Innovative Nanoparticulate Strategies in Colon Cancer Treatment: A Paradigm Shift.

As a major public health issue, colorectal cancer causes 9.4% of total cancer-related deaths and comprises 10% of new cancer diagnoses worldwide. In the year 2023, an estimated 153,020 people are expected to receive an identification of colorectal cancer (CRC), resulting in roughly 52,550 fatalities anticipated as a result of this illness. Among those impacted, approximately 19,550 cases and 3750 deaths are projected to occur in individuals under the age of 50. Irinotecan (IRN) is a compound derived from the chemical structure of camptothecin, a compound known for its action in inhibiting DNA topoisomerase I. It is employed in the treatment strategy for CRC therapies. Comprehensive in vivo and in vitro studies have robustly substantiated the anticancer efficacy of these compounds against colon cancer cell lines. Blending irinotecan in conjunction with other therapeutic cancer agents such as oxaliplatin, imiquimod, and 5 fluorouracil enhanced cytotoxicity and improved chemotherapeutic efficacy. Nevertheless, it is linked to certain serious complications and side effects. Utilizing nano-formulated prodrugs within "all-in-one" carrier-free self-assemblies presents an effective method to modify the pharmacokinetics and safety portfolio of cytotoxic chemotherapeutics. This review focuses on elucidating the mechanism of action, exploring synergistic effects, and innovating novel delivery approaches to enhance the therapeutic efficacy of irinotecan.

Sacituzumab Govitecan: A Review in Unresectable or Metastatic HR+/HER2- Breast Cancer.

Sacituzumab govitecan (TRODELVY®) is a first-in-class trophoblast cell-surface antigen 2 (Trop-2)-directed antibody and topoisomerase I inhibitor conjugate that is approved globally as monotherapy for the treatment of adults with unresectable locally advanced or metastatic, hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-; defined as immunohistochemistry 0, 1+ or 2+ and in situ hybridization-negative) breast cancer who have received endocrine-based therapy and ≥ 2 additional systemic therapies in the advanced setting. In the phase III TROPiCS-02 trial, intravenous sacituzumab govitecan demonstrated statistically significant and clinically meaningful improvements in progression-free survival and overall survival compared with physician's choice of chemotherapy (capecitabine, eribulin, gemcitabine or vinorelbine) in adults with metastatic HR+/HER2- breast cancer. Sacituzumab govitecan had a generally manageable tolerability profile in these patients; the most common treatment-related grade ≥ 3 adverse events included neutropenia, diarrhoea, leukopenia, anaemia, fatigue and febrile neutropenia. Sacituzumab govitecan carries regulatory warnings for severe neutropenia and severe diarrhoea. Sacituzumab govitecan demonstrated an overall benefit in terms of health-related quality of life. Current evidence indicates that sacituzumab govitecan is an effective treatment option, with a generally manageable tolerability profile, for patients with pre-treated, unresectable locally advanced or metastatic HR+/HER2- breast cancer.

The most common type of breast cancer is hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2−), and management of metastatic (spread to areas near the breast or to other areas) HR+/HER2− breast cancer eventually requires chemotherapy or surgery if resistance develops. Intravenous sacituzumab govitecan (TRODELVY^®) is approved globally for adults with inoperable or metastatic HR+/HER2− breast cancer who have previously received endocrine therapy and ≥ 2 additional systemic therapies for advanced disease. In a clinical trial, sacituzumab govitecan therapy significantly improved the duration adults with metastatic HR+/HER2− breast cancer survived without their disease progressing, along with overall survival time, versus standard chemotherapy. The tolerability profile of sacituzumab govitecan was generally manageable; the most common side effects were decreased neutrophil count, diarrhoea and decreased white blood cell count. Sacituzumab govitecan can severely reduce neutrophil count and cause severe diarrhoea. Sacituzumab govitecan demonstrated an overall benefit in terms of health-related quality of life. Current evidence indicates that sacituzumab govitecan is an effective treatment option, with a generally manageable tolerability profile, for patients with pre-treated, inoperable or metastatic HR+/HER2− breast cancer.

Transcriptomic and proteomic study of cancer cell lines exposed to actinomycin D and nutlin-3a reveals numerous, novel candidates for p53-regulated genes.

