Camptothecins

Biotechnological approaches for the production of camptothecin

Camptothecin (CPT), an indole alkaloid popular for its anticancer property, is considered the third most promising drug after taxol and famous alkaloids from Vinca for the treatment of cancer in humans. Camptothecin was first identified in Camptotheca acuminata followed by several other plant species and endophytic fungi. Increased harvesting driven by rising global demand is depleting the availability of elite plant genotypes, such as Camptotheca acuminata and Nothapodytes nimmoniana, crucial for producing alkaloids used in treating diseases like cancer. Conservation of these genotypes for the future is imperative. Therefore, research on different plant tissue culture techniques such as cell suspension culture, hairy roots, adventitious root culture, elicitation strategies, and endophytic fungi has been adopted for the production of CPT to meet the increasing demand without affecting the source plant's existence. Currently, another strategy to increase camptothecin yield by genetic manipulation is underway. The present review discusses the plants and endophytes that are employed for camptothecin production and throws light on the plant tissue culture techniques for the regeneration of plants, callus culture, and selection of cell lines for the highest camptothecin production. The review further explains the simple, accurate, and cost-effective extraction and quantification methods. There is enormous potential for the sustainable production of CPT which could be met by culturing of suitable endophytes or plant cell or organ culture in a bioreactor scale production. Also, different gene editing tools provide opportunities for engineering the biosynthetic pathway of CPT, and the overall CPT production can be improved . KEY POINTS: • Camptothecin is a naturally occurring alkaloid with potent anticancer properties, primarily known for its ability to inhibit DNA topoisomerase I. • Plants and endophytes offer a potential approach for camptothecin production. • Biotechnology approaches like plant tissue culture techniques enhanced camptothecin production.

Discovery of novel quinoline scaffold selective estrogen receptor degraders (SERDs) for treatment of ER positive breast cancer with enhanced antiproliferative bioactivity through immunogenic cell death (ICD) effects

Combination therapy proven to be an effective therapeutic approach for estrogen receptor (ER)-positive breast cancer. Currently, cyclin-dependent kinase 4/6 (CDK4/6) inhibitors are combined with aromatase inhibitors (AIs) or selective estrogen receptor degraders (SERDs) as first-line therapy for advanced ER-positive breast cancer. Herein, a new family of quinoline scaffold SERDs was synthesized and evaluated in MCF-7 cells. Among them, compounds 18j and 24d exhibited remarkable MCF-7 inhibition, both alone and in combination with ribociclib (CDK4/6 inhibitor), in vitro and in vivo. Meanwhile, compounds 18j and 24d effectively degraded ER and inhibited ER downstream signaling pathways. Interestingly, compounds 18j and 24d induced endoplasmic reticulum stress (ERS) and triggered immunogenic cell death (ICD) via damage-associated molecular patterns (DAMPs) in MCF-7 cells. These findings highlight the immune-related and enhanced antiproliferative effects of oral SERDs in ER positive breast cancer treatment.

Recent advances of tryptanthrin and its derivatives as potential anticancer agents

Tryptanthrin is one of the well-known natural alkaloids with a broad spectrum of biological activities and can act as anti-inflammatory, anticancer, antibacterial, antifungal, antiviral, antitubercular, and other agents. Owing to its potent anticancer activity, tryptanthrin has been widely explored for the therapy of various cancers besides being effective against other diseases. Tryptanthrin with a pharmacological indoloquinazoline moiety can not only be modified by different functional groups to achieve various tryptanthrin derivatives, which may realize the improvement of anticancer activity, but also bind with different metal ions to obtain varied tryptanthrin metal complexes as potential anticancer agents, due to their higher anticancer activities in comparison with tryptanthrin (or its derivatives) and cisplatin. This review outlines the recent advances in the syntheses, structures, and anticancer activities of tryptanthrin derivatives and their metal complexes, trying to reveal their structure-activity relationships and to provide a helpful way for medicinal chemists in the development of new and effective tryptanthrin-based anticancer agents.

N-methyl-D-aspartate receptors and thymoquinone induce apoptosis and alteration in mitochondria in colorectal cancer cells

Colon cancer is on the rise in both men and women. In addition to traditional treatment methods, herbal treatments from complementary and alternative medicine are actively followed. Naturally derived from plants, thymoquinone (TQ) has drawn a lot of attention in the field of cancer treatment. MK-801, an N-methyl-D-aspartate agonist, is used to improve memory and plasticity, but it has also lately been explored as a potential cancer treatment. This study aimed to determine the roles of N-Methyl-D-Aspartate agonists and Thymoquinone on mitochondria and apoptosis. HT-29 cells were treated with different TQ and MK-801 concentrations. We analyzed cell viability, apoptosis, and alteration of mitochondria. Cell viability significantly decreased depending on doses of TQ and MK-801. Apoptosis and mitochondrial dysfunctions induced by low and high doses of TQ and MK-801. Our study emphasizes the need for further safety evaluation of MK-801 due to the potential toxicity risk of TQ and MK-801. Optimal and toxic doses of TQ and MK-801 were determined for the treatment of colon cancer. It should be considered as a possibility that colon cancer can be treated with TQ and MK-801.

