Anti-cancer drug discovery and development: Bcl-2 family small molecule inhibitors

Cancer pharmacoinformatics: Databases and analytical tools

Cancer is a subject of extensive investigation, and the utilization of omics technology has resulted in the generation of substantial volumes of big data in cancer research. Numerous databases are being developed to manage and organize this data effectively. These databases encompass various domains such as genomics, transcriptomics, proteomics, metabolomics, immunology, and drug discovery. The application of computational tools into various core components of pharmaceutical sciences constitutes "Pharmacoinformatics", an emerging paradigm in rational drug discovery. The three major features of pharmacoinformatics include (i) Structure modelling of putative drugs and targets, (ii) Compilation of databases and analysis using statistical approaches, and (iii) Employing artificial intelligence/machine learning algorithms for the discovery of novel therapeutic molecules. The development, updating, and analysis of databases using statistical approaches play a pivotal role in pharmacoinformatics. Multiple software tools are associated with oncoinformatics research. This review catalogs the databases and computational tools related to cancer drug discovery and highlights their potential implications in the pharmacoinformatics of cancer.

Chemopreventive effect and induction of DNA repair by oenothein B ellagitannin isolated from leaves of Eugenia uniflora in Swiss Webster treated mice

Oenothein B (OeB) is a dimeric ellagitannin with potent antioxidative, antitumor, immunomodulatory, and anti-inflammatory properties. Despite the promising activities of OeB, studies examining the genotoxic or protective effects of this ellagitannin on DNA are scarce. Therefore, to further comprehensively elucidate the chemopreventive profile of OeB, the aim of this study was to evaluate the mutagenic and antimutagenic actions of OeB using Salmonella typhimurium strains with the Ames test. The micronucleus (MN) test and comet assay were used to assess the anticytotoxic and antigenotoxic effects of OeB on mouse bone marrow cells following differing treatments (pre-, co-, and post-treatment) in response to cyclophosphamide (CPA)-induced DNA damage. In addition, histopathological analyses were performed to assess liver and kidney tissues of Swiss Webster treated mice. Our results did not detect mutagenic or antimutagenic activity attributed to OeB at any concentration in the Ames test. Regarding the MN test, data showed that this ellagitannin exerted antigenotoxic and anticytotoxic effects against CPA-induced DNA damage under all treatment conditions. However, no anticytotoxic action was observed in MN test after pre-treatment with the highest doses of OeB. In addition, OeB demonstrated antigenotoxic effects in the comet assay for all treatments. Histopathological analyses indicated that OeB attenuated the toxic effects of CPA in mouse liver and kidneys. These findings suggest that OeB exerted a chemoprotective effect following pre- and co-treatments and a DNA repair action in post-treatment experiments. Our findings indicate that OeB protects DNA against CPA-induced damaging agents and induces post-damage DNA repair.

The Evolving Landscape of Antibody-Drug Conjugates: In Depth Analysis of Recent Research Progress

Antibody-drug conjugates (ADCs) are targeted immunoconjugate constructs that integrate the potency of cytotoxic drugs with the selectivity of monoclonal antibodies, minimizing damage to healthy cells and reducing systemic toxicity. Their design allows for higher doses of the cytotoxic drug to be administered, potentially increasing efficacy. They are currently among the most promising drug classes in oncology, with efforts to expand their application for nononcological indications and in combination therapies. Here we provide a detailed overview of the recent advances in ADC research and consider future directions and challenges in promoting this promising platform to widespread therapeutic use. We examine data from the CAS Content Collection, the largest human-curated collection of published scientific information, and analyze the publication landscape of recent research to reveal the exploration trends in published documents and to provide insights into the scientific advances in the area. We also discuss the evolution of the key concepts in the field, the major technologies, and their development pipelines with company research focuses, disease targets, development stages, and publication and investment trends. A comprehensive concept map has been created based on the documents in the CAS Content Collection. We hope that this report can serve as a useful resource for understanding the current state of knowledge in the field of ADCs and the remaining challenges to fulfill their potential.

Spatial Transcriptomics Identifies Expression Signatures Specific to Lacrimal Gland Adenoid Cystic Carcinoma Cells

Although primary tumors of the lacrimal gland are rare, adenoid cystic carcinoma (ACC) is the most common and lethal epithelial lacrimal gland malignancy. Traditional management of lacrimal gland adenoid cystic carcinoma (LGACC) involves the removal of the eye and surrounding socket contents, followed by chemoradiation. Even with this radical treatment, the 10-year survival rate for LGACC is 20% given the propensity for recurrence and metastasis. Due to the rarity of LGACC, its pathobiology is not well-understood, leading to difficulties in diagnosis, treatment, and effective management. Here, we integrate bulk RNA sequencing (RNA-seq) and spatial transcriptomics to identify a specific LGACC gene signature that can inform novel targeted therapies. Of the 3499 differentially expressed genes identified by bulk RNA-seq, the results of our spatial transcriptomic analysis reveal 15 upregulated and 12 downregulated genes that specifically arise from LGACC cells, whereas fibroblasts, reactive fibrotic tissue, and nervous and skeletal muscle account for the remaining bulk RNA-seq signature. In light of the analysis, we identified a transitional state cell or stem cell cluster. The results of the pathway analysis identified the upregulation of PI3K-Akt signaling, IL-17 signaling, and multiple other cancer pathways. This study provides insights into the molecular and cellular landscape of LGACC, which can inform new, targeted therapies to improve patient outcomes.

