Mechanisms of multidrug resistance: the potential role of microtubule-stabilizing agents

Synthesis, in silico, in vitro evaluation of furanyl- and thiophenyl-3-phenyl-1H-indole-2-carbohydrazide derivatives as tubulin inhibitors and anticancer agents

Twenty-one new indole derivatives comprising of seven furanyl-3-phenyl-1H-indole-carbohydrazide derivatives and fourteen thiophenyl-3-phenyl-1H-indole-carbohydrazide derivatives were synthesised and biologically evaluated for their microtubule-destabilising effects, and antiproliferative activities against the National Cancer Institute 60 (NCI60) human cancer cell line panel. Among the derivatives, 6i showed the best cytotoxic activity exhibiting selectivity for COLO 205 colon cancer (LC50 = 71 nM), SK-MEL-5 melanoma cells (LC50 = 75 nM), and MDA-MB-435 (LC50 = 259 nM). Derivative 6j showed the strongest microtubule-destabilising effect. Both 6i and 6j were able to induce G2/M cell cycle arrest and apoptosis in MDA-MB-231 triple-negative breast cancer cells. Molecular docking simulation results suggested that these derivatives inhibit tubulin by binding at the colchicine site. The calculated molecular descriptors showed that the most potent derivatives have acceptable pharmacokinetic profiles and are favourable for oral drug administration.

Endophytic fungi: A future prospect for breast cancer therapeutics and drug development

Globally, breast cancer is a primary contributor to cancer-related fatalities and illnesses among women. Consequently, there is a pressing need for safe and effective treatments for breast cancer. Bioactive compounds from endophytic fungi that live in symbiosis with medicinal plants have garnered significant interest in pharmaceutical research due to their extensive chemical composition and prospective medicinal attributes. This review underscores the potentiality of fungal endophytes as a promising resource for the development of innovative anticancer agents specifically tailored for breast cancer therapy. The diversity of endophytic fungi residing in medicinal plants, success stories of key endophytic bioactive metabolites tested against breast cancer and the current progress with regards to in vivo studies and clinical trials on endophytic fungal metabolites in breast cancer research forms the underlying theme of this article. A thorough compilation of putative anticancer compounds sourced from endophytic fungi that have demonstrated therapeutic potential against breast cancer, spanning the period from 1990 to 2022, has been presented. This review article also outlines the latest trends in endophyte-based drug discovery, including the use of artificial intelligence, machine learning, multi-omics approaches, and high-throughput strategies. The challenges and future prospects associated with fungal endophytes as substitutive sources for developing anticancer drugs targeting breast cancer are also being highlighted.

BP-M345 as a Basis for the Discovery of New Diarylpentanoids with Promising Antimitotic Activity

Recently, the diarylpentanoid BP-M345 (5) has been identified as a potent in vitro growth inhibitor of cancer cells, with a GI50 value between 0.17 and 0.45 µM, showing low toxicity in non-tumor cells. BP-M345 (5) promotes mitotic arrest by interfering with mitotic spindle assembly, leading to apoptotic cell death. Following on from our previous work, we designed and synthesized a library of BP-M345 (5) analogs and evaluated the cell growth inhibitory activity of three human cancer cell lines within this library in order to perform structure-activity relationship (SAR) studies and to obtain compounds with improved antimitotic effects. Four compounds (7, 9, 13, and 16) were active, and the growth inhibition effects of compounds 7, 13, and 16 were associated with a pronounced arrest in mitosis. These compounds exhibited a similar or even higher mitotic index than BP-M345 (5), with compound 13 displaying the highest antimitotic activity, associated with the interference with mitotic spindle dynamics, inducing spindle collapse and, consequently, prolonged mitotic arrest, culminating in massive cancer cell death by apoptosis.

Microtubule-Targeting Agents: Disruption of the Cellular Cytoskeleton as a Backbone of Ovarian Cancer Therapy

Microtubules are dynamic polymers composed of α- and β-tubulin heterodimers. Microtubules are universally conserved among eukaryotes and participate in nearly every cellular process, including intracellular trafficking, replication, polarity, cytoskeletal shape, and motility. Due to their fundamental role in mitosis, they represent a classic target of anti-cancer therapy. Microtubule-stabilizing agents currently constitute a component of the most effective regimens for ovarian cancer therapy in both primary and recurrent settings. Unfortunately, the development of resistance continues to present a therapeutic challenge. An understanding of the underlying mechanisms of resistance to microtubule-active agents may facilitate the development of novel and improved approaches to this disease.

EGFR-mediated hyperacetylation of tubulin induced docetaxel resistance by downregulation of HDAC6 and upregulation of MCAK and PLK1 in prostate cancer cells

Docetaxel-based chemotherapy has generally been considered as one of the effective treatments for castration-resistant prostate cancer (PCa). However, clinical treatment with docetaxel often encounters a number of undesirable effects, including drug resistance. Tubulin isoforms have been previously examined for their resistance to docetaxel in many cancers, but their real mechanisms remained unclear. In this study, a series of docetaxel-resistant PC/DX cell sublines were established by chronically exposing PC3 to progressively increased concentrations of docetaxel. Western blotting results showed significantly higher expression of acetyl-tubulin, α-tubulin, β-tubulin, γ-tubulin, and βIII-tubulin in PC/DX25 than in parental PC3 cells. PC/DX25 with greater resistance to docetaxel had higher levels of acetyl-tubulin and mitotic centromere-associated kinesin (MCAK) than PC3 cells. This study found that docetaxel induced the expression of acetyl-tubulin and MCAK in PC3 cells at a dose- and time-dependent manner. Both mRNA and protein levels of histone deacetylase 6 (HDAC6) were significantly decreased in PC/DX25 compared with PC3 cells. PC3 increased the resistance to docetaxel by HDAC6 knockdown and Tubastatin A (HDAC6 inhibitor). Conversely, PC/DX25 reversed the sensitivity to docetaxel by MCAK knockdown. Notably, flow cytometry analysis revealed that MCAK knockdown induced significantly sub G1 fraction in PC/DX cells. Overexpression of polo-like kinase-1 increased the cell survival rate and resistance to docetaxel in PC3 cells. Moreover, epidermal growth factor receptor (EGFR) activation induced the upregulation of acetyl-tubulin in docetaxel-resistant PCa cells. These findings demonstrated that the EGFR-mediated upregulated expression of acetyl-tubulin played an important role in docetaxel-resistant PCa.

Development of tubulin polymerization inhibitors as anticancer agents

INTRODUCTION

Microtubules are intracellular, filamentous, polymeric structures that extend throughout the cytoplasm, composed of α-tubulin and β-tubulin subunits. They regulate many cellular functions including cell polarity, cell shape, mitosis, intracellular transport, cell signaling, gene expression, cell integrity, and are associated with tumorigenesis. Inhibition of tubulin polymerization within tumor cells represents a crucial focus in the pursuit of developing anticancer treatments.

AREAS COVERED

This review focuses on the natural product and their synthetic congeners as tubulin inhibitors along with their site of interaction on tubulin. This review also covers the developed novel tubulin inhibitors and important patents focusing on the development of tubulin inhibition for cancer treatment reported from 2018 to 2023. The scientific and patent literature has been searched on PubMed, Espacenet, ScienceDirect, and Patent Guru from 2018-2023.

EXPERT OPINION

Tubulin is one of the promising targets explored extensively for drug discovery. Compounds binding in the colchicine site could be given importance because they can elude resistance mediated by the P-glycoprotein efflux pump and no colchicine site binding inhibitor is approved by FDA so far. The research on the development of antibody drug conjugates (ADCs) for tubluin polymerization inhibition could be significant strategy for cancer treatment.

