Targeting apoptosis in acute myeloid leukaemia

A biochemical assessment of apoptosis-inducing impact of Salinomycin in combination with ciprofloxacin on human leukemia KG1-a stem-like cells in the presence and absence of insulin

BACKGROUND

Acute Myeloid Leukemia (AML) is a fast-developing invading cancer that impacts the blood and bone marrow, marked by the rapid proliferation of abnormal white blood cells. Chemotherapeutic agents, a primary treatment for AML, encounter clinical limitations such as poor solubility and low bioavailability. Previous studies have highlighted antibiotics as effective in inducing cancer cell death and potentially preventing metastasis. Besides, insulin is known to activate the PI3K/Akt pathway, often disrupted in cancers, leading to enhanced cell survival and resistance to apoptosis. In light of the above-mentioned points, we examined the anti-cancer impact of antibiotics Ciprofloxacin (CP) and Salinomycin (SAL) and their combination on KG1-a cells in the presence and absence of insulin.

METHODS

This was accomplished by exposing KG1-a cells to different doses of CP and SAL alone, in combination, and with or without insulin for 24-72 h. Cell viability was evaluated using the MTT assay. Besides, apoptotic effects were examined using Hoechst staining and Annexin-V/PI flow cytometry. The expression levels of Bax, p53, BIRC5, Akt, PTEN, and FOXO1 were analyzed through Real-Time PCR.

RESULTS

CP and SAL demonstrated cytotoxic and notable pro-apoptotic impact on KG1-a cells by upregulating Bax and p53 and downregulating BIRC5, leading to G0/G1 cell cycle arrest and prevention of the PI3K-Akt signaling pathway. Our findings demonstrated that combination of CP and SAL promote apoptosis in the KG1-a cell line by down-regulating BIRC5 and Akt, as well as up-regulating Bax, p53, PTEN, and FOXO1. Additionally, the findings strongly indicated that insulin effectively mitigates apoptosis by enhancing Akt expression and reducing FOXO1 and PTEN gene expression in the cells treated with CP and SAL.

CONCLUSION

Our findings showed that the combined treatment of CP and SAL exhibit a strong anti-cancer effect on leukemia KG1-a cells. Moreover, it was discovered that the PI3K-Akt signaling can be a promising target in leukemia treatment particularly in hyperinsulinemia condition.

Anti-Leukemic Effects Induced by Dendritic Cells of Leukemic Origin from Leukemic Blood Samples Are Comparable under Hypoxic vs. Normoxic Conditions

Hypoxia can modulate the immune system by affecting the function and activity of immune cells, potentially leading to altered immune responses. This study investigated the generation of leukemia-derived dendritic cells (DCleu) from leukemic blasts and their impact on immune cell activation under hypoxic (5-10% O2) compared to normoxic (21% O2) conditions using various immunomodulatory Kits. The results revealed that DC/DCleu-generation was similar under hypoxic and normoxic conditions, with no significant differences observed in frequencies of generated DC/DCleu. Furthermore, the study showed that the activation of immune cells and their anti-leukemic activity improved when T cell-enriched immunoreactive cells were co-cultured with DC/DCleu which were generated with Kit I and M compared to the control after mixed lymphocyte cultures. The anti-leukemic activity was improved under hypoxic compared to normoxic conditions after MLCWB-DC Kit M. These findings suggest that DC/DCleu-cultures of leukemic whole blood with Kits under hypoxic conditions yield comparable frequencies of DC/DCleu and can even increase the anti-leukemic activity compared to normoxic conditions. Overall, this research highlights the potential of utilizing DC/DCleu (potentially induced in vivo with Kits) as a promising approach to enhance immune response in patients with acute myeloid leukemia.

Canonical and Noncanonical Functions of the BH3 Domain Protein Bid in Apoptosis, Oncogenesis, Cancer Therapeutics, and Aging

Effective cancer therapy with limited adverse effects is a major challenge in the medical field. This is especially complicated by the development of acquired chemoresistance. Understanding the mechanisms that underlie these processes remains a major effort in cancer research. In this review, we focus on the dual role that Bid protein plays in apoptotic cell death via the mitochondrial pathway, in oncogenesis and in cancer therapeutics. The BH3 domain in Bid and the anti-apoptotic mitochondrial proteins (Bcl-2, Bcl-XL, mitochondrial ATR) it associates with at the outer mitochondrial membrane provides us with a viable target in cancer therapy. We will discuss the roles of Bid, mitochondrial ATR, and other anti-apoptotic proteins in intrinsic apoptosis, exploring how their interaction sustains cellular viability despite the initiation of upstream death signals. The unexpected upregulation of this Bid protein in cancer cells can also be instrumental in explaining the mechanisms behind acquired chemoresistance. The stable protein associations at the mitochondria between tBid and anti-apoptotic mitochondrial ATR play a crucial role in maintaining the viability of cancer cells, suggesting a novel mechanism to induce cancer cell apoptosis by freeing tBid from the ATR associations at mitochondria.

Venetoclax therapy and emerging resistance mechanisms in acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a highly aggressive and devastating malignancy of the bone marrow and blood. For decades, intensive chemotherapy has been the frontline treatment for AML but has yielded only poor patient outcomes as exemplified by a 5-year survival rate of < 30%, even in younger adults. As knowledge of the molecular underpinnings of AML has advanced, so too has the development new strategies with potential to improve the treatment of AML patients. To date the most promising of these targeted agents is the BH3-mimetic venetoclax which in combination with standard of care therapies, has manageable non-haematological toxicity and exhibits impressive efficacy. However, approximately 30% of AML patients fail to respond to venetoclax-based regimens and almost all treatment responders eventually relapse. Here, we review the emerging mechanisms of intrinsic and acquired venetoclax resistance in AML and highlight recent efforts to identify novel strategies to overcome resistance to venetoclax.

Sennoside A induces autophagic death of prostate cancer via inactivation of PI3K/AKT/mTOR axis

Prostate cancer (PC) is the most common malignancy in male reproductive system. Sennoside A (SA) is an anthraquinone active ingredient extracted from Rheum officinale Baill., which exerts anti-tumor activity on different tumors. In the present study, the toxicity of SA on PC3 and DU 145 cells was detected via CCK-8. The effects of SA on growth, apoptosis, and autophagy were determined through CCK-8, Hoechst stain, flow cytometry, western blot, and immunofluorescence examinations. An in vivo experiment was performed in xenografted mice with intraperitoneal introduction of 10 mg/kg SA and validated via TUNEL, immunohistochemistry and western blot. The results showed that SA inhibited the cell viability with a IC50 value of 52.36 and 67.48 µM in DU 145 and PC3 cells respectively, and enhanced the apoptosis of PC3 and DU 145 cells. Additionally, SA elevated the relative LC3B expression, and the relative protein expression of LC3II/LC3I and Beclin-1, but diminished the P62 protein expression. The relative protein level of p-PI3K/PI3K, p-AKT/AKT and p-mTOR/mTOR was reduced with SA treatment, which was verified by the 740 Y-P application. The 740 Y-P treatments also restored the SA-induced the cell viability, apoptosis rate and relative LC3B expression. Meanwhile, SA inhibited the growth of PC cell and the relative protein level of PI3K/AKT/mTOR axis in vivo. Taken together, SA regulated the proliferation, apoptosis and autophagy via inactivating the PI3K/AKT/mTOR axis in PC.

In silico analysis prediction of HepTH1-5 as a potential therapeutic agent by targeting tumour suppressor protein networks

Many studies reported that the activation of tumour suppressor protein, p53 induced the human hepcidin expression. However, its expression decreased when p53 was silenced in human hepatoma cells. Contrary to Tilapia hepcidin TH1-5, HepTH1-5 was previously reported to trigger the p53 activation through the molecular docking approach. The INhibitor of Growth (ING) family members are also shown to directly interact with p53 and promote cell cycle arrest, senescence, apoptosis and participate in DNA replication and DNA damage responses to suppress the tumour initiation and progression. However, the interrelation between INGs and HepTH1-5 remains unknown. Therefore, this study aims to identify the mechanism and their protein interactions using in silico approaches. The finding revealed that HepTH1-5 and its ligands had interacted mostly on hotspot residues of ING proteins which involved in histone modifications via acetylation, phosphorylation, and methylation. This proves that HepTH1-5 might implicate in an apoptosis signalling pathway and preserve the protein structure and function of INGs by reducing the perturbation of histone binding upon oxidative stress response. This study would provide theoretical guidance for the design and experimental studies to decipher the role of HepTH1-5 as a potential therapeutic agent for cancer therapy. Communicated by Ramaswamy H. Sarma.