Design, Synthesis, and Antiproliferative Activity of Benzopyran-4-One-Isoxazole Hybrid Compounds

The biological significance of benzopyran-4-ones as cytotoxic agents against multi-drug resistant cancer cell lines and isoxazoles as anti-inflammatory agents in cellular assays prompted us to design and synthesize their hybrid compounds and explore their antiproliferative activity against a panel of six cancer cell lines and two normal cell lines. Compounds 5a-d displayed significant antiproliferative activities against all the cancer cell lines tested, and IC₅₀ values were in the range of 5.2-22.2 μM against MDA-MB-231 cancer cells, while they were minimally cytotoxic to the HEK-293 and LLC-PK1 normal cell lines. The IC₅₀ values of 5a-d against normal HEK-293 cells were in the range of 102.4-293.2 μM. Compound 5a was screened for kinase inhibitory activity, proteolytic human serum stability, and apoptotic activity. The compound was found inactive towards different kinases, while it completely degraded after 2 h of incubation with human serum. At 5 μM concentration, it induced apoptosis in MDA-MB-231 by 50.8%. Overall, these findings suggest that new benzopyran-4-one-isoxazole hybrid compounds, particularly 5a-d, are selective anticancer agents, potentially safe for human cells, and could be synthesized at low cost. Additionally, Compound 5a exhibits potential anticancer activity mediated via inhibition of cancer cell proliferation and induction of apoptosis.

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.

Melanoma Cellular Signaling Transduction Pathways Targeted by Polyphenols Action Mechanisms

Melanoma is the most aggressive type of skin cancer. Although different anti-melanoma treatments are available, their efficacy is still improvable, and the number of deaths continues to increase worldwide. A promising source of antitumor agents could be presented by polyphenols-natural plant-based compounds. Over the past decades, many studies have described multiple anticancer effects of polyphenols in melanoma, presenting their potential interactions with targeted molecules from different signaling pathways. However, to our knowledge, there is no comprehensive review on polyphenols-regulated mechanisms in melanoma cells available in the literature. To fulfill this gap, this article aims to summarize the current knowledge of molecular mechanisms of action regulated by polyphenols involved in melanoma initiation and progression. Here, we focus on in vitro and in vivo effects of polyphenol treatments on tumor-essential cellular pathways, such as cell proliferation, apoptosis, autophagy, inflammation, angiogenesis, and metastasis. Moreover, emerging studies regarding the well-marked role of polyphenols in the regulation of microRNAs (miRNAs), highlighting their contribution to melanoma development, are also epitomized. Finally, we hope this review will provide a firm basis for developing polyphenol-based therapeutic agents in melanoma treatment.

Recent Advances in Cancer Drug Discovery Through the Use of Phenotypic Reporter Systems, Connectivity Mapping, and Pooled CRISPR Screening

Multi-omic approaches offer an unprecedented overview of the development, plasticity, and resistance of cancer. However, the translation from anti-cancer compounds identified in vitro to clinically active drugs have a notoriously low success rate. Here, we review how technical advances in cell culture, robotics, computational biology, and development of reporter systems have transformed drug discovery, enabling screening approaches tailored to clinically relevant functional readouts (e.g., bypassing drug resistance). Illustrating with selected examples of “success stories,” we describe the process of phenotype-based high-throughput drug screening to target malignant cells or the immune system. Second, we describe computational approaches that link transcriptomic profiling of cancers with existing pharmaceutical compounds to accelerate drug repurposing. Finally, we review how CRISPR-based screening can be applied for the discovery of mechanisms of drug resistance and sensitization. Overall, we explore how the complementary strengths of each of these approaches allow them to transform the paradigm of pre-clinical drug development.

Combination Therapy of Navitoclax with Chemotherapeutic Agents in Solid Tumors and Blood Cancer: A Review of Current Evidence

Combination therapy emerges as a fundamental scheme in cancer. Many targeted therapeutic agents are developed to be used with chemotherapy or radiation therapy to enhance drug efficacy and reduce toxicity effects. ABT-263, known as navitoclax, mimics the BH3-only proteins of the BCL-2 family and has a high affinity towards pro-survival BCL-2 family proteins (i.e., BCL-XL, BCL-2, BCL-W) to induce cell apoptosis effectively. A single navitoclax action potently ameliorates several tumor progressions, including blood and bone marrow cancer, as well as small cell lung carcinoma. Not only that, but navitoclax alone also therapeutically affects fibrotic disease. Nevertheless, outcomes from the clinical trial of a single navitoclax agent in patients with advanced and relapsed small cell lung cancer demonstrated a limited anti-cancer activity. This brings accumulating evidence of navitoclax to be used concomitantly with other chemotherapeutic agents in several solid and non-solid tumors that are therapeutically benefiting from navitoclax treatment in preclinical studies. Initially, we justify the anti-cancer role of navitoclax in combination therapy. Then, we evaluate the current evidence of navitoclax in combination with the chemotherapeutic agents comprehensively to indicate the primary regulator of this combination strategy in order to produce a therapeutic effect.

SMAC exhibits anti-tumor effects in ECA109 cells by regulating expression of inhibitor of apoptosis protein family

BACKGROUND

The poor prognosis and rising incidence of esophageal cancer highlight the need for improved therapeutics that are essential prior to treatment. LCL161 is an SMAC (second mitochondrial activator of caspases) mimic and inhibitor of apoptosis protein (IAP) antagonist which exhibits anti-tumor effects and improves the chemical sensitivity of many cancers.

AIM

To ascertain the effects and mechanisms of the SMAC analog LCL161 on esophageal cancer cells.

