Vascular disrupting activity of combretastatin analogues

Combretastatin A-4 based compounds as potential anticancer agents: A review

The current review discusses the importance of combretastatin A-4 (CA-4) as a lead compound of microtubule targeting agents. CA-4 holds a unique place among naturally occurring compounds having cytotoxic activity. In this review an overall picture of design strategies, structure-activity relationship, synthesis, cytotoxic activity, and binding interactions of promising CA-4 analogues, are discussed and arranged chronologically from 2016 to early 2023. Also, this review emphasizes their biological activity as anticancer agents, within an overview of clinical application limitation and suggested strategies to overcome. Dual targeting tubulin inhibitors showed highpotentialto surpass medication resistance and provide synergistic efficacy. Linking platinum (IV), amino acids, and HDAC targeting moieties to active tubulin inhibitorsproduced potent active compounds. Analogues of CA-4 bridged with azetidin-2-one, pyrazole, sulfide, or carrying selenium atom exhibited cytotoxic action against a variety of malignant cell lines through different pathways.

Proteomic Analysis of Chicken Chorioallantoic Membrane (CAM) during Embryonic Development Provides Functional Insight

In oviparous animals, the egg contains all resources required for embryonic development. The chorioallantoic membrane (CAM) is a placenta-like structure produced by the embryo for acid-base balance, respiration, and calcium solubilization from the eggshell for bone mineralization. The CAM is a valuable in vivo model in cancer research for development of drug delivery systems and has been used to study tissue grafts, tumor metastasis, toxicology, angiogenesis, and assessment of bacterial invasion. However, the protein constituents involved in different CAM functions are poorly understood. Therefore, we have characterized the CAM proteome at two stages of development (ED12 and ED19) and assessed the contribution of the embryonic blood serum (EBS) proteome to identify CAM-unique proteins. LC/MS/MS-based proteomics allowed the identification of 1470, 1445, and 791 proteins in CAM (ED12), CAM (ED19), and EBS, respectively. In total, 1796 unique proteins were identified. Of these, 175 (ED12), 177 (ED19), and 105 (EBS) were specific to these stages/compartments. This study attributed specific CAM protein constituents to functions such as calcium ion transport, gas exchange, vasculature development, and chemical protection against invading pathogens. Defining the complex nature of the CAM proteome provides a crucial basis to expand its biomedical applications for pharmaceutical and cancer research.

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.

Discovery of novel 2-aryl-3-sulfonamido-pyridines (HoAns) as microtubule polymerization inhibitors with potent antitumor activities

Microtubules play a vital role in cell mitosis. Drugs targeting taxol or vinca binding site of tubulin have been proved an effective way to against cancer. However, drug resistance and cancer recurrence are inevitable, there is an urgent need to search for new microtubule-targeting agents (MTAs). In our study, a series of novel 2-aryl-3-sulfonamido-pyridines (HoAns) had been designed, synthesized, and evaluated for their antiproliferative activities in vitro and in vivo. Among them, compound HoAn32 exhibited the most potent activity with IC₅₀ values ranging from 0.170 to 1.193 μM in a panel of cancer cell lines. Mechanism studies indicated that compound HoAn32 bound to the colchicine site of β-tubulin, resulting in colony formation inhibition, G2/M phase cell cycle arrest, cell apoptosis as well as increased the generation of ROS in both RKO and SW620 cells. In addition, compound HoAn32 showed potent anti-vascular activity in vitro. Furthermore, compound HoAn32 also exhibited outstanding antitumor activity in SW620 xenograft tumor models without observable toxic effects, which was more potent than that of ABT-751. In conclusion, our findings suggest that compound HoAn32 may be a promising microtubule destabilizing agent and deserves for further development in cancer therapy.