Design, Synthesis, and Biological Evaluation of SSE1806, a Microtubule Destabilizer That Overcomes Multidrug Resistance

Microtubules are dynamic structures that form spindle fibers during cell division; pharmacological inhibition of microtubule dynamics arrests cells in mitosis, leading to apoptosis, and they have been extensively used to treat various cancers. However, the efficacy of such drugs is often limited by multidrug resistance. This study synthesized and evaluated 30 novel derivatives of podophyllotoxin, a natural antimitotic compound, for their antiproliferative activities. Compound SSE1806 exhibited the most potent antiproliferative activity with GI50 values ranging from 1.29 ± 0.01 to 21.15 ± 2.1 μM in cancer cell lines of different origins; it directly inhibited microtubule polymerization, causing aberrant mitosis and G2/M arrest. Prolonged treatment with SSE1806 increased p53 expression, induced cell death in monolayer cultures, and reduced the growth of mouse- and patient-derived human colon cancer organoids. Importantly, SSE1806 overcame multidrug resistance in a cell line overexpressing MDR-1. Thus, SSE1806 represents a potential anticancer agent that can overcome multidrug resistance.

Tirbanibulin for Actinic Keratosis: Insights into the Mechanism of Action

Actinic keratosis (AK) is a common pre-neoplastic skin lesion constituted by uncontrolled proliferation of atypical keratinocytes that may evolve to squamous cell carcinoma. With global prevalence increasing, AK is expected to be the most common carcinoma of the skin. Tirbanibulin is a reversible tubulin polymerization inhibitor with potent anti-proliferative and anti-tumoral effects. In-vivo and in-vitro studies have shown that tirbanibulin significantly inhibits cell proliferation, tumor growth and downregulates Src signaling with no overt toxicity. Early phase and Phase III trials have shown high lesion clearance, compliance, and few side effects of once daily tirbanibulin treatment. This review discusses tirbanibulin anti-cancer activity, focusing on tubulin polymerization and Src signaling inhibitory effects, highlighting relevant literature and novel preclinical results from the ATNXUS-KX01-001 study. Furthermore, we address the relevant findings obtained in recent clinical trials to evaluate the safety, efficacy, pharmacokinetics, clearance efficacy, and side effects of the 1% tirbanibulin ointment applied once daily. In summary, we highlight preclinical and clinical evidence on the use of tirbanibulin as an effective and safe treatment option for AK.

Taccalonolides: Structure, semi-synthesis, and biological activity

Microtubules are the fundamental part of the cell cytoskeleton intimately involving in cell proliferation and are superb targets in clinical cancer therapy today. Microtubule stabilizers have become one of the effectively main agents in the last decades for the treatment of diverse cancers. Taccalonolides, the highly oxygenated pentacyclic steroids isolated from the genus of Tacca, are considered a class of novel microtubule-stabilizing agents. Taccalonolides not only possess a similar microtubule-stabilizing activity as the famous drug paclitaxel but also reverse the multi-drug resistance of paclitaxel and epothilone in cellular and animal models. Taccalonolides have captured numerous attention in the field of medicinal chemistry due to their variety of structures, unique mechanism of action, and low toxicity. This review focuses on the structural diversity, semi-synthesis, modification, and pharmacological activities of taccalonolides, providing bright thoughts for the discovery of microtubule-stabilizing drugs.

Structural insight into SSE15206 in complex with tubulin provides a rational design for pyrazolinethioamides as tubulin polymerization inhibitors

Background: Tubulin protein is a promising target for antitumor drugs. Some tubulin inhibitors targeting the colchicine binding site are not substrates of the multidrug-resistance efflux pump, which can overcome the mechanism of drug resistance mediated by P-glycoprotein. Methodology/results: SSE15206 is a colchicine binding site inhibitor with antiproliferative activity against different drug-resistant cell lines. Unfortunately, the lack of detailed interaction information about SSE15206 in complex with tubulin impeded the development of potent drugs that possess similar scaffolds. Herein, the authors report the crystal structure of the tubulin-SSE15206 complex at a resolution of 2.8 Å. Conclusion: The complex structure reveals the intermolecular interactions between SSE15206 and tubulin, providing a rationale for the development of pyrazolinethioamides as tubulin polymerization inhibitors and to overcome multidrug resistance.

Structure-Based Design and Synthesis of N-Substituted 3-Amino-β-Carboline Derivatives as Potent αβ-Tubulin Degradation Agents

So far, relatively few small molecules have been reported to promote tubulin degradation. Our previous studies have found that compound 2, a noncovalent colchicine-site ligand, was capable of promoting αβ-tubulin degradation. To further improve its antiproliferative activity, 66 derivatives or analogues of 2 were designed and synthesized based on 2-tubulin cocrystal structure. Among them, 12b displayed nanomolar potency against a variety of tumor cells, including paclitaxel- and adriamycin-resistant cell lines. 12b binds to the colchicine site and promotes αβ-tubulin degradation in a concentration-dependent manner via the ubiquitin-proteasome pathway. The X-ray crystal structure revealed that 12b binds in a similar manner as 2, but there is a slight conformation change of the B ring, which resulted in better interaction of 12b with surrounding residues. 12b effectively suppressed tumor growth at an i.v. dose of 40 mg/kg (3 times a week) on both A2780S (paclitaxel-sensitive) and A2780T (paclitaxel-resistant) ovarian xenograft models, with respective TGIs of 92.42 and 79.75% without obvious side effects, supporting its potential utility as a tumor-therapeutic compound.

Synthesis, cytotoxicity assay, pharmacokinetics, biodistribution and modeling study of cabazitaxel-dextran nanoconjugates: targeted vs non targeted delivery

Cabazitaxel (CTX) is an anti-neoplastic agent of second-generation taxane derivatives, characterized by very low water solubility. The currently marketed formulation of CTX contains high concentrations of surfactant and ethanol, which causes severe hypersensitivity reactions in patients. To deal with aforementioned side effects, our previous study attempted to develop the prodrugs of CTX with dextran. Here our approach differs through synthesizing folate containing prodrug and also investigating cytotoxicity and pharmacokinetics parameters obtained with dextran and dextran-folate nanoconjugates versus free CTX. MCF-7 with medium folate receptor expression and MDA-MB-231 as high folate receptor expression cell lines were selected for cytotoxicity assay. Pharmacokinetics properties were studied by injecting prodrugs and CTX to Wistar rats, analyzing serum and selected tissue samples and the obtained results were sibjected to data modeling study. The size of synthesized prodrugs was mostly less than 90 nm. Folate conjugates provided higher toxicity in comparison with dextran conjugates on both cell lines. In vivo non-compartmental pharmacokinetics analysis revealed enhanced area under the curve (about 3-5 fold for different samples) and longer half-life (approximately 1.3-1.8 fold higher) which led to increased serum residence time of prodrugs in comparison to free CTX. Tissue accumulation data showed that liver was the major organ with high accumulation of CTX. The accumulation of folate conjugates was remarkably higher than dextran samples (p < 0.05 in samples of 2, 10 and 24 h). Data modeling by Principal Component Analysis (PCA) and Hierarchical Cluster models showed a significant difference between pharmacokinetics properties of CTX and prodrugs. In summary, prodrugs seem to be proper and promising CTX delivery systems as substitution for the current market formulation.

