MCL-1 is a master regulator of cancer dependency on fatty acid oxidation

Cell death and cancer: Metabolic interconnections

Recent findings in the cell death field have transformed our understanding of the interplay between metabolism and cell death in the context of cancer. In this review, we discuss the relationships between metabolism and the cell death pathways of apoptosis, necroptosis, pyroptosis, and ferroptosis, with a particular focus on recent advancements. We will also explore the regulation of metabolism by the BCL-2 family and the participation of oncometabolites in the regulation of cell death. Finally, we examine the emerging links between cell death signaling and cellular persistence. As we highlight in this review, the intersection of metabolic and cell death pathways has implications for cancer cell survival, treatment resistance, and the tumor microenvironment.

MCL-1 as a potent target for cancer: Recent advancements, structural insights and SAR studies

The myeloid cell leukemia-1 (Mcl-1) differentiation protein belongs to the B-cell lymphoma 2 (Bcl-2) family of proteins which regulates the apoptosis or cell death. Mcl-1 is known for its pro-survival in response to various stressors. Therefore, it acts as a prominent target in cancer treatment. Mcl-1 has emerged as one of the validated drug targets for anticancer drug discovery as their expression has been implicated in the pathogenesis of cancers. In this review, we have included the various inhibitors based on many heterocyclic rings such as pyrrole, pyrazole, coumarin, quinoline and indole. This manuscript incorporates the anticancer activity, structure activity relationship (SAR) and molecular modelling of recently synthesized Mcl-1 inhibitors. The clinical trial status of Mcl-1 inhibitors is also described. But till now, no Mcl-1 inhibitor has been approved by any drug authority. This review is based on extensive research in the field of designing Mcl-1 inhibitors from 2020 to till now. It will provide extensive information to researchers and scientists for designing of novel Mcl-1 inhibitors.

Multidimensional, integrative profiling identifies BCL2L1 methylation as a predictor of MCL1 dependency in pediatric malignancies

Pediatric high-grade gliomas (pHGGs) are the most aggressive brain tumors in children, necessitating innovative therapies to improve outcomes. Unlike adult gliomas, recent research reveals that childhood gliomas have distinct biological features, requiring specific treatment strategies. Here, we focused on deciphering unique genetic dependencies specific to childhood gliomas. Using a pooled CRISPR/Cas9 knockout screening approach on 65 pediatric and 10 adult high-grade glioma (HGG) cell lines, myeloid cell leukemia 1 (MCL1) emerged as a key antiapoptotic gene essential in pediatric but not adult gliomas. We demonstrated that MCL1 is targetable using current small molecule inhibitors, and its inhibition leads to potent anticancer activity across pediatric HGG cell lines irrespective of genotype. Employing predictive modeling approaches on a large set of childhood cancer cell lines with multiomics data features, we identified a potentially previously unreported cluster of CpG sites in the antiapoptotic BCL-xL/BCL2L1 gene, which predicted MCL1 inhibitor response. We extended these data across multiple pediatric tumor types, showing that BCL2L1 methylation is a broad predictor of MCL1 dependency in vitro and in vivo. Overall, our multidimensional, integrated genomic approach identified MCL1 as a promising therapeutic target in several BCL2L1-methylated pediatric cancers, offering a translational strategy to identify patients most likely to benefit from MCL1 inhibitor therapy.

MCL-1 regulates cellular transitions during oligodendrocyte development

Oligodendrocytes are the myelinating cells of the central nervous system. Regulation of the early stages of oligodendrocyte development is critical to the function of the cell. Specifically, myelin sheath formation is an energetically demanding event that requires precision, as alterations may lead to dysmyelination. Recent work has established that fatty acid β-oxidation is required for the function of oligodendrocytes. We have shown that MCL-1, a well-characterized anti-apoptotic protein, is required for the development of oligodendrocytes in vivo. Further, it was recently uncovered that MCL-1 regulates long-chain fatty acid β-oxidation through its interaction with acyl-CoA synthetase long-chain family member 1 (ACSL1), an enzyme responsible for the conversion of long-chain fatty acids into acyl-CoA. Here, we introduce an in vitro system to isolate human stem cell-derived oligodendrocyte progenitor cells and investigate the involvement of MCL-1 during human oligodendrocyte development. Using this system, we pharmacologically inhibited MCL-1 in oligodendrocyte progenitor cells (OPCs) to elucidate the non-apoptotic function of the protein at this developmental stage. Additionally, we used a motor neuron co-culture system to investigate the downstream effects that MCL-1 inhibition has at later developmental stages when oligodendrocytes begin to contact axons and generate myelin basic protein. We demonstrate that the mitochondrial network changes in human oligodendrocyte development resemble those reported in vivo. Our findings point to MCL-1 as a critical factor essential at the OPC stage for proper oligodendrocyte morphogenesis.