Vascular disrupting agents in cancer therapy

Tumor blood vessel formation is a key process for tumor expansion. Tumor vessels are abnormal and differ from normal vessels in architecture and components. Besides oxygen and nutrients supply, the tumor vessels system, due to its abnormality, is responsible for: hypoxia formation, and metastatic routes. Tumor blood vessels can be a target of anti-cancer therapies. There are two types of therapies that target tumor vessels. The first one is the inhibition of the angiogenesis process. However, the inhibition is often ineffective because of alternative angiogenesis mechanism activation. The second type is a specific targeting of existing tumor blood vessels by vascular disruptive agents (VDAs). There are three groups of VDAs: microtubule destabilizing drugs, flavonoids with anti-vascular functions, and tumor vascular targeted drugs based on endothelial cell receptors. However, VDAs possess some limitations. They may be cardiotoxic and their application in therapy may leave viable residual, so called, rim cells on the edge of the tumor. However, it seems that a well-designed combination of VDAs with other anti-cancer drugs may bring a significant therapeutic effect. In this article, we describe three groups of vascular disruptive agents with their advantages and disadvantages. We mention VDAs clinical trials. Finally, we present the current possibilities of VDAs combination with other anti-cancer drugs.

Combretastatins: An Overview of Structure, Probable Mechanisms of Action and Potential Applications

Combretastatins are a class of closely related stilbenes (combretastatins A), dihydrostilbenes (combretastatins B), phenanthrenes (combretastatins C) and macrocyclic lactones (combretastatins D) found in the bark of Combretum caffrum (Eckl. & Zeyh.) Kuntze, commonly known as the South African bush willow. Some of the compounds in this series have been shown to be among the most potent antitubulin agents known. Due to their structural simplicity many analogs have also been synthesized. Combretastatin A4 phosphate is the most frequently tested compounds in preclinical and clinical trials. It is a water-soluble prodrug that the body can rapidly metabolize to combretastatin A4, which exhibits anti-tumor properties. In addition, in vitro and in vivo studies on combretastatins have determined that these compounds also have antioxidant, anti-inflammatory and antimicrobial effects. Nano-based formulations of natural or synthetic active agents such as combretastatin A4 phosphate exhibit several clear advantages, including improved low water solubility, prolonged circulation, drug targeting properties, enhanced efficiency, as well as fewer side effects. In this review, a synopsis of the recent literature exploring the combretastatins, their potential effects and nanoformulations as lead compounds in clinical applications is provided.

Usefulness of melatonin as complementary to chemotherapeutic agents at different stages of the angiogenic process

Chemotherapeutics are sometimes administered with drugs, like antiangiogenic compounds, to increase their effectiveness. Melatonin exerts antitumoral actions through antiangiogenic actions. We studied if melatonin regulates the response of HUVECs to chemotherapeutics (docetaxel and vinorelbine). The inhibition that these agents exert on some of the processes involved in angiogenesis, such as, cell proliferation, migratory capacity or vessel formation, was enhanced by melatonin. Regarding to estrogen biosynthesis, melatonin impeded the negative effect of vinorelbine, by decreasing the activity and expression of aromatase and sulfatase. Docetaxel and vinorelbine increased the expression of VEGF-A, VEGF-B, VEGF-C, VEGFR-1, VEGFR-3, ANG1 and/or ANG-2 and melatonin inhibited these actions. Besides, melatonin prevented the positive actions that docetaxel exerts on the expression of other factors related to angiogenesis like JAG1, ANPEP, IGF-1, CXCL6, AKT1, ERK1, ERK2, MMP14 and NOS3 and neutralized the stimulating actions of vinorelbine on the expression of FIGF, FGFR3, CXCL6, CCL2, ERK1, ERK2, AKT1, NOS3 and MMP14. In CAM assay melatonin inhibited new vascularization in combination with chemotherapeutics. Melatonin further enhanced the chemotherapeutics-induced inhibition of p-AKT and p-ERK and neutralized the chemotherapeutics-caused stimulatory effect on HUVECs permeability by modifying the distribution of VE cadherin. Our results confirm that melatonin blocks proangiogenic and potentiates antiangiogenic effects induced by docetaxel and vinorelbine enhancing their antitumor effectiveness.

Synthesis and bioevaluation of new vascular-targeting and anti-angiogenic thieno[2,3-d]pyrimidin-4(3H)-ones

A series of forty-six 5,6-annulated 2-arylthieno [2,3-d]pyrimidin-4(3H)-ones were prepared as potentially pleiotropic anticancer drugs with variance in the tubulin-binding trimethoxyphenyl motif at C-2 of a thieno [2,3-d]pyrimidine fragment, enlarged by additional rings of different size and substitution. By assessing their cytotoxicity against various cancer cells, their influence on the polymerization of neat tubulin and the dynamics of microtubule and F-actin cytoskeletons, and their vascular-disrupting and anti-angiogenic activities in vitro and in vivo, structure-activity relations were identified which suggest the 3-iodo-4,5-dimethoxyphenyl substituted thienopyrimidine 2e as a promising anticancer drug candidate for further research. 2020 Elsevier Ltd. All rights reserved.