Formulating 10-hydroxycamptothecin into nanoemulsion with functional excipient tributyrin: An innovative strategy for targeted hepatic cancer chemotherapy

This study aimed to develop an innovative dosage form for 10-hydroxycamptothecin (HCPT), a chemotherapeutic agent with limited aqueous solubility and stability, to enhance its parenteral delivery and targeting to hepatic cancer. We formulated HCPT into a nanoemulsion using tributyrin, a dietary component with histone deacetylase inhibitor activity. The resulting HCPT-loaded tributyrin nanoemulsion (Tri-HCPT-E) underwent extensive evaluations. Tri-HCPT-E significantly improved the aqueous solubility, stability, and anti-cancer activities in HepG2 cells. Pharmacokinetic studies confirmed the increased stability and hepatic targeting, with Tri-HCPT-E leading to a 120-fold increase in plasma exposure of intact HCPT and a 10-fold increase in hepatic exposure compared to the commercial free solution. Co-administration of 17α-ethynylestradiol, an up-regulator of low-density lipoprotein (LDL) receptor, further enhanced the distribution and metabolism of HCPT, demonstrating an association between the LDL receptor pathway and hepatic targeting. Most importantly, Tri-HCPT-E exhibited superior in vivo anti-cancer efficacy in a mouse xenograft model compared to the commercial formulation, without causing escalated hepatic or renal toxicity. In conclusion, formulating HCPT into a nanoemulsion with tributyrin has proven to be an innovative and effective strategy for targeted hepatic cancer chemotherapy while tributyrin, a pharmacologically active dietary component, has emerged as a promising functional excipient for drug delivery.

Unleashing the Potential of Camptothecin: Exploring Innovative Strategies for Structural Modification and Therapeutic Advancements

Camptothecin (CPT) is a potent anti-cancer agent targeting topoisomerase I (TOP1). However, CPT has poor pharmacokinetic properties, causes toxicities, and leads to drug resistance, which limit its clinical use. In this paper, to review the current state of CPT research. We first briefly explain CPT's TOP1 inhibition mechanism and the key hurdles in CPT drug development. Then we examine strategies to overcome CPT's limitations through structural modifications and advanced delivery systems. Though modifications alone seem insufficient to fully enhance CPT's therapeutic potential, structure-activity relationship analysis provides insights to guide optimization of CPT analogs. In comparison, advanced delivery systems integrating controlled release, imaging capabilities, and combination therapies via stimulus-responsive linkers and targeting moieties show great promise for improving CPT's pharmacological profile. Looking forward, multifaceted approaches combining selective CPT derivatives with advanced delivery systems, informed by emerging biological insights, hold promise for fully unleashing CPT's anti-cancer potential.

Design and Evaluation of Phosphonamidate-Linked Exatecan Constructs for Highly Loaded, Stable, and Efficacious Antibody-Drug Conjugates

Topoisomerase I (TOP1) Inhibitors constitute an emerging payload class to engineer antibody-drug conjugates (ADC) as next-generation biopharmaceutical for cancer treatment. Existing ADCs are using camptothecin payloads with lower potency and suffer from limited stability in circulation. With this study, we introduce a novel camptothecin-based linker-payload platform based on the highly potent camptothecin derivative exatecan. First, we describe general challenges that arise from the hydrophobic combination of exatecan and established dipeptidyl p-aminobenzyl-carbamate (PAB) cleavage sites such as reduced antibody conjugation yields and ADC aggregation. After evaluating several linker-payload structures, we identified ethynyl-phosphonamidates in combination with a discrete PEG24 chain to compensate for the hydrophobic PAB-exatecan moiety. Furthermore, we demonstrate that the identified linker-payload structure enables the construction of highly loaded DAR8 ADCs with excellent solubility properties. Head-to-head comparison with Enhertu, an approved camptothecin-based ADC, revealed improved target-mediated killing of tumor cells, excellent bystander killing, drastically improved linker stability in vitro and in vivo and superior in vivo efficacy over four tested dose levels in a xenograft model. Moreover, we show that ADCs based on the novel exatecan linker-payload platform exhibit antibody-like pharmacokinetic properties, even when the ADCs are highly loaded with eight drug molecules per antibody. This ADC platform constitutes a new and general solution to deliver TOP1 inhibitors with highest efficiency to the site of the tumor, independent of the antibody and its target, and is thereby broadly applicable to various cancer indications.

Novel HER2-targeted therapy to overcome trastuzumab resistance in HER2-amplified gastric cancer

Trastuzumab is used to treat HER2-amplified metastatic gastric cancer; however, most patients become trastuzumab-resistant within a year. Knowledge of the mechanisms underlying trastuzumab resistance is required to overcome this limitation. Here, we aimed to elucidate this resistance mechanism using four trastuzumab-resistant (TR) cell lines and investigate the efficacy of HER2-targeted therapies to overcome treatment resistance. Each TR cell line had different phenotypic characteristics. Interestingly, HER2 expression remained as high as the parental cell lines in TR cell lines, suggesting that HER2-targeted agents were still useful. As expected, three tyrosine kinase inhibitors (lapatinib, neratinib, and tucatinib) and one antibody-drug conjugate (trastuzumab deruxtecan: T-DXd) exhibited good antitumor effects against TR cell lines. We further investigated the potential biological mechanism of T-DXd. When treated with trastuzumab or T-DXd, HER2 or its downstream signals were disrupted in parental cell lines, but not in TR cell lines. Moreover, T-DXd induced the expression of pH2A.X and cPARP and caused cell cycle arrest in the S or G2-M phase in TR cell lines. T-DXd showed promising antitumor activity in both parental and TR cell lines, suggesting that it is a potential candidate for overcoming trastuzumab resistance.

Natural product inspired leads in the discovery of anticancer agents: an update

Natural products have emerged as major leads for the discovery and development of new anti-cancer drugs. The plant-derived anti-cancer drugs account for approximately 60% and the quest for new anti-cancer agents is in progress. Anti-cancer leads have been isolated from plants, animals, marine organisms, and microorganisms from time immemorial. The process of semisynthetic modifications of the parent lead has led to the generation of new anti-cancer agents with improved therapeutic efficacy and minimal side effects. The various chemo-informatics tools, bioinformatics, high-throughput screening, and combinatorial synthesis are able to deliver the new natural product lead molecules. Plant-derived anticancer agents in either late preclinical development or early clinical trials include taxol, vincristine, vinblastine, topotecan, irinotecan, etoposide, paclitaxel, and docetaxel. Similarly, anti-cancer agents from microbial sources include dactinomycin, bleomycin, mitomycin C, and doxorubicin. In this review, we highlighted the importance of natural products leads in the discovery and development of novel anti-cancer agents. The semisynthetic modifications of the parent lead to the new anti-cancer agent are also presented. Further, the leads in the preclinical settings with the potential to become effective anticancer agents are also reviewed.Communicated by Ramaswamy H. Sarma.

