Targeting Bcl-2 Proteins in Acute Myeloid Leukemia

SR-B1 deficiency suppresses progression in acute myeloid leukemia via ferroptosis and reverses resistance to venetoclax

Increase of immature myeloid cells in the bone marrow drives the development of acute myeloid leukemia (AML). The study aimed to clarify the biological function and regulatory mechanism of scavenger receptor class B type 1 (SR-B1) in AML, mainly its effect on ferroptosis and the influences on leukemogenesis and resistance to venetoclax. In this study, we found that the SR-B1 deficiency directly reduced the invasion and promoted death of malignant cells in AML. Strikingly, SR-B1 deficiency could up-regulated the expression of ferroptosis-related proteins to facilitate the occurrence of ferroptosis in vivo, and could also down-regulated the expression of apoptosis related protein B-cell lymphoma-2 (BCL-2). And then, we confirmed SR-B1 inhibitor block lipid transport-1 (BLT-1) had a superior efficacy in AML cells and AML model mice. The study found that whether SR-B1 deficiency or BLT-1 treatment could cause iron deposition and the accumulation of lipid peroxides in vivo, thereby suppressing leukemogenesis through ferroptosis. Critically, we found that SR-B1 inhibitor BLT-1 could reverse drug-resistance of venetoclax to promote AML cells death via ferroptosis. Our finding identified that SR-B1 as a critical regulator of the proliferation in AML which could provide a promising therapeutic strategy against malignant myeloid leukemia cells and drug-resistance.

3-Bromopyruvate boosts the effect of chemotherapy in acute myeloid leukemia by a pro-oxidant mechanism

Acute myeloid leukemia (AML) comprises a diverse group of blood cancers with varying genetic, phenotypic, and clinical traits, making development of targeted therapy challenging. Metabolic reprogramming in AML has been described as relevant for chemotherapy effectiveness. 3-Bromopyruvate (3-BP) is an anticancer agent that undermines energy metabolism of cancer cells. However, the effect of 3-BP in hematologic malignancies, such as AML, needs further investigation. Thus, we aimed to explore 3-BP as a chemo-sensitizing agent in AML. Different approaches of combining 3-BP with classical chemotherapy (daunorubicin and cytarabin) were tested in diverse AML cell lines. Cell sensitivity to the different drug combinations was analyzed by Trypan blue staining. The effect of pre-treatment with a non-toxic concentration of 3-BP was assessed on the AML cell metabolic profile (Western blot and immunofluorescence), mitochondrial activity (cytometry flow), and antioxidant capacity (colorimetric detection kit). KG-1 and MOLM13 cells showed increased sensitivity to chemotherapy (decreased EC50 values) after exposure to a non-toxic concentration (5 μM) of 3-BP. In both cell lines, 5 μM 3-BP decreased glucose consumption without changing extracellular lactate levels. 5 μM 3-BP treatment increased reactive oxygen species levels and decreased cell antioxidant capacity by depleting reduced glutathione levels in both KG-1 and MOLM13 cells. Our results demonstrate that non-toxic concentrations of 3-BP enhance the effect of classical chemotherapy in AML cells through a pro-oxidant mechanism. These data unveiled a new approach for AML treatment, using 3-BP or other pro-oxidant agents as co-adjuvants of chemotherapy, subsiding chemotherapy-induced side effects.

A novel naphthylchalcone ([E]-4-(3-[naphthalen-2-yl]-3-oxoprop-1-en-1-yl) induces intrinsic and extrinsic apoptosis in human acute leukemia cell lines

BACKGROUND

Chalcones have been described in the literature as promising antineoplastic compounds.

OBJECTIVES

Therefore, the objective of this study was to analyze the cytotoxic effect of 23 synthetic chalcones on human acute leukemia (AL) cell lines (Jurkat and K562).

METHODS

Cytotoxicity assessment was performed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Cell death was evaluated using fluorescence microscopy, the DNA fragmentation technique, and the assessment of proteins involved in apoptosis by flow cytometry.

RESULTS

The most cytotoxic chalcone (R32) showed no cytotoxicity towards peripheral blood mononuclear cells (PBMC). It exhibited no hemolytic activity, did not alter platelet aggregation after adenosine diphosphate (ADP) and epinephrine stimulation, and did not affect blood coagulation as measured by prothrombin time (PT) and activated partial thromboplastin time (APTT). R32 demonstrated cytotoxic activity by inducing both intrinsic and extrinsic apoptosis, leading to caspase-3 activation and DNA fragmentation. In Jurkat and K562 cells, intrinsic apoptosis was associated with changes in mitochondrial membrane potential (MMP). There was a decreased expression of Bcl-2, increased expression of Bax, decreased expression of survivin, and increased expression of apoptosis-inducing factor (AIF). Extrinsic apoptosis involvement was also observed in both cell lines, characterized by increased expression of the Fas receptor. Additionally, Jurkat cells exhibited decreased expression of the KI-67 cell proliferation marker.

CONCLUSION

These findings suggest R32 as a potential compound for the development of novel drugs for the treatment of AL.

Inducing apoptosis in acute myeloid leukemia; mechanisms and limitations

Acute myeloid leukemia is the expansion of leukemic stem cells which might originate from a stem cell or a progenitor which has acquired self-renewal capacity. An aggregation of leukemic blasts in bone marrow, peripheral blood, and extramedullary tissue will result in acute myeloid leukemia. The main difficulty in treating acute myeloid leukemia is multidrug resistance, leading to treatment failure. This unfortunate phenomenon is practically elevated because of apoptosis inhibition in tumor cells. Two general apoptotic pathways are the Bcl-2 regulated pathway (the intrinsic pathway) and the death receptor pathway. Deficiencies in each of these apoptotic pathways can cause the usual resistance mechanism in this disease. This article reviews and highlights different antiapoptotic pathways, currently-used treatments, and new findings in this field, which may lead to the development of treatment methods for acute myeloid leukemia.

Safety and infection risk factors in elderly acute myeloid leukemia patients undergoing induction therapy with venetoclax combined with hypomethylating agents

OBJECTIVE

To retrospectively analyze the incidence of infections in elderly acute myeloid leukemia (AML) patients undergoing induction therapy with venetoclax combined with hypomethylating agents and to compare these findings with those from patients receiving standard or low-dose chemotherapy.

METHODS

Medical records of 169 elderly (≥60 years old) AML patients diagnosed via MICM (morphology, immunology, cytogenetics, and molecular genetics) at the First Affiliated Hospital of USTC between June 2019 and June 2022 were reviewed. Patients were divided into three groups: venetoclax combined with hypomethylating agents group (targeted therapy group), standard chemotherapy group, and low-dose chemotherapy group. Comparisons were made across groups regarding bacterial infection rates, fungal infection cases, infection sites, and severity.