Positioning Remodeling Nanogels Mediated Codelivery of Antivascular Drug and Autophagy Inhibitor for Cooperative Tumor Therapy

Tumor vasculature and enhanced autophagy collectively provide the source of nutrients for tumor growth, invasion, and metastasis. Blocking the source of nutrients will be a novel and promising antitumor approach. Herein, we exploited an intelligent nanogel (CA4-FeAlg/HCQ) with a positioning remodeling feature to precisely kill A549 cancer cells in all directions based on frontal and rear attack strategies. CA4-FeAlg/HCQ nanogels could remain stable during blood circulation. When they reached the tumor vascular site, the vascular blocker combretastatin A4 (CA4) would be released at first to exert an antiangiogenic effect. Thereafter, FeAlg/HCQ disintegrated into small nanogels (<30 nm) for tumor deep penetration. Once small nanogels entered tumor cells, FeAlg/HCQ would undergo phase remodeling (gel to sol) to release the autophagy inhibitor hydroxychloroquine (HCQ) quickly. The autophagy induced by CA4 can be effectively inhibited by HCQ to achieve synergistic treatment of tumors. In addition, after Fe³⁺ in FeAlg being reduced to Fe²⁺, it catalyzed intratumoral hydrogen peroxide (H₂O₂) to generate cytotoxic hydroxyl radicals (·OH), which further strengthened the antitumor effect. The in vivo pharmacodynamic result revealed that CA4-FeAlg/HCQ showed the greatest therapeutic effect, with the final V/V₀ of 0.40 ± 0.10. Our study provided a hopeful platform for rational and precise tumor treatment, which may be of great significance in the combined pharmacotherapy.

Melatonin Enhances the Usefulness of Ionizing Radiation: Involving the Regulation of Different Steps of the Angiogenic Process

Radiotherapy is a part of cancer treatment. To improve its efficacy has been combined with radiosensitizers such as antiangiogenic agents. Among the mechanisms of the antitumor action of melatonin are antiangiogenic effects. Our goal was to investigate whether melatonin may modulate the sensitivity of endothelial cells (HUVECs) to ionizing radiation. Melatonin (1 mM) enhanced the inhibition induced by radiation on different steps of the angiogenic process, cell proliferation, migration, and tubular network formation. In relation with the activity and expression of enzymes implicated in estrogen synthesis, in co-cultures HUVECs/MCF-7, radiation down-regulated aromatase mRNA expression, aromatase endothelial-specific promoter I.7, sulfatase activity and expression and 17β-HSD1 activity and expression and melatonin enhanced these effects. Radiation and melatonin induced a significant decrease in VEGF, ANG-1, and ANG-2 mRNA expression. In ANG-2 and VEGF mRNA expression melatonin potentiated the inhibitory effect induced by radiation. In addition, melatonin counteracted the stimulatory effect of radiation on FGFR3, TGFα, JAG1, IGF-1, and KDR mRNA expression and reduced ANPEP expression. In relation with extracellular matrix molecules, radiation increased MMP14 mRNA expression and melatonin counteracted the stimulatory effect of radiation on MMP14 mRNA expression and increased TIMP1 expression, an angiogenesis inhibitor. Melatonin also counteracted the stimulatory effect of radiation on CXCL6, CCL2, ERK1, ERK2, and AKT1 mRNA expression and increased the inhibitory effect of radiation on NOS3 expression. In CAM assay, melatonin enhanced the reduction of the vascular area induced by radiation. Melatonin potentiated the inhibitory effect on the activation of p-AKT and p-ERK exerted by radiation. Antiangiogenic effect of melatonin could be mediated through AKT and ERK pathways, proteins involved in vascular endothelial (VE) cell growth, cell proliferation, survival, migration, and angiogenesis. In addition, radiation increased endothelial cell permeability and melatonin counteracted it by regulating the internalization of VE-cadherin. Radiation has some side effects on angiogenesis that may reduce its effectiveness against tumor growth and melatonin is able to neutralize these negative actions of radiation. Additionally, melatonin potentiated radiation-induced antiangiogenic actions on several steps of the angiogenic process and enhanced its antitumor action. Our findings point to melatonin as a useful molecule as adjuvant to radiotherapy in cancer treatment.