Transcriptomic analyses have revealed hundreds of p53-regulated genes; however, these studies used a limited number of cell lines and p53-activating agents. Therefore, we searched for candidate p53-target genes by employing stress factors and cell lines never before used in a high-throughput search for p53-regulated genes. We performed RNA-Seq on A549 cells exposed to camptothecin, actinomycin D, nutlin-3a, as well as a combination of actinomycin D and nutlin-3a (A + N). The latter two substances synergise upon the activation of selected p53-target genes. A similar analysis was performed on other cell lines (U-2 OS, NCI-H460, A375) exposed to A + N. To identify proteins in cell lysates or those secreted into a medium of A549 cells in control conditions or treated with A + N, we employed mass spectrometry. The expression of selected genes strongly upregulated by A + N or camptothecin was examined by RT-PCR in p53-deficient cells and their controls. We found that p53 participates in the upregulation of: ACP5, APOL3, CDH3, CIBAR2, CRABP2, CTHRC1, CTSH, FAM13C, FBXO2, FRMD8, FRZB, GAST, ICOSLG, KANK3, KCNK6, KLRG2, MAFB, MR1, NDRG4, PTAFR, RETSAT, TMEM52, TNFRSF14, TRANK1, TYSND1, WFDC2, WFDC5, WNT4 genes. Twelve of these proteins were detected in the secretome and/or proteome of treated cells. Our data generated new hypotheses concerning the functioning of p53. Many genes activated by A + N or camptothecin are also activated by interferons, indicating a noticeable overlap between transcriptional programs of p53 and these antiviral cytokines. Moreover, several identified genes code for antagonists of WNT/ß-catenin signalling pathways, which suggests new connections between these two cancer-related signalling systems. One of these antagonists is DRAXIN. Previously, we found that its gene is activated by p53. In this study, using mass spectrometry and Western blotting, we detected expression of DRAXIN in a medium of A549 cells exposed to A + N. Thus, this protein functions not only in the development of the nervous system, but it may also have a new cancer-related function.

Tumor Microenvironment Activatable Nanoprodrug System for In Situ Fluorescence Imaging and Therapy of Liver Cancer.

The development of new imaging and treatment nanoprodrug systems is highly demanded for diagnosis and therapy of liver cancer, a severe disease characterized by a high recurrence rate. Currently, available small molecule drugs are not possible for cancer diagnosis because of the fast diffusion of imaging agents and low efficacy in treatment due to poor water solubility and significant toxic side effects. In this study, we report the development of a tumor microenvironment activatable nanoprodrug system for the diagnosis and treatment of liver cancer. This nanoprodrug system can accumulate in the tumor site and be selectively activated by an excess of hydrogen peroxide (H2O2) in the tumor microenvironment, releasing near-infrared solid-state organic fluorescent probe (HPQCY-1) and phenylboronic acid-modified camptothecin (CPT) prodrug. Both HPQCY-1 and CPT prodrugs can be further activated in tumor sites for achieving more precise in situ near-infrared (NIR) fluorescence imaging and treatment while reducing the toxic effects of drugs on normal tissues. Additionally, the incorporation of hydrophilic multivalent chitosan as a carrier effectively improved the water solubility of the system. This research thus provides a practical new approach for the diagnosis and treatment of liver cancer.

Bioreducible Amphiphilic Hyperbranched Polymer-Drug Conjugate for Intracellular Drug Delivery.