RESULTS

The median ages at diagnosis in the targeted therapy group, standard chemotherapy group, and low-dose chemotherapy group were 73, 68, and 71 years, respectively (P<0.05). Compared with the standard chemotherapy and low-dose chemotherapy groups, the targeted therapy group had a higher prevalence of comorbidities (P<0.05). Complete remission rates in targeted therapy group, standard chemotherapy group, and low-dose chemotherapy group were 68.8%, 51.2%, and 26.4%, respectively (P<0.05). The durations of neutropenia were 9.0±8.4, 15.0±15.0, and 9.3±9.1 days, respectively (P<0.05). Bacterial infection rates were 87.5%, 95.2%, and 94.3% (P<0.05), with the most common sites being the lungs, bloodstream, upper respiratory tract, and unspecified sites. The durations of fever were 2.34±3.59, 4.52±4.38, and 3.53±4.76 days, respectively (P<0.05). The proportions of patients receiving antifungal prophylaxis were 46.8%, 46.4%, and 41.5%, respectively (P>0.05), mainly involving voriconazole and posaconazole. The proportions of clinically diagnosed or confirmed fungal infections were 6.3%, 9.5%, and 9.4%, respectively (P>0.05). The proportions of patients requiring initiation of antifungal therapy were 34.4%, 48.8%, and 43.4%, respectively (P<0.05). Among the 169 elderly AML patients, three (1.8%) developed infection-induced multiple organ dysfunction syndrome (i-MODSE), all in the standard chemotherapy group.

CONCLUSION

Venetoclax combined with hypomethylating agents shows a favorable safety profile and reduced infection risk in the treatment of AML in the elderly patients. Meanwhile, nontargeted therapies, a prolonged duration of neutropenia, and a prolonged duration of fever were found to be independent risk factors for fungal infections and the need for antifungal intervention.

Immunosuppressive microenvironment in acute myeloid leukemia: overview, therapeutic targets and corresponding strategies

Similar to other malignancies, immune dysregulation is a key feature of acute myeloid leukemia (AML), manifesting as suppressed anti-leukemia immune cells, immune evasion by leukemia blasts, and disease progression. Various immunosuppressive factors within the AML microenvironment contribute to the weakening of host immune responses and the efficacy of cellular immunotherapy. To address these challenges, strategies targeting immunosuppressive elements within the AML microenvironment aim to bolster host or adoptive immune effector cells, ultimately enhancing leukemia treatment. Additionally, the off-target effects of certain targeted drugs (venetoclax, sorafenib, ivosidenib, etc.) may also positively impact anti-AML immunity and immunotherapy. This review provides an overview of the immunosuppressive factors present in AML microenvironment and the strategies developed to rescue immune cells from immunosuppression. We also outline how targeted agents can alter the immune landscape in AML patients, and discuss the potential of targeted drugs to benefit host anti-leukemia immunity and immunotherapy for AML.

Chemotherapy resistance in acute myeloid leukemia is mediated by A20 suppression of spontaneous necroptosis

Acute myeloid leukemia (AML) is a deadly hematopoietic malignancy. Although many patients achieve complete remission with standard induction therapy, a combination of cytarabine and anthracycline, ~40% of patients have induction failure. These refractory patients pose a treatment challenge, as they do not respond to salvage therapy or allogeneic stem cell transplant. Herein, we show that AML patients who experience induction failure have elevated expression of the NF-κB target gene tumor necrosis factor alpha-induced protein-3 (TNFAIP3/A20) and impaired necroptotic cell death. A20High AML are resistant to anthracyclines, while A20Low AML are sensitive. Loss of A20 in AML restores sensitivity to anthracycline treatment by inducing necroptosis. Moreover, A20 prevents necroptosis in AML by targeting the necroptosis effector RIPK1, and anthracycline-induced necroptosis is abrogated in A20High AML. These findings suggest that NF-κB-driven A20 overexpression plays a role in failed chemotherapy induction and highlights the potential of targeting an alternative cell death pathway in AML.

ONC212 enhances YM155 cytotoxicity by triggering SLC35F2 expression and NOXA-dependent MCL1 degradation in acute myeloid leukemia cells

Although the anticancer activity of ONC212 has been reported, the precise mechanism underlying its apoptotic effects remains unclear. In this study, we investigated the apoptotic mechanism of ONC212 in acute myeloid leukemia (AML) cells. ONC212 induces apoptosis, MCL1 downregulation, and mitochondrial depolarization in AML U937 cells. Ectopic MCL1 expression alleviates mitochondria-mediated apoptosis in ONC212-treated U937 cells. ONC212 triggers AKT phosphorylation, inducing NOX4-dependent ROS production and promoting HuR transcription. HuR-mediated ATF4 mRNA stabilization stimulates NOXA and SLC35F2 expression; ONC212-induced upregulation of NOXA leads to MCL1 degradation. The synergistic effect of ONC212 on YM155 cytotoxicity was dependent on increased SLC35F2 expression. In addition, YM155 feedback facilitated the activation of the ONC212-induced signaling pathway. A similar mechanism explains ONC212- and ONC212/YM155-induced AML HL-60 cell death. The continuous treatment of U937 cells with the benzene metabolite hydroquinone (HQ) generated U937/HQ cells, exhibiting enhanced responsiveness to the cytotoxic effects of ONC212. In U937/HQ cells, ONC212 triggered apoptosis through NOXA-mediated MCL1 downregulation, enhancing YM155 cytotoxicity. Collectively, our data suggested that ONC212 upregulated SLC35F2 expression and triggered NOXA-mediated MCL1 degradation in U937, U937/HQ, and HL-60 cells by activating the AKT/NOX4/HuR/ATF4 pathway. The ONC212-induced signaling pathway showed anti-AML activity and enhanced YM155 cytotoxicity.

Myeloid Targeted Human MLL-ENL and MLL-AF9 Induces cdk9 and bcl2 Expression in Zebrafish Embryos

Acute myeloid leukemia (AML) accounts for greater than twenty thousand new cases of leukemia annually in the United States. The average five-year survival rate is approximately 30%, pointing to the need for developing novel model systems for drug discovery. In particular, patients with chromosomal rearrangements in the mixed lineage leukemia (MLL) gene have higher relapse rates with poor outcomes. In this study we investigated the expression of human MLL-ENL and MLL-AF9 in the myeloid lineage of zebrafish embryos. We observed an expansion of MLL positive cells and determined these cells colocalized with the myeloid markers spi1b, mpx, and mpeg. In addition, expression of MLL-ENL and MLL-AF9 induced the expression of endogenous bcl2 and cdk9, genes that are often dysregulated in MLL-r-AML. Co-treatment of lyz: MLL-ENL or lyz:MLL-AF9 expressing embryos with the BCL2 inhibitor, Venetoclax, and the CDK9 inhibitor, Flavopiridol, significantly reduced the number of MLL positive cells compared to embryos treated with vehicle or either drug alone. In addition, cotreatment with Venetoclax and Flavopiridol significantly reduced the expression of endogenous mcl1a compared to vehicle, consistent with AML. This new model of MLL-r-AML provides a novel tool to understand the molecular mechanisms underlying disease progression and a platform for drug discovery.

