenotype, but recent developments in the understanding of LSC metabolism has demonstrated unique abilities to target LSCs while sparing normal hematopoietic stem cells (HSCs) through inhibition of mitochondrial function. Here we highlight the use of small molecules that have been demonstrated to effectively target mitochondrial function. IACS-010759 and ME-344 target the electron transport chain (ETC) to inhibit oxidative phosphorylation (OXPHOS). The imipridone family (ONC201, ONC206, ONC212) of inhibitors target mitochondria through activation of ClpP mitochondrial protease and reduce function of essential pathways. These molecules offer a new mechanism for developing clinical therapies in AML and support novel strategies to target LSCs in parallel with conventional therapies.

Pharmacology of ME-344, a novel cytotoxic isoflavone

Isoflavones isolated from members of the Fabaceae (primarily Leguminosae) family have been characterized for their phytoestrogenic properties, but certain derivatives have also shown potential as possible cancer therapeutic agents. ME-344, related to phenoxodiol (Fig. 1), is a second generation isoflavone with a recent history of both preclinical and early clinical testing. The drug has unusual cytotoxicity profiles, where cancer cell lines can be categorized as either intrinsically sensitive or resistant to the drug. Evolving studies show that the cytotoxic properties of the drug are enacted through targeting mitochondrial bioenergetics. While the drug has undergone early Phase I/II trials in solid tumors with confined dose limiting effects and some evidence of disease response, there is a continuing need to define specific cellular targets that determine sensitivity, with the long-term goal of applying such information to individualized therapy. This review article details some of the existing and ongoing studies that are assisting in the continued drug development processes that may lead to new drug application (NDA) status.

Mechanism of action of the third generation benzopyrans and evaluation of their broad anti-cancer activity in vitro and in vivo

Successive rounds of chemical modification in three generations of benzopyran molecules have shown to select for different mechanisms of actions and progressive increases in anti-cancer activity. In this study, we investigated the mechanism of action of the third-generation benzopyran compounds, TRX-E-002-1 and TRX-E-009-1. High-content screening of a panel of 240 cancer cell lines treated with TRX-E-009-1 demonstrated it has broad anti-cancer potential. Within this screen, melanoma cell lines showed a range of sensitivities and subsequently a second independent panel of 21 melanoma 3D spheroid lines were assessed for their responses to both TRX-E-002-1 and TRX-E-009-1 compounds. Time-lapse microscopy illustrated both of these compounds caused mitotic delays in treated cells, resulting in either mitotic slippage or apoptosis. This finding along with immunostaining, in vitro polymerization assays, and animal experiments in both athymic and immunocompetent mice, demonstrates that these third-generation benzopyran compounds are potent tubulin polymerization inhibitors in vitro and in vivo, and this is the molecular basis of their anti-cancer activity in melanoma. These findings indicate these BP compounds may offer a novel anti-microtubule strategy for cancer intervention and provides the basis for further investigation into biomarkers of clinical sensitivity.

Cell internalization of 7-ketocholesterol-containing nanoemulsion through LDL receptor reduces melanoma growth in vitro and in vivo: a preliminary report

Oxysterols are cholesterol oxygenated derivatives which possess several biological actions. Among oxysterols, 7-ketocholesterol (7KC) is known to induce cell death. Here, we hypothesized that 7KC cytotoxicity could be applied in cancer therapeutics. 7KC was incorporated into a lipid core nanoemulsion. As a cellular model the murine melanoma cell line B16F10 was used. The nanoparticle (7KCLDE) uptake into tumor cells was displaced by increasing amounts of low-density-lipoproteins (LDL) suggesting a LDL-receptor-mediated cell internalization. 7KCLDE was mainly cytostatic, which led to an accumulation of polyploid cells. Nevertheless, a single dose of 7KCLDE killed roughly 10% of melanoma cells. In addition, it was observed dissipation of the transmembrane potential, evidenced with flow cytometry; presence of autophagic vacuoles, visualized and quantified with flow cytometry and acridine orange; and presence of myelin figures, observed with ultrastructural microscopy. 7KCLDE impaired cytokenesis was accompanied by changes in cellular morphology into a fibroblastoid shape which is supported by cytoskeletal rearrangements, as shown by the increased actin polymerization. 7KCLDE was injected into B16 melanoma tumor-bearing mice. 7KCLDE accumulated in the liver and tumor. In melanoma tumor 7KCLDE promoted a >50% size reduction, enlarged the necrotic area, and reduced intratumoral vasculature. 7KCLDE increased the survival rates of animals, without hematologic or liver toxicity. Although more pre-clinical studies should be performed, our preliminary results suggested that 7KCLDE is a promising novel preparation for cancer chemotherapy.

Phase Ib study of the mitochondrial inhibitor ME-344 plus topotecan in patients with previously treated, locally advanced or metastatic small cell lung, ovarian and cervical cancers

Background This multicenter, open-label, phase Ib study was designed to assess the safety, pharmacokinetics and preliminary efficacy of ME-344, a mitochondrial inhibitor, administered in combination with the topoisomerase I inhibitor, topotecan, in patients with previously treated, locally advanced or metastatic small cell lung (SCLC), ovarian and cervical cancers. Patients and methods In Part 1, patients received ME-344 10 mg/kg intravenously weekly on days 1, 8, 15 and 22 in combination with topotecan 4 mg/m² on days 1, 8, and 15 of a 28 day cycle. Cycles were repeated until disease progression or unacceptable toxicity. Patients were evaluated for dose-limiting toxicity (DLT) in cycle 1 and ME-344 pharmacokinetic samples were obtained. In Part 2, patients with locally advanced or metastatic SCLC and ovarian cancer were enrolled in expansion cohorts treated at the recommended phase II dose (RP2D) determined in Part 1. Results Fourteen patients were enrolled in Part 1 and no DLTs were observed. The RP2D of ME-344 in combination with topotecan was established as 10 mg/kg. In Part 2, 32 patients were enrolled. The most common treatment-emergent all-grade and grade 3/4 toxicities included fatigue (65.2%, 6.5%), neutropenia (56.5%, 43.5%) and thrombocytopenia (50%, 23.9%). One patient with recurrent ovarian cancer experienced a partial response by RECIST 1.1 and 21 patients achieved stable disease as best response. Conclusions The combination of ME-344 10 mg/kg weekly and topotecan 4 mg/m² was tolerable, however, the degree of anti-cancer activity does not support further investigation of the combination in unselected patients with SCLC, ovarian and cervical cancers.