Mcl-1 Inhibition: Managing Malignancy in Multiple Myeloma

Discovery of Novel Mcl-1 Inhibitors with a 3-Substituted-1H-indole-1-yl Moiety Binding to the P1-P3 Pockets to Induce Apoptosis in Acute Myeloid Leukemia Cells

Mcl-1 is a main antiapoptotic protein in acute myeloid leukemia (AML) and is used as a target to develop inhibitors. Currently, potent Mcl-1 inhibitors primarily interact with the P2-P4 pockets of Mcl-1, but pharmacological modulation by targeting the P1 pocket is less explored. We designed a series of 1H-indole-2-carboxylic acid compounds as novel Mcl-1 inhibitors occupying the P1-P3 pockets and evaluated their Mcl-1 inhibition and apoptosis induction in AML cells. Two-dimensional 15N-HSQC spectroscopy indicated that 47 (Ki = 24 nM) bound to the BH3 binding groove, occupied the P1 pocket in Mcl-1, and formed interactions with Lys234 and Val249. 47 exhibited good microsomal stability and pharmacokinetic profiles, with low potential risk of cardiotoxicity. 47 inhibited tumor growth in HL-60 and THP-1 xenograft models with growth inhibition rate of 63.7% and 57.4%, respectively. Collectively, 47 represents a novel Mcl-1 inhibitor targeting the P1-P3 pockets with excellent antileukemia effects.

Discovering Potential in Non-Cancer Medications: A Promising Breakthrough for Multiple Myeloma Patients

MM is a common type of cancer that unfortunately leads to a significant number of deaths each year. The majority of the reported MM cases are detected in the advanced stages, posing significant challenges for treatment. Additionally, all MM patients eventually develop resistance or experience relapse; therefore, advances in treatment are needed. However, developing new anti-cancer drugs, especially for MM, requires significant financial investment and a lengthy development process. The study of drug repurposing involves exploring the potential of existing drugs for new therapeutic uses. This can significantly reduce both time and costs, which are typically a major concern for MM patients. The utilization of pre-existing non-cancer drugs for various myeloma treatments presents a highly efficient and cost-effective strategy, considering their prior preclinical and clinical development. The drugs have shown promising potential in targeting key pathways associated with MM progression and resistance. Thalidomide exemplifies the success that can be achieved through this strategy. This review delves into the current trends, the challenges faced by conventional therapies for MM, and the importance of repurposing drugs for MM. This review highlights a noncomprehensive list of conventional therapies that have potentially significant anti-myeloma properties and anti-neoplastic effects. Additionally, we offer valuable insights into the resources that can help streamline and accelerate drug repurposing efforts in the field of MM.

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.

Targeting Myeloid Leukemia-1 in Cancer Therapy: Advances and Directions

As a tripartite cell death switch, B-cell lymphoma protein 2 (Bcl-2) family members precisely regulate the endogenous apoptosis pathway in response to various cell signal stresses through protein-protein interactions. Myeloid leukemia-1 (Mcl-1), a key anti-apoptotic Bcl-2 family member, is positioned downstream in the endogenous apoptotic pathway and plays a central role in regulating mitochondrial function. Mcl-1 is highly expressed in a variety of hematological malignancies and solid tumors, contributing to tumorigenesis, poor prognosis, and chemoresistance, making it an attractive target for cancer treatment. This Perspective aims to discuss the mechanism by which Mcl-1 regulates apoptosis and non-apoptotic functions in cancer cells and to outline the discovery and optimization process of potent Mcl-1 modulators. In addition, we summarize the structural characteristics of potent inhibitors that bind to Mcl-1 through multiple co-crystal structures and analyze the cardiotoxicity caused by current Mcl-1 inhibitors, providing prospects for rational targeting of Mcl-1.

Anlotinib Inhibits Cisplatin Resistance in Non-Small-Cell Lung Cancer Cells by Inhibiting MCL-1 Expression via MET/STAT3/Akt Pathway

Background

Anlotinib is an effective targeted therapy for advanced non-small-cell lung cancer (NSCLC) and has been found to mediate chemoresistance in many cancers. However, the underlying molecular mechanism of anlotinib mediates cisplatin (DDP) resistance in NSCLC remains unclear.