Synergistic cytotoxicity of decitabine and YM155 in leukemia cells through upregulation of SLC35F2 and suppression of MCL1 and survivin expression

The hypomethylation agent decitabine (DAC), in combination with other apoptosis inducers, is considered a potential modality for cancer treatment. We investigated the mechanism underlying the combined cytotoxicity of DAC and YM155 in acute myeloid leukemia (AML) cells because of increasing evidence that YM155 induces apoptosis in cancer cells. Co-administration of DAC and YM155 resulted in synergistic cytotoxicity in AML U937 cells, which was characterized by the induction of apoptosis, NOXA-dependent degradation of MCL1 and survivin, and depolarization of mitochondria. Restoration of MCL1 or survivin expression attenuated DAC/YM155-induced U937 cell death. DAC initiated AKT and p38 MAPK phosphorylation in a Ca2+/ROS-dependent manner, thereby promoting autophagy-mediated degradation of β-TrCP mRNA, leading to increased Sp1 expression. DAC-induced Sp1 expression associated with Ten-eleven-translocation (TET) dioxygenases and p300 was used to upregulate the expression of SLC35F2. Simultaneously, the activation of p38 MAPK induced by DAC, promoted CREB-mediated NOXA expression, resulting in survivin and MCL1 degradation. The synergistic cytotoxicity of DAC and YM155 in U937 cells was dependent on elevated SLC35F2 expression. Additionally, YM155 facilitated DAC-induced degradation of MCL1 and survivin. A similar mechanism explained DAC/YM155-mediated cytotoxicity in AML HL-60 cells. Our data demonstrated that the synergistic cytotoxicity of DAC and YM155 in AML cell lines U937 and HL-60 is dependent on AKT- and p38 MAPK-mediated upregulation of SLC35F2 and p38 MAPK-mediated degradation of survivin and MCL1. This indicates that a treatment regimen that amalgamates YM155 and DAC may be beneficial for AML.

A case report of atypical chronic myeloid leukemia with complete hematological and major molecular response to Venetoclax/Azacitidine treatment

Atypical Chronic Myeloid Leukemia (aCML), a myeloproliferative neoplasm with poor prognosis, was reclassified as aCML by the ICC classification, and as MDS/MPN with neutrophilia by the WHO 2022 classification. Due to the heterogeneity of its clinical features and the lack of unique biomarkers, as well as limited treatment options, aCML currently lacks a standardized treatment protocol. In this case report, we reviewed a young man diagnosed with aCML who achieved complete clinical and hematologic remission subsequent to receiving a therapeutic regimen combining Venetoclax and Azacitidine.

Characteristics and treatment results of refractory and relapsed acute myeloid leukaemia in paediatric patients treated in Polish Paediatric Leukaemia/Lymphoma Study Group institutions according to the Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012 and a review of novel treatment possibilities in paediatric acute myeloid leukaemia

Introduction

This study aimed to present the clinical features and results of treatment of patients diagnosed with refractory or relapsed acute myeloid leukaemia (AML) in Polish Paediatric Leukaemia/Lymphoma Study Group (PPL/LSG) institutions, treated in accordance with the Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012, as their first-line therapy.

Material and methods

The outcome data of 10 patients with refractory AML (median age 9.5 years) and 30 with relapsed AML (median age 12 years) were analysed retrospectively. Re-induction was usually based on idarubicin, fludarabine, and cytarabine along with allogeneic haematopoietic stem cell transplant (allo-HSCT) in 5 patients with refractory AML and 7 relapsed AML children.

Results

37.5% (3/8) of refractory AML patients achieved second complete remission second complete remission (CRII). One of ten patients (1/10; 10%) was alive and stayed in complete remission for 34 months after the allo-HSCT. The probability of 3-year event-free survival (pEFS) in this group was 0.125 ±0.11. In the group of relapsed AML patients, the CRII was achieved in 9 patients (34%), and the probability of survival was: pEFS = 0.24 ±0.08; probability overall survival (pOS) = 0.34 ±0.09, with significantly better results achieved in patients who underwent allo-HSCT (pOS = 0.54 ±0.14 vs. 0.08 ±0.08, p < 0.0001).

Conclusions

The prognosis of refractory AML and the first AML recurrence in children who were first-line treated in PPL/LSG centres according to Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012 is poor. Failures of re-induction treatment particularly result from difficulties in achieving remission. Allogeneic HSCT improves prognosis in children with refractory and first recurrent AML, under the condition it is performed in complete remission. Novel therapeutic approaches are needed to increase the remission rate and improve the outcomes.

Combating Acute Myeloid Leukemia via Sphingosine Kinase 1 Inhibitor-Nanomedicine Combination Therapy with Cytarabine or Venetoclax

MP-A08 is a novel sphingosine kinase 1 (SPHK1) inhibitor with activity against acute myeloid leukemia (AML). A rationally designed liposome-based encapsulation and delivery system has been shown to overcome the physicochemical challenges of MP-A08 and enable its effective delivery for improved efficacy and survival of mice engrafted with human AML in preclinical models. To establish therapies that overcome AML's heterogeneous nature, here we explored the combination of MP-A08-loaded liposomes with both the standard chemotherapy, cytarabine, and the targeted therapy, venetoclax, against human AML cell lines. Cytarabine (over the dose range of 0.1-0.5 µM) in combination with MP-A08 liposomes showed significant synergistic effects (as confirmed by the Chou-Talalay Combination Index) against the chemosensitised human AML cell lines MV4-11 and OCI-AML3. Venetoclax (over the dose range of 0.5-250 nM) in combination with MP-A08 liposomes showed significant synergistic effects against the chemosensitised human AML cell lines, particularly in venetoclax-resistant human AML cells. This strong synergistic effect is due to multiple mechanisms of action, i.e., inhibiting MCL-1 through SPHK1 inhibition, leading to ceramide accumulation, activation of protein kinase R, ATF4 upregulation, and NOXA activation, ultimately resulting in MCL-1 degradation. These combination therapies warrant further consideration and investigation in the search for a more comprehensive treatment strategy for AML.

Venetoclax in adult acute myeloid leukemia

Venetoclax is a potent inhibitor that specifically targets B-cell lymphoma-2 (BCL-2), which has been demonstrated to be effective in preclinical studies utilizing acute myeloid leukemia (AML) cell lines and xenograft models. Significant antileukemic activity was also observed in clinical trials, both as a monotherapy and in combination with other drugs. This novel therapeutic approach has revolutionized the treatment prospects for AML patients with unfavorable prognoses and those who are unable to tolerate intensive chemotherapy. Nevertheless, further investigations are required to establish the optimal dosing, sequencing, and combinational strategies of venetoclax for AML treatments. Additionally, identifying biomarkers is crucial for predicting response and resistance to this targeted intervention. In this review, we provide an overview of venetoclax-based therapy for AML and explore potential avenues for future research.