SPHINX-Based Combination Therapy as a Potential Novel Treatment Strategy for Acute Myeloid Leukaemia

Introduction: Dysregulated alternative splicing is a prominent feature of cancer. The inhibition and knockdown of the SR splice factor kinase SRPK1 reduces tumour growth in vivo. As a result several SPRK1 inhibitors are in development including SPHINX, a 3-(trifluoromethyl)anilide scaffold. The objective of this study was to treat two leukaemic cell lines with SPHINX in combination with the established cancer drugs azacitidine and imatinib. Materials and Methods: We selected two representative cell lines; Kasumi-1, acute myeloid leukaemia, and K562, BCR-ABL positive chronic myeloid leukaemia. Cells were treated with SPHINX concentrations up to 10μM, and in combination with azacitidine (up to 1.5 μg/ml, Kasumi-1 cells) and imatinib (up to 20 μg/ml, K562 cells). Cell viability was determined by counting the proportion of live cells and those undergoing apoptosis through the detection of activated caspase 3/7. SRPK1 was knocked down with siRNA to confirm SPHINX results. Results: The effects of SPHINX were first confirmed by observing reduced levels of phosphorylated SR proteins. SPHINX significantly reduced cell viability and increased apoptosis in Kasumi-1 cells, but less prominently in K562 cells. Knockdown of SRPK1 by RNA interference similarly reduced cell viability. Combining SPHINX with azacitidine augmented the effect of azacitidine in Kasumi-1 cells. In conclusion, SPHINX reduces cell viability and increases apoptosis in the acute myeloid leukaemia cell line Kasumi-1, but less convincingly in the chronic myeloid leukaemia cell line K562. Conclusion: We suggest that specific types of leukaemia may present an opportunity for the development of SRPK1-targeted therapies to be used in combination with established chemotherapeutic drugs.

Halogenated boroxine increases propensity to apoptosis in leukemia (UT-7) but not non-tumor cells in vitro

A hallmark of the development of solid and hematological malignancies is the dysregulation of apoptosis, which leads to an imbalance between cell proliferation, cell survival and death. Halogenated boroxine [K₂ (B₃ O₃ F₄ OH)] (HB) is a derivative of cyclic anhydride of boronic acid, with reproducible anti-tumor and anti-proliferative effects in different cell models. Notably, these changes are observed to be more profound in tumor cells than in normal cells. Here, we investigated the underlying mechanisms through an extensive evaluation of (a) deregulated target genes and (b) their interactions and links with main apoptotic pathway genes upon treatment with an optimized concentration of HB. To provide deeper insights into the mechanism of action of HB, we performed identification, visualization, and pathway association of differentially expressed genes (DEGs) involved in regulation of apoptosis among tumor and non-tumor cells upon HB treatment. We report that HB at a concentration of 0.2 mg·mL^-1 drives tumor cells to apoptosis, whereas non-tumor cells are not affected. Comparison of DEG profiles, gene interactions and pathway associations suggests that the HB effect and tumor-'selectivity' can be explained by Bax/Bak-independent mitochondrial depolarization by ROS generation and TRAIL-like activation, followed by permanent inhibition of NFκB signaling pathway specifically in tumor cells.

Targeting Apoptosis in AML: Where Do We Stand?

Simple Summary

In patients with acute myeloid leukemia (AML), genetic mutations can cause cells to evade regulated cell death (RCD), resulting in excessive cell proliferation. The best-known form of RCD is apoptosis, which prevents the emergence of cancer cells; disturbances in this process are an important factor in the development and progression of AML. Clearly, it is essential to understand the mechanisms of apoptosis to establish a personalized, patient-specific approach in AML therapy. Therefore, this paper comprehensively reviews the current range of AML treatment approaches related to apoptosis and highlights other promising concepts such as neddylation.

Abstract

More than 97% of patients with acute myeloid leukemia (AML) demonstrate genetic mutations leading to excessive proliferation combined with the evasion of regulated cell death (RCD). The most prominent and well-defined form of RCD is apoptosis, which serves as a defense mechanism against the emergence of cancer cells. Apoptosis is regulated in part by the BCL-2 family of pro- and anti-apoptotic proteins, whose balance can significantly determine cell survival. Apoptosis evasion plays a key role in tumorigenesis and drug resistance, and thus in the development and progression of AML. Research on the structural and biochemical aspects of apoptosis proteins and their regulators offers promise for new classes of targeted therapies and strategies for therapeutic intervention. This review provides a comprehensive overview of current AML treatment options related to the mechanism of apoptosis, particularly its mitochondrial pathway, and other promising concepts such as neddylation. It pays particular attention to clinically-relevant aspects of current and future AML treatment approaches, highlighting the molecular basis of individual therapies.

Small molecule MMRi62 targets MDM4 for degradation and induces leukemic cell apoptosis regardless of p53 status

MDM2 and MDM4 proteins are key negative regulators of tumor suppressor p53. MDM2 and MDM4 interact via their RING domains and form a heterodimer polyubiquitin E3 ligase essential for p53 degradation. MDM4 also forms heterodimer E3 ligases with MDM2 isoforms that lack p53-binding domains, which regulate p53 and MDM4 stability. We are working to identify small-molecule inhibitors targeting the RING domain of MDM2-MDM4 (MMRi) that can inactivate the total oncogenic activity of MDM2-MDM4 heterodimers. Here, we describe the identification and characterization of MMRi62 as an MDM4-degrader and apoptosis inducer in leukemia cells. Biochemically, in our experiments, MMRi62 bound to preformed RING domain heterodimers altered the substrate preference toward MDM4 ubiquitination and promoted MDM2-dependent MDM4 degradation in cells. This MDM4-degrader activity of MMRi62 was found to be associated with potent apoptosis induction in leukemia cells. Interestingly, MMRi62 effectively induced apoptosis in p53 mutant, multidrug-resistant leukemia cells and patient samples in addition to p53 wild-type cells. In contrast, MMRi67 as a RING heterodimer disruptor and an enzymatic inhibitor of the MDM2-MDM4 E3 complex lacked MDM4-degrader activity and failed to induce apoptosis in these cells. In summary, this study identifies MMRi62 as a novel MDM2-MDM4-targeting agent and suggests that small molecules capable of promoting MDM4 degradation may be a viable new approach to killing leukemia cells bearing non-functional p53 by apoptosis.

Eleutheroside E functions as anti-cervical cancer drug by inhibiting the phosphatidylinositol 3-kinase pathway and reprogramming the metabolic responses

OBJECTIVES

Cervical cancer (CC) is the common female malignant tumour with non-negligible morbidity and mortality. Eleutheroside E (EE) has anti-oxidative stress, anti-inflammatory and anti-proliferation effects in diverse disease models. However, its anti-tumour role remains unclear.

METHODS

The cell viability, apoptosis rate and protein expressions were detected by CCK-8, flow cytometry and western blot assays, respectively. The metabolic profile was performed by GC/MS analysis. Furthermore, the effect of EE on CC was verified in nude mice.

KEY FINDINGS

EE notably decreased the viability and increased the cell apoptosis, which could be reversed with 740Y-P treatment. EE treatment changed the metabolic categories of SiHa cells. The fatty acids signalling pathway was the most outstanding differential pathway. Myo-inositol prominently enhanced the level of phosphorylated Akt in a dose-dependent way. Moreover, EE declined the tumour volume and weight and the proliferation, but promoted the apoptosis in vivo. EE reduced the relative expression of phosphorylated PI3K and Akt. However, all these in-vivo results were observably antagonized with myo-inositol treatment.

CONCLUSIONS

EE plays an anti-tumour role in CC via inhibiting the PI3K pathway and reprogramming the metabolic responses.