This paper reports synthesis of a bioreducible hyperbranched (HB) polymer by A2+B3 approach from commercially available dithiothreitol (DTT) (A2) and an easily accessible trifunctional monomer (B3) containing three reactive pyridyl-disulfide groups. Highly efficient thiol-activated disulfide exchange reaction leads to the formation of the HB polymer (Mw = 21000; D = 2.3) with bioreducible disulfide linkages in the backbone and two different functional groups, namely, hydroxyl and pyridyl-disulfide in the core and periphery, respectively, of the HB-polymer. Postpolymerization functionalization of the hydroxyl-groups with camptothecin (CPT), a topoisomerase inhibitor and known anticancer drug, followed by replacing the terminal pyridyl-disulfide groups with oligo-oxyethylene-thiol resulted in easy access to an amphiphilic HB polydisulfide-CPT conjugate (P1) with a very high drug loading content of ∼40%. P1 aggregated in water (above ∼10 µg/mL) producing drug-loaded nanoparticles (Dh ∼ 135 nm), which showed highly efficient glutathione (GSH)-triggered release of the active CPT. Mass spectrometry analysis of the GSH-treated P1 showed the presence of the active CPT drug as well as a cyclic monothiocarbonate product, which underpins the cascade-degradation mechanism involving GSH-triggered cleavage of the labile disulfide linkage, followed by intramolecular nucleophilic attack by the in situ generated thiol to the neighboring carbonate linkage, resulting in release of the active CPT drug. The P1 nanoparticle showed excellent cellular uptake as tested by confocal fluorescence microscopy in HeLa cells by predominantly endocytosis mechanism, resulting in highly efficient cell killing (IC50 ∼ 0.6 µg/mL) as evident from the results of the MTT assay, as well as the apoptosis assay. Comparative studies with an analogous linear polymer-CPT conjugate showed much superior intracellular drug delivery potency of the hyperbranched polymer.

Screening for cold tolerance genes in C. elegans, whose expressions are affected by anticancer drugs camptothecin and leptomycin B.

Temperature is a vital environmental factor affecting organisms' survival as they determine the mechanisms to tolerate rapid temperature changes. We demonstrate an experimental system for screening chemicals that affect cold tolerance in Caenorhabditis elegans. The anticancer drugs leptomycin B and camptothecin were among the 4000 chemicals that were screened as those affecting cold tolerance. Genes whose expression was affected by leptomycin B or camptothecin under cold stimuli were investigated by transcriptome analysis. Abnormal cold tolerance was detected in several mutants possessing genes that were rendered defective and whose expression altered after exposure to either leptomycin B or camptothecin. The genetic epistasis analysis revealed that leptomycin B or camptothecin may increase cold tolerance by affecting a pathway upstream of the insulin receptor DAF-2 that regulates cold tolerance in the intestine. Our experimental system combining drug and cold tolerance could be used for a comprehensive screening of genes that control cold tolerance at a low cost and in a short time period.

Glutathione - IR 797 coupled Casein Nano-Trojan for augmenting the therapeutic efficacy of camptothecin in highly invasive triple negative breast cancer.

The rapid metastasis & heterogenic constitution of triple negative breast cancer (TNBC) limits drug entry to the tumor, reducing treatment effectiveness. To address this, we have synthesized Casein nanoparticles (Cn NPs) with attached glutathione (GSH), a natural ligand for cancer cell overexpressed γ-glutamyl transpeptidase (GGT). Cn NPs encapsulated with Camptothecin and NIR dye IR 797 (CCN NPs) for combinatorial therapy of TNBC. The GSH-CCN nanoparticles (CCNG NPs) act as a Nano-Trojan to deceive the cancer cells by delivering therapeutic payloads directly to specific target cells. In this study, Casein Nano-Trojan is equipped with GSH as a targeting ligand for GGT. The binding of CCNG NPs with cell surface receptors switched the anionic charge to catanionic, prompting the target cell to engulf the nanoparticles. The Casein Nano-Trojan releases its therapeutic payload inside the target cell, potentially inhibiting proliferation & inducing a high percentage of cell death (85 ± 7 %). Disintegration of mitochondrial membrane potential, inhibition of both migration & re-growth were observed. Immunofluorescence, acridine orange/ethidium bromide stain, and nuclear fragmentation assay further confirmed the substantial DNA damage induced by the high expression of γH2AX and p53. Significant therapeutic efficacy was observed in the 3D spheroids of 4T1 cells and in vivo breast cancer mice model (BALB/c). These findings demonstrate that CCNG NPs could be an effective treatment approach for highly metastatic triple negative breast cancer.

Bimetallic Gold/Silver and Bioactive Camptothecin Hybrid Nanoparticles for Eradication of Cancer Stem Cells in a Combination Manner.