Adamantoid Scaffolds for Multiple Cargo Loading and Cellular Delivery as β-Cyclodextrin Inclusion Complexes

There is huge demand for developing guests that bind β-CD and can conjugate multiple cargos for cellular delivery. We synthesized trioxaadamantane derivatives, which can conjugate up to three cargos per guest. 1 H NMR titration and isothermal titration calorimetry revealed these guests form 1 : 1 inclusion complexes with β-CD with association constants in the order of 103  M-1 . Co-crystallization of β-CD with guests yielded crystals of their 1 : 1 inclusion complexes as determined by single-crystal X-ray diffraction. In all cases, trioxaadamantane core is buried within the hydrophobic cavity of β-CD and three hydroxyl groups are exposed outside. We established biocompatibility using representative candidate G4 and its inclusion complex with β-CD (β-CD⊂G4), by MTT assay using HeLa cells. We incubated HeLa cells with rhodamine-conjugated G4 and established cellular cargo delivery using confocal laser scanning microscopy (CLSM) and fluorescence-activated cell sorting (FACS) analysis. For functional assay, we incubated HeLa cells with β-CD-inclusion complexes of G4-derived prodrugs G6 and G7, containing one and three units of the antitumor drug (S)-(+)-camptothecin, respectively. Cells incubated with β-CD⊂G7 displayed the highest internalization and uniform distribution of camptothecin. β-CD⊂G7 showed higher cytotoxicity than G7, camptothecin, G6 and β-CD⊂G6, affirming the efficiency of adamantoid derivatives in high-density loading and cargo delivery.

In Situ Encapsulation of Camptothecin by Self-Assembly of Poly(acrylic acid)-b-Poly(N-Isopropylacrylamide) and Chitosan for Controlled Drug Delivery

Camptothecin (CPT) has been shown to exhibit anticancer activity against several cancers. Nevertheless, CPT is very hydrophobic with poor stability, and thus its medical application is limited. Therefore, various drug carriers have been exploited for effectively delivering CPT to the targeted cancer site. In this study, a dual pH/thermo-responsive block copolymer of poly(acrylic acid-b-N-isopropylacrylamide) (PAA-b-PNP) was synthesized and applied to encapsulate CPT. At temperatures above its cloud point, the block copolymer self-assembled to form nanoparticles (NPs) and in situ encapsulate CPT, owing to their hydrophobic interaction as evidenced by fluorescence spectrometry. Chitosan (CS) was further applied on the surface through the formation of a polyelectrolyte complex with PAA for improving biocompatibility. The average particle size and zeta potential of the developed PAA-b-PNP/CPT/CS NPs in a buffer solution were 168 nm and -30.6 mV, respectively. These NPs were still stable at least for 1 month. The PAA-b-PNP/CS NPs exhibited good biocompatibility toward NIH 3T3 cells. Moreover, they could protect the CPT at pH 2.0 with a very slow-release rate. At pH 6.0, these NPs could be internalized by Caco-2 cells, followed by intracellular release of the CPT. They became highly swollen at pH 7.4, and the released CPT was able to diffuse into the cells at higher intensity. Among several cancer cell lines, the highest cytotoxicity was observed for H460 cells. As a result, these environmentally-responsive NPs have the potential to be applied in oral administration.

Copper(II)-Catalyzed Synthesis of Pyrrolo[3,4-b]quinolinediones from o-Amino Carbonyl Compounds and Maleimides

A copper(II)-catalyzed cascade synthesis of 1H-pyrrolo[3,4-b]quinoline-1,3(2H)-diones has been achieved from readily available o-amino carbonyl compounds and maleimides. This one-pot cascade strategy involves a copper-catalyzed aza-Michael addition followed by condensation and oxidation to deliver the target molecules. The protocol features a broad substrate scope and excellent functional group tolerance and affords products in moderate to good (44-88%) yields.

Camptothecin-Loaded and Manganese Dioxide-Coated Polydopamine Nanomedicine Used for Magnetic Resonance Imaging Diagnosis and Chemo-Photothermal Therapy for Lung Cancer

Introduction

Camptothecin (CPT) is a cytotoxic quinolone alkaloid (isolated from a traditional Chinese medicine Camptotheca acuminata), used for the treatment of various malignancies, which inhibits DNA topoisomerase I (Topo I). However, its drawbacks, such as poor water solubility, stability, and highly toxic side effects, limit its clinical application. Therefore, CPT needs to be prepared as a nanomedicine to improve solubility, reduce side effects, and synergize with other therapies to improve efficacy.

Methods

In this work, we constructed CPT NPs (nanoparticles), which were CPT-loaded and manganese dioxide (MnO₂)-coated polydopamine (PDA) nanomedicine. In vitro, we explored the antitumor effect including CPT NPs-induced cell proliferation inhibition, apoptosis and ferroptosis for tumor cell lines. In vivo, we established LLC tumor-bearing mice model to evaluate their tumor imaging and anticancer effects.

Results

CPT NPs improve the water solubility and stability of CPT and reduce its toxic effects. It has good biocompatibility, excellent photothermal conversion ability for photothermal therapy (PTT) and pH release in the tumor microenvironment. It can inhibit tumor cell proliferation, induce apoptosis and result in ferroptosis of tumor cells. More significantly, this nanomedicine can provide information for the location and diagnosis of tumors via magnetic resonance imaging. In general, the nanomedicine integrated with diagnosis and treatment has excellent anticancer effect.