Microtubule Targeting Agents in Disease: Classic Drugs, Novel Roles

Microtubule-targeting agents (MTAs) represent one of the most successful first-line therapies prescribed for cancer treatment. They interfere with microtubule (MT) dynamics by either stabilizing or destabilizing MTs, and in culture, they are believed to kill cells via apoptosis after eliciting mitotic arrest, among other mechanisms. This classical view of MTA therapies persisted for many years. However, the limited success of drugs specifically targeting mitotic proteins, and the slow growing rate of most human tumors forces a reevaluation of the mechanism of action of MTAs. Studies from the last decade suggest that the killing efficiency of MTAs arises from a combination of interphase and mitotic effects. Moreover, MTs have also been implicated in other therapeutically relevant activities, such as decreasing angiogenesis, blocking cell migration, reducing metastasis, and activating innate immunity to promote proinflammatory responses. Two key problems associated with MTA therapy are acquired drug resistance and systemic toxicity. Accordingly, novel and effective MTAs are being designed with an eye toward reducing toxicity without compromising efficacy or promoting resistance. Here, we will review the mechanism of action of MTAs, the signaling pathways they affect, their impact on cancer and other illnesses, and the promising new therapeutic applications of these classic drugs.

Hyperosmotic Stress Induces a Specific Pattern for Stress Granule Formation in Human-Induced Pluripotent Stem Cells

Stress granules (SGs) are assemblies of selective messenger RNAs (mRNAs), translation factors, and RNA-binding proteins in small untranslated messenger ribonucleoprotein (mRNP) complexes in the cytoplasm. Evidence indicates that different types of cells have shown different mechanisms to respond to stress and the formation of SGs. In the present work, we investigated how human-induced pluripotent stem cells (hiPSCs/IMR90-1) overcome hyperosmotic stress compared to a cell line that does not harbor pluripotent characteristics (SH-SY5Y cell line). Gradient concentrations of NaCl showed a different pattern of SG formation between hiPSCs/IMR90-1 and the nonpluripotent cell line SH-SY5Y. Other pluripotent stem cell lines (hiPSCs/CRTD5 and hESCs/H9 (human embryonic stem cell line)) as well as nonpluripotent cell lines (BHK-21 and MCF-7) were used to confirm this phenomenon. Moreover, the formation of hyperosmotic SGs in hiPSCs/IMR90-1 was independent of eIF2α phosphorylation and was associated with low apoptosis levels. In addition, a comprehensive proteomics analysis was performed to identify proteins involved in regulating this specific pattern of hyperosmotic SG formation in hiPSCs/IMR90-1. We found possible implications of microtubule organization on the response to hyperosmotic stress in hiPSCs/IMR90-1. We have also unveiled a reduced expression of tubulin that may protect cells against hyperosmolarity stress while inhibiting SG formation without affecting stem cell self-renewal and pluripotency. Our observations may provide a possible cellular mechanism to better understand SG dynamics in pluripotent stem cells.

Chemotherapy-induced peripheral neuropathy and rehabilitation: A review

Chemotherapy-induced peripheral neuropathy (CIPN) is a common complication after chemotherapy that can damage the sensory, motor, autonomic, or cranial nerves in approximately 30%-60% of patients with cancer. CIPN can lead to detrimental dose modifications and/or premature chemotherapy discontinuation due to patient intolerance. The long-term impact of CIPN is particularly challenging and can have a profound impact on the quality of life (QoL) and survivorship. However, this condition is often underdiagnosed. No agents have been established to prevent CIPN. Pre-chemotherapy testing is recommended for high-risk patients. Duloxetine is considered a first-line treatment, whereas gabapentin, pregabalin, tricyclic antidepressants, and topical compounding creams may be used for neuropathic pain control. Home-based, low-to-moderate walking, and resistance exercise during chemotherapy can reduce the severity and prevalence of CIPN symptoms, especially in older patients. Pre-habilitation and rehabilitation should be recommended for all patients receiving cytotoxic chemotherapies. The purpose of this article is to review common chemotherapeutic drugs causing CIPN, risk factors, diagnosis and treatment of CIPN, and evidence of the benefits of rehabilitation.

Akt inhibition improves the efficacy of cabazitaxel nanomedicine in preclinical taxane-resistant cancer models

Drug resistance remains a major challenge in achieving cures in cancer patients. Cabazitaxel has shown the ability to overcome drug resistance induced by paclitaxel and docetaxel; however, substantially high toxicity has been observed in patients receiving this agent, which compromises its efficacy. We have previously demonstrated that a polymeric platform (termed cabazitaxel-NPs) encapsulating the oligolactide-cabazitaxel conjugate exhibits desired antitumor efficacy and improved in vivo tolerability. However, we found that upon cabazitaxel treatment, cancer cells adapted to activate Akt signaling, which potentially discounts the drug efficacy. We therefore hypothesized that combing cabazitaxel nanotherapeutics with a pan-Akt inhibitor MK-2206 would synergistically sensitize the resistant cancer. In this study, we confirmed that nanoparticle formulation reduced the systemic toxicity, with higher tolerance than solution-based free cabazitaxel agent in animals. Interestingly, the activation of Akt signaling in the resistant cancer was reversed by the addition of MK-2206. In particular, the collaboration of these two ingredients was demonstrated to maximize the efficacy in vitro and in a xenograft model bearing paclitaxel-resistant tumors. Mechanistically, Akt inhibition increased the microtubule-stabilizing effect of cabazitaxel nanomedicine. Collectively, this report introduced a binary platform composed of cytotoxic nanotherapeutics and inhibitors with certain targets to combat multidrug resistance, and such a combined regimen has the potential for the clinical treatment of patients with resistant cancer.

Molecular mechanisms of chemo- and radiotherapy resistance and the potential implications for cancer treatment

Cancer is a leading cause of death worldwide. Surgery is the primary treatment approach for cancer, but the survival rate is very low due to the rapid progression of the disease and presence of local and distant metastasis at diagnosis. Adjuvant chemotherapy and radiotherapy are important components of the multidisciplinary approaches for cancer treatment. However, resistance to radiotherapy and chemotherapy may result in treatment failure or even cancer recurrence. Radioresistance in cancer is often caused by the repair response to radiation-induced DNA damage, cell cycle dysregulation, cancer stem cells (CSCs) resilience, and epithelial-mesenchymal transition (EMT). Understanding the molecular alterations that lead to radioresistance may provide new diagnostic markers and therapeutic targets to improve radiotherapy efficacy. Patients who develop resistance to chemotherapy drugs cannot benefit from the cytotoxicity induced by the prescribed drug and will likely have a poor outcome with these treatments. Chemotherapy often shows a low response rate due to various drug resistance mechanisms. This review focuses on the molecular mechanisms of radioresistance and chemoresistance in cancer and discusses recent developments in therapeutic strategies targeting chemoradiotherapy resistance to improve treatment outcomes.

Breast Cancer Treatments: Updates and New Challenges

Breast cancer (BC) is the most frequent cancer diagnosed in women worldwide. This heterogeneous disease can be classified into four molecular subtypes (luminal A, luminal B, HER2 and triple-negative breast cancer (TNBC)) according to the expression of the estrogen receptor (ER) and the progesterone receptor (PR), and the overexpression of the human epidermal growth factor receptor 2 (HER2). Current BC treatments target these receptors (endocrine and anti-HER2 therapies) as a personalized treatment. Along with chemotherapy and radiotherapy, these therapies can have severe adverse effects and patients can develop resistance to these agents. Moreover, TNBC do not have standardized treatments. Hence, a deeper understanding of the development of new treatments that are more specific and effective in treating each BC subgroup is key. New approaches have recently emerged such as immunotherapy, conjugated antibodies, and targeting other metabolic pathways. This review summarizes current BC treatments and explores the new treatment strategies from a personalized therapy perspective and the resulting challenges.