The Prognosis of Cancer Depends on the Interplay of Autophagy, Apoptosis, and Anoikis within the Tumor Microenvironment

Within the tumor microenvironment, the fight between the immune system and cancer influences tumor transformation. Metastasis formation is an important stage in the progression of cancer. This process is aided by cellular detachment and resistance to anoikis, which are achieved by altering intercellular signaling. Autophagy, specifically pro-survival autophagy, aids cancer cells in developing treatment resistance. Numerous studies have shown that autophagy promotes tumor growth and resistance to anoikis. To regulate protective autophagy, cancer-related genes phosphorylate both pro- and anti-apoptotic proteins. Apoptosis, a type of controlled cell death, eliminates damaged or unwanted cells. Anoikis is a type of programmed cell death in which cells lose contact with the extracellular matrix. The dysregulation of these cellular pathways promotes tumor growth and spread. Apoptosis, anoikis, and autophagy interact meticulously and differently depending on the cellular circumstances. For instance, autophagy can protect cancer cells from apoptosis by removing cellular components that are damaged and might otherwise trigger apoptotic pathways. Similarly, anoikis dysregulation can trigger autophagy by causing cellular harm and metabolic stress. In order to prevent or treat metastatic disease, specifically, targeting these cellular mechanisms may present a promising prospect for cancer therapy. This review discourses the state of our understanding of the molecular and cellular mechanisms underlying tumor transformation and the establishment of metastatic tumors. To enhance the prognosis for cancer, we highlight and discuss potential therapeutic approaches that target these processes and genes involved in them.

The Small-Molecule E26-Transformation-Specific Inhibitor TK216 Attenuates the Oncogenic Properties of Pediatric Leukemia

The E26-transformation-specific (ETS) transcription factors regulate multiple aspects of the normal hematopoietic system. There is an increasing body of evidence suggesting aberrant ETS activity and its contribution to leukemia initiation and progression. In this study, we evaluated the small-molecule ETS inhibitor TK216 and demonstrated its anti-tumor activity in pediatric leukemia. We found TK216 induced growth inhibition, cell cycle arrest and apoptosis and inhibited the migratory capability of leukemic cells, without significantly inhibiting the cell viability of normal blood mononuclear cells. Priming the leukemic cells with 5-Azacitidine enhanced the cytotoxic effects of TK216 on pediatric leukemia cells. Importantly, we found purine-rich box1 (PU.1) to be a potential target of TK216 in myeloid and B-lymphoid leukemic cells. In addition, TK216 sharply decreased Mcl-1 protein levels in a dose-dependent manner. Consistent with this, TK216 also potentiated the cytotoxic effects of Bcl-2 inhibition in venetoclax-resistant cells. The sustained survival benefit provided to leukemic cells in the presence of bone-marrow-derived conditioned media is also found to be modulated by TK216. Taken together, our data indicates that TK216 could be a promising targeted therapeutic agent for the treatment of acute myeloid and B-lymphoid leukemia.

B-cell lymphoma 2 family members and sarcomas: a promising target in a heterogeneous disease

Targeting the B-cell lymphoma 2 (Bcl-2) family proteins has been the backbone for hematological malignancies with overall survival improvements. The Bcl-2 family is a major player in apoptosis regulation and, has captured the researcher's interest in the treatment of solid tumors. Sarcomas are a heterogeneous group of diseases, comprising several entities, with high morbidity and mortality and with few specific therapies available. The treatment for sarcomas is based on platinum regimens, with variable results and poor outcomes, especially in advanced lesions. The high number of different sarcoma entities makes treatment standardization as well as the performance of clinical trials difficult. The use of Bcl-2 family members modifiers has revealed promising results in in vitro and in vivo models and may be a valid option, especially when used in combination with chemotherapy. In this article, a revision of these results and possibilities for the use of Bcl-2 family members inhibitors in sarcomas was performed.

Venetoclax is safe and tolerable as post-transplant maintenance therapy for AML patients at high risk for relapse

Relapse is the most common cause of mortality in acute myeloid leukemia (AML) patients after allogeneic stem cell transplant (SCT). Post-SCT maintenance strategies that prevent relapse are desirable but must be well tolerated and convenient to administer. We hypothesized single agent venetoclax (ven) may be an effective maintenance therapy among high relapse risk patients. Between February 2019 and December 2021, we administered post-SCT ven maintenance to 49 AML patients at high-risk for relapse as a prospectively defined off-label practice at our institution. Ven was planned to be administered until 1-year post-SCT. While temporary interruptions were common (67.3% of all patients), of those with >1 year follow up, 22/25 (88%) completed the full year of planned therapy. Cytopenias (40.8%) and gastrointestinal adverse events (34.7%) were the most common toxicities. At 1-year post-SCT, overall survival (OS) and relapse-free survival (RFS) were 70% and 67% respectively. Our experience demonstrates single agent ven is a safe, tolerable, and feasible maintenance therapy that may improve RFS and OS in high relapse risk post-SCT patients.

Epigenetic silencing of ZCCHC10 by the lncRNA SNHG1 promotes progression and venetoclax resistance of acute myeloid leukemia

The gene encoding the tumor suppressor p53 is the most frequently mutated gene in cancers. However, p53 mutation is rare in acute myeloid leukemia (AML), and p53 is inactivated predominantly by aberrant expression of p53 regulators (such as MDM2). A previous study by the authors revealed that the ZCCHC10 protein suppressed MDM2‑mediated degradation of the p53 protein in lung cancer. However, the expression and role of the ZCCHC10 gene in AML have not been investigated. In the present study, it was found that ZCCHC10 expression was downregulated in bone marrow samples of AML patients and that ZCCHC10 expression was significantly and negatively correlated with the expression of the lncRNA SNHG1. Suppression of SNHG1 decreased ZCCHC10 promoter methylation and increased ZCCHC10 expression. Notably, there is a putative binding motif in SNHG1 with full complementarity to five sites surrounding the CpG island in the ZCCHC10 promoter. Overexpression of wild‑type SNHG1 promoted ZCCHC10 methylation, but overexpression of SNHG1 with deletion of the binding motif did not. Further study identified that SNHG1 simultaneously bound to the ZCCHC10 promoter and the DNA methyltransferases DNMT1 and DNMT3B. These results indicated that SNHG1 recruits DNMT1 and DNMT3B to the ZCCHC10 promoter, resulting in hypermethylation of the ZCCHC10 promoter. Kaplan‑Meier survival analysis showed that ZCCHC10 expression was positively associated with overall survival in AML patients. In vitro experiments demonstrated that ZCCHC10 increased p53 expression and suppressed AML cell proliferation and survival. In the xenograft mouse model, ZCCHC10 decreased the proliferation of leukemic cells, improved the survival of leukemic mice, and increased sensitivity to the BCL inhibitor venetoclax. In conclusion, ZCCHC10 expression is suppressed by SNHG1‑induced DNA methylation in AML. Downregulation of ZCCHC10 decreases p53 activation, promotes cell proliferation and survival, and thereby accelerates AML progression and the acquisition of venetoclax resistance. The present study identified a SNHG1/ZCCHC10/p53 signaling axis in AML that may be a therapeutic target in this malignancy.