BCL2 inhibitor ABT-199 and BCL2L1 inhibitor WEHI-539 coordinately promote NOXA-mediated degradation of MCL1 in human leukemia cells

Human leukemia U937 cells that were continuously treated with hydroquinone (HQ) were transformed into U937/HQ cells with increased MCL1 and BCL2L1 expression. Compared with their parental cells, U937/HQ cells were less sensitive to ABT-263 (BCL2/BCL2L1 inhibitor)/ABT-199 (BCL2 inhibitor) cytotoxicity. The combination of WEHI-539 (BCL2L1 inhibitor) with either ABT-199 or ABT-263 showed synergistic cytotoxicity to U937 and U937/HQ cells. Therefore, we further investigated the cytotoxic mechanism induced by the combination of WEHI-539 and ABT-199. The combined treatment of WEHI-539 and ABT-199 induced NOX4/ROS/p38 MAPK axis-mediated autophagy, which in turn accelerated β-TrCP mRNA turnover. Downregulation of β-TrCP increased Sp1 expression, thereby promoting Sp1-mediated NOXA transcription, which in turn induced NOXA-dependent MCL1 degradation. Enforced expression of MCL1 alleviated the cytotoxicity of WEHI-539 plus ABT-199 to induce the loss of mitochondrial membrane potential and cell viability. WEHI-539 alone induced Sp1/NOXA axis-mediated MCL1 downregulation, while ABT-199 significantly decreased the dose of WEHI-539 by approximately 350- and 50-fold to induce MCL1 suppression in parental and HQ-selected cells, respectively. Furthermore, WEHI-539 sensitized ABT-199-resistant U937 cells to ABT-199 cytotoxicity by inducing NOXA-mediated degradation of MCL1. Collectively, the data in this study indicate that ABT-199 and WEHI-539 cooperatively induce NOXA-dependent MCL1 degradation, and the inhibition of MCL1 mainly explains their combined cytotoxicity in parental, HQ-selected, and ABT-199-resistant U937 cells.

Neferine Exerts Ferroptosis-Inducing Effect and Antitumor Effect on Thyroid Cancer through Nrf2/HO-1/NQO1 Inhibition

Thyroid cancer is the most prevalent endocrine malignancy with an increasing incidence in the past few decades. Neferine possesses various pharmacological activities, which have been applied in diverse disease models, including various tumors. However, the detailed effect and mechanism of neferine on thyroid cancer are still unclear. In the current study, the viability of IHH-4 and CAL-62 cells was examined by the CCK-8 assay. The effect of neferine on the proliferation, apoptosis, invasion, vascular endothelial growth factor (VEGF), epithelial-mesenchymal transition (EMT), and ferroptosis was evaluated by CCK-8, flow cytometry, western blot, and spectrophotometry assays. Mechanically, the expressions levels of Nrf2/HO-1/NQO1 signaling were first determined by a western blot, which was then verified by Nrf2 overexpression. In vivo validation was also conducted on BALB/c nude mice with an inoculation dose of 2 × 106 IHH-4 cells. The results showed that neferine repressed the viability of both IHH-4 and CAL-62 cells both in a dose-dependent way and in a time-dependent fashion, in which the IC50 value of neferine on IHH-4 and CAL-62 cells was 9.47 and 8.72 μM, respectively. Besides, neferine enhanced apoptosis but suppressed invasion, angiogenesis, and EMT of IHH-4 and CAL-62 cells. Moreover, neferine induced the activation of ferroptosis in thyroid cancer cells. Notably, it was revealed that the Nrf2/HO-1/NQO1 pathway was strongly associated with the effect of neferine on the modulation of thyroid cancer. Furthermore, these outcomes were validated in xenografted mice. Therefore, neferine exerted an antitumor effect and ferroptosis-inducing effect on thyroid cancer via inhibiting the Nrf2/HO-1/NQO1 pathway.

TPEN selectively eliminates lymphoblastic B cells from bone marrow pediatric acute lymphoblastic leukemia patients

B-cell acute lymphoblastic leukemia (B-ALL) is a hematologic disorder characterized by the abnormal proliferation and accumulation of immature B-lymphoblasts arrested at various stages of differentiation. Despite advances in treatment, a significant percentage of pediatric patients with precursor B-ALL still relapse. Therefore, alternative therapies are needed to improve the cure rates for pediatric patients. TPEN (N, N, N', N'-tetrakis(2-pyridylmethyl)-ethylenediamine) is a pro-oxidant agent capable of selectively inducing apoptosis in leukemia cell lines. Consequently, it has been suggested that TPEN could be a potential agent for oxidative therapy. However, it is not yet known whether TPEN can selectively destroy leukemia cells in a more disease-like model, for example, the bloodstream and bone marrow (BM), ex vivo. This investigation is an extension of a previous study that dealt with the effect of TPEN on ex vivo isolated/purified refractory B-ALL cells. Here, we evaluated the effect of TPEN on whole BM from nonleukemic patients (control) or pediatric patients diagnosed with de novo B-ALL or refractory B-ALL cells by analyzing the hematopoietic cell lineage marker CD34/CD19. Although TPEN was innocuous to nonleukemic BM (n = 3), we found that TPEN significantly induced apoptosis in de novo (n = 5) and refractory B-ALL (n = 6) leukemic cell populations. Moreover, TPEN significantly increased the counts of cells positive for the oxidation of the stress sensor protein DJ-1, a sign of the formation of H₂O₂, and significantly increased the counts of cells positive for the pro-apoptotic proteins TP53, PUMA, and CASPASE-3 (CASP-3), indicative of apoptosis, in B-ALL cells. We demonstrate that TPEN selectively eliminates B-ALL cells (CD34 + /CD19 +) but no other cell populations in BM (CD34 + /CD19-; CD34-/CD19 + ; CD34-/CD19-) independent of age, diagnosis status (de novo or refractory), sex, karyotype, or immunophenotype. Understanding TPEN-induced cell death in leukemia cells provides insight into more effective therapeutic oxidation-inducing anticancer agents.

The effect of apigenin and chemotherapy combination treatments on apoptosis-related genes and proteins in acute leukaemia cell lines

Apigenin is a dietary polyphenol found abundantly in fruit and vegetables, which sensitizes leukaemia cells to topoisomerase inhibitor agents (e.g., etoposide), and alkylating agents (e.g., cyclophosphamide), reducing ATP levels and inducing apoptosis; whilst being protective to control haematopoietic stem cells. This study analysed the expression profiles of intrinsic and extrinsic apoptosis-related genes and proteins to help elucidate the mechanisms of action of apigenin when used in combination with etoposide or cyclophosphamide in lymphoid and myeloid leukaemia cell lines (Jurkat and THP-1). Expression of apoptosis-related genes were measured using a TaqMan® Human Apoptosis Array and the StepOne Plus RT-qPCR System, whilst apoptosis-related proteins were determined using a protein profiler™-human apoptosis array and the LI-COR Odyssey^R Infrared Imaging System. Apigenin when combined with etoposide or cyclophosphamide-induced apoptosis via the mitochondrial pathway, increasing the expression of pro-apoptotic cytochrome c, SMAC/DIABLO, and HTRA2/OMI, which promoted caspase-9 and -3 activation. Targeting anti-apoptotic and/or pro-apoptotic members of the apoptotic pathways is a promising strategy to induce cancer cell death and improve sensitivity to chemotherapy agents. Here the apoptotic pathways induced by apigenin in combination with etoposide or cyclophosphamide were identified within human leukaemia cell lines, such applications could provide combination therapies for the treatment of leukaemia.

Subcellular Proteome Analysis Reveals Apoptotic Vulnerability of T-Cell Acute Lymphoblastic Leukemia

Targeting death receptor-mediated apoptosis in T-cell acute lymphoblastic leukemia (T-ALL), an aggressive disease with poor prognosis, is hindered by the inherent resistance of primary leukemia cells. Knowledge on therapeutic vulnerabilities in these malignant cells will provide opportunities for developing novel combinatory treatments for patients. Using label-free quantitative mass spectrometry and subcellular fractionation techniques, we systematically compared organelle-specific proteomes between Jurkat cells, an in vitro model for T-ALL, and a Jurkat mutant with increased resistance to death receptor-mediated apoptosis. By identifying several differentially regulated protein clusters, our data argued that extensive metabolic reprograming in the mitochondria, characterized by enhanced respiration and energy production, might allow cells to evade DR5-mediated cytotoxicity. Further analysis using clinical datasets demonstrated that the elevated expression of a three-gene signature, consisting of SDHA, IDH3A, and ANXA11, was significantly associated with poor survival of acute leukemia patients. Our analysis therefore provided a unique dataset for a mechanistic understanding of T-ALL and for the design of novel ALL treatments.