Discussion

Altogether, this nanomedicine possesses the ability to diagnose and therapy through magnetic resonance imaging and chemo-photothermal therapy, respectively. In addition, the integrated diagnosis and treatment nanomedicine has potential clinical application prospects through treating lung cancer with high efficiency and low side effect. It can support the construction of related nano-delivery systems.

Engineering Multishelled Nanostructures Enables Stepwise Self-Degradability for Drug-Release Optimization

The balance between degradability and drug release kinetics is a major challenge for the development of drug delivery systems. Here we develop hierarchically structured nanoparticles comprising multiple noncontact silica shells using an amorphous calcium carbonate template. The system could be degraded in a sequential fashion on account of the molecularly engineered multishelled structures. The hydrolysis rate of drug-containing cores is inversely correlated with the nanoparticle concentration due to the shielding effect of the hierarchical nanostructure and could be exploited to regulate the release kinetics. Specifically, multishelled nanospheres show a low drug release rate with high doses that increases steadily as the concentration decreases due to continuous degradation, thus stabilizing the local drug concentration for effective tumor therapy. Moreover, the nanoparticles could be eventually degraded completely, which may reduce their health risks. This kind of hierarchically structured silica-based nanoparticle could serve as a sustainable drug depot and provides a new avenue for tumor treatment.

Natural products in drug discovery and development: Synthesis and medicinal perspective of leonurine

Natural products, those molecules derived from nature, have been used by humans for thousands of years to treat ailments and diseases. More recently, these compounds have inspired chemists to use natural products as structural templates in the development of new drug molecules. One such compound is leonurine, a molecule isolated and characterized in the tissues of Herb leonuri. This molecule has received attention from scientists in recent years due to its potent anti-oxidant, anti-apoptotic, and anti-inflammatory properties. More recently researchers have shown leonurine to be useful in the treatment of cardiovascular and nervous system diseases. Like other natural products such as paclitaxel and artemisinin, the historical development of leonurine as a therapeutic is very interesting. Therefore, this review provided an overview of natural product discovery, through to the development of a potential new drug. Content will summarize known plant sources, the pathway used in the synthesis of leonurine, and descriptions of leonurine’s pharmacological properties in mammalian systems.

Pulmonary delivery of liposomes co-loaded with SN38 prodrug and curcumin for the treatment of lung cancer

A co-delivery system of SN38 (7-ethyl-10-hydroxyl camptothecin) prodrug and CUR (curcumin) was designed for the treatment of lung cancer by pulmonary delivery. SN38 was linked to cell-penetrating peptide (CPP) TAT via a polyethylene glycol (PEG) linker to form the SN38 prodrug (TAT-PEG-SN38). Liposomes co-loaded with amphiphilic TAT-PEG-SN38 and curcumin (Lip-TAT-PEG-SN38/CUR) were successfully prepared by a microfluidic method for the treatment of lung cancer via pulmonary delivery. Lip-TAT-PEG-SN38/CUR showed nanometer-sized sphericity and a particle size of 171.21 nm. Besides, Lip-TAT-PEG-SN38/CUR exhibited enhanced antiproliferative effect, increased cell apoptosis induction and improved cell cycle arrest compared to the single agents in vitro. The combination induced significant tumor inhibition in a BALB/c mouse lung cancer model. These results indicated that our SN38 prodrug and curcumin co-delivery system was a promising candidate for lung cancer treatment.

C60 Fullerene Clusters Stabilize the Biologically Inactive Form of Topotecan

There is a range of experimental proofs that biologically relevant compounds change their activity in the presence of C₆₀ fullerene clusters in aqueous solution, which most frequently act as a nanoplatform for drug delivery. Inspired by this evidence, we made an effort to investigate the interaction of fullerene clusters with the antibiotic topotecan (TPT). This study proceeded in three steps, namely, UV/vis titration to confirm complexation and in vitro assays on proliferating and nonproliferating cells to elucidate the role of C₆₀ fullerene in the putative change in TPT activity. Surprisingly, although the nonproliferating cell assay is consistent with the titration data and confirms complex formation, it contradicted the results of the proliferating cell assay. The latter showed that the mixture of TPT and fullerene affects the cells in the same way as pure TPT, as if there were no fullerenes in solution at all, whereas the action of TPT was expected to be enhanced. We explained this contradiction by the specific stabilization of the biologically inactive carboxylate form of the antibiotic adsorbed in the alkaline shell of large fullerene clusters, which leads to neutralization of the drug delivery function and almost zero net biological effect of the antibiotic in vitro. The practical outcome of the work is that fullerene clusters can be used for the selective delivery of pH-sensitive drug forms.

Anti-tumor pharmacology of natural products targeting mitosis

Cancer has been an insurmountable problem in the history of medical science. The uncontrollable proliferation of cancer cells is one of cancer’s main characteristics, which is closely associated with abnormal mitosis. Targeting mitosis is an effective method for cancer treatment. This review summarizes several natural products with anti-tumor effects related to mitosis, focusing on targeting microtubulin, inducing DNA damage, and modulating mitosis-associated kinases. Furthermore, the main disadvantages of several typical compounds, including drug resistance, toxicity to non-tumor tissues, and poor aqueous solubility and pharmacokinetic properties, are also discussed, together with strategies to address them. Improved understanding of cancer cell mitosis and natural products may pave the way to drug development for the treatment of cancer.