METHODS

MTT assay and TUNEL assay were used to detect cell proliferation and apoptosis, respectively. Western blot analysis was used to study the molecular mechanisms of LCL161-induced death of ECA109 cells.

RESULTS

LCL161 decreased ECA109 cell proliferation in dose- and time-dependent manner and induced apoptosis of ECA109 cells in a dose-dependent manner. Also, LCL161 induced a significant decrease in the expression of the XIAP and significant increase in the expression of Caspase-3. In addition, Bax increased significantly with increasing concentrations of LCL161, and the relative expression of Bax was significantly different between groups.

CONCLUSION

These findings support the hypothesis that LCL161 can inhibit proliferation and induce apoptosis in esophageal cancer cells by regulating the expression of IAP family members, suggesting that it has potential to be an effective treatment for esophageal squamous cell carcinoma.

A novel Bcl-2 inhibitor, BM-1197, induces apoptosis in malignant lymphoma cells through the endogenous apoptotic pathway

Background

Bcl-2 family members play an important role in the development of malignant lymphoma and can induce drug resistance in anticancer treatment. The development of small molecules targeting Bcl-2 family proteins may be a new strategy for the treatment of malignant lymphoma. In this study, we investigate the antitumor effect and cellular mechanism of a novel Bcl-2/Bcl-xL dual inhibitor, BM-1197, in DCBCL and Burkitt lymphoma cells.

Methods

The CCK-8 assay was used to detect cell viability. Apoptosis was determined by Hoechst 33258 staining and flow cytometry. The activity of caspase-3/caspase-9 was determined using a caspase-3/caspase-9 activity kit. Western blotting analysis was performed to evaluate the changes in protein expression. Functional analysis was performed via immunoprecipitation and siRNA interference. Human malignant lymphoma xenograft models in nude mice were established for in vivo efficacy detection.

Results

We find that BM-1197 exerts potent growth-inhibitory activity against lymphoma cells that harbor high expression of Bcl-2 and Bcl-xL in vitro and has a synergistic effect with chemotherapeutic drugs. Mechanistically, we see that the intrinsic apoptosis pathway is activated upon BM-1197 treatment. BM-1197 affects the protein interactions of Bak/Bcl-xl, Bim/Bcl-2, Bim/Bcl-xl, and PUMA/Bcl-2 and induces conformational changes in the Bax protein, which result in the activation of Bax and release of cytochrome c, activate caspase − 9, − 3, and − 7 and finally induce cell apoptosis. Furthermore, our data demonstrate that BM-1197 exhibits strong anti-tumor effects against established human malignant lymphoma xenograft models.

Conclusions

Our study demonstrated BM-1197 exerts potent antitumor effects both in vitro and in vivo and provides promising preclinical data for the further development of BM-1197 in malignant lymphoma.

p53-Bad: A Novel Tumor Suppressor/Proapoptotic Factor Hybrid Directed to the Mitochondria for Ovarian Cancer Gene Therapy

Clinical trials involving p53 gene therapy for ovarian cancer failed due to the dominant negative inhibition of wild-type p53 and multiple genetic aberrations in ovarian cancer. To overcome this problem, we have designed a more potent chimeric gene fusion, called p53-Bad, that combines p53 with the mitochondrial pro-apoptotic factor Bad. Unlike wild-type p53, which acts as a nuclear transcription factor, this novel p53-Bad construct has multiple unique mechanisms of action including a direct and rapid apoptotic effect at the mitochondria. The mitochondrial localization, transcription activity, and apoptotic activity of the constructs were tested. The results suggest that p53 can be effectively targeted to the mitochondria by controlling the phosphorylation of pro-apoptotic Bad, which can only localize to the mitochondria when Ser-112 and Ser-136 of Bad are unphosphorylated. By introducing S112A and S136A mutations, p53-Bad fusion cannot be phosphorylated at these two sites and always localizes to the mitochondria. p53-Bad constructs also have superior activity over p53 and Bad alone. The apoptotic activity is consistent in many ovarian cancer cell lines regardless of the endogenous p53 status. Both p53 and the BH3 domain of Bad contribute to the superior activity of p53-Bad. Our data suggests that p53-Bad fusions are capable of inducing apoptosis and should be further pursued for gene therapy for ovarian cancer.

Mitochondrially targeted p53 or DBD subdomain is superior to wild type p53 in ovarian cancer cells even with strong dominant negative mutant p53

Background

While tumor suppressor p53 functions primarily as a transcription factor in the nucleus, cellular stress can cause p53 to translocate to the mitochondria and directly trigger a rapid apoptotic response. We have previously shown that fusing p53 (or its DNA binding domain, DBD, alone) to the mitochondrial targeting signal (MTS) from Bak or Bax can target p53 to the mitochondria and induce apoptosis in gynecological cancer cell lines including cervical cancer cells (HeLa; wt p53), ovarian cancer cells (SKOV-3; p53 267del non-expressing), and breast cancer cells (T47D; L194F p53 mutation). However, p53 with Bak or Bax MTSs have not been previously tested in cancers with strong dominant negative (DN) mutant p53 which are capable of inactivating wt p53 by homo-oligomerization. Since p53-Bak or Bax MTS constructs act as monomers, they are not subject to DN inhibition. For this study, the utility of p53-Bak or p53-Bax MTS constructs was tested for ovarian cancers which are known to have varying p53 statuses, including a strong DN contact mutant p53 (Ovcar-3 cells), a p53 DN structural mutant (Kuramochi cells), and a p53 wild type, low expressing cells (ID8).