Methods

Cell viability was assessed by the cell counting kit 8 assay. Cell proliferation, migration, and invasion were determined using the colony formation assay and transwell assay. The mRNA expression levels of mesenchymal-epithelial transition factor (MET) and myeloid cell leukemia-1 (MCL-1) were measured by quantitative real-time PCR. Protein expression levels of MET, MCL-1, and STAT3/Akt pathway-related markers were examined using western blot analysis.

Results

Our data showed that anlotinib inhibited the DDP resistance of NSCLC cells by regulating cell proliferation and metastasis. Moreover, MET and MCL-1 expression could be decreased by anlotinib treatment. Silencing of MET suppressed the activity of the STAT3/Akt pathway and MCL-1 expression. Furthermore, MET overexpression reversed the inhibitory effect of anlotinib on the DDP resistance of NSCLC cells, and this effect could be eliminated by MCL-1 knockdown or ACT001 (an inhibitor for STAT3/Akt pathway).

Conclusion

Our results confirmed that anlotinib inhibited DDP resistance in NSCLC cells, which might decrease MCL-1 expression via mediating the MET/STAT3/Akt pathway.

B-cell lymphoma-2 family proteins in the crosshairs: Small molecule inhibitors and activators for cancer therapy

The B-cell lymphoma-2 (BCL-2) family of proteins plays a crucial role in the regulation of apoptosis, offering a dual mechanism for its control. Numerous studies have established a strong association between gene disorders of these proteins and the proliferation of diverse cancer cell types. Consequently, the identification and development of drugs targeting BCL-2 family proteins have emerged as a prominent area in antitumor therapy. Over the last two decades, several small-molecules have been designed to modulate the protein-protein interactions between anti- and proapoptotic BCL-2 proteins, effectively suppressing tumor growth and metastasis in vivo. The primary focus of research has been on developing BCL-2 homology 3 (BH3) mimetics to target antiapoptotic BCL-2 proteins, thereby competitively releasing proapoptotic BCL-2 proteins and restoring the blocked intrinsic apoptotic program. Additionally, for proapoptotic BCL-2 proteins, exogenous small molecules have been explored to activate cell apoptosis by directly interacting with executioner proteins such as BCL-2-associated X protein (BAX) or BCL-2 homologous antagonist/killer protein (BAK). In this comprehensive review, we summarize the inhibitors and activators (sensitizers) of BCL-2 family proteins developed over the past decades, highlighting their discovery, optimization, preclinical and clinical status, and providing an overall landscape of drug development targeting these proteins for therapeutic purposes.

An overview of multiple myeloma: A monoclonal plasma cell malignancy's diagnosis, management, and treatment modalities

Multiple Myeloma (MM) is a plasma cell cancer with high mortality and morbidity rates. Its incidence rate has increased by 143% since 1975. Adipokines, cytokines, chemokines, and genetic variations influence the development and progression of MM. Chromosomal translocations cause mutations associated with MM. The pathogenesis of MM is complicated by novel issues like miRNAs, RANKL, Wnt/DKK1, Wnt, and OPG. Conventional diagnosis methods include bone marrow biopsy, sPEP or uPEP, sIFE and uIFE, and sFLC assay, along with advanced techniques such as FISH, SNPA, and gene expression technologies. A novel therapeutic strategy has been developed recently. Chemotherapy, hematopoietic stem cell transplantation, and a variety of drug classes in combination are used to treat patients with high-risk diseases. Alkylating agents, PIs, and IMiDs have all been developed as effective treatment options for MM in recent years. This review overviews the current recommendations for managing MGUS, SMM, MM, SP and NSMM and discusses practices in diagnosing and treating MM.