Ixabepilone: Overview of Effectiveness, Safety, and Tolerability in Metastatic Breast Cancer

Treatment algorithms for metastatic breast cancer describe sequential treatment with chemotherapy and, if appropriate, targeted therapy for as long as the patient receives benefit. The epothilone ixabepilone is a microtubule stabilizer approved as a monotherapy and in combination with capecitabine for the treatment of metastatic breast cancer in patients with demonstrated resistance to anthracyclines and taxanes. While chemotherapy and endocrine therapy form the backbone of treatment for metastatic breast cancer, the epothilone drug class has distinguished itself for efficacy and safety among patients with disease progression during treatment with chemotherapy. In phase III trials, ixabepilone has extended progression-free survival and increased overall response rates, with a manageable toxicity profile. Recent analyses of subpopulations within large pooled datasets have characterized the clinical benefit for progression-free survival and overall survival for ixabepilone in special populations, such as patients with triple-negative breast cancer or those who relapsed within 12 months of prior treatment. Additional investigation settings for ixabepilone therapy discussed here include adjuvant therapy, weekly dosing schedules, and ixabepilone in new combinations of treatment. As with other microtubule stabilizers, ixabepilone treatment can lead to peripheral neuropathy, but evidence-based management strategies may reverse these symptoms. Dose reductions did not appear to have an impact on the efficacy of ixabepilone plus capecitabine. Incorporation of ixabepilone into individualized treatment plans can extend progression-free survival in a patient population that continues to represent an unmet need.

Nuclear Lamin A/C Expression Is a Key Determinant of Paclitaxel Sensitivity

Paclitaxel is a key member of the Taxane (paclitaxel [originally named taxol], docetaxel/Taxotere) family of successful drugs used in the current treatment of several solid tumors, including ovarian cancer. The molecular target of paclitaxel has been identified as tubulin, and paclitaxel binding alters the dynamics and thus stabilizes microtubule bundles. Traditionally, the anticancer mechanism of paclitaxel has been thought to originate from its interfering with the role of microtubules in mitosis, resulting in mitotic arrest and subsequent apoptosis. However, recent evidence suggests that paclitaxel operates in cancer therapies via an as-yet-undefined mechanism rather than as a mitotic inhibitor. We found that paclitaxel caused a striking break up of nuclei (referred to as multimicronucleation) in malignant ovarian cancer cells but not in normal cells, and susceptibility to undergo nuclear fragmentation and cell death correlated with a reduction in nuclear lamina proteins, lamin A/C. Lamin A/C proteins are commonly lost, reduced, or heterogeneously expressed in ovarian cancer, accounting for the aberration of nuclear shape in malignant cells. Mouse ovarian epithelial cells isolated from lamin A/C-null mice were highly sensitive to paclitaxel and underwent nuclear breakage, compared to control wild-type cells. Forced overexpression of lamin A/C led to resistance to paclitaxel-induced nuclear breakage in cancer cells. Additionally, paclitaxel-induced multimicronucleation occurred independently of cell division that was achieved by either the withdrawal of serum or the addition of mitotic inhibitors. These results provide a new understanding for the mitotis-independent mechanism for paclitaxel killing of cancer cells, where paclitaxel induces nuclear breakage in malignant cancer cells that have a malleable nucleus but not in normal cells that have a stiffer nuclear envelope. As such, we identify that reduced nuclear lamin A/C protein levels correlate with nuclear shape deformation and are a key determinant of paclitaxel sensitivity of cancer cells.

Overview of Evidence-Based Chemotherapy for Oral Cancer: Focus on Drug Resistance Related to the Epithelial-Mesenchymal Transition

The increasing incidence of resistance to chemotherapeutic agents has become a major issue in the treatment of oral cancer (OC). Epithelial-mesenchymal transition (EMT) has attracted a great deal of attention in recent years with regard to its relation to the mechanism of chemotherapy drug resistance. EMT-activating transcription factors (EMT-ATFs), such as Snail, TWIST, and ZEB, can activate several different molecular pathways, e.g., PI3K/AKT, NF-κB, and TGF-β. In contrast, the activated oncological signal pathways provide reciprocal feedback that affects the expression of EMT-ATFs, resulting in a peritumoral extracellular environment conducive to cancer cell survival and evasion of the immune system, leading to resistance to multiple chemotherapeutic agents. We present an overview of evidence-based chemotherapy for OC treatment based on the National Comprehensive Cancer Network (NCCN) Chemotherapy Order Templates. We focus on the molecular pathways involved in drug resistance related to the EMT and highlight the signal pathways and transcription factors that may be important for EMT-regulated drug resistance. Rapid progress in antitumor regimens, together with the application of powerful techniques such as high-throughput screening and microRNA technology, will facilitate the development of therapeutic strategies to augment chemotherapy.

Structural insights into targeting of the colchicine binding site by ELR510444 and parbendazole to achieve rational drug design

Microtubules consisting of α- and β-tubulin heterodimers have proven to be an efficient drug target for cancer therapy. A broad range of agents, including ELR510444 and parbendazole, can bind to tubulin and interfere with microtubule assembly. ELR510444 and parbendazole are colchicine binding site inhibitors with antiproliferative activities. However, the lack of structural information on the tubulin–ELR510444/parbendazole complex has hindered the design and development of more potent drugs with similar scaffolds. Therefore, we report the crystal structures of tubulin complexed with ELR510444 at a resolution of 3.1 Å and with parbendazole at 2.4 Å. The structure of these complexes revealed the intermolecular interactions between the two colchicine binding site inhibitors and tubulin, thus providing a rationale for the development of novel benzsulfamide and benzimidazole derivatives targeting the colchicine binding site.

Crystal structures of tubulin complexed with ELR510444 and parbendazole facilitate the design of novel colchicine binding site inhibitors.

Hybrid Drugs-A Strategy for Overcoming Anticancer Drug Resistance?

Despite enormous progress in the treatment of many malignancies, the development of cancer resistance is still an important reason for cancer chemotherapy failure. Increasing knowledge of cancers' molecular complexity and mechanisms of their resistance to anticancer drugs, as well as extensive clinical experience, indicate that an effective fight against cancer requires a multidimensional approach. Multi-target chemotherapy may be achieved using drugs combination, co-delivery of medicines, or designing hybrid drugs. Hybrid drugs simultaneously targeting many points of signaling networks and various structures within a cancer cell have been extensively explored in recent years. The single hybrid agent can modulate multiple targets involved in cancer cell proliferation, possesses a simpler pharmacokinetic profile to reduce the possibility of drug interactions occurrence, and facilitates the process of drug development. Moreover, a single medication is expected to enhance patient compliance due to a less complicated treatment regimen, as well as a diminished number of adverse reactions and toxicity in comparison to a combination of drugs. As a consequence, many efforts have been made to design hybrid molecules of different chemical structures and functions as a means to circumvent drug resistance. The enormous number of studies in this field encouraged us to review the available literature and present selected research results highlighting the possible role of hybrid drugs in overcoming cancer drug resistance.

Transcriptome profiling of long noncoding RNAs and mRNAs in spinal cord of a rat model of paclitaxel-induced peripheral neuropathy identifies potential mechanisms mediating neuroinflammation and pain

Background

Paclitaxel is a widely prescribed chemotherapy drug for treating solid tumors. However, paclitaxel-induced peripheral neuropathy (PIPN) is a common adverse effect during paclitaxel treatment, which results in sensory abnormalities and neuropathic pain among patients. Unfortunately, the mechanisms underlying PIPN still remain poorly understood. Long noncoding RNAs (lncRNAs) are novel and promising targets for chronic pain treatment, but their involvement in PIPN still remains unexplored.