Combination Therapies Targeting Apoptosis in Paediatric AML: Understanding the Molecular Mechanisms of AML Treatments Using Phosphoproteomics

Paediatric acute myeloid leukaemia (AML) continues to present treatment challenges, as no “standard approach” exists to treat those young patients reliably and safely. Combination therapies could become a viable treatment option for treating young patients with AML, allowing multiple pathways to be targeted. Our in silico analysis of AML patients highlighted “cell death and survival” as an aberrant, potentially targetable pathway in paediatric AML patients. Therefore, we aimed to identify novel combination therapies to target apoptosis. Our apoptotic drug screening resulted in the identification of one potential “novel” drug pairing, comprising the Bcl-2 inhibitor ABT-737 combined with the CDK inhibitor Purvalanol-A, as well as one triple combination of ABT-737 + AKT inhibitor + SU9516, which showed significant synergism in a series of paediatric AML cell lines. Using a phosphoproteomic approach to understand the apoptotic mechanism involved, proteins related to apoptotic cell death and cell survival were represented, in agreement with further results showing differentially expressed apoptotic proteins and their phosphorylated forms among combination treatments compared to single-agent treated cells such upregulation of BAX and its phosphorylated form (Thr167), dephosphorylation of BAD (Ser 112), and downregulation of MCL-1 and its phosphorylated form (Ser159/Thr 163). Total levels of Bcl-2 were decreased but correlated with increased levels of phosphorylated Bcl-2, which was consistent with our phosphoproteomic analysis predictions. Bcl-2 phosphorylation was regulated by extracellular-signal-regulated kinase (ERK) but not PP2A phosphatase. Although the mechanism linking to Bcl-2 phosphorylation remains to be determined, our findings provide first-hand insights on potential novel combination treatments for AML.

A Ferroptosis-Inducing and Leukemic Cell-Targeting Drug Nanocarrier Formed by Redox-Responsive Cysteine Polymer for Acute Myeloid Leukemia Therapy

Ferroptosis is an alternative strategy to overcome chemoresistance, but effective therapeutic approaches to induce ferroptosis for acute myeloid leukemia (AML) treatment are limited. Here, we developed glutathione (GSH)-responsive cysteine polymer-based ferroptosis-inducing nanomedicine (GCFN) as an efficient ferroptosis inducer and chemotherapeutic drug nanocarrier for AML treatment. GCFN depleted intracellular GSH and inhibited glutathione peroxidase 4, a GSH-dependent hydroperoxidase, to cause lipid peroxidation and ferroptosis in AML cells. Furthermore, GCFN-loaded paclitaxel (PTX@GCFN) targeted AML cells and spared normal hematopoietic cells to limit the myeloablation side effects caused by paclitaxel. PTX@GCFN treatment extended the survival of AML mice by specifically releasing paclitaxel and simultaneously inducing ferroptosis in AML cells with restricted myeloablation and tissue damage side effects. Overall, the dual-functional GCFN acts as an effective ferroptosis inducer and a chemotherapeutic drug carrier for AML treatment.

The Class IIA Histone Deacetylase (HDAC) Inhibitor TMP269 Downregulates Ribosomal Proteins and Has Anti-Proliferative and Pro-Apoptotic Effects on AML Cells

Acute myeloid leukemia (AML) is a hematopoietic malignancy characterized by altered myeloid progenitor cell proliferation and differentiation. As in many other cancers, epigenetic transcriptional repressors such as histone deacetylases (HDACs) are dysregulated in AML. Here, we investigated (1) HDAC gene expression in AML patients and in different AML cell lines and (2) the effect of treating AML cells with the specific class IIA HDAC inhibitor TMP269, by applying proteomic and comparative bioinformatic analyses. We also analyzed cell proliferation, apoptosis, and the cell-killing capacities of TMP269 in combination with venetoclax compared to azacitidine plus venetoclax, by flow cytometry. Our results demonstrate significantly overexpressed class I and class II HDAC genes in AML patients, a phenotype which is conserved in AML cell lines. In AML MOLM-13 cells, TMP269 treatment downregulated a set of ribosomal proteins which are overexpressed in AML patients at the transcriptional level. TMP269 showed anti-proliferative effects and induced additive apoptotic effects in combination with venetoclax. We conclude that TMP269 exerts anti-leukemic activity when combined with venetoclax and has potential as a therapeutic drug in AML.

A novel Mcl-1 inhibitor synergizes with venetoclax to induce apoptosis in cancer cells

BACKGROUND

Evading apoptosis by overexpression of anti-apoptotic Bcl-2 family proteins is a hallmark of cancer cells and the Bcl-2 selective inhibitor venetoclax is widely used in the treatment of hematologic malignancies. Mcl-1, another anti-apoptotic Bcl-2 family member, is recognized as the primary cause of resistance to venetoclax treatment. However, there is currently no Mcl-1 inhibitor approved for clinical use.

METHODS

Paired parental and Mcl-1 knockout H1299 cells were used to screen and identify a small molecule named MI-238. Immunoprecipitation (IP) and flow cytometry assay were performed to analyze the activation of pro-apoptotic protein Bak. Annexin V staining and western blot analysis of cleaved caspase 3 were employed to measure the cell apoptosis. Mouse xenograft AML model using luciferase-expressing Molm13 cells was employed to evaluate in vivo therapeutic efficacy. Bone marrow samples from newly diagnosed AML patients were collected to evaluate the therapeutic potency.

RESULTS

Here, we show that MI-238, a novel and specific Mcl-1 inhibitor, can disrupt the association of Mcl-1 with BH3-only pro-apoptotic proteins, selectively leading to apoptosis in Mcl-1 proficient cells. Moreover, MI-238 treatment also potently induces apoptosis in acute myeloid leukemia (AML) cells. Notably, the combined treatment of MI-238 with venetoclax exhibited strong synergistic anti-cancer effects in AML cells in vitro, MOLM-13 xenografts mouse model and AML patient samples.

CONCLUSIONS

This study identified a novel and selective Mcl-1 inhibitor MI-238 and demonstrated that the development of MI-238 provides a novel strategy to improve the outcome of venetoclax therapy in AML.

A DNA Damage Response Related Signature to Predict Prognosis in Patients with Acute Myeloid Leukemia

The prognosis of acute myeloid leukemia (AML) is disappointing in most subtypes and varies widely. DNA damage response (DDR) is associated with prognosis and immunotherapy in multiple cancers. Here, we identify a signature of eight DDR-related genes associated with overall survival, which stratifies AML patients into high- and low-risk groups. Patients in low-risk group were more likely to respond to sorafenib. The signature could be an independent prognostic predictor for patients treated with ADE and ADE plus gemtuzumab ozogamicin. Therefore, this DDR prognostic signature might be applied to prognostic stratification and treatment selection in AML patients, which warrants further studies.

The function of p53 and its role in Alzheimer's and Parkinson's disease compared to age-related macular degeneration

The protein p53 is the main human tumor suppressor. Since its discovery, extensive research has been conducted, which led to the general assumption that the purview of p53 is also essential for additional functions, apart from the prevention of carcinogenesis. In response to cellular stress and DNA damages, p53 constitutes the key point for the induction of various regulatory processes, determining whether the cell induces cell cycle arrest and DNA repair mechanisms or otherwise cell death. As an implication, aberrations from its normal functioning can lead to pathogeneses. To this day, neurodegenerative diseases are considered difficult to treat, which arises from the fact that in general the underlying pathological mechanisms are not well understood. Current research on brain and retina-related neurodegenerative disorders suggests that p53 plays an essential role in the progression of these conditions as well. In this review, we therefore compare the role and similarities of the tumor suppressor protein p53 in the pathogenesis of Alzheimer's (AD) and Parkinson's disease (PD), two of the most prevalent neurological diseases, to the age-related macular degeneration (AMD) which is among the most common forms of retinal degeneration.