Overexpression of MCL1 attenuates irritable bowel syndrome by regulating cuproptosis: Screening and validation

Irritable bowel syndrome (IBS) is a type of chronic bowel disorder with a poorly understood pathophysiology. Recently, the imbalance of copper has been reported to influence the progression of IBS, suggesting cuproptosis, a new type of copper-induced cell death, may play a role in IBS. This study found 17 cuproptosis-related differentially expressed genes in IBS through bioinformatic analysis. Six hub genes were identified after the protein-protein interaction network analysis, namely myeloid cell leukemia 1 (MCL1), epidermal growth factor receptor 2, cadherin-associated protein beta 1, solute carrier family 25 members 37, solute carrier family 39 members 14, and six transmembrane epithelial antigens of the prostate 3. We selected MCL1 for further verification. Human normal colon epithelial cell line (NCM460) was used to construct models of IBS or cuproptosis in vitro by lipopolysaccharide (LPS) or LPS combined with copper (II) chloride (CuCl2). We observed that overexpression of MCL1 promoted cell viability and proliferation ability, and inhibited the secretion of inflammatory factors and expression of Bax and caspase-3 of NCM460 cells treated with LPS or LPS combined with CuCl2. In addition, up-regulated MCL1 significantly suppressed the protein levels of ferredoxin 1 and lipoyl synthase, two key regulators of cuproptosis. In conclusion, our study demonstrates that cuproptosis is involved in IBS and identifies a cuproptosis-related gene, MCL1, that helps alleviate IBS by promoting cell growth, reducing inflammation, and suppressing cuproptosis, making it a promising therapeutic target in IBS.

A Phase 1 First-in-Human Study of the MCL-1 Inhibitor AZD5991 in Patients with Relapsed/Refractory Hematologic Malignancies

PURPOSE

AZD5991, a human MCL-1 inhibitor, was assessed for safety, tolerability, pharmacokinetics, and antitumor activity as monotherapy and in combination with venetoclax in patients with relapsed or refractory hematologic malignancies.

PATIENTS AND METHODS

In the monotherapy cohort (n = 61), patients with hematologic malignancies received AZD5991 intravenously in escalating doses either once or twice weekly, following intrapatient dose escalation, during a 3-week cycle. In the combination cohort (n = 17), patients with acute myeloid leukemia and myelodysplastic syndrome received escalating doses of AZD5991 and venetoclax during either a 3- or 4-week cycle. Primary objectives were safety and maximum tolerated dose; secondary objectives included plasma pharmacokinetics and antitumor activity.

RESULTS

The most common (≥30%) adverse events were diarrhea (59.0%), nausea (55.1%), and vomiting (47.4%). Four deaths occurred because of adverse events: cardiac arrest, sepsis, tumor lysis syndrome, and acute respiratory failure; only tumor lysis syndrome was related to AZD5991. Dose-limiting toxicities occurred in five patients. Three patients with myelodysplastic syndrome achieved an objective response: one marrow complete remission without hematologic improvement, one partial remission with AZD5991 monotherapy, and one marrow complete remission with AZD5991 + venetoclax. Asymptomatic elevations of troponin I or T were observed in eight (10.3%) patients. Post hoc retrospective analysis revealed elevated troponin T in 14/31 patients before any AZD5991 dose and in 54/65 patients after any AZD5991 dose at or after Cycle 1. No associations were found between elevated troponin and cardiovascular risk factors.

CONCLUSIONS

Treatment with AZD5991 was associated with high incidence of laboratory troponin elevation and a low overall response rate.

Regulation of leukemogenesis via redox metabolism

Redox metabolism plays a central role in the cellular metabolism network, involves catabolic and anabolic reactions of diverse biomass, and determines the redox state of cells. It can be quantitatively and conveniently measured in living cells and organisms with genetically encoded fluorescent sensors, providing novel insights that cannot be readily acquired via conventional metabolic assays. Here, we review the recent progress on the regulation of leukemogenesis via redox metabolism, especially redox biosensor-based findings. In general, low reactive oxygen species levels and high reductive capacity promote leukemogenesis and chemotherapy resistance in leukemia cells, and acute leukemia cells rewire metabolism of glucose, fatty acids, and some amino acids, together with oxidative phosphorylation, to fuel energy production, support biomass-related synthesis, and survive oxidative stress. In summary, redox metabolism is a potential target for the development of novel therapies for leukemia or beneficial dietary regimens for patients with refractory and relapsed leukemia.