Tumor-targeted/reduction-triggered composite multifunctional nanoparticles for breast cancer chemo-photothermal combinational therapy

Breast cancer has become the most commonly diagnosed cancer type in the world. A combination of chemotherapy and photothermal therapy (PTT) has emerged as a promising strategy for breast cancer therapy. However, the intricacy of precise delivery and the ability to initiate drug release in specific tumor sites remains a challenging puzzle. Therefore, to ensure that the therapeutic agents are synchronously delivered to the tumor site for their synergistic effect, a multifunctional nanoparticle system (PCRHNs) is developed, which is grafted onto the prussian blue nanoparticles (PB NPs) by reduction-responsive camptothecin (CPT) prodrug copolymer, and then modified with tumor-targeting peptide cyclo(Asp-d-Phe-Lys-Arg-Gly) (cRGD) and hyaluronic acid (HA). PCRHNs exhibited nano-sized structure with good monodispersity, high load efficiency of CPT, triggered CPT release in response to reduction environment, and excellent photothermal conversion under laser irradiation. Furthermore, PCRHNs can act as a photoacoustic imaging contrast agent-guided PTT. In vivo studies indicate that PCRHNs exhibited excellent biocompatibility, prolonged blood circulation, enhanced tumor accumulation, allow tumor-specific chemo-photothermal therapy to achieve synergistic antitumor effects with reduced systemic toxicity. Moreover, hyperthermia-induced upregulation of heat shock protein 70 in the tumor cells could be inhibited by CPT. Collectively, PCRHNs may be a promising therapeutic way for breast cancer therapy.

Synthesis and Prediction of Antitumor Activity of New Fused Pyrano[3,4-c]pyridines and Pyrano[4′,3′:4,5]pyrido[2,3-d]pyrimidines

Abstract

One-pot methods were developed for the preparation of 6-amino-3-isopropyl-7-aryl substituted-8-thioxo(oxo)pyrano[3,4-c]pyridines derivatives. The latter served as starting materials for the synthesis of a new pyrano[4′,3′:4,5]pyrido[2,3-d]pyrimidine heterosystems. The proposed mechanisms of one-pot reactions were presented. Antitumor activity of new synthesized compounds was predicted by in silico methods.

Can Exposure to Environmental Pollutants Be Associated with Less Effective Chemotherapy in Cancer Patients?

Since environmental pollutants are ubiquitous and many of them are resistant to degradation, we are exposed to many of them on a daily basis. Notably, these pollutants can have harmful effects on our health and be linked to the development of disease. Epidemiological evidence together with a better understanding of the mechanisms that link toxic substances with the development of diseases, suggest that exposure to some environmental pollutants can lead to an increased risk of developing cancer. Furthermore, several studies have raised the role of low-dose exposure to environmental pollutants in cancer progression. However, little is known about how these compounds influence the treatments given to cancer patients. In this work, we present a series of evidences suggesting that environmental pollutants such as bisphenol A (BPA), benzo[a]pyrene (BaP), persistent organic pollutants (POPs), aluminum chloride (AlCl₃), and airborne particulate matter may reduce the efficacy of some common chemotherapeutic drugs used in different types of cancer. We discuss the potential underlying molecular mechanisms that lead to the generation of this chemoresistance, such as apoptosis evasion, DNA damage repair, activation of pro-cancer signaling pathways, drug efflux and action of antioxidant enzymes, among others.

Engineering Cellular Membrane for Dual Mode Therapy Using NIR Responsive Photosensitizer and Reversible Topoisomerase Inhibition Activity

Extensive research over past few decades has highlighted the challenges of chemotherapy and prompted the need for multimodality therapy because chemotherapy alone cannot fully eradicate the tumor due to physiological barriers in its effective delivery and systemic side effects. It can be mitigated by adopting nanoparticles as more effective delivery method, but none of them completely prevents drug toxicities. Utilizing multiple therapeutic modes such as phototherapy that can act synergistically with chemotherapy in controlling tumor growth, while reducing the overall dosage, could become a preferred route for cancer management. Careful selection of nanoparticle system, which can simultaneously deliver both drug and photosensitizer, can significantly enhance the therapeutic outcome. Therefore, in this paper, we report development and potential of immune-compatible and long circulating nanoerythrosomes for enhancing the therapeutic potential of camptothecin and indocyanine green against murine cancer model. The RBCs membrane simultaneously loaded the nonpolar drug and amphiphilic photosensitizer in its lipid bilayer, which self-assembled to form stable nanoparticles. These nano constructs absorbed light in the near-infrared region and hence are suitable for targeting deep seated tissues. The dual chemo-phototherapy had great effect on cell viability and had therapeutic value.

Electrochemical Selective C3-Thiolation of Quinolines

An electrochemical method has been developed to achieve C3-thiolation of quinoline compounds. This new strategy highlights the maximum atom economy, direct conversion and also the use of simple and readily...

A designed cyclic peptide based on Trastuzumab used to construct peptide-drug conjugates for its HER2-targeting ability

Human epidermal growth factor receptor 2 (HER2) has been recognized as an important therapeutic target for its overexpression in many cancers. Trastuzumab is a monoclonal antibody targeting HER2, which has been approved by FDA to treat HER2-positive cancer. In this research, cyclic peptide Cyclo-GCGPep1 was designed based on the binding mode between antibody and HER2 protein in silico, which has been confirmed possessing good affinity with HER2. Cyclo-GCGPep1 was also used to construct peptide-drug conjugates with Camptothecin. Biological evaluations demonstrated that Conjugate 1 has a good antiproliferative activity on SK-BR-3 and NCI-N87 cells. Conjugate 1 retained the pro-apoptotic and Topo I inhibitory ability of Camptothecin. Meanwhile, it has good targeting ability towards HER2-positive cells with the help of Cyclo-GCGPep1. It also has better permeability in the tumor spheroid model than Camptothecin. In summary, the design of cyclic peptide derived from antibody is of significance for the discovery of targeting peptides and Conjugate 1 is expected as a good therapeutic agent for HER2-positive cancers.