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.

Bcl-2 and Noxa are potential prognostic indicators for patients with gastroenteropancreatic neuroendocrine neoplasms

PURPOSE

Bcl-2 family proteins are of great significance in the pathogenesis and development of tumors. In this study, the correlations between the expression of Bcl-2 family proteins and clinicopathological features and prognosis of neuroendocrine neoplasms (NENs) were further investigated.

METHODS

105 Patients diagnosed with gastroenteropancreatic NENs (GEP-NENs) with the paraffin specimen of the tumor available were retrospectively included. Immunohistochemistry (IHC) was performed to detect the expression of Bcl-2 family proteins in paraffin-embedded samples. Student's t-test and Chi-square test were applied to compare the difference of quantitative and categorical variables, respectively. Survival analysis was conducted according to Kaplan-Meier method. Univariate and multivariate cox regression analysis were used to identify the independent prognostic factors.

RESULTS

The IHC score of Bcl-2 was significantly higher in neuroendocrine carcinoma (NEC) patients (65.6%), while a higher IHC score of Noxa was more common in neuroendocrine tumor (NET) patients (49.3%). Survival analysis indicated that patients with higher Bcl-2 expression and lower Noxa expression had worse 5-year survival (39.3% vs. 75.6%, p < 0.001; 40.6% vs. 84.9%, p < 0.001). Multivariate cox analysis indicated that high Bcl-2 expression was an independent factor associated with inferior DFS (hazard ratio [HR]: 2.092; 95% confidence interval [CI]: 1.106-3.955; p = 0.023) and OS (HR: 2.784; 95% CI: 1.326-5.846; p = 0.007), while higher Noxa expression was associated with superior DFS (HR:0.398; 95% CI: 0.175-0.907; p = 0.028) and OS (HR: 0.274; 95% CI: 0.110-0.686; p = 0.006).

CONCLUSIONS

Higher expression of Bcl-2 and lower expression of Noxa were associated with unfavorable prognosis of GEP-NENs patients.

Identification of bicyclic compounds that act as dual inhibitors of Bcl-2 and Mcl-1

Elevated expression of anti-apoptotic proteins, such as Bcl-2 and Mcl-1 contributes to poor prognosis and resistance to current treatment modalities in multiple cancers. Here, we report the design, synthesis and characterization of benzimidazole chalcone and flavonoid scaffold-derived bicyclic compounds targeting both Bcl-2 and Mcl-1 by optimizing the structural differences in the binding sites of both these proteins. Initial docking screen of Bcl-2 and Mcl-1 with pro-apoptotic protein Bim revealed possible hits with optimal binding energies. All the optimized bicyclic compounds were screened for their in vitro cytotoxic activity against two oral cancer cell lines (AW8507 and AW13516) which express high levels of Bcl-2 and Mcl-1. Compound 4d from the benzimidazole chalcone series and compound 6d from the flavonoid series exhibited significant cytotoxic activity (IC₅₀ 7.12 μM and 17.18 μM, respectively) against AW13516 cell line. Time Resolved-Fluorescence Resonance Energy Transfer (TR-FRET) analysis further demonstrated that compound 4d and compound 6d could effectively inhibit the Bcl-2 and Mcl-1 proteins by displacing their BH3 binding partners. Both compounds exhibited potent activation of canonical pathway of apoptosis evident from appearance of cleaved Caspase-3 and PARP. Further, treatment of oral cancer cells with the inhibitors induced dissociation of the BH3 only protein Bim from Mcl-1 and Bak from Bcl-2 but failed to release Bax from Bcl-xL thereby confirming the nature of compounds as BH3-mimetics selectively targeting Bcl-2 and Mcl-1. Our study thus identifies bicyclic compounds as promising candidates for anti-apoptotic Bcl-2/Mcl-1 dual inhibitors with a potential for further development.

Doxorubicin-conjugated siRNA lipid nanoparticles for combination cancer therapy

Evasion of apoptosis is a hallmark of cancer, attributed in part to overexpression of the anti-apoptotic protein B-cell lymphoma 2 (Bcl-2). In a variety of cancer types, including lymphoma, Bcl-2 is overexpressed. Therapeutic targeting of Bcl-2 has demonstrated efficacy in the clinic and is the subject of extensive clinical testing in combination with chemotherapy. Therefore, the development of co-delivery systems for Bcl-2 targeting agents, such as small interfering RNA (siRNA), and chemotherapeutics, such as doxorubicin (DOX), holds promise for enabling combination cancer therapies. Lipid nanoparticles (LNPs) are a clinically advanced nucleic acid delivery system with a compact structure suitable for siRNA encapsulation and delivery. Inspired by ongoing clinical trials of albumin-hitchhiking doxorubicin prodrugs, here we developed a DOX-siRNA co-delivery strategy via conjugation of doxorubicin to the surface of siRNA-loaded LNPs. Our optimized LNPs enabled potent knockdown of Bcl-2 and efficient delivery of DOX into the nucleus of Burkitts' lymphoma (Raji) cells, leading to effective inhibition of tumor growth in a mouse model of lymphoma. Based on these results, our LNPs may provide a platform for the co-delivery of various nucleic acids and DOX for the development of new combination cancer therapies.

A Novel BRD Family PROTAC Inhibitor dBET1 Exerts Great Anti-Cancer Effects by Targeting c-MYC in Acute Myeloid Leukemia Cells

Acute myeloid leukemia (AML) represents an aggressive hematopoietic malignancy with a prognosis inferior to that of other leukemias. Recent targeted therapies offer new opportunities to achieve better treatment outcomes. However, due to the complex heterogeneity of AML, its prognosis remains dismal. In this study, we first identified the correlation between high expression of BRD4 and overall survival of patients with AML. Targeted degradation of BRD2, BRD3, and BRD4 proteins by dBET1, a proteolysis-targeting chimera (PROTAC) against the bromodomain and extra-terminal domain (BET) family members, showed cytotoxic effects on Kasumi (AML1-ETO), NB4 (PML-RARa), THP-1 (MLL-AF9), and MV4-11 (MLL-AF4) AML cell lines representing different molecular subtypes of AML. Furthermore, we determined that dBET1 treatment arrested cell cycling and enhanced apoptosis and c-MYC was identified as the downstream target. Collectively, our results indicated that dBET1 had broad anti-cancer effects on AML cell lines with different molecular lesions and provided more benefits to patients with AML.

Targeted Degradation of mRNA Decapping Enzyme DcpS by a VHL-Recruiting PROTAC

The RNA decapping scavenger protein, DcpS, has recently been identified as a dependency in acute myeloid leukemia (AML). The potent DcpS inhibitor RG3039 attenuates AML cell viability, and shRNA knockdown of DcpS is also antiproliferative. Importantly, DcpS was found to be non-essential in normal human hematopoietic cells, which opens a therapeutic window for AML treatment by DcpS modulation. Considering this strong DcpS dependence in AML cell lines, we explored PROTAC-mediated degradation as an alternative strategy to modulate DcpS activity. Herein, we report the development of JCS-1, a PROTAC exhibiting effective degradation of DcpS at nanomolar concentrations. JCS-1 non-covalently binds DcpS with a RG3039-based warhead and recruits the E3 ligase VHL, which induces potent, rapid, and sustained DcpS degradation in several AML cell lines. JCS-1 serves as a chemical biology tool to interrogate DcpS degradation and associated changes in RNA processes in different cellular contexts, which may be an attractive strategy for the treatment of AML and other DcpS-dependent genetic disorders.