Dissecting the neuroprotective interaction between the BH4 domain of BCL-w and the IP3 receptor

BCL-w is a BCL-2 family protein that promotes cell survival in tissue- and disease-specific contexts. The canonical anti-apoptotic functionality of BCL-w is mediated by a surface groove that traps the BCL-2 homology 3 (BH3) α-helices of pro-apoptotic members, blocking cell death. A distinct N-terminal portion of BCL-w, termed the BCL-2 homology 4 (BH4) domain, selectively protects axons from paclitaxel-induced degeneration by modulating IP3 receptors, a noncanonical BCL-2 family target. Given the potential of BCL-w BH4 mimetics to prevent or mitigate chemotherapy-induced peripheral neuropathy, we sought to characterize the interaction between BCL-w BH4 and the IP3 receptor, combining "staple" and alanine scanning approaches with molecular dynamics simulations. We generated and identified stapled BCL-w BH4 peptides with optimized IP3 receptor binding and neuroprotective activities. Point mutagenesis further revealed the sequence determinants for BCL-w BH4 specificity, providing a blueprint for therapeutic targeting of IP3 receptors to achieve neuroprotection.

BRD-810 is a highly selective MCL1 inhibitor with optimized in vivo clearance and robust efficacy in solid and hematological tumor models

The MCL1 gene is frequently amplified in cancer and codes for the antiapoptotic protein myeloid cell leukemia 1 (MCL1), which confers resistance to the current standard of care. Therefore, MCL1 is an attractive anticancer target. Here we describe BRD-810 as a potent and selective MCL1 inhibitor and its key design principle of rapid systemic clearance to potentially minimize area under the curve-driven toxicities associated with MCL1 inhibition. BRD-810 induced rapid cell killing within 4 h in vitro but, in the same 4-h window, had no impact on cell viability or troponin I release in human induced pluripotent stem cell-derived cardiomyocytes, even at suprapharmacologic concentrations. In vivo BRD-810 induced efficacy in xenograft hematological and solid tumor models despite the short residence time of BRD-810 in plasma. In totality, our data support the hypothesis that short-term inhibition of MCL1 with BRD-810 can induce apoptosis in tumor cells while maintaining an acceptable safety profile. We, therefore, intend to advance BRD-810 to clinical trials.

Functional overlap of inborn errors of immunity and metabolism genes defines T cell metabolic vulnerabilities

Inborn errors of metabolism (IEMs) and immunity (IEIs) are Mendelian diseases in which complex phenotypes and patient rarity have limited clinical understanding. Whereas few genes have been annotated as contributing to both IEMs and IEIs, immunometabolic demands suggested greater functional overlap. Here, CRISPR screens tested IEM genes for immunologic roles and IEI genes for metabolic effects and found considerable previously unappreciated crossover. Analysis of IEMs showed that N-linked glycosylation and the hexosamine pathway enzyme Gfpt1 are critical for T cell expansion and function. Further, T helper (TH1) cells synthesized uridine diphosphate N-acetylglucosamine more rapidly and were more impaired by Gfpt1 deficiency than TH17 cells. Screening IEI genes found that Bcl11b promotes the CD4 T cell mitochondrial activity and Mcl1 expression necessary to prevent metabolic stress. Thus, a high degree of functional overlap exists between IEM and IEI genes, and immunometabolic mechanisms may underlie a previously underappreciated intersection of these disorders.