TP53 Expression and Mutational Analysis in Hematological Malignancy in Jeddah, Saudi Arabia

Background: Tumor protein 53 (TP53) is a tumor-suppressor gene and plays an essential role in apoptosis, cell cycle arrest, genomic stability, and DNA repair. Although it is the most often mutated gene in human cancer, it has respectively low frequency in hematological malignancy but is significantly linked with complex karyotype, poor prognosis, and chemotherapeutic response. Nevertheless, the prevalence and prognostic role of TP53 mutations in hematological malignancy in Saudi patients are not well reported. We, therefore, aim to assess the frequency of TP53 mutations in hematological malignancies in Saudi Arabia. Method: 20 different hematological malignancy samples were tested using fluorescence in situ hybridization (FISH) technique for TP53 deletion detection and next-generation sequencing (NGS) targeted panel was applied on 10 samples for mutations identification specifically TP53 mutation. Results: TP53 deletion was detected in 6 of 20 samples by FISH. Most of the 6 patients with TP53 deletion had acute lymphoblastic leukemia (ALL), and majority of them were child. NGS result revealed one heterozygous missense mutation in exon 5 of the TP53 gene (c. G9963A, p.H175R). Conclusion: To the best of our knowledge, the TP53 mutation is novel variant, and the first time we are reporting their association with myelodysplastic syndromic individual with complex karyotype. This study recommends further analysis of genomic mutations on bigger cohorts, utilizing high throughput technologies.

Novel boron-containing compound, halogenated boroxine, induces selective cytotoxicity through apoptosis triggering in UT-7 leukemia

Apoptosis induction is a promising approach in targeting tumor cells. As halogenated boroxine (HB) shows antitumor activity, but its mechanism of action in hematological tumors remains unclear, in this study, we aimed to analyze apoptosis triggering in normal and UT-7 leukemia cells by HB. Methods for assessing cell viability and cytotoxicity, apoptosis detection, relative expression of 84 apoptosis-associated genes and BCL-2, and functional analysis were applied. Pronounced HB activities in inhibition of cell viability, cytotoxicity, and apoptosis induction with measurable differences between tumor and normal cells were found. HB modulated the expression of 21 genes, predominantly downregulated the antiapoptotic genes in leukemia. The functional association revealed HB's impact on inhibition of NF-κB signaling pathway. BCL-2 expression decreasing was found only in UT-7 leukemia. This study identified HB as an apoptosis inducer affecting leukemia but not normal cells considering mechanisms of selective activity that may be a great advantage of HB applications.

Circular RNA circ_0040823 inhibits the proliferation of acute myeloid leukemia cells and induces apoptosis by regulating miR-516b/PTEN

OBJECTIVE

Endogenous circular RNAs (circRNAs) and microRNAs (miRNAs) have been shown to regulate the pathogenesis of acute myeloid leukemia (AML). The current study aimed to identify the role of circRNA 0040823 (circ_0040823) in AML.

METHODS

Microarray datasets were analyzed to identify differentially expressed circRNAs in AML patients. Peripheral blood samples were obtained from healthy volunteers and AML patients for the measurement of circ_0040823 and miR-516b levels. The overexpression or knockdown of a target gene in AML cells was achieved by the transfection with lentiviral vectors or small interfering RNAs. BALB/c nude mice were inoculated with AML cells and monitored for tumor growth. Dual-luciferase reporter assay, RNA immunoprecipitation, and RNA pull-down assay were used to determine the binding relationship between circRNA and miRNA.

RESULTS

circ_0040823 was significantly downregulated in AML patients and leukemia cells. Overexpression of circ_0040823 inhibited AML cell proliferation, and induced apoptosis and cell cycle arrest. Upregulation of circ_0040823 also repressed the growth of xenograft tumors in vivo. circ_0040823 acted as a miR-516b sponge and regulated key cellular events in leukemia cells via downregulating miR-516b. Moreover, tumor suppressor phosphatase and tensin homolog (PTEN) was a downstream target of miR-516b. The inhibition of miR-516b impaired the proliferation capacity of leukemia cells and induced apoptosis, while PTEN deficiency attenuated these effects.

CONCLUSION

This study showed that circ_0040823 inhibited proliferation and induced apoptosis of AML cells by sponging miR-516b, thereby diminishing the regulatory effect of miR-516b on PTEN. These findings identified circ_0040823/miR-516b/PTEN as a new therapeutic target for AML.

Single cell RNA sequencing of AML initiating cells reveals RNA-based evolution during disease progression

The prognosis of most patients with AML is poor due to frequent disease relapse. The cause of relapse is thought to be from the persistence of leukemia initiating cells (LIC's) following treatment. Here we assessed RNA based changes in LICs from matched patient diagnosis and relapse samples using single-cell RNA sequencing. Previous studies on AML progression have focused on genetic changes at the DNA mutation level mostly in bulk AML cells and demonstrated the existence of DNA clonal evolution. Here we identified in LICs that the phenomenon of RNA clonal evolution occurs during AML progression. Despite the presence of vast transcriptional heterogeneity at the single cell level, pathway analysis identified common signaling networks involving metabolism, apoptosis and chemokine signaling that evolved during AML progression and become a signature of relapse samples. A subset of this gene signature was validated at the protein level in LICs by flow cytometry from an independent AML cohort and functional studies were performed to demonstrate co-targeting BCL2 and CXCR4 signaling may help overcome therapeutic challenges with AML heterogeneity. It is hoped this work will facilitate a greater understanding of AML relapse leading to improved prognostic biomarkers and therapeutic strategies to target LIC's.

DNA-PK inhibitor peposertib enhances p53-dependent cytotoxicity of DNA double-strand break inducing therapy in acute leukemia

Peposertib (M3814) is a potent and selective DNA-PK inhibitor in early clinical development. It effectively blocks non-homologous end-joining repair of DNA double-strand breaks (DSB) and strongly potentiates the antitumor effect of ionizing radiation (IR) and topoisomerase II inhibitors. By suppressing DNA-PK catalytic activity in the presence of DNA DSB, M3814 potentiates ATM/p53 signaling leading to enhanced p53-dependent antitumor activity in tumor cells. Here, we investigated the therapeutic potential of M3814 in combination with DSB-inducing agents in leukemia cells and a patient-derived tumor. We show that in the presence of IR or topoisomerase II inhibitors, M3814 boosts the ATM/p53 response in acute leukemia cells leading to the elevation of p53 protein levels as well as its transcriptional activity. M3814 synergistically sensitized p53 wild-type, but not p53-deficient, AML cells to killing by DSB-inducing agents via p53-dependent apoptosis involving both intrinsic and extrinsic effector pathways. The antileukemic effect was further potentiated by enhancing daunorubicin-induced myeloid cell differentiation. Further, combined with the fixed-ratio liposomal formulation of daunorubicin and cytarabine, CPX-351, M3814 enhanced the efficacy against leukemia cells in vitro and in vivo without increasing hematopoietic toxicity, suggesting that DNA-PK inhibition could offer a novel clinical strategy for harnessing the anticancer potential of p53 in AML therapy.