The defeat of cancer is still a challenge due to the existence of cancer stem cells (CSCs) because they resist conventional chemotherapy via multifactor regulated mechanisms. Consequently, one-dimensional action toward CSCs cannot work. Herein, we used rationally designed hybrid nanoparticles as a combined cancer therapy, hoping to form a multidimensional control network. In this paper, gold/silver alloy nanoparticle decorated camptothecin nanocrystals were formulated according to complementary anti-CSC mechanisms from gold, silver, and organic drug. This smart drug formulation could combine chemotherapy and thermotherapy, target different tumor sites, and demonstrate versatile toxicity profiles from each component. Major results indicated that this nanosystem demonstrated indiscriminately effective cytotoxic/proapoptotic/necrotic activity against bulk MCF-7 cells and their CSC subpopulation, in particular under laser ablation. Moreover, this nanosystem displayed enhanced antineoplastic activity against CSC spheroids, resulting in a significant reduction in their number and size, that is, their self-renewal capacity. All the results indicated that CSCs upon treatment of these new hybrid nanoparticles underwent reduced stemness and conversion from the original quiescent state and recovered their sensitivity toward chemotherapy. The relevant anticancer mechanism was ascribed to NIR-pH dual responsive drug release, synergistic/combined thermo-chemotherapy of organic drug and inorganic alloy nanoparticles, enhanced cellular uptake mediated by alloy nanoparticles, and Ag+-induced biomembrane damage. This thermo-chemotherapy platform provides a new combinatorial strategy for inorganic and organic agents in the complete elimination of CSCs.

Facile synthesis and cytotoxicity of substituted uracil-1'(N)-acetic acid and 4-pyridone-1'(N)-acetic acid esters of 20(S)-camptothecins.

A series of novel substituted uracil-1'(N)-acetic acid esters (5-9) and 4-pyridone-1'(N)-acetic acid esters (10-11) of 20(S)-camptothecins (CPTs) have been synthesized by the acylation method. All of these new esters were assayed for in vitro cytotoxicity against five human cancer cell lines A549, Bel7402, BGC-823, HCT-8 and A2780. The in vitro bioassay results showed that all the synthesized compounds 5-11 had cytotoxities that were higher than TPT and comparable to CPT on these five tumor cell lines, some of them even showed comparable or superior cytotoxic activity to CPT. The in vitro data exhibited the cytotoxicity of the ester depended on that of its parent compound. The ester 5, 6, 8, 10, 11 even possessed the cytotoxity activity comparable to or even a little better than CPT on A549, HCT-8 and A2780. The compound 11 had the same level of cytoxity on Bel7402 as that of CPT. Here the synthesis and the in vitro antitumor evaluation of a series of novel 20-O-linked substituted uracil-1'(N)-acetic acid and 4-pyridone-1'(N)-acetic acid esters derivatives of CPTs are reported.

pH-Responsive Micellar Nanoparticles for the Delivery of a Self-Amplifying ROS-Activatable Prodrug.

The objective of this study is to enhance the therapeutic efficacy of the anticancer drug, camptothecin (CPT) via a nanoparticle (NP) formulation using a novel amphiphilic biopolymer. We have designed a dimeric prodrug of CPT with the ability to self-amplify and respond to reactive oxygen species (ROS). For this, we incorporated the intracellular ROS generator cinnamaldehyde into a ROS-cleavable thioacetal (TA) linker to obtain the dimeric prodrug of CPT (DCPT(TA)). For its efficient NP delivery, a pH-responsive block copolymer of acetalated dextran and poly(2-ethyl-2-oxazoline) (AcDex-b-PEOz) was synthesized. The amphiphilic feature of the block copolymer enables its self-assembly into micellar NPs and results in high prodrug loading capacity and a rapid release of the prodrug under acidic conditions. Upon cellular uptake by HeLa cells, DCPT(TA)-loaded micellar NPs induce intracellular ROS generation, resulting in accelerated prodrug activation and enhanced cytotoxicity. These results indicate that this system holds significant potential as an effective prodrug delivery strategy in anticancer treatment.

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.

Camptothecin structure simplification elaborated new imidazo[2,1-b]quinazoline derivative as a human topoisomerase I inhibitor with efficacy against bone cancer cells and colon adenocarcinoma.