Venetoclax cooperates with ionizing radiation to attenuate Diffuse Midline Glioma tumor growth

PURPOSE

Tumor relapse after radiation therapy (RT) is a major hurdle in treating pediatric H3K27M-mutant diffuse midline gliomas (DMGs). RT-induced stress increases association of BCL2 family of proteins with BH3 pro-apoptotic activators preventing apoptosis. We hypothesized that inhibition of RT-induced BCL2 with a clinically relevant inhibitor, venetoclax, will block BCL2 activity leading to increased apoptosis. BCL2 has never been implicated in DMG as a RT-induced resistant mechanism.

EXPERIMENTAL DESIGN

We performed an integrated genomic analysis to determine genes responsible for radioresistance and a targeted drug screen to identify drugs that synergize with radiation in DMG. Effect of venetoclax on radiation-na�ve and 6Gy radiation on cells was evaluated by studying cell death, changes in BCL2 phosphorylation, reactive oxygen species (ROS), and apoptosis, as well as BCL2 association with BH3 apoptosis initiators. The efficacy of combining venetoclax with radiation was evaluated in vivo using orthotopic xenograft models.

RESULTS

BCL2 was identified as a key regulator of tumor growth after radiation in DMGs. Radiation sensitizes DMGs to venetoclax treatment independent of p53 status. Venetoclax as a monotherapy was not cytotoxic to DMG cells. Post-radiation venetoclax treatment significantly increased cell death, reduced BCL2-BIM association and augmented mitochondrial ROS leading to increased apoptosis. Combining venetoclax with RT significantly enhanced the survival of mice with DMG tumors.

CONCLUSIONS

This study shows that venetoclax impedes the anti-apoptotic function of radiation-induced BCL2 in DMG leading to increased apoptosis. Results from these pre-clinical studies demonstrate the potential use of the BCL2 inhibitor, venetoclax, combined with RT for pediatric DMG.

A distinct core regulatory module enforces oncogene expression in KMT2A-rearranged leukemia

In this study, Harada et al. identified the transcription factors MEF2D and IRF8 as selective transcriptional dependencies of KMT2A-rearranged AML, where MEF2D displays partially redundant functions with its paralog, MEF2C. This study illustrates a mechanism of context-specific transcriptional addiction whereby a specific AML subclass depends on a highly specialized core regulatory module to directly enforce expression of common leukemia oncogenes.

Acute myeloid leukemia with KMT2A (MLL) rearrangements is characterized by specific patterns of gene expression and enhancer architecture, implying unique core transcriptional regulatory circuitry. Here, we identified the transcription factors MEF2D and IRF8 as selective transcriptional dependencies of KMT2A-rearranged AML, where MEF2D displays partially redundant functions with its paralog, MEF2C. Rapid transcription factor degradation followed by measurements of genome-wide transcription rates and superresolution microscopy revealed that MEF2D and IRF8 form a distinct core regulatory module with a narrow direct transcriptional program that includes activation of the key oncogenes MYC, HOXA9, and BCL2. Our study illustrates a mechanism of context-specific transcriptional addiction whereby a specific AML subclass depends on a highly specialized core regulatory module to directly enforce expression of common leukemia oncogenes.

A systems genetics approach delineates the role of Bcl2 in leukemia pathogenesis

Leukemia is a group of malignancies of the blood forming tissues, and is characterized by the uncontrolled proliferation of blood cells. In the United States, it accounts for approximately 3.5% and 4% of all cancer-related incidences and mortalities, respectively. The current study aimed to explore the role of Bcl2 and associated genes in leukemia pathogenesis using a systems genetics approach. The transcriptome data from BXD Recombinant Inbred (RI) mice was analyzed to identify the expression of Bcl2 in myeloid cells. eQTL mapping was performed to select the potential chromosomal region and subsequently identify the candidate gene modulating the expression of Bcl2. Furthermore, gene enrichment and protein-protein interaction (PPI) analyses of the Bcl2-coexpressed genes were performed to demonstrate the role of Bcl2 in leukemia pathogenesis. The Bcl2-coexpressed genes were found to be enriched in various hematopoietic system related functions, and multiple pathways related to signaling, immune response, and cancer. The PPI network analysis demonstrated direct interaction of hematopoietic function related genes, such as Bag3, Bak1, Bcl2l11, Bmf, Mapk9, Myc, Ppp2r5c, and Ppp3ca with Bcl2. The eQTL mapping identified a 4.5 Mb genomic region on chromosome 11, potentially regulating the expression of Bcl2. A multi-criteria filtering process identified Top2a, among the genes located in the mapped locus, as the best candidate upstream regulator for Bcl2 expression variation. Hence, the current study provides better insights into the role of Bcl2 in leukemia pathogenesis and demonstrates the significance of our approach in gaining new knowledge on leukemia. Furthermore, our findings from the PPI network analysis and eQTL mapping provide supporting evidence of leukemia-associated genes, which can be further explored for their functional importance in leukemia. DATA AVAILABILITY: The myeloid cell transcriptomic data of the BXD mice used in this study can be accessed through our GeneNetwork (http://www.genenetwork.org) with the accession number of GN144.

Targeting AraC-Resistant Acute Myeloid Leukemia by Dual Inhibition of CDK9 and Bcl-2: A Systematic Review and Meta-Analysis

PURPOSE

This study aims to determine the influence of targeting araC-resistant acute myeloid leukemia by dual inhibition cyclin-dependent protein kinase (CDK9) and B-cell lymphoma-2 （Bcl-2).

METHOD

The c-Myc inhibitor 10058-F4 and the CDK9 inhibitor AZD4573 were used to determine the cell cycle arrest and apoptosis.

RESULTS

10058-F4 reduces c-Myc protein levels and suppresses HepG2 cell proliferation, possibly by upregulating cyclin-dependent kinase (CDK) inhibitors, p21WAF1, and reducing intracellular alpha-fetal protein (AFP) levels.

CONCLUSION

The combination of AZD4573 and 10058-F4 has a synergistic anti-araC-resistant AML activity, providing a solid database for the aforementioned scientific hypothesis.