Design and Applications of Tumor Microenvironment-Responsive Nanogels as Drug Carriers

In recent years, the exploration of tumor microenvironment has provided a new approach for tumor treatment. More and more researches are devoted to designing tumor microenvironment-responsive nanogels loaded with therapeutic drugs. Compared with other drug carriers, nanogel has shown great potential in improving the effect of chemotherapy, which is attributed to its stable size, superior hydrophilicity, excellent biocompatibility, and responsiveness to specific environment. This review primarily summarizes the common preparation techniques of nanogels (such as free radical polymerization, covalent cross-linking, and physical self-assembly) and loading ways of drug in nanogels (including physical encapsulation and chemical coupling) as well as the controlled drug release behaviors. Furthermore, the difficulties and prospects of nanogels as drug carriers are also briefly described.

Valproic Acid and Breast Cancer: State of the Art in 2021

Valproic acid (2-propylpentanoic acid, VPA) is a short-chain fatty acid, a member of the group of histone deacetylase inhibitors (HDIs). VPA has been successfully used in the treatment of epilepsy, bipolar disorders, and schizophrenia for over 50 years. Numerous in vitro and in vivo pre-clinical studies suggest that this well-known anticonvulsant drug significantly inhibits cancer cell proliferation by modulating multiple signaling pathways. Breast cancer (BC) is the most common malignancy affecting women worldwide. Despite significant progress in the treatment of BC, serious adverse effects, high toxicity to normal cells, and the occurrence of multi-drug resistance (MDR) still limit the effective therapy of BC patients. Thus, new agents which improve the effectiveness of currently used methods, decrease the emergence of MDR, and increase disease-free survival are highly needed. This review focuses on in vitro and in vivo experimental data on VPA, applied individually or in combination with other anti-cancer agents, in the treatment of different histological subtypes of BC.

Divergent camptothecin biosynthetic pathway in Ophiorrhiza pumila

BACKGROUND

The anticancer drug camptothecin (CPT), first isolated from Camptotheca acuminata, was subsequently discovered in unrelated plants, including Ophiorrhiza pumila. Unlike known monoterpene indole alkaloids, CPT in C. acuminata is biosynthesized via the key intermediate strictosidinic acid, but how O. pumila synthesizes CPT has not been determined.

RESULTS

In this study, we used nontargeted metabolite profiling to show that 3α-(S)-strictosidine and 3-(S), 21-(S)-strictosidinic acid coexist in O. pumila. After identifying the enzymes OpLAMT, OpSLS, and OpSTR as participants in CPT biosynthesis, we compared these enzymes to their homologues from two other representative CPT-producing plants, C. acuminata and Nothapodytes nimmoniana, to elucidate their phylogenetic relationship. Finally, using labelled intermediates to resolve the CPT biosynthesis pathway in O. pumila, we showed that 3α-(S)-strictosidine, not 3-(S), 21-(S)-strictosidinic acid, is the exclusive intermediate in CPT biosynthesis.

CONCLUSIONS

In our study, we found that O. pumila, another representative CPT-producing plant, exhibits metabolite diversity in its central intermediates consisting of both 3-(S), 21-(S)-strictosidinic acid and 3α-(S)-strictosidine and utilizes 3α-(S)-strictosidine as the exclusive intermediate in the CPT biosynthetic pathway, which differs from C. acuminata. Our results show that enzymes likely to be involved in CPT biosynthesis in O. pumila, C. acuminata, and N. nimmoniana have evolved divergently. Overall, our new data regarding CPT biosynthesis in O. pumila suggest evolutionary divergence in CPT-producing plants. These results shed new light on CPT biosynthesis and pave the way towards its industrial production through enzymatic or metabolic engineering approaches.

Quinoline anticancer agents active on DNA and DNA-interacting proteins: From classical to emerging therapeutic targets

Quinoline is one of the most important and versatile nitrogen heterocycles embodied in several biologically active molecules. Within the numerous quinolines developed as antiproliferative agents, this review is focused on compounds interfering with DNA structure or with proteins/enzymes involved in the regulation of double helix functional processes. In this light, a special focus is given to the quinoline compounds, acting with classical/well-known mechanisms of action (DNA intercalators or Topoisomerase inhibitors). In particular, the quinoline drugs amsacrine and camptothecin (CPT) have been studied as key lead compounds for the development of new agents with improved PK and tolerability properties. Moreover, notable attention has been paid to the quinoline molecules, which are able to interfere with emerging targets involved in cancer progression, as G-quadruplexes or the epigenetic ones (e.g.: histone deacetylase, DNA and histones methyltransferase). The antiproliferative and the enzymatic inhibition data of the reviewed compounds have been analyzed. Furthermore, concerning the SAR (structure-activity relationship) aspects, the most recurrent ligand-protein interactions are summarized, underling the structural requirements for each kind of mechanism of action.

Synthesis, molecular modeling and biological evaluation of new benzo[4,5]thieno[3,2-b]pyran derivatives as topoisomerase I-DNA binary complex poisons