Inhibition of Sp1-mediated survivin and MCL1 expression cooperates with SLC35F2 and myeloperoxidase to modulate YM155 cytotoxicity to human leukemia cells

Although YM155 is reported to suppress survivin (also known as BIRC5) expression in cancer cells, its cytotoxic mechanism in human acute myeloid leukemia (AML) cells has not been clearly resolved. In this study, we analyzed the mechanistic pathways that modulate the sensitivity of human AML U937 and HL-60 cells to YM155. YM155 induced apoptosis in AML cells, which was characterized by p38 MAPK phosphorylation and downregulation of survivin and MCL1 expression. Phosphorylated p38 MAPK causes autophagy-mediated Sp1 degradation, thereby inhibiting the transcription of survivin and MCL1. The reduction of survivin and MCL1 levels further facilitated Sp1 protein degradation through autophagy. The restoration of Sp1, survivin, or MCL1 expression protected U937 and HL-60 cells from YM155-mediated cytotoxicity. U937 and HL-60 cells were continuously exposed to hydroquinone (HQ) to generate U937/HQ and HL-60/HQ cells, which showed increased SLC35F2 expression. The increase in SLC35F2 expression led to an increase in the sensitivity of U937/HQ cells to YM155-mediated cytotoxicity, whereas no such effect was observed in HL-60/HQ cells. Of note, myeloperoxidase (MPO) activity in HL-60 and HL-60/HQ cells enhanced YM155 cytotoxicity in these cells, and the enforced expression of MPO also increased the sensitivity of U937 cells to YM155. Taken together, we conclude that p38 MAPK-modulated autophagy inhibits Sp1-mediated survivin and MCL1 expression, which, in turn, leads to the death of U937 and HL-60 cells following YM155 treatment. In addition, our data indicate that SLC35F2 increases the sensitivity of U937 cells to YM155-mediated cytotoxicity, whereas MPO enhances YM155 cytotoxicity in U937 and HL-60 cells.

NOXA-mediated degradation of MCL1 and BCL2L1 causes apoptosis of daunorubicin-treated human acute myeloid leukemia cells

Daunorubicin (DNR) is used clinically to treat acute myeloid leukemia (AML), while the signaling pathways associated with its cytotoxicity are not fully elucidated. Thus, we investigated the DNR-induced death pathway in the human AML cell lines U937 and HL-60. DNR-induced apoptosis in U937 cells accompanied by downregulation of MCL1 and BCL2L1, upregulation of Phorbol-12-myristate-13-acetate-induced protein 1 (NOXA), and mitochondrial depolarization. DNR induced NOX4-mediated reactive reactive oxygen species (ROS) production, which in turn inactivated Akt and simultaneously activated p38 mitogen-activated protein kinase (MAPK). Activated p38 MAPK and inactivated Akt coordinately increased GSK3β-mediated cAMP response element-binding protein (CREB) phosphorylation, which promoted NOXA transcription. NOXA upregulation critically increased the proteasomal degradation of MCL1 and BCL2L1. The same pathway was also responsible for the DNR-induced death of HL-60 cells. Restoration of MCL1 or BCL2L1 expression alleviated DNR-induced mitochondrial depolarization and cell death. Furthermore, ABT-199 (a BCL2 inhibitor) synergistically enhanced the cytotoxicity of DNR in AML cell lines. Notably, DNR-induced DNA damage was not related to NOXA-mediated degradation of MCL1 and BCL2L1. Collectively, these results indicate that the upregulation of NOXA expression through the NOX4-ROS-p38 MAPK-GSK3β-CREB axis results in the degradation of MCL1 and BCL2L1 in DNR-treated U937 and HL-60 cells. This signaling pathway may provide insights into the mechanism underlying DNR-triggered apoptosis in AML cells.

Platelet Microparticles Protect Acute Myelogenous Leukemia Cells against Daunorubicin-Induced Apoptosis

The role of platelets in cancer development and progression is increasingly evident, and several platelet-cancer interactions have been discovered, including the uptake of platelet microparticles (PMPs) by cancer cells. PMPs inherit a myriad of proteins and small RNAs from the parental platelets, which in turn can be transferred to cancer cells following internalization. However, the exact effect this may have in acute myelogenous leukemia (AML) is unknown. In this study, we sought to investigate whether PMPs could transfer their contents to the THP-1 cell line and if this could change the biological behavior of the recipient cells. Using acridine orange stained PMPs, we demonstrated that PMPs were internalized by THP-1 cells, which resulted in increased levels of miR-125a, miR-125b, and miR-199. In addition, co-incubation with PMPs protected THP-1 and primary AML cells against daunorubicin-induced cell death. We also showed that PMPs impaired cell growth, partially inhibited cell cycle progression, decreased mitochondrial membrane potential, and induced differentiation toward macrophages in THP-1 cells. Our results suggest that this altering of cell phenotype, in combination with decrease in cell activity may offer resistance to daunorubicin-induced apoptosis, as serum starvation also yielded a lower frequency of dead and apoptotic cells when treated with daunorubicin.

HLA-DQB1 mismatch increase risk of severe bleeding independently in recipients of allogeneic stem cell transplant

Severe bleeding is a major cause of death in acute leukemia (AL) patients with graft-versus-host disease (GVHD) after allogene hematopoietic stem-cell transplantation (allo-HSCT). However, the prognostic value and prediction of HSCT-associated severe bleeding in GVHD patients have not been reported in cohort studies. We did a retrospective analysis of 200 AL patients with GVHD after allo-HSCT from Feb 1, 2014, to Dec 1, 2015. Multivariate analysis showed that the severe bleeding class was associated with the risk of death (HR 2.26, 95% CI 1.31-3.92, p<0.001***). In order to predict severe bleeding and figure out the solution to bleeding events, we established a multiple logistic regression model. HLA-DQB1 unmatching, megakaryocyte reconsititution failure, and III or IV GVHD were the independent risk factors for severe bleeding. Among all the variations above, OR of HLA-DQB1 was the highest (OR: 16.02, 95% CI: 11.54-48.68). Adding HLA-DQB1 to other factors improved the reclassification for predicting severe bleeding (NRI=0.195, z=2.634, p=0.008**; IDI=0.289, z=3.249, p<0.001***). Lasso regression was used to select variants. A nomogram of the logistic model was generated and displayed. Calibration curve demonstrated excellent accuracy in estimating severe bleeding (C index of 0.935). HLA-DQB1 showed excellent efficacy of predicting severe bleeding in HSCT patients.

Bioactive peptide isolated from sesame seeds inhibits cell proliferation and induces apoptosis and autophagy in leukemic cells

Leukemia is the most common type of hematological malignancies. Several natural products including bioactive peptides have been explored and studied for their anti-leukemic activities. In the present study, anti-leukemic peptide, IGTLILM (IM-7), was isolated and identified from the protein hydrolysate of sesame seeds by reverse phase-solid phase extraction, off-gel fractionation and nano LC-MS/MS. The cytotoxic effects of IM-7 were studied in MOLT-4 and NB4 acute leukemic cell lines using an MTT assay. The induction of apoptosis and autophagy was investigated by flow cytometry using Annexin V-FITC/PI staining and anti-LC3/FITC antibodies, respectively. The mRNA alterations of apoptotic and autophagic-related genes were determined by reverse transcription-quantitative PCR. The present study found that IM-7 inhibited the proliferation of MOLT-4 and NB4 cells in dose-dependent manner, but it showed a minimal effect on healthy mononuclear cells. IM-7 activated apoptosis and autophagy through the upregulation of CASP3, ULK1 and BECN1 and the downregulation of BCL2. In addition, IM-7 enhanced the cytotoxic effect of the anti-leukemic drug, daunorubicin. The findings suggested that IM-7 was potent to suppress the proliferation of MOLT-4 and NB4 leukemic cells and induce apoptosis and autophagy through the regulation of caspase 3-Bcl-2 and ULK1-Beclin1, respectively.

Phyllanthin inhibits MOLT-4 leukemic cancer cell growth and induces apoptosis through the inhibition of AKT and JNK signaling pathway

Among cancers, leukemia is a multistep progression that involves genetic modifications of normal hematopoietic progenitor cells to cancerous cells. In recent times, leukemia cases and their mortality rate have increased rapidly. Therefore, the immense need for a therapeutic approach is crucial that can control this type of cancer. Phyllanthin is a lignan compound constituent from the Phyllanthus species and has numerous beneficial effects as a dietary component. The present study aims to determine the impact of phyllanthin on the MOLT-4 cytotoxic effect. MOLT-4 cells and MS-5 cells were cultured at different concentrations of phyllanthin (5, 10, 25, 50, 75, and 100 μM/ml), and the viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. The level of reactive oxygen species, the membrane potential of mitochondria, apoptosis by 2',7'-dichlorofluorescin-diacetate (DCF-DA), rhodamine, acridine orange (AO)/ethidium bromide (EB), 4',6-diamidino-2-phenylindole (DAPI)/propidium iodide (PI) staining, gene expression of signaling molecules, and protein levels were assessed by reverse-transcription polymerase chain reaction and western blot analysis. Phyllanthin did not show toxicity toward MS-5 cells and significantly decreased the cell viability of MOLT-4 cells with an IC₅₀ value of 25 µM/ml. Also, phyllanthin induced the production of reactive oxygen species and led to the loss of mitochondrial membrane potential. AO/EB and DAPI/PI staining fluorescent image confirmed the induction of apoptosis by phyllanthin treatment. The messenger RNA (mRNA) expression of cell cycle regulator cyclin D1, antiapoptotic gene Bcl-2, NF-κB, and TNF-α decreased, but the proapoptotic Bax mRNA expression was increased. The phosphorylated protein levels of p-PI3K1/2, p-ERK1/2, and p-AKT were decreased, whereas the levels of p-p38 and p-JNKT1/2 increased. Our results confirmed that phyllanthin inhibits the MOLT-4 cells, increases apoptosis, and inhibits MOLT-4 migration and cell invasion. Therefore, phyllanthin can be used as a potential target for leukemia treatment.