Autophagy-related mechanisms for treatment of multiple myeloma

Multiple myeloma (MM) is a type of hematological cancer that occurs when B cells become malignant. Various drugs such as proteasome inhibitors, immunomodulators, and compounds that cause DNA damage can be used in the treatment of MM. Autophagy, a type 2 cell death mechanism, plays a crucial role in determining the fate of B cells, either promoting their survival or inducing cell death. Therefore, autophagy can either facilitate the progression or hinder the treatment of MM disease. In this review, autophagy mechanisms that may be effective in MM cells were covered and evaluated within the contexts of unfolded protein response (UPR), bone marrow microenvironment (BMME), drug resistance, hypoxia, DNA repair and transcriptional regulation, and apoptosis. The genes that are effective in each mechanism and research efforts on this subject were discussed in detail. Signaling pathways targeted by new drugs to benefit from autophagy in MM disease were covered. The efficacy of drugs that regulate autophagy in MM was examined, and clinical trials on this subject were included. Consequently, among the autophagy mechanisms that are effective in MM, the most suitable ones to be used in the treatment were expressed. The importance of 3D models and microfluidic systems for the discovery of new drugs for autophagy and personalized treatment was emphasized. Ultimately, this review aims to provide a comprehensive overview of MM disease, encompassing autophagy mechanisms, drugs, clinical studies, and further studies.

Role of the Mitochondrial E3 Ubiquitin Ligases as Possible Therapeutic Targets in Cancer Therapy

Ubiquitination is a post-translational modification that targets specific proteins on their lysine residues. Depending on the type of ubiquitination, this modification ultimately regulates the stability or degradation of the targeted proteins. Ubiquitination is mediated by three different classes of enzymes: the E1 ubiquitin-activating enzymes, the E2 ubiquitin-conjugating enzymes and, most importantly, the E3 ubiquitin ligases. E3 ligases are responsible for the final step of the ubiquitin cascade, interacting directly with the target proteins. E3 ligases can also be involved in DNA repair, cell cycle regulation and response to stress; alteration in their levels can be involved in oncogenic transformation and cancer progression. Of all the six hundred E3 ligases of the human genome, only three of them are specific to the mitochondrion: MARCH5, RNF185 and MUL1. Their alterations (that reflect on the alteration of the mitochondria functions) can be related to cancer progression, as underlined by the increasing research performed in recent years on these three mitochondrial enzymes. This review will focus on the function and mechanisms of the mitochondrial E3 ubiquitin ligases, as well as their important targets, in cancer development and progression, also highlighting their potential use for cancer therapy.

Enabling, Decagram-Scale Synthesis of Macrocyclic MCL-1 Inhibitor ABBV-467

ABBV-467 is a highly potent and selective MCL-1 inhibitor that was advanced to a phase I clinical trial for the treatment of multiple myeloma. Due to its large size and structural complexity, ABBV-467 is a challenging synthetic target. Herein, we describe the synthesis of ABBV-467 on a decagram scale, which enabled preclinical characterization. The strategy is convergent and stereoselective, featuring a hindered biaryl cross coupling, enantioselective hydrogenation, and conformationally preorganized macrocyclization by C-O bond formation as key steps.

Selective MCL-1 inhibitor ABBV-467 is efficacious in tumor models but is associated with cardiac troponin increases in patients

BACKGROUND

MCL-1 is a prosurvival B-cell lymphoma 2 family protein that plays a critical role in tumor maintenance and survival and can act as a resistance factor to multiple anticancer therapies. Herein, we describe the generation and characterization of the highly potent and selective MCL-1 inhibitor ABBV-467 and present findings from a first-in-human trial that included patients with relapsed/refractory multiple myeloma (NCT04178902).

METHODS

Binding of ABBV-467 to human MCL-1 was assessed in multiple cell lines. The ability of ABBV-467 to induce tumor growth inhibition was investigated in xenograft models of human multiple myeloma and acute myelogenous leukemia. The first-in-human study was a multicenter, open-label, dose-escalation study assessing safety, pharmacokinetics, and efficacy of ABBV-467 monotherapy.

RESULTS

Here we show that administration of ABBV-467 to MCL-1-dependent tumor cell lines triggers rapid and mechanism-based apoptosis. In vivo, intermittent dosing of ABBV-467 as monotherapy or in combination with venetoclax inhibits the growth of xenografts from human hematologic cancers. Results from a clinical trial evaluating ABBV-467 in patients with multiple myeloma based on these preclinical data indicate that treatment with ABBV-467 can result in disease control (seen in 1 patient), but may also cause increases in cardiac troponin levels in the plasma in some patients (seen in 4 of 8 patients), without other corresponding cardiac findings.