Camptothecin is a pentacyclic natural alkaloid that inhibits the hTop1 enzyme involved in DNA transcription and cancer cell growth. Camptothecin structure pitfalls prompted us to design new congeners using a structure simplification strategy to reduce the ring extension number from pentacyclic to tetracyclic while maintaining potential stacking of the new compounds with the DNA base pairs at the Top1-mediated cleavage complex and aqueous solubility, as well as minimizing compound-liver toxicity. The principal axis of this study was the verification of hTop1 inhibiting activity as a possible mechanism of action and the elaboration of new simplified inhibitors with improved pharmacodynamic and pharmacokinetic profiling using three structure panels (A-C) of (isoquinolinoimidazoquinazoline), (imidazoquinazoline), and (imidazoisoquinoline), respectively. DNA relaxation assay identified five compounds as hTop1 inhibitors belonging to the imidazoisoquinolines 3a,b, the imidazoquinazolines 12, and the isoquinolinoimidazoquinazolines 7a,b. In an MTT cytotoxicity assay against different cancer cell lines, compound 12 was the most potent against HOS bone cancer cells (IC50 = 1.47 µM). At the same time, the other inhibitors had no detectable activity against any cancer cell type. Compound (12) demonstrated great penetrating power in the HOS cancer cells' 3D-multicellular tumor spheroid model. Bioinformatics research of the hTop1 gene revealed that the TP53 cell proliferative gene is in the network of hTop1. The finding is confirmed empirically using the gene expression assay that proved the increase in p53 expression. The impact of structure simplification on compound 12 profile, characterized by the absence of acute oral liver toxicity when compared to Doxorubicin as a standard inhibitor, the lethal dose measured on Swiss Albino female mice and reported at LD50 = 250 mg/kg, and therapeutic significance in reducing colon adenocarcinoma tumor volume by 75.36 % after five weeks of treatment with compound 12. The molecular docking solutions of the active CPT-based derivative 12 and the inactive congener 14 into the active site of hTop1 and the activity cliffing of such MMP directed us to recommend the addition of HBD and HBA variables to compound 12 imidazoquinazoline core scaffold to enhance the potency via hydrogen bond formation with the major groove amino acids (Asp533, Lys532) as well as maintaining the hydrogen bond with the minor groove amino acid Arg364.

Camptothecin bioprocessing from Aspergillus terreus, an endophyte of Catharanthus roseus: antiproliferative activity, topoisomerase inhibition and cell cycle analysis.

Attenuation of camptothecin (CPT) productivity by fungi with preservation and subculturing is the challenge that halts fungi to be an industrial platform of CPT production. Thus, screening for novel endophytic fungal isolates with metabolic stability for CPT production was the objective. Catharanthus roseus is one of the medicinal plants with diverse bioactive metabolites that could have a plethora of novel endophytes with unique metabolites. Among the endophytes of C. roseus, Aspergillus terreus EFBL-NV OR131583.1 had the most CPT producing potency (90.2 µg/l), the chemical identity of the putative CPT was verified by HPLC, FT-IR, NMR and LC-MS/MS. The putative A. terreus CPT had the same molecular mass (349 m/z), and molecular fragmentation patterns of the authentic one, as revealed from the MS/MS analyses. The purified CPT had a strong activity against MCF7 (5.27 µM) and UO-31 (2.2 µM), with a potential inhibition to Topo II (IC50 value 0.52 nM) than Topo 1 (IC50 value 6.9 nM). The CPT displayed a high wound healing activity to UO-31 cells, stopping their metastasis, matrix formation and cell immigration. The purified CPT had a potential inducing activity to the cellular apoptosis of UO-31 by ~ 17 folds, as well as, arresting their cellular division at the S-phase, compared to the control cells. Upon Plackett-Burman design, the yield of CPT by A. terreus was increased by ~ 2.6 folds, compared to control. The yield of CPT by A. terreus was sequentially suppressed with the fungal storage and subculturing, losing ~ 50% of their CPT productivity by 3rd month and 5th generation. However, the productivity of the attenuated A. terreus culture was completely restored by adding 1% surface sterilized leaves of C. roseus, and the CPT yield was increased over-the-first culture by ~ 3.2 folds (315.2 µg/l). The restoring of CPT productivity of A. terreus in response to indigenous microbiome of C. roseus, ensures the A. terreus-microbiome interactions, releasing a chemical signal that triggers the CPT productivity of A. terreus. This is the first reports exploring the potency of A. terreus, endophyte of C. roseus" to be a platform for industrial production of CPT, with an affordable sustainability with addition of C. roseus microbiome.