A series of new benzo[b]thiophenes 2a-f and benzo[4,5]thieno[3,2-b]pyran derivatives 3a-f and 4a-f were synthesized and their structures were confirmed by elemental analyses and spectral data. All synthesized compounds were evaluated by the National Cancer Institute (NCI, USA) against 60 human tumor cell lines. Compounds 3a-f and 4a-f showed potent cytotoxic effects in one dose assay with mean growth inhibition ranging from 62% to 80%. Six compounds 3a, 3d, 3e, 3f, 4d and 4e were selected by NCI, USA for five dose evaluation against 60 human tumor cell lines. Compounds 3a, 3d, 3e and 3f exhibited very potent and broad spectrum cytotoxicity against almost all cancer cell lines with mean concentration that yield 50% growth inhibition (MG-MID GI₅₀) of 0.1-0.58 µM and mean concentration that produce 100% growth inhibition (MG-MID TGI) of 6.03-10.00 µM. Compounds 4d and 4e exhibited very potent and selective cytotoxic activity against MDA-MB-435 subpanel (melanoma cancer) with GI₅₀ of 0.45 µM and 0.59 µM, respectively. The mechanism of antiproliferative activity was determined for the most active compounds 3a, 3d, 3e, 3f, 4d, and 4evia measuring their half maximal inhibitory concentration (IC₅₀) against topoisomerase I enzyme at different concentrations. Compounds 3a and 3e exhibited excellent activity compared with reference drugs with IC₅₀ of 0.295 µM and 0.219 µM, respectively. Plasmid DNA nicking assay verified that these compounds are topoisomerase I poisons not suppressors. The active compound 3e induced a significant disruption in the cell cycle profile parallel to its effect on apoptosis induction.

Polymeric micelles coated with hybrid nanovesicles enhance the therapeutic potential of the reversible topoisomerase inhibitor camptothecin in a mouse model

Nanoparticles with longer blood circulation, high loading capacity, controlled release at the targeted site, and preservation of camptothecin (CPT) in its lactone form are the key characteristics for the effective delivery of CPT. In this regard, natural membrane-derived nanovesicles, particularly those derived from RBC membrane, are important. RBC membrane can be engineered to form vesicles or can be coated over synthetic nanoparticles, without losing their basic structural features and can have prolonged circulation time. Here, we developed a hybrid system to encapsulate CPT inside the amphiphilic micelle and coat it with RBC membrane. Thus, it uses the dual ability of polymeric micelles to preserve CPT in its active form, while maintaining its "stealth" effect due to conserved RBC membrane coating. The hybrid system stabilized 60% of the drug in its active form even after 30 h of incubation in serum, in contrast to 15% active form present in free drug formulation after 1 h of incubation. It showed strong retention inside the Ehrlich Ascites Carcinoma (EAC) mice models for at least 72 h, suggesting camouflaging ability conferred by RBC membrane. Additionally, the nano formulation retarded the tumor growth rate more efficiently than free drug, with no evident signs of necrotic skin lesions. Histopathological analysis showed a significant reduction in cardiac atrophy, hepato-renal degeneration, and lung metastasis, which resulted in the increased overall survival of mice treated with the nano formulation. Hence, CPT-loaded polymeric micelles when coated with RBC membrane can prove to be a better system for the delivery of poorly soluble drug camptothecin.

Dynamics of delivering aptamer targeted nano-drugs into cells

A targeted nano-drug delivery system has provided great potential and benefits to the diagnosis and therapy of cancers. Cell entry is a critical step for taking effect of the targeted nano-drug. In this report, the dynamics of delivering a single aptamer targeted polyamindoamine-camptothecin-AS1411 (PAMAM-CPT-AS1411) nano-drug into cells was investigated using a force tracing technique based on atomic force microscopy. The results show that the specific interaction of AS1411 and nucleolin, which is overexpressed on cancer cells, enhances the efficiency of the PAMAM-CPT-AS1411 cell entry. Moreover, the specific interaction induced receptor-mediated endocytosis prolongs the duration and decreases the speed of a single PAMAM-CPT-AS1411 cell entry, which is helpful to understand the targeted nano-drugs prolonging the therapeutic drug level. However, the required force for PAMAM-CPT-AS1411 cell entry is not changed. This report will provide a novel and potential method for achieving the precise dynamics of targeted nano-drug delivery.

Crystal Growth, Single Crystal Structure, and Biological Activity of Thiazolo-Pyridine Dicarboxylic Acid Derivatives

Four novel TPDCA derivatives were prepared via a supersaturation method combining TPDCA with water, N-methyl-2-pyrrolidone (NMP), Na(PO₂H₂), and ammonia solution: 2(C₉H₇NO₅S)H₂O (1), (C₉H₇NO₅S)C₅H₉NO (2), (C₉H₇NO₅S)Na(PO₂H₂) (3), and (C₉H₅NO₅S)(NH₄)₂(H₂O) (4). Their crystal structures were determined by single-crystal X-ray diffraction. Compounds (1) and (2) crystallize in the monoclinic space groups P2₁ and P2₁/c, respectively, whereas compounds (3) and (4) crystallize in the triclinic space group P1̅. Weak and moderate hydrogen bonds were detected in the four compounds. In the biological tests, (1) and (3) exhibited significant antibacterial activity against Escherichia coli and Staphylococcus aureus; in addition, (1) was cytotoxic against leukemia HL-60 cells with the IC₅₀ value of 158.5 ± 12.5 μM.

RBMX is required for activation of ATR on repetitive DNAs to maintain genome stability

ATR is a master regulator of cell response to replication stress. Adequate activation of ATR is essential for preventing genome aberrance induced by replication defect. However, the mechanism underlying ATR activation is not fully understood. Here, we identify that RBMX is an ssDNA binding protein that orchestrates a novel pathway to activate ATR. Using super-resolution STORM, we observe that RBMX and RPA bind to adjacent but nonoverlapping sites on ssDNA in response to replication stress. RBMX then binds to and facilitates positioning of TopBP1, which activates nearby ATR associated with RPA. In addition, ATR activation by ssDNA-RBMX-TopBP1 is independent of ssDNA-dsDNA junction and 9-1-1 complex. ChIP-seq analysis reveals that RBMX/RPA are highly enriched on repetitive DNAs, which are considered as fragile sites with high replication stress. RBMX depletion leads to defective localization of TopBP1 to replication stressed sites and inadequate activation of ATR. Furthermore, cells with deficient RBMX demonstrate replication defect, leading to formation of micronuclei and a high rate of sister-chromatin exchange, indicative of genome instability. Together, the results identify a new ssDNA-RBMX-TopBP1 pathway that is specifically required for activation of ATR on repetitive DNAs. Therefore, RBMX is a key factor to ensure genome stability during replication.