CONCLUSIONS

The selectivity of ABBV-467 suggests that treatment-induced troponin release is a consequence of MCL-1 inhibition and therefore may represent a class effect of MCL-1 inhibitors in human patients.

Pathogenesis, clinical characteristics and personalized managements of multiple myeloma with chromosome 1 abnormalities

Multiple myeloma (MM) is a biologically heterogeneous malignancy defined by the proliferation of monoclonal plasma cells. Despite the tremendous advancement in MM treatment over the past decades, relapse remains a major problem which is inevitable for most patients. In particular, a partial of patients with early relapse and poor outcomes are classified as a high-risk group. Apart from the clinical stage, genetic aberrations are now recognized as important prognostic factors for identifying high-risk patients. Chromosome 1 abnormalities (C1As), particularly 1q21 gain or amplification, have been identified as common genetic aberrations in patients with MM and are often considered unfavorable prognostic markers for progression-free survival and overall survival. However, more effective therapeutic approaches are still needed to overcome the negative impact of C1As. Therefore, we summarize the prevalence, pathogenesis, clinical significance and present therapeutic condition of C1As in MM, and attempt to conclude the precise and personalized management for patients with C1As.

The Impact of Panobinostat on Cell Death in Combination with S63845 in Multiple Myeloma Cells

Multiple myeloma is a B cell neoplasm characterized by bone marrow infiltration with malignant plasma cells. The Overexpression of histone deacetylase prevents apoptosis of myeloma cells by different mechanisms. The combination of Panobinostat with a BH3 mimetic, S63845, has demonstrated significant antitumor activity in multiple myeloma. We examined the impact of Panobinostat combined with MCL-1 inhibitor on multiple myeloma cell lines in vivo and in vitro as well as on fresh human myeloma cells. Our study shows that MCL-1 remains a major resistant factor to cell death induced by Panobinostat. Therefore, the inhibition of the MCL-1 member is considered a therapeutic strategy to kill the myeloma cells. We examined that the MCL-1 inhibitor (S63845) enhanced the cytotoxic effect of Panobinostat and decreased the viability of human cell lines and primary myeloma patient cells. Mechanistically, Panobinostat/S63845 control cell death via an intrinsic pathway. Given these data, the combination can be a promising therapeutic target for myeloma patients and should be further explored in clinical trials.

Past, Present, and a Glance into the Future of Multiple Myeloma Treatment

Multiple myeloma (MM) is a challenging hematological cancer which typically grows in bone marrow. MM accounts for 10% of hematological malignancies and 1.8% of cancers. The recent treatment strategies have significantly improved progression-free survival for MM patients in the last decade; however, a relapse for most MM patients is inevitable. In this review we discuss current treatment, important pathways for proliferation, survival, immune suppression, and resistance that could be targeted for future treatments.

Bone marrow microenvironment- induced regulation of Bcl-2 family members in multiple myeloma (MM): Therapeutic implications

In Multiple Myeloma (MM) the finely tuned homeostasis of the bone marrow (BM) microenvironment is disrupted. Evasion of programmed cell death (apoptosis) represents a hallmark of cancer. Besides genetic aberrations, the supportive and protective MM BM milieu, which is constituted by cytokines and growth factors, intercellular and cell: extracellular matrix (ECM) interactions and exosomes, in particular, plays a key role in the abundance of pro-survival members of the Bcl-2 family (i.e., Mcl-1, Bcl-2, and Bcl-xL) in tumor cells. Moreover, microenvironmental cues have also an impact on stability- regulating post-translational modifications of anti-apoptotic proteins including de/phosphorylation, polyubiquitination; on their intracellular binding affinities, and localization. Advances of our molecular knowledge on the escape of cancer cells from apoptosis have informed the development of a new class of small molecules that mimic the action of BH3-only proteins. Indeed, approaches to directly target anti-apoptotic Bcl-2 family members are among today's most promising therapeutic strategies and BH3-mimetics (i.e., venetoclax) are currently revolutionizing not only the treatment of CLL and AML, but also hold great therapeutic promise in MM. Furthermore, approaches that activate apoptotic pathways indirectly via modification of the tumor microenvironment have already entered clinical practice. The present review article will summarize our up-to-date knowledge on molecular mechanisms by which the MM BM microenvironment, cytokines, and growth factors in particular, mediates tumor cell evasion from apoptosis. Moreover, it will discuss some of the most promising science- derived therapeutic strategies to overcome Bcl-2- mediated tumor cell survival in order to further improve MM patient outcome.