Results

Our mitochondrial p53 constructs were tested for their ability to localize to the mitochondria in both mutant non-expressing p53 (Skov-3) and p53 structural mutant (Kuramochi) cell lines using fluorescence microscopy and a nuclear transcriptional activity assay. The apoptotic activity of these mitochondrial constructs was determined using a mitochondrial outer membrane depolarization assay (TMRE), caspase assay, and a late stage cell death assay (7-AAD). We also tested the possibility of using our constructs with paclitaxel, the current standard of care in ovarian cancer treatment. Our data indicates that our mitochondrial p53 constructs are able to effectively localize to the mitochondria in cancer cells with structural mutant p53 and induce apoptosis in many ovarian cancer cell lines with different p53 statuses. These constructs can also be used in combination with paclitaxel for an increased apoptotic effect.

Conclusions

The results suggest that targeting p53 to mitochondria can be a new strategy for ovarian cancer treatment.

Electronic supplementary material

The online version of this article (10.1186/s13048-019-0516-2) contains supplementary material, which is available to authorized users.

The chemical biology of apoptosis: Revisited after 17 years

A balance of Bcl-2 family proteins dictates cell survival or death, as the interactions between these proteins regulate mitochondrial apoptotic signaling pathways. However, cancer cells frequently show upregulation of pro-survival Bcl-2 proteins and sequester activated pro-apoptotic BH3-only proteins driven by diverse cytotoxic stresses, resulting in tumor progression and chemoresistance. Synthetic molecules from either structure-based design or screening procedures to engage and inactivate pro-survival Bcl-2 proteins and restore apoptotic process represent a chemical biological means of selectively killing malignant cells. 17 years ago, one of us reviewed on the discovery of novel Bcl-2 targeted agents [1]. Here we revisit this area and examine the progress and current status of small molecule Bcl-2 inhibitor development, demonstrating the Bcl-2 family as a valid target for cancer therapy and providing successful examples for the discovery of inhibitors that target protein-protein interactions.

Decoding the antineoplastic efficacy of Aplysin targeting Bcl-2: A de novo perspective

The B-cell lymphoma-2 (Bcl-2) family proteins have been attributed to be the key regulators in programmed cell death and apoptosis with a prominent role in human cancer. Understanding the fundamental principles of cell survival and death have been the main cornerstone in cancer drug discovery for identification of novel anticancer agents. In this context the Bcl-2 family of anti-and pro-apoptotic proteins provide an excellent opportunity for development of anticancer agents, as blocking the Bcl-2 or Bcl-XL functionally promotes apoptosis in tumor cells and also sensitize them to chemo- and radiotherapies. The present study reports the identification of novel Aplysin analogs as BCL-2 inhibitors from a sequential virtual screening approach using drug-like, ADMET, docking, pharmacophore filters and molecular dynamics simulation. We identified promising Aplysin analogs that have a potential to be Bcl-2 inhibitors just like the standard drug Obatoclax. One of the compound analog 11 was identified to be a promising inhibitor of Bcl-2 in the docking, pharmacophore and simulation based models.The molecular modeling information provided here can be vital in designing of the novel Bcl-2 inhibitors.

Identifying the druggable interactome of EWS-FLI1 reveals MCL-1 dependent differential sensitivities of Ewing sarcoma cells to apoptosis inducers

Ewing sarcoma (EwS) is an aggressive pediatric bone cancer in need of more effective therapies than currently available. Most research into novel targeted therapeutic approaches is focused on the fusion oncogene EWSR1-FLI1, which is the genetic hallmark of this disease. In this study, a broad range of 3,325 experimental compounds, among them FDA approved drugs and natural products, were screened for their effect on EwS cell viability depending on EWS-FLI1 expression. In a network-based approach we integrated the results from drug perturbation screens and RNA sequencing, comparing EWS-FLI1-high (normal expression) with EWS-FLI1-low (knockdown) conditions, revealing novel interactions between compounds and EWS-FLI1 associated biological processes. The top candidate list of druggable EWS-FLI1 targets included genes involved in translation, histone modification, microtubule structure, topoisomerase activity as well as apoptosis regulation. We confirmed our in silico results using viability and apoptosis assays, underlining the applicability of our integrative and systemic approach. We identified differential sensitivities of Ewing sarcoma cells to BCL-2 family inhibitors dependent on the EWS-FLI1 regulome including altered MCL-1 expression and subcellular localization. This study facilitates the selection of effective targeted approaches for future combinatorial therapies of patients suffering from Ewing sarcoma.

Identification of JNK1 as a predicting biomarker for ABT-199 and paclitaxel combination treatment

Targeting Bcl-2 with ABT-199 (Venetoclax) shows limited single-agent activity against many cancers in both preclinical and clinical investigations. Combination therapies have attracted great attention. The principal purpose of this study was to investigate the mechanism of synergism between ABT-199 and paclitaxel. Moreover, we analyzed the biomarker to identify tumors which are most likely to respond to this combination. We evaluated the effect of this combination in a panel of nine cancer cell lines including cervical cancer, lung cancer, ovarian cancer, lymphoma, leukemia and breast cancer. Combination index (CI) assay showed that four of nine call lines exhibited synergistic respond to ABT-199/paclitaxel combination due to enhanced intrinsic apoptosis. However, paclitaxel-induced Bcl-2 phosphorylation impaired the synergistic effect by impeding the freeing of Bax and Bim by ABT-199 because ABT-199 cannot hit phosphorylated Bcl-2 (pBcl-2). By means of a correlation analysis of JNK level with CI value in combination with overexpressing or silencing JNK protein in cancer cells, we identified basal JNK1 level as a potential biomarker for predicting the level of pBcl-2 upon paclitaxel treatment, and thus for predicting a synergistic response. A cut-off value of 0.37 for relative JNK1 expression level was determined using receiver operating characteristic (ROC) analysis to distinguish between synergistic and non-synergistic response cancers. A more accurate and valid cut-off value for JNK1 will be gained based on a large-scale clinical samples analysis.