Targeting BCL-2 in Cancer: Advances, Challenges, and Perspectives

Simple Summary

Apoptosis, a programmed form of cell death, represents the main mechanism by which cells die. Such phenomenon is highly regulated by the BCL-2 family of proteins, which includes both pro-apoptotic and pro-survival proteins. The decision whether cells live or die is tightly controlled by a balance between these two classes of proteins. Notably, the pro-survival Bcl-2 proteins are frequently overexpressed in cancer cells dysregulating this balance in favor of survival and also rendering cells more resistant to therapeutic interventions. In this review, we outlined the most important steps in the development of targeting the BCL-2 survival proteins, which laid the ground for the discovery and the development of the selective BCL-2 inhibitor venetoclax as a therapeutic drug in hematological malignancies. The limitations and future directions are also discussed.

Abstract

The major form of cell death in normal as well as malignant cells is apoptosis, which is a programmed process highly regulated by the BCL-2 family of proteins. This includes the antiapoptotic proteins (BCL-2, BCL-XL, MCL-1, BCLW, and BFL-1) and the proapoptotic proteins, which can be divided into two groups: the effectors (BAX, BAK, and BOK) and the BH3-only proteins (BIM, BAD, NOXA, PUMA, BID, BIK, HRK). Notably, the BCL-2 antiapoptotic proteins are often overexpressed in malignant cells. While this offers survival advantages to malignant cells and strengthens their drug resistance capacity, it also offers opportunities for novel targeted therapies that selectively kill such cells. This review provides a comprehensive overview of the extensive preclinical and clinical studies targeting BCL-2 proteins with various BCL-2 proteins inhibitors with emphasis on venetoclax as a single agent, as well as in combination with other therapeutic agents. This review also discusses recent advances, challenges focusing on drug resistance, and future perspectives for effective targeting the Bcl-2 family of proteins in cancer.

Recent Advances in the Development of Selective Mcl-1 Inhibitors for the Treatment of Cancer (2017-Present)

Background:

Myeloid cell leukemia-1 (Mcl-1) protein, as a critical pro-survival member of the B-cell lymphoma 2 (Bcl-2) protein family, plays an important role in apoptosis, carcinogenesis and resistance to chemotherapies. Hence, potently and selectively inhibiting Mcl-1 to induce apoptosis has become a widely accepted anticancer strategy.

Objective:

This review intends to provide a comprehensive overview of patents and primary literature, published from 2017 to present, on small molecule Mcl-1 inhibitors with various scaffolds. By analyzing the modes of compound-protein interactions, the similarities and differences of those structures are discussed, which could provide guidance for future drug design.

Methods:

The primary accesses for patent searching are SciFinder and Espacenet®. Besides the data disclosed in patents, some results published in the follow-up research papers will be included in this review.

Results:

The review covers dozens of patents on Mcl-1 inhibitors in the past three years, and the scaffolds of compounds are mainly divided into indole scaffolds and non-indole scaffolds. The compounds described here are compared with the relevant inhibitors disclosed in previous patents, and representative compounds, especially those launched in clinical trials, are emphasized in this review.

Conclusion:

For most of the compounds in these patents, analyses of the binding affinity to Mcl-1 and studies in multiple cell lines were conducted, wherein some compounds were tested in preclinical cancer models or were included in other biological studies. Some compounds showed promising results and potential for further study.

Silencing long non-coding RNA XIST suppresses drug resistance in acute myeloid leukemia through down-regulation of MYC by elevating microRNA-29a expression

Background

Long non-coding RNAs (lncRNAs) are biomarkers participating in multiple disease development including acute myeloid leukemia (AML). Here, we investigated molecular mechanism of X Inactive-Specific Transcript (XIST) in regulating cellular viability, apoptosis and drug resistance in AML.

Methods

XIST, miR-29a and myelocytomatosis oncogene (MYC) expression in AML bone marrow cells collected from 62 patients was evaluated by RT-qPCR and Western blot analysis. Besides, the relationship among XIST, miR-29a and MYC was analyzed by dual luciferase reporter assay, RIP, and RNA pull down assays. AML KG-1 cells were treated with anti-tumor drug Adriamycin. The role of XIST/miR-29a/MYC in cellular viability, apoptosis and drug resistance in AML was accessed via gain- and loss-of-function approaches. At last, we evaluated role of XIST/miR-29a/MYC on tumorigenesis in vivo.

Results

XIST and MYC were up-regulated, and miR-29a was down-regulated in AML bone marrow cells. Silencing XIST inhibited cellular activity and drug resistance but promoted cellular apoptosis of KG-1 cells by down-regulating MYC. XIST inhibited miR-29a expression to up-regulate MYC. Moreover, silencing XIST inhibited tumorigenesis of AML cells in vivo.

Conclusions

Overall, down-regulation of XIST decreased MYC expression through releasing the inhibition on miR-29a, thereby reducing drug resistance, inhibiting viability and promoting apoptosis of AML cells.

Characterization of p190-Bcr-Abl chronic myeloid leukemia reveals specific signaling pathways and therapeutic targets

The oncogenic protein Bcr-Abl has two major isoforms, p190^Bcr-Abl and p210^Bcr-Abl. While p210^Bcr-Abl is the hallmark of chronic myeloid leukemia (CML), p190^Bcr-Abl occurs in the majority of Philadelphia-positive acute lymphoblastic leukemia (Ph + ALL) patients. In CML, p190^Bcr-Abl occurs in a minority of patients associating with distinct hematological features and inferior outcomes, yet the pathogenic role of p190^Bcr-Abl and potential targeting therapies are largely uncharacterized. We employed next generation sequencing, phospho-proteomic profiling, and drug sensitivity testing to characterize p190^Bcr-Abl in CML and hematopoietic progenitor cell line models (Ba/f3 and HPC-LSK). p190^Bcr-Abl CML patients demonstrated poor response to imatinib and frequent mutations in epigenetic modifiers genes. In contrast with p210^Bcr-Abl, p190^Bcr-Abl exhibited specific transcriptional upregulation of interferon, interleukin-1 receptor, and P53 signaling pathways, associated with hyperphosphorylation of relevant signaling molecules including JAK1/STAT1 and PAK1 in addition to Src hyperphosphorylation. Comparable to p190^Bcr-Abl CML patients, p190^Bcr-Abl cell lines demonstrated similar transcriptional and phospho-signaling signatures. With the drug sensitivity screening we identified targeted drugs with specific activity in p190^Bcr-Abl cell lines including IAP-, PAK1-, and Src inhibitors and glucocorticoids. Our results provide novel insights into the mechanisms underlying the distinct features of p190^Bcr-Abl CML and promising therapeutic targets for this high-risk patient group.

Inhibition of Anti-Apoptotic Bcl-2 Proteins in Preclinical and Clinical Studies: Current Overview in Cancer

The dynamic interplay between pro-death and pro-survival Bcl-2 family proteins is responsible for a cell’s fate. Due to the recognized relevance of this family in cancer progression and response to therapy, different efforts have made in recent years in order to develop small molecules able to target anti-apoptotic proteins such as Bcl-2, Bcl-xL and Mcl-1. The limitations of the first Bcl-2 family targeted drugs, regarding on-target and off-target toxicities, have been overcome with the development of venetoclax (ABT-199), the first BH3 mimetic inhibitor approved by the FDA. The purpose of this review is to discuss the state-of-the-art in the development of drugs targeting Bcl-2 anti-apoptotic proteins and to highlight the potential of their application as single agents or in combination for improving anti-cancer therapy, focusing in particular on solid tumors.