Methods

We established a rat PIPN model by repetitive paclitaxel application. Immunostaining, RNA sequencing (RNA-Seq) and bioinformatics analysis were performed to study glia cell activation and explore lncRNA/mRNA expression profiles in spinal cord dorsal horn (SCDH) of PIPN model rats. qPCR and protein assay were used for further validation.

Results

PIPN model rats developed long-lasting mechanical and thermal pain hypersensitivities in hind paws, accompanied with astrocyte and microglia activation in SCDH. RNA-Seq identified a total of 814 differentially expressed mRNAs (DEmRNA) (including 467 upregulated and 347 downregulated) and 412 DElncRNAs (including 145 upregulated and 267 downregulated) in SCDH of PIPN model rats vs. control rats. Functional analysis of DEmRNAs and DElncRNAs identified that the most significantly enriched pathways include immune/inflammatory responses and neurotrophin signaling pathways, which are all important mechanisms mediating neuroinflammation, central sensitization, and chronic pain. We further compared our dataset with other published datasets of neuropathic pain and identified a core set of immune response-related genes extensively involved in PIPN and other neuropathic pain conditions. Lastly, a competing RNA network analysis of DElncRNAs and DEmRNAs was performed to identify potential regulatory networks of lncRNAs on mRNA through miRNA sponging.

Conclusions

Our study provided the transcriptome profiling of DElncRNAs and DEmRNAs and uncovered immune and inflammatory responses were predominant biological events in SCDH of the rat PIPN model. Thus, our study may help to identify promising genes or signaling pathways for PIPN therapeutics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02098-y.

Histone Deacetylase Inhibitors and Microtubule Inhibitors Induce Apoptosis in Feline Luminal Mammary Carcinoma Cells

Simple Summary

Feline mammary tumors (FMT) are very common in cats, associated with very aggressive behavior and a short life expectancy. Surgery is the most used treatment but tumor recurrence is common. Currently, available therapies are insufficient, therefore, new molecular targets are needed to develop more efficient therapeutics. Histone deacetylases inhibitors (HDACis) have been developed to target tumor cells, by disrupting gene expression and leading to cell death. Microtubules inhibitors (MTIs) have also been a focus of research, to target polymerization of microtubules, and consequently disturbing the cytoskeleton and leading to cell cycle arrest and apoptosis. However, there are few studies on the use of HDACis and MTIs in cats. In this study, we addressed if these two drug classes could be used as new therapeutic options in FMTs. All HDACis and MTIs exhibited suitable and dose-dependent antitumor effects in FMT cell lines. Immunoblot analysis confirmed that the mode of action of HDACis is conserved in feline mammary tumor cell lines. Finally, flow cytometry showed that exposure with HDACis and MTIs lead to the induction of cellular apoptosis. In summary, HDACis and MTIs possess antitumor properties suggesting further studies on their use in the treatment of feline mammary tumors.

Abstract

Feline mammary carcinoma (FMC) is the third most common type of neoplasia in cats, sharing similar epidemiological features with human breast cancer. In humans, histone deacetylases (HDACs) play an important role in the regulation of gene expression, with HDAC inhibitors (HDACis) disrupting gene expression and leading to cell death. In parallel, microtubules inhibitors (MTIs) interfere with the polymerization of microtubules, leading to cell cycle arrest and apoptosis. Although HDACis and MTIs are used in human cancer patients, in cats, data is scarce. In this study, we evaluated the antitumor properties of six HDACis (CI-994, panobinostat, SAHA, SBHA, scriptaid, and trichostatin A) and four MTIs (colchicine, nocodazole, paclitaxel, and vinblastine) using three FMC cell lines (CAT-MT, FMCp, and FMCm), and compared with the human breast cancer cell line (SK-BR-3). HDACis and MTIs exhibited dose-dependent antitumor effects in FMC cell lines, and for all inhibitors, the IC50 values were determined, with one feline cell line showing reduced susceptibility (FMCm). Immunoblot analysis confirmed an increase in the acetylation status of core histone protein HDAC3 and flow cytometry showed that HDACis and MTIs lead to cellular apoptosis. Overall, our study uncovers HDACis and MTIs as promising anti-cancer agents to treat FMCs.

Newly Developed Self-Assembling Antioxidants as Potential Therapeutics for the Cancers

Elevated reactive oxygen species (ROS) have been implicated as significant for cancer survival by functioning as oncogene activators and secondary messengers. Hence, the attenuation of ROS-signaling pathways in cancer by antioxidants seems a suitable therapeutic regime for targeting cancers. Low molecular weight (LMW) antioxidants such as 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO), although they are catalytically effective in vitro, exerts off-target effects in vivo due to their size, thus, limiting their clinical use. Here, we discuss the superior impacts of our TEMPO radical-conjugated self-assembling antioxidant nanoparticle (RNP) compared to the LMW counterpart in terms of pharmacokinetics, therapeutic effect, and adverse effects in various cancer models.

CypA: A Potential Target of Tumor Radiotherapy and/or Chemotherapy

Cyclophilin A (CypA) is a ubiquitous and highly conserved protein. CypA, the intracellular target protein for the immunosuppressant cyclosporine A (CsA), plays important cellular roles through peptidyl-prolyl cis-trans isomerase (PPIase). Increasing evidence shows that CypA is up-regulated in a variety of human cancers. In addition to being involved in the occurrence and development of multiple tumors, overexpression of CypA has also been shown to be strongly associated with malignant transformation. Surgery, chemotherapy and radiotherapy are the three main treatments for cancer. Chemotherapy and radiotherapy are often used as direct or adjuvant treatments for cancer. However, various side effects and resistance to both chemotherapy and radiotherapy bring great challenges to these two forms of treatment. According to recent reports, CypA can improve the chemosensitivity and/or radiosensitivity of cancers, possibly by affecting the expression of drug-resistant related proteins, cell cycle arrest and activation of the mitogen-activated protein kinase (MAPK) signaling pathways. In this review, we focus on the role of CypA in cancer, its impact on cancer chemotherapeutic and radiotherapy sensitivity, and the mechanism of action. It is suggested that CypA may be a novel potential therapeutic target for cancer chemotherapy and/or radiotherapy.

Breaking malignant nuclei as a non-mitotic mechanism of taxol/paclitaxel

Discovered in a large-scale screening of natural plant chemicals, Taxol/paclitaxel and the taxane family of compounds are surprisingly successful anti-cancer drugs, used in treatment of the majority of solid tumors, and especially suitable for metastatic and recurrent cancer. Paclitaxel is often used in combination with platinum agents and is administrated in a dose dense regimen to treat recurrent cancer. The enthusiasm and clinical development were prompted by the discovery that Taxol binds beta-tubulins specifically found within microtubules and stabilizes the filaments, and consequently inhibits mitosis. However, questions on how paclitaxel suppresses cancer persist, as other specific mitotic inhibitors are impressive in pre-clinical studies but fail to achieve significant clinical activity. Thus, additional mechanisms, such as promoting mitotic catastrophe and impacting non-mitotic targets, have been proposed and studied. A good understanding of how paclitaxel, and additional new microtubule stabilizing agents, kill cancer cells will advance the clinical application of these common chemotherapeutic agents. A recent study provides a potential non-mitotic mechanism of paclitaxel action, that paclitaxel-induced rigid microtubules act to break malleable cancer nuclei into multiple micronuclei. Previous studies have established that cancer cells have a less sturdy, more pliable nuclear envelope due to the loss or reduction of lamin A/C proteins. Such changes in nuclear structure provide a selectivity for paclitaxel to break the nuclear membrane and kill cancer cells over non-neoplastic cells that have a sturdier nuclear envelope. The formation of multiple micronuclei appears to be an important aspect of paclitaxel in the killing of cancer cells, either by a mitotic or non-mitotic mechanism. Additionally, by binding to microtubule, paclitaxel is readily sequestered and concentrated within cells. This unique pharmacokinetic property allows the impact of paclitaxel on cells to persist for several days, even though the circulating drug level is much reduced following drug administration/infusion. The retention of paclitaxel within cells likely is another factor contributing to the efficacy of the drugs. Overall, the new understanding of Taxol/paclitaxel killing mechanism-rigid microtubule-induced multiple micronucleation-will likely provide new strategies to overcome drug resistance and for rational drug combination.