PNT2258, a novel deoxyribonucleic acid inhibitor, induces cell cycle arrest and apoptosis via a distinct mechanism of action: a new class of drug for non-Hodgkin's lymphoma

Current therapy for BCL-2-associated tumors such as Non-Hodgkin Lymphomas (NHL) is inadequate. The DNAi PNT2258, a 24 base single-stranded phosphodiester DNA oligodeoxynucleotide (PNT100) encapsulated in a protective liposome, was precisely designed to treat cancers that over-express BCL-2. PNT2258 strongly inhibited BCL-2 promoter activity, confirming its predicted mechanism of action. BCL-2 mRNA and protein expression were significantly downregulated in a follicular small cleaved cell lymphoma (WSU-FSCCL) cell line. 2.5μM PNT2258 induced an initial S- phase arrest followed by a gradual increase in the sub-G0 (apoptosis) compartment and a reciprocal progressive decrease of the S phase. Terminal deoxynucleotidyl transferase (TdT)-positive populations and cleaved caspase-3 and PARP were also increased. The data are consistent with the idea that BCL-2 inhibition by PNT2258 activates apoptotic pathways in WSU-FSCCL cells. This is the first report to address the distinct mechanism of action underlying the anti-BCL-2 functions of PNT2258. Growth inhibition in two other cell lines, WSU-DLCL2 and WSU-WM, supports broad applicability of BCL-2 DNAi to treatment of B-cell NHL.

Deciphering the crucial residues involved in heterodimerization of Bak peptide and anti-apoptotic proteins for apoptosis

B-cell lymphoma 2 (Bcl-2) family proteins are the central regulators of apoptosis, functioning via mitochondrial outer membrane permeabilization. The family members are involved in several stages of apoptosis regulation. The overexpression of the anti-apoptotic proteins leads to several cancer pathological conditions. This overexpression is modulated or inhibited by heterodimerization of pro-apoptotic BH3 domain or BH3-only peptides to the hydrophobic groove present at the surface of anti-apoptotic proteins. Additionally, the heterodimerization displayed differences in binding affinity profile among the pro-apoptotic peptides binding to anti-apoptotic proteins. In light of discovering the novel peptide/drug molecules that contain the potential to inhibit specific anti-apoptotic protein, it is necessary to understand the molecular basis of recognition between the protein and its binding partner (peptide or ligand) along with its binding energies. Therefore, the present work focused on deciphering the molecular basis of recognition between pro-apoptotic Bak peptide binding to different anti-apoptotic (Bcl-xL, Bfl-1, Bcl-W, Mcl-1, and Bcl-2) proteins using advanced Molecular Dynamics (MD) approach such as Molecular Mechanics-Generalized Born Solvent Accessible. The results from our investigation revealed that the predicted binding free energies showed excellent correlation with the experimental values (r² = .95). The electrostatic (ΔG_ele) contributions are the major component that drives the interaction between Bak peptides and different anti-apoptotic peptides. Additionally, van der Waals (ΔG_vdw) energies also play an indispensible role in determining the binding free energy. Furthermore, the decomposition analysis highlighted the comprehensive information about the energy contributions of hotspot residues involved in stabilizing the interaction between Bak peptide and different anti-apoptotic proteins.

Injectable (-)-gossypol-loaded Pluronic P85 micelles for cancer chemoradiotherapy

PURPOSE

The aim of tumor-specific chemoradiotherapy is to achieve synergistic anticancer effects with clinically acceptable toxicity. Our previous studies showed that Pluronic P85 augments radiation cancer cell killing of (±)-gossypol in vitro. In this study, the radiosensitizing effect of (-)-gossypol, more potent Bcl protein inhibitor, with Pluronic P85 was investigated.

MATERIALS AND METHODS

The inhibitory effect of (-)-gossypol solubilized Pluronic P85 with 0-8 Gy of radiation on clonogenic survival rate of A549 human lung adenocarcinoma cells was investigated in vitro. The anticancer effect of (-)-gossypol-solubilized Pluronic P85 with fractionated radiation of 15 Gy was assessed by A549 tumor-bearing mice.

RESULTS

(-)-Gossypol-loaded Pluronic P85 was found to be a more potent radiosensitizer in vitro. Pluronic P85 increased the anti-proliferative activity of (-)-gossypol against A549 cells (82 ± 42 versus 190 ± 60 nM). In addition, the combination of P85 and (-)-gossypol effectively reduced clonogenic survival of A549 cells: (11 ± 5%) compared to (-)-gossypol and P85 alone (62 ± 27% and 93 ± 13%, respectively), and enhanced radiation cancer cell killing. In vivo, P85 (200 mg/kg/day) and (-)-gossypol (15 mg/kg/day) could be safely injected intravenously over 5 days and enhanced radiation-related tumor control in an A549 xenograft model.

CONCLUSION

Pluronic P85 and (-)-gossypol act as a novel dual agent radiosensitizer and holds promise as a chemoradiotherapeutic strategy.