Mechanistic Study of Triazole Based Aminodiol Derivatives in Leukemic Cells-Crosstalk between Mitochondrial Stress-Involved Apoptosis and Autophagy

Various derivatives that mimic ceramide structures by introducing a triazole to connect the aminodiol moiety and long alkyl chain have been synthesized and screened for their anti-leukemia activity. SPS8 stood out among the derivatives, showing cytotoxic selectivity between leukemic cell lines and human peripheral blood mononuclear cells (about ten times). DAPI nuclear staining and H&E staining revealed DNA fragmentation under the action of SPS8. SPS8 induced an increase in intracellular Ca²⁺ levels and mitochondrial stress in HL-60 cells identified by the loss of mitochondrial membrane potential, transmission electron microscopy (TEM) examination, and altered expressions of Bcl-2 family proteins. SPS8 also induced autophagy through the detection of Atg5, beclin-1, and LC3 II protein expression, as well as TEM examination. Chloroquine, an autophagy inhibitor, promoted SPS8-induced apoptosis, suggesting the cytoprotective role of autophagy in hindering SPS8 from apoptosis. Furthermore, SPS8 was shown to alter the expressions of a variety of genes using a microarray analysis and volcano plot filtering. A further cellular signaling pathways analysis suggested that SPS8 induced several cellular processes in HL-60, including the sterol biosynthesis process and cholesterol biosynthesis process, and inhibited some cellular pathways, in which STAT3 was the most critical nuclear factor. Further identification revealed that SPS8 inhibited the phosphorylation of STAT3, representing the loss of cytoprotective activity. In conclusion, the data suggest that SPS8 induces both apoptosis and autophagy in leukemic cells, in which autophagy plays a cytoprotective role in impeding apoptosis. Moreover, the inhibition of STAT3 phosphorylation may support SPS8-induced anti-leukemic activity.

Glucocorticoids uncover a critical role for ASH2L on BCL-X expression regulation in leukemia cells

Targeting the apoptosis machinery is a promising therapeutic approach in myeloid malignancies. BCL2L1 is a well-known glucocorticoid-responsive gene and a key apoptosis regulator that, when over-expressed, can contribute to tumor development, progression and therapeutic resistance. Moreover, synthetic glucocorticoids, like dexamethasone, are frequently used in the treatment of hematopoietic diseases due to its pro-apoptotic properties. We report here that the trithorax protein ASH2L, considered one of the core subunits of H3K4-specific MLL/SET methyltransferase complexes, contributes to anti-apoptotic BCL-X_L over-expression and cell survival in patient-derived myeloid leukemia cells. We find that the unliganded glucocorticoid receptor (uGR) and ASH2L interact in a common protein complex through a chromatin looping determined by uGR and ASH2L binding to BCL2L1 specific +58 HRE and promoter region, respectively. Upon addition of dexamethasone, GR and ASH2L recruitment is reduced, BCL-X_L expression diminishes and apoptosis is induced consequently. Overall, our findings indicate that uGR and ASH2L may act as key regulatory players of BCL- X_L upregulation in AML cells.

Transcriptional Silencing of MCL-1 Through Cyclin-Dependent Kinase Inhibition in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the most common adult acute leukemia. Survival remains poor, despite decades of scientific advances. Cytotoxic induction chemotherapy regimens are standard-of-care for most patients. Many investigations have highlighted the genomic heterogeneity of AML, and several new targeted therapeutic options have recently been approved. Additional novel therapies are showing promising clinical results and may rapidly transform the therapeutic landscape of AML. Despite the emerging clinical success of B-cell lymphoma (BCL)-2 targeting in AML and a large body of preclinical data supporting myeloid leukemia cell (MCL)-1 as an attractive therapeutic target for AML, MCL-1 targeting remains relatively unexplored, although novel MCL-1 inhibitors are under clinical investigation. Inhibitors of cyclin-dependent kinases (CDKs) involved in the regulation of transcription, CDK9 in particular, are being investigated in AML as a strategy to target MCL-1 indirectly. In this article, we review the basis for CDK inhibition in oncology with a focus on relevant preclinical mechanism-of-action studies of CDK9 inhibitors in the context of their therapeutic potential specifically in AML.

Melatonin: A promising agent targeting leukemia

Leukemia or cancer of blood is a well-known cancer, which affects a range of people from newborns to the very old. It is a public health problem throughout the world. By way of treatment, due to the lack of specific anticancer therapies, common treatments of leukemia lead to severe side effects. Nonspecific anticancer drugs result in inhibition of normal cell growth and thereby their necrosis. Moreover, drug resistance is an additional problem, which stands in the way of leukemia treatment. Thus, finding new treatments for leukemia is essential. Melatonin, as a natural product, has been shown to be effective in a wide variety of diseases such as coronary heart disease, schizophrenia, chronic pain, and Alzheimer's disease. In addition, melatonin levels have been observed to be altered in different cancers, such as breast cancer, colorectal cancer endometrial cancer, and hematopoetical cancers. Anticancer features of melatonin such as pro-oxidation, apoptosis induction, antiangiogenesis property and metastasis and invasion inhibition suggest that this natural compound can be used as a potential agent in novel therapeutic strategies for cancers. Also, it has been reported that melatonin has positive and protective effects on different physiological reactions and in normal bone marrow cells suggesting effectiveness in leukemia therapy. Thus, the aim of our paper was to depict and summarize the main molecular targets of melatonin on leukemia models.

Knockdown of RNF2 enhances the radiosensitivity of squamous cell carcinoma in lung

A previous study has reported that knockdown of RING finger protein 2 (RNF2) increases the radiosensitivity of esophageal cancer cells both in vitro and in vivo. However, the effect of RNF2 knockdown on radiosensitivity in squamous cell carcinoma (SqCC) remains unknown. For this, NCI-H226 and SK-MES-1 cells were exposed to X-ray irradiation and then RNF2 levels were determined. RNF2 was knocked-down and stable transfectants were selected. Radiosensitivity, cell proliferation, apoptosis, cell cycle, and γ-H2AX foci formation were evaluated. Interaction among ataxia telangiectasia mutated protein (ATM), mediator of DNA damage checkpoint 1 (MDC1), and H2AX were examined. Xenograft models were used to explore the effect of RNF2 knockdown on radiosensitivity in vivo. The results showed that RNF2 expression was significantly increased by X-ray irradiation. RNF2 knockdown combined with X-ray irradiation markedly inhibited cell proliferation, caused cell cycle arrest at the G1 phase, and induced cell apoptosis. In addition, RNF2 knockdown enhanced the radiosensitivity of SqCC cells, inhibited irradiation-induced γ-H2AX foci formation, and impaired the interactions among ATM, MDC1, and H2AX. Furthermore, combination of RNF2 knockdown and X-ray irradiation suppressed tumor growth and promoted tumor cell apoptosis in vivo. RNF2 may be a new therapeutic target to enhance the radiosensitivity of SqCC cells in lung.

Phase 1 study of the MDM2 inhibitor AMG 232 in patients with advanced P53 wild-type solid tumors or multiple myeloma

Background This open-label, first-in-human, phase 1 study evaluated AMG 232, an oral selective MDM2 inhibitor in patients with TP53 wild-type (P53WT), advanced solid tumors or multiple myeloma (MM). Methods In the dose escalation (n = 39), patients with P53WT refractory solid tumors enrolled to receive once-daily AMG 232 (15, 30, 60, 120, 240, 480, and 960 mg) for seven days every 3 weeks (Q3W). In the dose expansion (n = 68), patients with MDM2-amplified (well-differentiated and de-differentiated liposarcomas [WDLPS and DDLPS], glioblastoma multiforme [GBM], or other solid tumors [OST]), MDM2-overexpressing ER+ breast cancer (BC), or MM received AMG 232 at the maximum tolerated dose (MTD). Safety, pharmacokinetics, pharmacodynamics, and efficacy were assessed. Results AMG 232 had acceptable safety up to up to 240 mg. Three patients had dose-limiting toxicities of thrombocytopenia (n = 2) and neutropenia (n = 1). Due to these and other delayed cytopenias, AMG 232 240 mg Q3W was determined as the highest tolerable dose assessed in the dose expansion. Adverse events were typically mild/moderate and included diarrhea, nausea, vomiting, fatigue, decreased appetite, and anemia. AMG 232 plasma concentrations increased dose proportionally. Increases in serum macrophage inhibitor cytokine-1 from baseline were generally dose dependent, indicating p53 pathway activation. Per local review, there were no responses. Stable disease (durability in months) was observed in patients with WDLPS (3.9), OST (3.3), DDLPS (2.0), GBM (1.8), and BC (1.4–2.0). Conclusions In patients with P53WT advanced solid tumors or MM, AMG 232 showed acceptable safety and dose-proportional pharmacokinetics, and stable disease was observed.