Raludotatug Deruxtecan, a CDH6-Targeting Antibody-Drug Conjugate with a DNA Topoisomerase I Inhibitor DXd, Is Efficacious in Human Ovarian and Kidney Cancer Models.

Cadherin-6 (CDH6) is expressed in several cancer types, but no CDH6-targeted therapy is currently clinically available. Here, we generated raludotatug deruxtecan (R-DXd; DS-6000), a novel CDH6-targeting antibody-drug conjugate with a potent DNA topoisomerase I inhibitor, and evaluated its properties, pharmacologic activities, and safety profile. In vitro pharmacologic activities and the mechanisms of action of R-DXd were assessed in serous-type ovarian cancer and renal cell carcinoma cell lines. In vivo pharmacologic activities were evaluated with several human cancer cell lines and patient-derived xenograft mouse models. The safety profile in cynomolgus monkeys was also assessed. R-DXd exhibited CDH6 expression-dependent cell growth-inhibitory activity and induced tumor regression in xenograft models. In this process, R-DXd specifically bound to CDH6, was internalized into cancer cells, and then translocated to the lysosome. The DXd released from R-DXd induced the phosphorylation of Chk1, a DNA damage marker, and cleaved caspase-3, an apoptosis marker, in cancer cells. It was also confirmed that the DXd payload had a bystander effect, passing through the cell membrane and impacting surrounding cells. The safety profile of R-DXd was favorable and the highest non-severely toxic dose was 30 mg/kg in cynomolgus monkeys. R-DXd demonstrated potent antitumor activity against CDH6-expressing tumors in mice and an acceptable safety profile in monkeys. These findings indicate the potential of R-DXd as a new treatment option for patients with CDH6-expressing serous-type ovarian cancer and renal cell carcinoma in a clinical setting.

Tight-Binding Small-Molecule Carboxylesterase 2 Inhibitors Reduce Intracellular Irinotecan Activation.

As the primary enzyme responsible for the activatable conversion of Irinotecan (CPT-11) to SN-38, carboxylesterase 2 (CES2) is a significant predictive biomarker toward CPT-11-based treatments for pancreatic ductal adenocarcinoma (PDAC). High SN-38 levels from high CES2 activity lead to harmful effects, including life-threatening diarrhea. While alternate strategies have been explored, CES2 inhibition presents an effective strategy to directly alter the pharmacokinetics of CPT-11 conversion, ultimately controlling the amount of SN-38 produced. To address this, we conducted a high-throughput screening to discover 18 small-molecule CES2 inhibitors. The inhibitors are validated by dose-response and counter-screening and 16 of these inhibitors demonstrate selectivity for CES2. These 16 inhibitors inhibit CES2 in cells, indicating cell permeability, and they show inhibition of CPT-11 conversion with the purified enzyme. The top five inhibitors prohibited cell death mediated by CPT-11 when preincubated in PDAC cells. Three of these inhibitors displayed a tight-binding mechanism of action with a strong binding affinity.

CaERF1- mediated ABA signal positively regulates camptothecin biosynthesis by activating the iridoid pathway in Camptotheca acuminata.

Camptotheca acuminata is one of the primary sources of camptothecin (CPT), which is widely used in the treatment of human malignancies because of its inhibitory activity against DNA topoisomerase I. Although several transcription factors have been identified for regulating CPT biosynthesis in other species, such as Ophiorrhiza pumila, the specific regulatory components controlling CPT biosynthesis in C. acuminata have yet to be definitively determined. In this study, CaERF1, an DREB subfamily of the APETALA2/ethylene response factors (AP2ERFs), was identified in C. acuminata. The transient overexpression and silencing of CaERF1 in C. acuminata leaves confirmed that it positively regulates the accumulation of CPT by inducing the expression of CaCYC1 and CaG8O in the iridoid pathway. Results of transient transcriptional activity assay and yeast one-hybrid assays have showed that CaERF1 transcriptionally activates the expression of CaCYC1 and CaG8O by binding to RAA and CEI elements in the promoter regions of these two genes. Furthermore, the expression of CaCYC1 and CaG8O in CaERF1-silenced leaves was less sensitive to ABA treatment, indicating that CaERF1 is a crucial component involved in ABA-regulated CPT biosynthesis in C. acuminata.