Autophagy and Apoptosis: Current Challenges of Treatment and Drug Resistance in Multiple Myeloma

Over the past two decades, the natural history of multiple myeloma (MM) has evolved dramatically, owing primarily to novel agents targeting MM in the bone marrow microenvironment (BMM) pathways. However, the mechanisms of resistance acquisition remain a mystery and are poorly understood. Autophagy and apoptosis are tightly controlled processes and play a critical role in the cell growth, development, and survival of MM. Genetic instability and abnormalities are two hallmarks of MM. During MM progression, plasma malignant cells become genetically unstable and activate various signaling pathways, resulting in the overexpression of abnormal proteins that disrupt autophagy and apoptosis biological processes. Thus, achieving a better understanding of the autophagy and apoptosis processes and the proteins that crosslinked both pathways, could provide new insights for the MM treatment and improve the development of novel therapeutic strategies to overcome resistance. This review presents a sufficient overview of the roles of autophagy and apoptosis and how they crosslink and control MM progression and drug resistance. Potential combination targeting of both pathways for improving outcomes in MM patients also has been addressed.

Mcl-1 Differentially Regulates Autophagy in Response to Changes in Energy Status and Mitochondrial Damage

Myeloid cell leukemia-1 (Mcl-1) is a unique antiapoptotic Bcl-2 member that is critical for mitochondrial homeostasis. Recent studies have demonstrated that Mcl-1′s functions extend beyond its traditional role in preventing apoptotic cell death. Specifically, data suggest that Mcl-1 plays a regulatory role in autophagy, an essential degradation pathway involved in recycling and eliminating dysfunctional organelles. Here, we investigated whether Mcl-1 regulates autophagy in the heart. We found that cardiac-specific overexpression of Mcl-1 had little effect on baseline autophagic activity but strongly suppressed starvation-induced autophagy. In contrast, Mcl-1 did not inhibit activation of autophagy during myocardial infarction or mitochondrial depolarization. Instead, overexpression of Mcl-1 increased the clearance of depolarized mitochondria by mitophagy independent of Parkin. The increase in mitophagy was partially mediated via Mcl-1′s LC3-interacting regions and mutation of these sites significantly reduced Mcl-1-mediated mitochondrial clearance. We also found that Mcl-1 interacted with the mitophagy receptor Bnip3 and that the interaction was increased in response to mitochondrial stress. Overall, these findings suggest that Mcl-1 suppresses nonselective autophagy during nutrient limiting conditions, whereas it enhances selective autophagy of dysfunctional mitochondria by functioning as a mitophagy receptor.

Bone Marrow Stroma-Induced Transcriptome and Regulome Signatures of Multiple Myeloma

Multiple myeloma (MM) is a hematological cancer with inevitable drug resistance. MM cells interacting with bone marrow stromal cells (BMSCs) undergo substantial changes in the transcriptome and develop de novo multi-drug resistance. As a critical component in transcriptional regulation, how the chromatin landscape is transformed in MM cells exposed to BMSCs and contributes to the transcriptional response to BMSCs remains elusive. We profiled the transcriptome and regulome for MM cells using a transwell coculture system with BMSCs. The transcriptome and regulome of MM cells from the upper transwell resembled MM cells that coexisted with BMSCs from the lower chamber but were distinctive to monoculture. BMSC-induced genes were enriched in the JAK2/STAT3 signaling pathway, unfolded protein stress, signatures of early plasma cells, and response to proteasome inhibitors. Genes with increasing accessibility at multiple regulatory sites were preferentially induced by BMSCs; these genes were enriched in functions linked to responses to drugs and unfavorable clinic outcomes. We proposed JUNB and ATF4::CEBPβ as candidate transcription factors (TFs) that modulate the BMSC-induced transformation of the regulome linked to the transcriptional response. Together, we characterized the BMSC-induced transcriptome and regulome signatures of MM cells to facilitate research on epigenetic mechanisms of BMSC-induced multi-drug resistance in MM.