Randomized phase II clinical trial and biomarker analysis of paclitaxel plus epirubicin versus vinorelbine plus epirubicin as neoadjuvant chemotherapy in locally advanced HER2-negative breast cancer with TEKT4 variations

PURPOSE

Resistance to paclitaxel remains a major challenge in treating breast cancer. Our preclinical study suggested that TEKT4 germline variations in breast cancer are associated with paclitaxel resistance and increase vinorelbine sensitivity. This clinical trial compared the efficacy of paclitaxel and vinorelbine in breast cancer neoadjuvant chemotherapy.

METHODS

In this open-label, single-center, phase II trial, female patients with human epidermal growth factor receptor 2 (HER2)-negative, stage IIB-IIIC breast cancer harboring TEKT4 germline variations were randomly assigned to the paclitaxel plus epirubicin (PE) or vinorelbine plus epirubicin (NE). The primary endpoint was the pathologic complete response (pCR) rate, and the secondary endpoints were the objective response rate (ORR) and safety. Targeted sequencing of a panel comprising 484 breast-related genes was performed to identify pCR-associated somatic mutations in each group.

RESULTS

91 Patients were assigned to PE (46 patients) or NE (45 patients). NE numerically increased the pCR rate (22.2% versus 8.7%, P = 0.074). The ORRs for NE and PE were 82.2% and 76.1%, respectively. Interestingly, NE (15.4%) showed a significantly higher pCR rate than PE (0%) in the hormone receptor (HR)-positive subgroup (P = 0.044). Both regimens were well tolerated, with grade 3 and 4 toxicities reported at the expected levels. The biomarker analysis showed that UNC13D mutation predicted the pCR rate in NE (P = 0.011).

CONCLUSIONS

Although the primary endpoint was not met, NE might bring clinical benefit to HR-positive patients or patients simultaneously carrying UNC13D mutations.

Role of membrane-embedded drug efflux ABC transporters in the cancer chemotherapy

One of the major problems being faced by researchers and clinicians in leukemic treatment is the development of multidrug resistance (MDR) which restrict the action of several tyrosine kinase inhibitors (TKIs). MDR is a major obstacle to the success of cancer chemotherapy. The mechanism of MDR involves active drug efflux transport of ABC superfamily of proteins such as Pglycoprotein (P-gp/ABCB1), multidrug resistance-associated protein 2 (MRP2/ABCC2), and breast cancer resistance protein (BCRP/ABCG2) that weaken the effectiveness of chemotherapeutics and negative impact on the future of anticancer therapy. In this review, the authors aim to provide an overview of various multidrug resistance (MDR) mechanisms observed in cancer cells as well as the various strategies developed to overcome these MDR. Extensive studies have been carried out since last several years to enhance the efficacy of chemotherapy by defeating these MDR mechanisms with the use of novel anticancer drugs that could escape from the efflux reaction, MDR modulators or chemosensitizers, multifunctional nanotechnology, and RNA interference (RNAi) therapy.

Mechanistic Involvement of Long Non-Coding RNAs in Oncotherapeutics Resistance in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is one of the most lethal forms of breast cancer (BC), with a significant disease burden worldwide. Chemoresistance and lack of targeted therapeutics are major hindrances to effective treatments in the clinic and are crucial causes of a worse prognosis and high rate of relapse/recurrence in patients diagnosed with TNBC. In the last decade, long non-coding RNAs (lncRNAs) have been found to perform a pivotal role in most cellular functions. The aberrant functional expression of lncRNAs plays an ever-increasing role in the progression of diverse malignancies, including TNBC. Therefore, lncRNAs have been recently studied as predictors and modifiers of chemoresistance. Our review discusses the potential involvement of lncRNAs in drug-resistant mechanisms commonly found in TNBC and highlights various therapeutic strategies to target lncRNAs in this malignancy.

Microtubule-targeting agents and their impact on cancer treatment

Microtubule-targeting agents (MTAs) constitute a diverse group of chemical compounds that bind to microtubules and affect their properties and function. Disruption of microtubules induces various cellular responses often leading to cell cycle arrest or cell death, the most common effect of MTAs. MTAs have found a plethora of practical applications in weed control, as fungicides and antiparasitics, and particularly in cancer treatment. Here we summarize the current knowledge of MTAs, the mechanisms of action and their role in cancer treatment. We further outline the potential use of MTAs in anti-metastatic therapy based on inhibition of cancer cell migration and invasiveness. The two main problems associated with cancer therapy by MTAs are high systemic toxicity and development of resistance. Toxic side effects of MTAs can be, at least partly, eliminated by conjugation of the drugs with various carriers. Moreover, some of the novel MTAs overcome the resistance mediated by both multidrug resistance transporters as well as overexpression of specific β-tubulin types. In anti-metastatic therapy, MTAs should be combined with other drugs to target all modes of cancer cell invasion.

Electroacupuncture Alleviates Paclitaxel-Induced Peripheral Neuropathic Pain in Rats via Suppressing TLR4 Signaling and TRPV1 Upregulation in Sensory Neurons

Paclitaxel-induced peripheral neuropathy is a common adverse effect during paclitaxel treatment resulting in sensory abnormalities and neuropathic pain during chemotherapy and in cancer survivors. Conventional therapies are usually ineffective and possess adverse effects. Here, we examined the effects of electroacupuncture (EA) on a rat model of paclitaxel-induced neuropathic pain and related mechanisms. EA robustly and persistently alleviated paclitaxel-induced pain hypersensitivities. Mechanistically, TLR4 (Toll-Like Receptor 4) and downstream signaling MyD88 (Myeloid Differentiation Primary Response 88) and TRPV1 (Transient Receptor Potential Vallinoid 1) were upregulated in dorsal root ganglion (DRGs) of paclitaxel-treated rats, whereas EA reduced their overexpression. Ca²⁺ imaging further indicated that TRPV1 channel activity was enhanced in DRG neurons of paclitaxel-treated rats whereas EA suppressed the enhanced TRPV1 channel activity. Pharmacological blocking of TRPV1 mimics the analgesic effects of EA on the pain hypersensitivities, whereas capsaicin reversed EA’s effect. Spinal astrocytes and microglia were activated in paclitaxel-treated rats, whereas EA reduced the activation. These results demonstrated that EA alleviates paclitaxel-induced peripheral neuropathic pain via mechanisms possibly involving suppressing TLR4 signaling and TRPV1 upregulation in DRG neurons, which further result in reduced spinal glia activation. Our work supports EA as a potential alternative therapy for paclitaxel-induced neuropathic pain.