Anticancer Activity of γ-Bisabolene in Human Neuroblastoma Cells via Induction of p53-Mediated Mitochondrial Apoptosis

γ-Bisabolene has demonstrated antiproliferative activities against several human cancer cell lines. This study first discloses the antiproliferative and apoptosis induction activities of γ-bisabolene to human neuroblastoma TE671 cells. A CC50 value of γ-bisabolene was 8.2 μM to TE671 cells. Cell cycle analysis with PI staining showed γ-bisabolene elevating the sub-G1 fractions in a time-dependent manner. In addition, annexin V-FITC/PI staining showed γ-bisabolene significantly triggering early (annexin-V positive/PI negative) and late (annexin-V positive/PI positive) apoptosis in dose-dependent manners. γ-Bisabolene induced caspase 3/8/9 activation, intracellular ROS increase, and mitochondrial membrane potential decrease in apoptosis of human neuro-blastoma cells. Moreover, γ-bisabolene increased p53 phosphorylation and up-regulated p53-mediated apoptotic genes Bim and PUMA, as well as decreased the mRNA and protein levels of CK2α. Notably, the results indicated the involvement of CK2α-p53 pathways in mitochondria-mediated apoptosis of human neuroblastoma cells treated with γ-bisabolene. This study elucidated the apoptosis induction pathways of γ-bisabolene-treated neuroblastoma cells, in which could be useful for developing anti-neuroblastoma drugs.

Small-Molecule and Peptide Inhibitors of the Pro-Survival Protein Mcl-1

The ability of protein-protein interactions to regulate cellular processes in both beneficial and detrimental ways has made them obvious drug targets. The Bcl-2 family of proteins undergo a series of protein-protein interactions which regulate the intrinsic cell-death pathway. The pro-survival members of the Bcl-2 family, including Bcl-2, Bcl-xL , and Mcl-1, are commonly overexpressed in a number of human cancers. Effective modulators of members of the Bcl-2 family have been developed and are undergoing clinical trials, but the efficient modulation of Mcl-1 is still not represented in the clinic. In addition, Mcl-1 is a major cause of resistance to radio- and chemotherapies, including inhibitors that target other Bcl-2 family members. Subsequently, the inhibition of Mcl-1 has become of significant interest to the scientific community. This review covers the progress made to date in modulating the activity of Mcl-1, by both stapled peptides and small molecules. The development of peptides as drug candidates, and the advancement of experimental and computational techniques used to discover small molecules are also highlighted.

Nanotechnology inspired tools for mitochondrial dysfunction related diseases

Mitochondrial dysfunctions are recognized as major factors for various diseases including cancer, cardiovascular diseases, diabetes, neurological disorders, and a group of diseases so called "mitochondrial dysfunction related diseases". One of the major hurdles to gain therapeutic efficiency in diseases where the targets are located in the mitochondria is the accessibility of the targets in this compartmentalized organelle that imposes barriers toward internalization of ions and molecules. Over the time, different tools and techniques were developed to improve therapeutic index for mitochondria acting drugs. Nanotechnology has unfolded as one of the logical and encouraging tools for delivery of therapeutics in controlled and targeted manner simultaneously reducing side effects from drug overdose. Tailor-made nanomedicine based therapeutics can be an excellent tool in the toolbox for diseases associated with mitochondrial dysfunctions. In this review, we present an extensive coverage of possible therapeutic targets in different compartments of mitochondria for cancer, cardiovascular, and mitochondrial dysfunction related diseases.

Bcl-2/MDM2 Dual Inhibitors Based on Universal Pyramid-Like α-Helical Mimetics

No α-helical mimetic that exhibits Bcl-2/MDM2 dual inhibition has been rationally designed due to the different helicities of the α-helixes at their binding interfaces. Herein, we extracted a one-turn α-helix-mimicking ortho-triarene unit from o-phenylene foldamers. Linking benzamide substrates with a rotatable C-N bond, we constructed a novel semirigid pyramid-like scaffold that could support its two-turn α-helix mimicry without aromatic stacking interactions and could adopt the different dihedral angles of the key residues of p53 and BH3-only peptides. On the basis of this universal scaffold, a series of substituent groups were installed to capture the key residues of both p53TAD and BimBH3 and balance the differences of the bulks between them. Identified by FP, ITC, and NMR spectroscopy, a compound 6e (zq-1) that directly binds to Mcl-1, Bcl-2, and MDM2 with balanced submicromolar affinities was obtained. Cell-based experiments demonstrated its antitumor ability through Bcl-2/MDM2 dual inhibition simultaneously.

Sequence and partial functional analysis of canine Bcl-2 family proteins

Dogs present with spontaneous neoplasms biologically similar to human cancers. Apoptotic pathways are deregulated during cancer genesis and progression and are important for therapy. We have assessed the degree of conservation of a set of canine Bcl-2 family members with the human and murine orthologs. To this end, seven complete canine open reading frames were cloned in this family, four of which are novel for the dog, their sequences were analyzed, and their functional interactions were studied in yeasts. We found a high degree of overall and domain sequence homology between canine and human proteins. It was slightly higher than between murine and human proteins. Functional interactions between canine pro-apoptotic Bax and Bak and anti-apoptotic Bcl-xL, Bcl-w, and Mcl-1 were recapitulated in yeasts. Our data provide support for the notion that systems based on canine-derived proteins might faithfully reproduce Bcl-2 family member interactions known from other species and establish the yeast as a useful tool for functional studies with canine proteins.