Phase 1b study of the MDM2 inhibitor AMG 232 with or without trametinib in relapsed/refractory acute myeloid leukemia

This open-label, phase 1 study evaluated the safety, pharmacokinetics, and maximum tolerated dose of AMG 232, an investigational oral, selective mouse double minute 2 homolog inhibitor in relapsed/refractory acute myeloid leukemia (AML). AMG 232 was administered orally once daily for 7 days every 2 weeks (7 on/off) at 60, 120, 240, 360, 480, or 960 mg as monotherapy (arm 1) or at 60 mg with trametinib 2 mg (arm 2). Dose-limiting toxicities (DLTs), adverse events (AEs), pharmacokinetics, clinical and pharmacodynamic response, and expression of p53 target genes were assessed. All 36 patients received AMG 232. No DLTs occurred in arm 1, and 360 mg was the highest test dose; dose escalation was halted due to gastrointestinal AEs at higher doses. One of ten patients in arm 2 had a DLT (grade 3 fatigue); 60 mg was the highest dose tested with trametinib. Common treatment-related AEs (any grade) included nausea (58%), diarrhea (56%), vomiting (33%), and decreased appetite (25%). AMG 232 exhibited linear pharmacokinetics unaffected by coadministration with trametinib. Serum macrophage inhibitor cytokine-1 and bone marrow expression of BAX, PUMA, P21, and MDM2 increased during treatment. Of 30 evaluable patients, 1 achieved complete remission, 4 had morphologic leukemia-free state, and 1 had partial remission. Four of 13 (31%) TP53-wild-type patients and 0 of 3 (0%) TP53-mutant patients were responders. AMG 232 was associated with gastrointestinal AEs at higher doses but had acceptable pharmacokinetics, on-target effects, and promising clinical activity warranting further investigation in patients with relapsed/refractory AML. This trial was registered at www.clinicaltrials.gov as #NCT02016729.

MDM2 antagonists as a novel treatment option for acute myeloid leukemia: perspectives on the therapeutic potential of idasanutlin (RG7388)

Acute myeloid leukemia (AML) is a clonal heterogenous malignancy of the myeloid cells with a poor prognosis lending itself to novel treatment strategies. TP53 is a critical tumor suppressor and plays an essential role in leukemogenesis. Although TP53 is relatively unusual in de novo AML, inactivation of wild-type p53 (WT-p53) is a common event. Murine double minute 2 (MDM2) is a key negative regulator of p53 and its expression; inhibition of MDM2 is postulated to reactivate WT-p53 and its tumor suppressor functions. Nutlins were the first small molecule inhibitors that bind to MDM2 and target its interaction with p53. RG7388 (idasanutlin), a second-generation nutlin, was developed to improve upon the potency and toxicity profile of earlier nutlins. Preliminary data from early phase trials and ongoing studies suggest clinical response with RG7388 (idasanutlin) both in monotherapy and combination strategies in AML. We herein briefly discuss currently approved therapies in AML and review the clinical data for RG7388 (idasanutlin) and MDM2 inhibition as novel treatment strategies in AML. We further describe efficacy and toxicity profile data from completed and ongoing trials of RG7388 (idasanutlin) and other MDM2-p53 inhibitors in development. Many targeted therapies have been approved recently in AML, with a focus on the older and unfit population for intensive induction therapy and in relapsed/refractory disease. The "nutlins", including RG7388 (idasanutlin), merit continued investigation in such settings.

DIAPH1 Is Upregulated and Inhibits Cell Apoptosis through ATR/p53/Caspase-3 Signaling Pathway in Laryngeal Squamous Cell Carcinoma

Cancer bioinformatics has been used to screen possible key cancer genes and pathways. Here, through bioinformatics analysis, we found that high expression of diaphanous related formin 1 (DIAPH1) was associated with poor overall survival in head and neck squamous cell carcinoma and laryngeal squamous cell carcinoma (LSCC). The effect of DIAPH1 in LSCC has not been previously investigated. Therefore, we evaluated the expression, function, and molecular mechanisms of DIAPH1 in LSCC. Immunohistochemistry and western blot analysis confirmed the significant upregulation of DIAPH1 in LSCC. We used DIAPH1 RNA interference to construct two DIAPH1-knockdown LSCC cell lines, AMC-HN-8 and FD-LSC-1, and validated the knockdown efficiency. Flow cytometry data showed that DIAPH1 inhibited apoptosis. Further, western blot analysis revealed that DIAPH1 knockdown increased the protein levels of ATR, p-p53, Bax, and cleaved caspase-3, -8, and -9. Thus, DIAPH1 is upregulated in LSCC and may act as an oncogene by inhibiting apoptosis through the ATR/p53/caspase-3 pathway in LSCC cells.

Molecular Approaches to Treating Pediatric Leukemias

Over the past decades, striking progress has been made in the treatment of pediatric leukemia, approaching 90% overall survival in children with acute lymphoblastic leukemia (ALL) and 75% in children with acute myeloid leukemia (AML). This has mainly been achieved through multiagent chemotherapy including CNS prophylaxis and risk-adapted therapy within collaborative clinical trials. However, prognosis in children with refractory or relapsed leukemia remains poor and has not significantly improved despite great efforts. Hence, more effective and less toxic therapies are urgently needed. Our understanding of disease biology, molecular drivers, drug resistance and, thus, the possibility to identify children at high-risk for treatment failure has significantly improved in recent years. Moreover, several new drugs targeting key molecular pathways involved in leukemia development, cell growth, and proliferation have been developed and approved. These striking achievements are linked to the great hope to further improve survival in children with refractory and relapsed leukemia. This review gives an overview on current molecularly targeted therapies in children with leukemia, including kinase, and proteasome inhibitors, epigenetic and enzyme targeting, as well as apoptosis regulators among others.

Piceatannol-Induced Apoptosis Is Reversed by N-Acetyl-L-cysteine through Restoration of XIAP Expression

Piceatannol, a naturally occurring stilbene derivative mainly found in grapes, possesses apoptotic activity in various cancer cell lines, in addition to potent antioxidant activity. In the current study, we showed that piceatannol exhibits potent cytotoxic effects in all tested leukemia cell lines (THP-1, HL-60, U937, and K562). These effects were accompanied by induction of DNA damage, an increase in the proportion of cells in the sub-G₁ phase of the cell cycle, and inhibition of reactive oxygen species (ROS) generation. However, N-acetyl-L-cysteine (NAC), a strong ROS scavenger, significantly inhibited piceatannol-induced apoptosis, suggesting that piceatannol-induced apoptosis does not occur via inhibition of ROS generation. Piceatannol also resulted in a significant increase in mitochondrial depolarization, along with a decline in Bcl-2 expression, which was not restored by NAC. Conversely, ectopic Bcl-2 overexpression moderately inhibited piceatannol-induced apoptosis. Furthermore, piceatannol strongly inhibited X-linked inhibitor of apoptosis protein (XIAP) expression, which was restored by NAC. A transient knockdown of XIAP significantly increased piceatannol-induced apoptosis in the presence of NAC, suggesting that XIAP downregulation increases piceatannol-induced apoptosis, and that NAC could reverse this effect by increasing XIAP expression. Taken together, these results suggest that piceatannol induces apoptosis in human leukemia cell lines by downregulating XIAP expression, regardless of antioxidant activity.