The miR-195 Axis Regulates Chemoresistance through TUBB and Lung Cancer Progression through BIRC5

Chemoresistance and metastasis are the major reasons for non-small cell lung cancer (NSCLC) treatment failure and patient deaths. We and others have shown that miR-195 regulates the sensitivity of NSCLC to microtubule-targeting agents (MTAs) in vitro and in vivo and that miR-195 represses the migration and invasion of NSCLC cells in vitro. However, the relationship between miR-195 and microtubule structure and function and whether miR-195 represses NSCLC metastasis in vivo remain unknown. We assessed the correlation between tumor levels of TUBB and patient survival, the effect of TUBB on drug response, and the effect of miR-195 on migration, invasion, and metastasis in vitro and in vivo. We found that miR-195 directly targets TUBB; knockdown of TUBB sensitizes cells to MTAs, while overexpression confers resistance; high expression of TUBB is correlated with worse survival of lung adenocarcinoma; TUBB is also regulated by CHEK1, which has been shown to regulate chemoresistance; and miR-195 targets BIRC5 to repress migration and invasion in vitro and metastasis in vivo. Our findings highlight the relevance of the miR-195/TUBB axis in regulating the response of NSCLC to MTAs and the importance of the miR-195/BIRC5 axis in regulating NSCLC metastasis.

Colchicine Binding Site Agent DJ95 Overcomes Drug Resistance and Exhibits Antitumor Efficacy

Interfering with microtubule dynamics is a well-established strategy in cancer treatment; however, many microtubule-targeting agents are associated with drug resistance and adverse effects. Substantial evidence points to ATP-binding cassette (ABC) transporters as critical players in the development of resistance. Herein, we demonstrate the efficacy of DJ95 (2-(1H-indol-6-yl)-4-(3,4,5-trimethoxyphenyl)-1H-imidazo[4,5-c]pyridine), a novel tubulin inhibitor, in a variety of cancer cell lines, including malignant melanomas, drug-selected resistant cell lines, specific ABC transporter-overexpressing cell lines, and the National Cancer Institute 60 cell line panel. DJ95 treatment inhibited cancer cell migration, caused morphologic changes to the microtubule network foundation, and severely disrupted mitotic spindle formation of mitotic cells. The high-resolution crystal structure of DJ95 in complex with tubulin protein and the detailed molecular interactions confirmed its direct binding to the colchicine site. In vitro pharmacological screening of DJ95 using SafetyScreen44 (Eurofins Cerep-Panlabs) revealed no significant off-target interactions, and pharmacokinetic analysis showed that DJ95 was maintained at therapeutically relevant plasma concentrations for up to 24 hours in mice. In an A375 xenograft model in nude mice, DJ95 inhibited tumor growth and disrupted tumor vasculature in xenograft tumors. These results demonstrate that DJ95 is potent against a variety of cell lines, demonstrated greater potency to ABC transporter-overexpressing cell lines than existing tubulin inhibitors, directly targets the colchicine binding domain, exhibits significant antitumor efficacy, and demonstrates vascular-disrupting properties. Collectively, these data suggest that DJ95 has great potential as a cancer therapeutic, particularly for multidrug resistance phenotypes, and warrants further development. SIGNIFICANCE STATEMENT: Paclitaxel is a widely used tubulin inhibitor for cancer therapy, but its clinical efficacy is often limited by the development of multidrug resistance. In this study, we reported the preclinical characterization of a new tubulin inhibitor DJ95, and demonstrated its abilities to overcome paclitaxel resistance, disrupt tumor vasculature, and exhibit significant antitumor efficacy.

Molecular, Biological and Structural Features of VL CDR-1 Rb44 Peptide, Which Targets the Microtubule Network in Melanoma Cells

Microtubules are important drug targets in tumor cells, owing to their role in supporting and determining the cell shape, organelle movement and cell division. The complementarity-determining regions (CDRs) of immunoglobulins have been reported to be a source of anti-tumor peptide sequences, independently of the original antibody specificity for a given antigen. We found that, the anti-Lewis B mAb light-chain CDR1 synthetic peptide Rb44, interacted with microtubules and induced depolymerization, with subsequent degradation of actin filaments, leading to depolarization of mitochondrial membrane-potential, increase of ROS, cell cycle arrest at G2/M, cleavage of caspase-9, caspase-3 and PARP, upregulation of Bax and downregulation of Bcl-2, altogether resulting in intrinsic apoptosis of melanoma cells. The in vitro inhibition of angiogenesis was also an Rb44 effect. Peritumoral injection of Rb44L1 delayed growth of subcutaneously grafted melanoma cells in a syngeneic mouse model. L1-CDRs from immunoglobulins and their interactions with tubulin-dimers were explored to interpret effects on microtubule stability. The opening motion of tubulin monomers allowed for efficient L1-CDR docking, impairment of dimer formation and microtubule dissociation. We conclude that Rb44 V_L-CDR1 is a novel peptide that acts on melanoma microtubule network causing cell apoptosis in vitro and melanoma growth inhibition in vivo.

Nuclear Imaging Study of the Pharmacodynamic Effects of Debio 1143, an Antagonist of Multiple Inhibitor of Apoptosis Proteins (IAPs), in a Triple-Negative Breast Cancer Model

Background

Debio 1143, a potent orally available SMAC mimetic, targets inhibitors of apoptosis proteins (IAPs) members and is currently in clinical trials. In this study, nuclear imaging evaluated the effects of Debio 1143 on tumor cell death and metabolism in a triple-negative breast cancer (TNBC) cell line (MDA-MB-231)-based animal model.

Methods

Apoptosis induced by Debio 1143 was assessed by FACS (caspase-3, annexin 5 (A5)), binding of ^99mTc-HYNIC-Annexin V, and a cell proliferation assay. ^99mTc-HYNIC-Annexin V SPECT and [¹⁸F]-FDG PET were also performed in mice xenografted with MDA-MB-231 cells.

Results

Debio 1143 induced early apoptosis both in vitro and in vivo 6 h after treatment. Debio 1143 inhibited tumor growth, which was associated with a decreased tumor [¹⁸F]-FDG uptake when measured during treatment.

Conclusions

This imaging study combining SPECT and PET showed the early proapoptotic effects of Debio 1143 resulting in a robust antitumor activity in a preclinical TNBC model. These imaging biomarkers represent valuable noninvasive tools for translational and clinical research in TNBC.

A Pharmacological Strategy Using Stemofoline for more Efficacious Chemotherapeutic Treatments Against Human Multidrug Resistant Leukemic Cells

Our previous study reported that stemofoline (STF) exhibited a synergistic effect with chemotherapeutic drugs in human multidrug-resistant (MDR) leukemic cells (K526/Adr) by inhibiting the function of P-glycoprotein, which is a membrane transporter that is overexpressed in several types of MDR cancers. This study further investigated the effects of a combination treatment of STF and doxorubicin (DOX) in vitro and in vivo. The combination treatment of 50 mg/kg of STF strongly enhanced the anti-tumor activity of DOX in SCID-beige mice bearing K562/Adr xenografts without additional toxicity when compared to the single treatment groups. Additionally, an examination of the proliferation markers (Ki67) and the apoptotic marker (TUNEL) in tumor tissues in each group revealed that the combination therapy significantly reduced Ki67 positive cells and increased apoptotic cells. From the in vitro experiments we also found that this combination treatment dramatically induced G1 and G2M arrest in K562/Adr when compared to a single treatment of DOX. STF treatment alone did not show any cytotoxic effect to the cells. These results suggest that the accumulation of DOX enhanced by STF was sufficient to induce cell cycle arrest in K562/Adr. These findings support our previous in vitro data and indicate the possibility of developing STF as an adjuvant therapy in cancer treatments.