Unlocking the Therapeutic Potential of BCL-2 Associated Protein Family: Exploring BCL-2 Inhibitors in Cancer Therapy

Apoptosis, programmed cell death pathway, is a vital physiological mechanism that ensures cellular homeostasis and overall cellular well-being. In the context of cancer, where evasion of apoptosis is a hallmark, the overexpression of anti-apoptotic proteins like Bcl2, Bcl-xL and Mcl-1 has been documented. Consequently, these proteins have emerged as promising targets for therapeutic interventions. The BCL-2 protein family is central to apoptosis and plays a significant importance in determining cellular fate serving as a critical determinant in this biological process. This review offers a comprehensive exploration of the BCL-2 protein family, emphasizing its dual nature. Specifically, certain members of this family promote cell survival (known as anti-apoptotic proteins), while others are involved in facilitating cell death (referred to as pro-apoptotic and BH3-only proteins). The potential of directly targeting these proteins is examined, particularly due to their involvement in conferring resistance to traditional cancer therapies. The effectiveness of such targeting strategies is also discussed, considering the tumor's propensity for anti-apoptotic pathways. Furthermore, the review highlights emerging research on combination therapies, where BCL-2 inhibitors are used synergistically with other treatments to enhance therapeutic outcomes. By understanding and manipulating the BCL-2 family and its associated pathways, we open doors to innovative and more effective cancer treatments, offering hope for resistant and aggressive cases.

Butein inhibits oral squamous cell carcinoma growth via promoting MCL-1 ubiquitination

Oral squamous cell carcinoma (OSCC) is the most common malignant head and neck carcinoma type. Myeloid cell leukemia-1 (MCL-1), an anti-apoptotic BCL-1 protein, has been verified to be among the most highly upregulated pathologic proteins in human cancers linked to tumor relapse, poor prognosis and therapeutic resistance. Herein, therapeutic targeting MCL-1 is an attractive focus for cancer treatment. The present study found that butein, a potential phytochemical compound, exerted profound antitumor effects on OSCC cells. Butein treatment significantly inhibited cell viability, proliferation capacity and colony formation ability, and activated cell apoptotic process. Further potential mechanism investigation showed that promoting MCL-1 ubiquitination and degradation is the major reason for butein-mediated OSCC cell cytotoxicity. Our results uncovered that butein could facilitate E3 ligase FBW7 combined with MCL-1, which contributed to an increase in the ubiquitination of MCL-1 Ub-K48 and degradation. The results of both in vitro cell experiments and in vivo xenograft models imply a critical antitumor function of butein with the well-tolerated feature, and it might be an attractive and promising agent for OSCC treatment.

Anti-apoptotic MCL-1 promotes long-chain fatty acid oxidation through interaction with ACSL1

MCL-1 is essential for promoting the survival of many normal cell lineages and confers survival and chemoresistance in cancer. Beyond apoptosis regulation, MCL-1 has been linked to modulating mitochondrial metabolism, but the mechanism(s) by which it does so are unclear. Here, we show in tissues and cells that MCL-1 supports essential steps in long-chain (but not short-chain) fatty acid β-oxidation (FAO) through its binding to specific long-chain acyl-coenzyme A (CoA) synthetases of the ACSL family. ACSL1 binds to the BH3-binding hydrophobic groove of MCL-1 through a non-conventional BH3-domain. Perturbation of this interaction, via genetic loss of Mcl1, mutagenesis, or use of selective BH3-mimetic MCL-1 inhibitors, represses long-chain FAO in cells and in mouse livers and hearts. Our findings reveal how anti-apoptotic MCL-1 facilitates mitochondrial metabolism and indicate that disruption of this function may be associated with unanticipated cardiac toxicities of MCL-1 inhibitors in clinical trials.

Targeting MCL-1 triggers DNA damage and an anti-proliferative response independent from apoptosis induction

MCL-1 is a high-priority target due to its dominant role in the pathogenesis and chemoresistance of cancer, yet clinical trials of MCL-1 inhibitors are revealing toxic side effects. MCL-1 biology is complex, extending beyond apoptotic regulation and confounded by its multiple isoforms, its domains of unresolved structure and function, and challenges in distinguishing noncanonical activities from the apoptotic response. We find that, in the presence or absence of an intact mitochondrial apoptotic pathway, genetic deletion or pharmacologic targeting of MCL-1 induces DNA damage and retards cell proliferation. Indeed, the cancer cell susceptibility profile of MCL-1 inhibitors better matches that of anti-proliferative than pro-apoptotic drugs, expanding their potential therapeutic applications, including synergistic combinations, but heightening therapeutic window concerns. Proteomic profiling provides a resource for mechanistic dissection and reveals the minichromosome maintenance DNA helicase as an interacting nuclear protein complex that links MCL-1 to the regulation of DNA integrity and cell-cycle progression.