SN-38, an active metabolite of irinotecan, inhibits transcription of nuclear factor erythroid 2-related factor 2 and enhances drug sensitivity of colorectal cancer cells.

Nuclear factor erythroid 2-related factor 2 (Nrf2) significantly contributes to drug resistance of cancer cells, and Nrf2 inhibitors have been vigorously pursued. Repurposing of existing drugs, especially anticancer drugs, is a straightforward and promising strategy to find clinically available Nrf2 inhibitors and effective drug combinations. Topoisomerase inhibitors SN-38 (an active metabolite of irinotecan), topotecan, mitoxantrone, and epirubicin were found to significantly suppress Nrf2 transcriptional activity in cancer cells. SN-38, the most potent one among them, significantly inhibited the transcription of Nrf2, as indicated by decreased mRNA level and binding of RNA polymerase II to NFE2L2 gene, while no impact on Nrf2 protein or mRNA degradation was observed. SN-38 synergized with Nrf2-sensitive anticancer drugs such as mitomycin C in killing colorectal cancer cells, and irinotecan and mitomycin C synergistically inhibited the growth of SW480 xenografts in nude mice. Our study identified SN-38 and three other topoisomerase inhibitors as Nrf2 inhibitors, revealed the Nrf2-inhibitory mechanism of SN-38, and indicate that clinically feasible drug combinations could be designed based on their interactions with Nrf2 signaling.

Novel GSH-responsive prodrugs derived from indole-chalcone and camptothecin trigger apoptosis and autophagy in colon cancer.

Antineoplastic agents that target tubulin have shown efficacy as chemotherapeutic drugs, yet they are often constrained by multidrug resistance (MDR) and unwanted side effects. A multi-targeted strategy demonstrates great potency in reducing toxicity and enhancing efficacy and provides an alternative way for attenuating MDR. In this study, a series of dual-targeted anti-cancer agents based on indole-chalcone derivatives and the camptothecin (CPT) scaffold were synthesized. Among them, 14-1 demonstrated superior anti-proliferative activity than its precursor 13-1, CPT or their physical mixtures against tested cancer cells, including multidrug-resistant variants, while exhibited moderate cytotoxicity toward human normal cells. Mechanistic studies revealed that 14-1 acted as a glutathione-responsive prodrug, inducing apoptosis by substantially enhancing intracellular uptake of CPT, inhibiting tubulin polymerization, increasing the accumulation of intracellular reactive oxygen species, and initiating a mitochondrion-dependent apoptotic pathway. Moreover, 14-1 notably induced autophagy and suppressed topoisomerase I activity to further promote apoptosis. Importantly, 14-1 displayed potent inhibitory effect on tumor growth in paclitaxel (PTX)-resistant colorectal cancer (HCT-116/PTX) xenograft models without inducing obvious toxicity compared with CPT- or combo-treated group. These results suggest that 14-1 holds promise as a novel candidate for anti-cancer therapy, particularly in PTX-resistant cancers.

Natural products fragment-based design and synthesis of a novel pentacyclic ring system as potential MAPK inhibitor.

The synthesis of compounds based on fragments derived from natural products (NPs) serves as a source of inspiration for the design of pseudo-natural products (PNPs), to identify bioactive molecules that exhibit similar characteristics to NPs. These novel molecular scaffolds exhibit previously unexplored biological activities as well. This study reports the development and synthesis of a novel pentacyclic ring system, the indole-pyrimidine-quinoline (IPQ) scaffold. The design of this scaffold was based on the structural characteristics of four natural products, namely tryptanthrin, luotonin A, rutaecarpine, and camptothecin. Several successive steps accomplished the effective synthesis of the IPQ scaffold. The constituent components of the pentacycle, containing the indole, quinazolinone, pyrimidone, and quinoline units, possess significant biological significance. Compound 1a demonstrated noteworthy anti-tumor activity efficacy against A549 cell lines among the tested compounds. The compound 1a was observed to elicit cell cycle arrest in both the G2/M and S phases, as well as trigger apoptosis in A549 cells. These effects were attributed to its ability to modulate the activation of mitochondrial-related mitogen-activated protein kinase (MAPK) signaling pathways.

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.