Palladium(ii) complexes with thiosemicarbazones derived from pyrene as topoisomerase IB inhibitors

New palladium complexes with thiosemicarbazonate ligands derived from pyrene exhibit potent antiproliferative activity against A2780 and cisplatin-resistant A2780Cis human ovarian cancer cells, which is dependent on substituent groups of the thiosemicarbazone ligands. Cellular accumulation and distribution studies confirmed that palladium enters the cell nucleus. DNA and topoisomerase IB studies show that one complex is a potent TopIB inhibitor, with selectivity for cancer versus normal cells.

Novel polymeric micelles as enzyme-sensitive nuclear-targeted dual-functional drug delivery vehicles for enhanced 9-nitro-20(S)-camptothecin delivery and antitumor efficacy

9-Nitro-20(S)-camptothecin (9-NC) is a broad-spectrum antitumor drug used in tumor treatments, but its clinical applications and antitumor efficacy are limited by its structural instability, poor solubility, and extremely low drug utilization in tumor tissues. In this study, enzyme-sensitive nuclear-targeted dual-functional polymeric micelles were developed for 9-NC delivery with a high drug loading content (12.93 ± 0.88%), steady-state circulation, and a rapid attack at the "heart" of tumor cells. Briefly, chrysin (CHR) as a π-conjugated moiety was immobilized on the PCL terminal in the TAT-PCL amphiphiles and combined with the ALAL peptide as a linker on HA chains to yield the ultimate CHR-PCL-TAT-ALAL-HA (HATPC) amphiphiles. Spherical 9-NC-loaded micelles were obtained from the self-assembly of the dual-functional amphiphiles comprising HATPC and 9-NC with uniform nanosize (121.6 ± 5.79 nm), well-distributed morphology (PDI: 0.256), and negative surface charge (-23.2 ± 0.5 mV), yielding high stability during blood circulation. In this drug delivery system, HA acts as an active tumor-targeting instrument via CD44-receptor-mediated endocytosis; further, the ALAL peptide could be cutoff in the lysosomes of the tumor cells due to the high expression of cathepsin B, leading to lysosomal escape, while the secondary polymeric micelles targeted the tumor cell nucleus via the exposed TAT peptide. The enzyme sensitivity and nuclei targetability of the 9-NC/HATPC micelles were confirmed by dynamic light scattering and confocal laser scanning microscopy analyses. As compared to free 9-NC and traditional mPEG2k-PCL2k polymeric micelles, 9-NC/HATPC micelles were the most concentrated in the tumor cell nucleus; therefore, they exhibited the highest cytotoxicity against SKOV3 tumor cells both in vitro (IC50 = 0.03 μg mL-1) and in vivo. This enzyme-sensitive nuclear-targeted dual-functional drug delivery system involving HATPC provided a new and promising strategy for enhanced 9-NC delivery and antitumor efficacy.

Sub-10 nm Theranostic Unimolecular Micelles with High Tumor-Specific Accumulation, Retention, and Inhibitory Effect

Theranostic agents that integrate far-red/near-infrared fluorescence and anticancer drugs are useful for biomedical applications such as imaging-guided therapy of cancers. However, the clinical translation of previously reported theranostic agents is still limited by factors such as weak fluorescence of the imaging probe, premature and off-target release of fluorophores and drugs during blood circulation, the long-term retention in the reticuloendothelial system, and side effects of toxicity. Here, we report a new type of ultrasmall theranostic unimolecular micelles with an average diameter below 10 nm, and dual functionalities of bright fluorescence in the spectral window of 600-800 nm toward noninvasive in vivo bioimaging and covalently bound anticancer drugs for specific cancer treatment. Each unimolecular micelle is formed by an amphiphilic bottlebrush copolymer containing a fluorescent conjugated backbone of poly(fluorene-alt-(4,7-bis(hexylthien)-2,1,3-benzothiadiazole)), from which hydrophobic disulfide-linked camptothecin as an anticancer drug and hydrophilic oligo(ethylene glycol) are grafted. These ultrasmall unimolecular micelles exhibit remarkably high efficiency of accumulation and retention in tumor tissues with a tumor inhibitory rate of 50%, but little distribution in other healthy organs and tissues. Such a feature of enhanced tumor targeting and reduced toxic side effects against healthy cells and tissues is promising for future clinical translation of imaging-guided cancer therapy.

Substitution-Inert Polynuclear Platinum Complexes with Dangling Amines: Condensation/Aggregation of Nucleic Acids and Inhibition of DNA-Related Enzymatic Activities

The substitution-inert polynuclear platinum complexes (SI-PPCs) are now recognized as a distinct subclass of platinum anticancer drugs with high DNA binding affinity. Here, we investigate the effects of SI-PPCs containing dangling amine groups in place of NH₃ as ligands to increase the length of the molecule and therefore overall charge and its distribution. The results obtained with the aid of biophysical techniques, such as total intensity light scattering, gel electrophoresis, and atomic force microscopy, show that addition of dangling amine groups considerably augments the ability of SI-PPCs to condense/aggregate nucleic acids. Moreover, this enhanced capability of SI-PPCs correlates with their heightened efficiency to inhibit DNA-related enzymatic activities, such as those connected with DNA transcription, catalysis of DNA relaxation by DNA topoisomerase I, and DNA synthesis catalyzed by Taq DNA polymerase. Thus, the addition of the dangling amine groups resulting in structures of SI-PPCs, which differ so markedly from the derivatives of cisplatin used in the clinic, appears to contribute to the overall biological activity of these molecules.