Marine steroids as potential anticancer drug candidates: In silico investigation in search of inhibitors of Bcl-2 and CDK-4/Cyclin D1

Star fishes (Asteroidea) are rich in polar steroids with diverse structural characteristics. The structural modifications of star fish steroids occur at 3β, 4β, 5α, 6α (or β), 7α (or β), 8, 15α (or β) and 16β positions of the steroidal nucleus and in the side chain. Widely found polar steroids in starfishes include polyhydroxysteroids, steroidal sulfates, glycosides, steroid oligoglycosides etc. Bioactivity of these steroids is less studied; only a few reports like antibacterial, cytotoxic activity etc. are available. In continuation of our search for bioactive molecules from natural sources, we undertook in silico screening of steroids from star fishes against Bcl-2 and CDK-4/Cyclin D1 - two important targets of progression and proliferation of cancer cells. We have screened 182 natural steroids from star fishes occurring in different parts of the world and their 282 soft-derivatives by in silico methods. Their physico-chemical properties, drug-likeliness, binding potential with the selected targets, ADMET (absorption, distribution, metabolism, toxicity) were predicted. Further, the results were compared with those of existing steroidal and non steroidal drugs and inhibitors of Bcl-2 and CDK-4/Cyclin D1. The results are promising and unveil that some of these steroids can be potent leads for cancer treatments.

Pyoluteorin derivatives induce Mcl-1 degradation and apoptosis in hematological cancer cells

Mcl-1, a pro-survival member of the Bcl-2 protein family, is an attractive target for cancer therapy. We have recently identified the natural product marinopyrrole A (maritoclax) as a novel small molecule Mcl-1 inhibitor. Here, we describe the structure-activity relationship study of pyoluteorin derivatives based on maritoclax. To date, we synthesized over 30 derivatives of maritoclax and evaluated their inhibitory actions and cytotoxicity toward Mcl-1-dependent cell lines. As a result, several functional groups were identified in the pyoluteorin motif that significantly potentiate biological activity. A number of such derivatives, KS04 and KS18, interacted with Mcl-1 in a conserved fashion according to NMR spectroscopy and molecular modeling. KS04 and KS18 induced apoptosis selectively in Mcl-1-dependent but not Bcl-2-dependent K562 cells through selective Mcl-1 down-regulation, and synergistically enhanced apoptosis in combination with ABT-737. Moreover, the intraperitoneal administration of KS18 (10 mg/kg/d) and ABT-737 (20 mg/kg/d) significantly suppressed the growth of ABT-737-resistant HL-60 xenografts in nude mice without apparent toxicity. Overall, we identified the pharmacophore of pyoluteorin derivatives that act as potent and promising Mcl-1 antagonists against Mcl-1-dependent hematological cancers.

Novel Pharmacotherapies for B-Cell Lymphomas and Leukemias

Novel pharmacotherapeutic agents were recently approved for treatment of low-grade B-cell neoplasms, and many other agents are under investigation. Several agents have demonstrated impressive activity in targeting malignant B-cell processes and specific pathways, all with the potential to expand our ability to effectively treat B-cell malignancies. The inhibitors of several cell regulatory proteins, including Bruton tyrosine kinase (Btk), phosphoinositide 3-kinase (PI3-K), B-cell lymphoma/leukemia-2 (Bcl-2), and histone deacetylases, as well as immunomodulatory agents are a few of the many pharmacotherapeutic agents under study. A comprehensive review and assessment is presented of the current pharmacotherapies under investigation targeting B-cell lymphomas and leukemias.

Maritoclax induces apoptosis in acute myeloid leukemia cells with elevated Mcl-1 expression

Acute myeloid leukemia (AML) is one of the deadliest leukemias for which there is an urgent and unmet need for the development of novel treatment strategies. Multiple drug resistance mechanisms mediate poor drug response and relapse in patients, and a selective Mcl-1 inhibitor has been speculated to be a promising agent in the treatment of AML. Here, we describe that maritoclax, a small molecule Mcl-1 inhibitor, induces Mcl-1 proteasomal degradation without transcriptional downregulation. Maritoclax killed AML cell lines and primary cells with elevated Mcl-1 levels through selective Mcl-1 downregulation, and synergized with ABT-737 to overcome Mcl-1-mediated ABT-737 resistance. Maritoclax was more effective than daunorubicin at inducing leukemic cell death when co-cultured with HS-5 bone marrow stroma cells, while being less toxic than daunorubicin against HS-5 stroma cells, primary mouse bone marrow cells, and hematopoietic progenitor cells. Moreover, maritoclax administration at 20 mg/kg/d intraperitoneally caused significant U937 tumor shrinkage, as well as 36% tumors remission rate in athymic nude mice, without apparent toxicity to healthy tissue or circulating blood cells. In summary, our studies suggest that maritoclax belongs to a novel class of Mcl-1 inhibitors that has the potential to be developed for the treatment of AML.

TWEAK/Fn14 pathway is a novel mediator of retinal neovascularization

PURPOSE

Retinal neovascularization (NV) is a major cause of vision loss in ischemia-induced retinopathy. Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) and its receptor, fibroblast growth factor inducible-14 (Fn14), have been implicated in angiogenesis, but their role in retinal diseases is unknown. The goal of this study was to investigate the role of TWEAK/Fn14 pathway in retinal NV.

METHODS

Studies were performed in a mouse model of oxygen-induced retinopathy (OIR) and in primary human retinal microvascular endothelial cells (HRMECs). Hyperoxia treatment was initiated on postnatal day (P)14. Immunohistochemistry and quantitative PCR (qPCR) were used to assess retinal vascular changes in relation to expression of Fn14 and TWEAK.