SQ1274, a novel microtubule inhibitor, inhibits ovarian and uterine cancer cell growth

OBJECTIVE

Paclitaxel, a microtubule inhibitor, is subject to tumor resistance while treating high-grade serous ovarian and uterine cancer. This study aims to directly compare the effects of SQ1274, a novel microtubule inhibitor that binds to the colchicine-binding site on tubulin, and paclitaxel in high-grade serous ovarian and uterine cancer cell lines both in vitro and in vivo.

METHODS

We assessed the sensitivity of ovarian (OVCAR8) and uterine (ARK1) cancer cell lines to SQ1274 and paclitaxel using XTT assays. We used western blot and quantitative real-time PCR to analyze changes in AXL RNA and protein expression by SQ1274 and paclitaxel. Differences in cell-cycle arrest and apoptosis were investigated using flow cytometry. Finally, we treated ovarian and uterine xenograft models with vehicle, paclitaxel, or SQ1274.

RESULTS

First, we demonstrate that SQ1274 has a much lower IC₅₀ than paclitaxel in both ARK1 (1.26 nM vs. 15.34 nM, respectively) and OVCAR8 (1.34 nM vs. 10.29 nM, respectively) cancer cell lines. Second, we show SQ1274 decreases both RNA and protein expression of AXL. Third, we show that SQ1274 causes increased cell-cycle arrest and apoptosis compared to paclitaxel. Finally, we report that SQ1274 more effectively inhibits tumor growth in vivo compared to paclitaxel.

CONCLUSIONS

SQ1274 presents as a viable alternative to paclitaxel for treating ovarian and uterine cancer. This study supports the development of SQ1274 as a chemotherapeutic to treat ovarian and uterine cancer.

Targeting of apoptotic pathways by SMAC or BH3 mimetics distinctly sensitizes paclitaxel-resistant triple negative breast cancer cells

Standard chemotherapy is the only systemic treatment for triple-negative breast cancer (TNBC), and despite the good initial response, resistance remains a major therapeutic obstacle. Here, we employed a High-Throughput Screen to identify targeted therapies that overcome chemoresistance in TNBC. We applied short-term paclitaxel treatment and screened 320 small-molecule inhibitors of known targets to identify drugs that preferentially and efficiently target paclitaxel-treated TNBC cells. Among these compounds the SMAC mimetics (BV6, Birinapant) and BH3-mimetics (ABT-737/263) were recognized as potent targeted therapy for multiple paclitaxel-residual TNBC cell lines. However, acquired paclitaxel resistance through repeated paclitaxel pulses result in desensitization to BV6, but not to ABT-263, suggesting that short- and long-term paclitaxel resistance are mediated by distinct mechanisms. Gene expression profiling of paclitaxel-residual, -resistant and naïve MDA-MB-231 cells demonstrated that paclitaxel-residual, as opposed to -resistant cells, were characterized by an apoptotic signature, with downregulation of anti-apoptotic genes (BCL2, BIRC5), induction of apoptosis inducers (IL24, PDCD4), and enrichment of TNFα/NF-κB pathway, including upregulation of TNFSF15, coupled with cell-cycle arrest. BIRC5 and FOXM1 downregulation and IL24 induction was also evident in breast cancer patient datasets following taxane treatment. Exposure of naïve or paclitaxel-resistant cells to supernatants of paclitaxel-residual cells sensitized them to BV6, and treatment with TNFα enhanced BV6 potency, suggesting that sensitization to BV6 is mediated, at least partially, by secreted factor(s). Our results suggest that administration of SMAC or BH3 mimetics following short-term paclitaxel treatment could be an effective therapeutic strategy for TNBC, while only BH3-mimetics could effectively overcome long-term paclitaxel resistance.

Optimization Of Cancer Treatment Through Overcoming Drug Resistance

Cancer Drug resistance is a medical concern that requires extensive research and a thorough understanding in order to overcome. Remarkable achievements related to this field have been accomplished and further work is needed in order to optimize the cure for cancer and serve as the basis for precise medicine with few or no side effects.

Identification and characterization of SSE15206, a microtubule depolymerizing agent that overcomes multidrug resistance

Microtubules are highly dynamic structures that form spindle fibres during mitosis and are one of the most validated cancer targets. The success of drugs targeting microtubules, however, is often limited by the development of multidrug resistance. Here we describe the discovery and characterization of SSE15206, a pyrazolinethioamide derivative [3-phenyl-5-(3,4,5-trimethoxyphenyl)-4,5-dihydro-1H-pyrazole-1-carbothioamide] that has potent antiproliferative activities in cancer cell lines of different origins and overcomes resistance to microtubule-targeting agents. Treatment of cells with SSE15206 causes aberrant mitosis resulting in G2/M arrest due to incomplete spindle formation, a phenotype often associated with drugs that interfere with microtubule dynamics. SSE15206 inhibits microtubule polymerization both in biochemical and cellular assays by binding to colchicine site in tubulin as shown by docking and competition studies. Prolonged treatment of cells with the compound results in apoptotic cell death [increased Poly (ADP-ribose) polymerase cleavage and Annexin V/PI staining] accompanied by p53 induction. More importantly, we demonstrate that SSE15206 is able to overcome resistance to chemotherapeutic drugs in different cancer cell lines including multidrug-resistant KB-V1 and A2780-Pac-Res cell lines overexpressing MDR-1, making it a promising hit for the lead optimization studies to target multidrug resistance.

Novel anti-cancer drug COTI-2 synergizes with therapeutic agents and does not induce resistance or exhibit cross-resistance in human cancer cell lines

Emerging drug-resistance and drug-associated toxicities are two major factors limiting successful cancer therapy. Combinations of chemotherapeutic drugs have been used in the clinic to improve patient outcome. However, cancer cells can acquire resistance to drugs, alone or in combination. Resistant tumors can also exhibit cross-resistance to other chemotherapeutic agents, resulting in sub-optimal treatment and/or treatment failure. Therefore, developing novel oncology drugs that induce no or little acquired resistance and with a favorable safety profile is essential. We show here that combining COTI-2, a novel clinical stage agent, with multiple chemotherapeutic and targeted agents enhances the activity of these drugs in vitro and in vivo. Importantly, no overt toxicity was observed in the combination treatment groups in vivo. Furthermore, unlike the tested chemotherapeutic drugs, cancer cells did not develop resistance to COTI-2. Finally, some chemo-resistant tumor cell lines only showed mild cross-resistance to COTI-2 while most remained sensitive to it.

Synthesis and biological evaluation of novel aliphatic acid-conjugated antimicrobial peptides as potential agents with anti-tumor, multidrug resistance-reversing activity and enhanced stability

Compared with traditional anti-tumor drugs, antimicrobial peptides as novel anti-tumor agents have prominent advantages of higher specificity and circumvention of multi-drug resistance. BP100 is a multifunctional membrane-active peptide with high antimicrobial activity. Taking BP100 as a lead peptide, we designed and synthesized a series of aliphatic chain-conjugated peptides through solid-phase synthesis. Biological evaluation revealed that these peptides exhibited better anti-cancer activity than BP100. Further investigations revealed that these peptides could disrupt the cell membrane and trigger the cytochrome C release into cytoplasm, which ultimately resulted in apoptosis. Meanwhile, these peptides also exhibited effective anti-tumor activity against multidrug resistant cells and had multidrug resistance-reversing effect. Additionally, conjugation of aliphatic acid to those peptides could enhance their stability in plasma. In conclusion, aliphatic acid-modified peptides might be promising anti-tumor agents for cancer therapy.