Prevention and Treatment of Acute Myeloid Leukemia Relapse after Hematopoietic Stem Cell Transplantation: The State of the Art and Future Perspectives

Allogeneic hematopoietic stem cell transplantation (HSCT) for high-risk acute myeloid leukemia (AML) represents the only curative option. Progress has been made in the last two decades in the pre-transplant induction therapies, supportive care, selection of donors and conditioning regimens that allowed to extend the HSCT to a larger number of patients, including those aged over 65 years and/or lacking an HLA-identical donor. Furthermore, improvements in the prophylaxis of the graft-versus-host disease and of infection have dramatically reduced transplant-related mortality. The relapse of AML remains the major reason for transplant failure affecting almost 40-50% of the patients. From 10 to 15 years ago to date, treatment options for AML relapsing after HSCT were limited to conventional cytotoxic chemotherapy and donor leukocyte infusions (DLI). Nowadays, novel agents and targeted therapies have enriched the therapeutic landscape. Moreover, very recently, the therapeutic landscape has been enriched by manipulated cellular products (CAR-T, CAR-CIK, CAR-NK). In light of these new perspectives, careful monitoring of minimal-residual disease (MRD) and prompt application of pre-emptive strategies in the post-transplant setting have become imperative. Herein, we review the current state of the art on monitoring, prevention and treatment of relapse of AML after HSCT with particular attention on novel agents and future directions.

The role of caspases as executioners of apoptosis

Caspases are a family of cysteine aspartyl proteases mostly involved in the execution of apoptotic cell death and in regulating inflammation. This article focuses primarily on the evolutionarily conserved function of caspases in apoptosis. We summarise which caspases are involved in apoptosis, how they are activated and regulated, and what substrates they target for cleavage to orchestrate programmed cell death by apoptosis.

Synthesis and Antiproliferative Evaluation of 3-Chloroazetidin-2-ones with Antimitotic Activity: Heterocyclic Bridged Analogues of Combretastatin A-4

Antimitotic drugs that target tubulin are among the most widely used chemotherapeutic agents; however, the development of multidrug resistance has limited their clinical activity. We report the synthesis and biological properties of a series of novel 3-chloro-β-lactams and 3,3-dichloro-β-lactams (2-azetidinones) that are structurally related to the tubulin polymerisation inhibitor and vascular targeting agent, Combretastatin A-4. These compounds were evaluated as potential tubulin polymerisation inhibitors and for their antiproliferative effects in breast cancer cells. A number of the compounds showed potent activity in MCF-7 breast cancer cells, e.g., compound 10n (3-chloro-4-(3-hydroxy-4-methoxy-phenyl)-1-(3,4,5-trimethoxyphenyl)azetidin-2-one) and compound 11n (3,3-dichloro-4-(3-hydroxy-4-methoxyphenyl)-1-(3,4,5-trimethoxyphenyl)-azetidin-2-one), with IC50 values of 17 and 31 nM, respectively, and displayed comparable cellular effects to those of Combretastatin A-4. Compound 10n demonstrated minimal cytotoxicity against non-tumorigenic HEK-293T cells and inhibited the in vitro polymerisation of tubulin with significant G2/M phase cell cycle arrest. Immunofluorescence staining of MCF-7 cells confirmed that β-lactam 10n caused a mitotic catastrophe by targeting tubulin. In addition, compound 10n promoted apoptosis by regulating the expression of pro-apoptotic protein BAX and anti-apoptotic proteins Bcl-2 and Mcl-1. Molecular docking was used to explore the potential molecular interactions between novel 3-chloro-β-lactams and the amino acid residues of the colchicine binding active site cavity of β-tubulin. Collectively, these results suggest that 3-chloro-2-azetidinones, such as compound 10n, could be promising lead compounds for further clinical anti-cancer drug development.

FLT3 inhibition by olverembatinib (HQP1351) downregulates MCL-1 and synergizes with BCL-2 inhibitor lisaftoclax (APG-2575) in preclinical models of FLT3-ITD mutant acute myeloid leukemia

Introduction

FLT3-ITD mutations occur in approximately 25% of patients with acute myeloid leukemia (AML) and are associated with poor prognosis. Despite initial efficacy, short duration of response and high relapse rates limit clinical use of selective FLT3 inhibitors. Combination approaches with other targeted therapies may achieve better clinical outcomes.

Materials and methods

Anti-leukemic activity of multikinase inhibitor olverembatinib (HQP1351), alone or in combination with BCL-2 inhibitor lisaftoclax (APG-2575), was evaluated in FLT3-ITD mutant AML cell lines in vitro and in vivo. A patient-derived FLT3-ITD mutant AML xenograft model was also used to assess the anti-leukemic activity of this combination.

Results

HQP1351 potently induced apoptosis and inhibited FLT3 signaling in FLT3-ITD mutant AML cell lines MV-4-11 and MOLM-13. HQP1351 monotherapy also significantly suppressed growth of FLT3-ITD mutant AML xenograft tumors and prolonged survival of tumor-bearing mice. HQP1351 and APG-2575 synergistically induced apoptosis in FLT3-ITD mutant AML cells and suppressed growth of MV-4–11 xenograft tumors. Combination therapy improved survival of tumor bearing-mice in a systemic MOLM-13 model and showed synergistic anti-leukemic effects in a patient-derived FLT3-ITD mutant AML xenograft model. Mechanistically, HQP1351 downregulated expression of myeloid-cell leukemia 1 (MCL-1) by suppressing FLT3-STAT5 (signal transducer and activator of transcription 5) signaling and thus enhanced APG-2575-induced apoptosis in FLT3-ITD mutant AML cells.

Conclusions

FLT3 inhibition by HQP1351 downregulates MCL-1 and synergizes with BCL-2 inhibitor APG-2575 to potentiate cellular apoptosis in FLT3-ITD mutant AML. Our findings provide a scientific rationale for further clinical investigation of HQP1351 combined with APG-2575 in patients with FLT3-ITD mutant AML.

MCL-1 Inhibition Overcomes Anti-apoptotic Adaptation to Targeted Therapies in B-Cell Precursor Acute Lymphoblastic Leukemia

Multiple targeted therapies are currently explored for pediatric and young adult B-cell precursor acute lymphoblastic leukemia (BCP-ALL) treatment. However, this new armamentarium of therapies faces an old problem: choosing the right treatment for each patient. The lack of predictive biomarkers is particularly worrying for pediatric patients since it impairs the implementation of new treatments in the clinic. In this study, we used the functional assay dynamic BH3 profiling (DBP) to evaluate two new treatments for BCP-ALL that could improve clinical outcome, especially for relapsed patients. We found that the MEK inhibitor trametinib and the multi-target tyrosine kinase inhibitor sunitinib exquisitely increased apoptotic priming in an NRAS-mutant and in a KMT2A-rearranged cell line presenting a high expression of FLT3, respectively. Following these observations, we sought to study potential adaptations to these treatments. Indeed, we identified with DBP anti-apoptotic changes in the BCL-2 family after treatment, particularly involving MCL-1 - a pro-survival strategy previously observed in adult cancers. To overcome this adaptation, we employed the BH3 mimetic S63845, a specific MCL-1 inhibitor, and evaluated its sequential addition to both kinase inhibitors to overcome resistance. We observed that the metronomic combination of both drugs with S63845 was synergistic and showed an increased efficacy compared to single agents. Similar observations were made in BCP-ALL KMT2A-rearranged PDX cells in response to sunitinib, showing an analogous DBP profile to the SEM cell line. These findings demonstrate that rational sequences of targeted agents with BH3 mimetics, now extensively explored in clinical trials, may improve treatment effectiveness by overcoming anti-apoptotic adaptations in BCP-ALL.