RESULTS

Fibroblast growth factor-inducible 14 mRNA was prominently increased from P13 to P17 in OIR retinas, whereas TWEAK level was slightly decreased. These alterations were normalized by hyperoxia treatment and were more striking in isolated retinal vessels. There was a discernible shift in the immunoreactivity of Fn14 and TWEAK from the neuronal layers in the healthy retina to the neovascular tufts in that of OIR. Blockade of TWEAK/Fn14 significantly prevented retinal NV while slightly accelerated revascularization. In contrast, activation of Fn14 positively regulated survival pathways in the B-cell lymphoma-2 (Bcl2) family and robustly enhanced HRMEC survival. Furthermore, gene analysis revealed the regulatory region of Fn14 gene contains several conserved hypoxia inducible factor (HIF)-1α binding sites. Overexpression of HIF-1α prominently induced Fn14 expression in HRMECs.

CONCLUSIONS

We found that the TNF-like weak inducer of apoptosis (TWEAK)/fibroblast growth factor inducible-14 (Fn14) pathway is involved in the development of pathologic retinal neovascularization. Hypoxia inducible factor-1α is likely implicated in the upregulation of Fn14.

Autophagy contributes to modulating the cytotoxicities of Bcl-2 homology domain-3 mimetics

The dysregulation of apoptosis is a key step in developing cancers, and mediates resistance to cancer therapy. Commitment to apoptosis is caused by permeabilization of the outer mitochondrial membrane, a process regulated by the interactions between different proteins of Bcl-2 family. Furthermore, Bcl-2 family proteins also bind to the endoplasmic reticulum, where they modulate autophagy, another important pathway regulating cell survival and death. Dysregulation of Bcl-2 family has been demonstrated in a wide spectrum of human cancers, including gastrointestinal cancers. Therefore, targeting the Bcl-2 family of proteins represents a promising therapeutic approach for these malignancies. Recent advances have yielded small molecules that have close structural or functional similarity to BH3-only proteins and are therefore named BH3 mimetics. Of these BH3 mimetics, obatoclax, (-)-gossypol, and ABT-263 are currently in clinical trials for multiple cancers. Growing evidence indicates that these BH3 mimetics not only induce apoptosis, but also regulate autophagy which may serve as a pro-survival or pro-death mechanism to counteract or mediate the cytotoxicity of BH3 mimetics. This review discusses the role of autophagy in cell-fate decision upon BH3 mimetics treatment. Further exploration of our understanding of the association between autophagy and cellular outcomes in response to BH3 mimetics treatment will likely offer improved therapies for patients with cancer.

Proteasomal degradation of Mcl-1 by maritoclax induces apoptosis and enhances the efficacy of ABT-737 in melanoma cells

Background and purpose

Metastatic melanoma remains one of the most invasive and highly drug resistant cancers. The over expression of anti-apoptotic protein Mcl-1 has been associated with inferior survival, poor prognosis and chemoresistance of malignant melanoma. A BH3 mimetic, ABT-737, has demonstrated efficacy in several forms of cancers. However, the efficacy of ABT-737 depends on Mcl-1. Because the over expression of Mcl-1 is frequently observed in melanoma, specifically targeting of Mcl-1 may overcome the resistance of ABT-737. In this study, we investigated the effects of Maritoclax, a novel Mcl-1-selective inhibitor, alone and in combination with ABT-737, on the survival of human melanoma cells.

Experimental approach

For cell viability assessment we performed MTT assay. Apoptosis was determined using western blot and flow cytometric analysis.

Key results

The treatment of Maritoclax reduced the cell viability of melanoma cells with an IC₅₀ of between 2.2–5.0 µM. Further, treatment of melanoma cells with Maritoclax showed significant decrease in Mcl-1 expression. We found that Maritoclax was able to induce apoptosis in melanoma cells in a caspase-dependent manner. Moreover, Maritoclax induced Mcl-1 degradation via the proteasome system, which was associated with its pro-apoptotic activity. We also found that Maritoclax treatment increased mitochondrial translocation of Bim and Bmf. Importantly, Maritoclax markedly enhanced the efficacy of ABT-737 against melanoma cells in both two- and three-dimensional spheroids.

Conclusions and implications

Taken together, these results suggest that targeting of Mcl-1 by Maritoclax may represent a new therapeutic strategy for melanoma treatment that warrants further investigation as a single therapy or in combination with other agents such as Bcl-2 inhibitors.

CT perfusion can predict overexpression of CXCL8 (interleukin-8) in head and neck squamous cell carcinoma

BACKGROUND AND PURPOSE

Increased angiogenesis in head and neck squamous cell carcinoma correlates to more aggressive tumors with increased morbidity. Because both elevated blood flow and high serum CXCL8 levels are correlated with increased angiogenesis, our objective was to see if elevated blood flow measured with CT perfusion correlated with CXCL8 levels, thereby helping to identify candidates for targeted therapies that inhibit the Bcl-2 proangiogenic pathway associated with CXCL8.

MATERIALS AND METHODS

Seven patients with locally recurrent or metastatic head and neck squamous cell carcinoma were enrolled in the trial. These patients underwent CT perfusion and the following parameters were measured: blood volume, blood flow, capillary permeability, and MTT; relative values were calculated by dividing by normal-appearing muscle. Serum was drawn for CXCL8 enzyme-linked immunosorbent assay analysis in these patients.

RESULTS

There was a significant positive correlation between the CXCL8 levels and relative blood flow (r = 0.94; P = .01). No correlation was found between CXCL8 and relative blood volume, relative capillary permeability, or relative MTT.

CONCLUSIONS

Relative blood flow may be useful as a surrogate marker for elevated CXCL8 in patients with head and neck squamous cell cancer. Patients with elevated relative blood flow may benefit from treatment targeting the Bcl-2 proangiogenic pathways.