The Illustration of Altered Glucose Dependency in Drug-Resistant Cancer Cells

A chemotherapeutic approach is crucial in malignancy management, which is often challenging due to the development of chemoresistance. Over time, chemo-resistant cancer cells rapidly repopulate and metastasize, increasing the recurrence rate in cancer patients. Targeting these destined cancer cells is more troublesome for clinicians, as they share biology and molecular cross-talks with normal cells. However, the recent insights into the metabolic profiles of chemo-resistant cancer cells surprisingly illustrated the activation of distinct pathways compared with chemo-sensitive or primary cancer cells. These distinct metabolic dynamics are vital and contribute to the shift from chemo-sensitivity to chemo-resistance in cancer. This review will discuss the important metabolic alterations in cancer cells that lead to drug resistance.

Regulators mount up: the metabolic roles of apoptotic proteins

The induction of apoptosis, a programmed cell death pathway governed by activation of caspases, can result in fundamental changes in metabolism that either facilitate or restrict the execution of cell death. In addition, metabolic adaptations can significantly impact whether cells in fact initiate the apoptotic cascade. In this mini-review, we will highlight and discuss the interconnectedness of apoptotic regulation and metabolic alterations, two biological outcomes whose regulators are intertwined.

The Role of Reprogrammed Glucose Metabolism in Cancer

Cancer cells reprogram their metabolism to meet biosynthetic needs and to adapt to various microenvironments. Accelerated glycolysis offers proliferative benefits for malignant cells by generating glycolytic products that move into branched pathways to synthesize proteins, fatty acids, nucleotides, and lipids. Notably, reprogrammed glucose metabolism and its associated events support the hallmark features of cancer such as sustained cell proliferation, hijacked apoptosis, invasion, metastasis, and angiogenesis. Overproduced enzymes involved in the committed steps of glycolysis (hexokinase, phosphofructokinase-1, and pyruvate kinase) are promising pharmacological targets for cancer therapeutics. In this review, we summarize the role of reprogrammed glucose metabolism in cancer cells and how it can be manipulated for anti-cancer strategies.

Targeting Mcl-1 Degradation by Bergenin Inhibits Tumorigenesis of Colorectal Cancer Cells

Myeloid leukemia 1 (Mcl-1) is frequently overexpressed in human malignancies and emerged as a promising drug target. In this study, we verified the inhibitory effect of bergenin on colorectal cancer cells both in vivo and in vitro. In an in vitro setting, bergenin significantly reduced the viability and colony formation and promoted apoptosis of CRC cells dose-dependently. Bergenin decreased the activity of Akt/GSK3β signaling and enhanced the interaction between FBW7 and Mcl-1, which eventually induced Mcl-1 ubiquitination and degradation. Using the HA-Ub K48R mutant, we demonstrated that bergenin promotes Mcl-1 K48-linked polyubiquitination and degradation. In vivo studies showed that bergenin significantly reduced tumor size and weight without toxicity to vital organs in mice. Overall, our results support the role of bergenin in inhibiting CRC cells via inducing Mcl-1 destruction, suggesting that targeting Mcl-1 ubiquitination could be an alternative strategy for antitumor therapy.

Functional Overlap of Inborn Errors of Immunity and Metabolism Genes Define T Cell Immunometabolic Vulnerabilities

Inborn Errors of Metabolism (IEM) and Immunity (IEI) are Mendelian diseases in which complex phenotypes and patient rarity can limit clinical annotations. Few genes are assigned to both IEM and IEI, but immunometabolic demands suggest functional overlap is underestimated. We applied CRISPR screens to test IEM genes for immunologic roles and IEI genes for metabolic effects and found considerable crossover. Analysis of IEM showed N-linked glycosylation and the de novo hexosamine synthesis enzyme, Gfpt1 , are critical for T cell expansion and function. Interestingly, Gfpt1 -deficient T H 1 cells were more affected than T H 17 cells, which had increased Nagk for salvage UDP-GlcNAc synthesis. Screening IEI genes showed the transcription factor Bcl11b promotes CD4 + T cell mitochondrial activity and Mcl1 expression necessary to prevent metabolic stress. These data illustrate a high degree of functional overlap of IEM and IEI genes and point to potential immunometabolic mechanisms for a previously unappreciated set of these disorders.

HIGHLIGHTS

Inborn errors of immunity and metabolism have greater overlap than previously known Gfpt1 deficiency causes an IEM but also selectively regulates T cell subset fate Loss of Bcl11b causes a T cell deficiency IEI but also harms mitochondrial function Many IEM may have immune defects and IEI may be driven by metabolic mechanisms.