Tumor-Microenvironment-Responsive Nanoconjugate for Synergistic Antivascular Activity and Phototherapy

Insufficient oxygen supply (hypoxia), short half-life (<40 ns) of singlet oxygen, and up-regulation of the heat shock protein expression in solid tumors impede the photodynamic and photothermal therapeutic efficacy. Herein, a near-infrared carrier-free nanoconjugate direct-acting antiviral (DAA) with synergistic antivascular activity and pH-responsive photodynamic/photothermal behavior was designed and synthesized to improve cancer treatment efficacy. Obtained by the self-assembly approach, the biocompatible DAA nanoparticles (NPs) displayed amplifying pH-responsive photodynamic/photothermal performance in an acidic tumor microenvironment due to the protonation of diethylaminophenyl units. Most important, the antivascular agent 5,6-dimethylxanthenone-4-acetic acid, targeting the vascular endothelial growth factor, can be smartly released from the pro-drug DAA via ester bond hydrolysis at the subacid endocytosis organelles in the endothelial cells, which can effectively destroy the vascular region to prevent tumor proliferation and metastasis. Hence, DAA NPs can specifically target vascular endothelial cells and tumorous lysosomes with desired cellular damage properties in vitro. Therefore, the tumors can be ablated completely with no recurrence and side effects in vivo, which implies that DAA NPs provide a promising approach for cancer treatment via synergistic antivascular activity and photodynamic/photothermal therapy.

Overexpression of preeclampsia induced microRNA-26a-5p leads to proteinuria in zebrafish

So far the pathomechanism of preeclampsia in pregnancy is focussed on increased circulating levels of soluble fms-like tyrosin kinase-1 (sFLT-1) that neutralizes glomerular VEGF-A expression and prevents its signaling at the glomerular endothelium. As a result of changed glomerular VEGF-A levels endotheliosis and podocyte foot process effacement are typical morphological features of preeclampsia. Recently, microRNA-26a-5p (miR-26a-5p) was described to be also upregulated in the preeclamptic placenta. We found that miR-26a-5p targets VEGF-A expression by means of PIK3C2α in cultured human podocytes and that miR-26a-5p overexpression in zebrafish causes proteinuria, edema, glomerular endotheliosis and podocyte foot process effacement. Interestingly, recombinant zebrafish Vegf-Aa protein could rescue glomerular changes induced by miR-26a-5p. In a small pilot study, preeclamptic patients with podocyte damage identified by podocyturia, expressed significantly more urinary miR-26a-5p compared to healthy controls. Thus, functional and ultrastructural glomerular changes after miR-26a-5p overexpression can resemble the findings seen in preeclampsia and indicate a potential pathophysiological role of miR-26a-5p in addition to sFLT-1 in this disease.

Local chemical sympathectomy of rat bone marrow and its effect on marrow cell composition

Existing experimental studies of the effect of sympathetic nerve fibers on bone marrow cells are based on the systemic administration of neurotoxic 6-hydroxydopamine. The method of global chemical sympathectomy has some serious disadvantages and could lead to questionable results. We describe a new method of local chemical sympathectomy of rat femoral bone marrow using guanethidine (Ismelin) delivery using an osmotic mini pump. Local guanethidine treatment for 14days led to complete elimination of sympathetic fibers in femoral bone marrow in contrast to bone marrow of contralateral or naïve femurs. Ablation of sympathetic fibers was associated with a loss of rat endothelial cell marker (RECA) indicating immunophenotype changes in blood vessel endothelial cells, but no significant effect of guanethidine was found on the survival of endothelial cells and mesenchymal stem cells in vitro. Moreover, local guanethidine treatment also elicited a significant reduction of Nestin+/SDF1+ mesenchymal stem cells and c-Kit+/CD90+ hematopoietic stem cells in femoral bone marrow. Tissue-specific chemical sympathectomy of rat bone marrow by guanethidine overcomes some of the drawbacks of systemic administration of neurotoxic compounds like 6-hydroxydopamine and delivers unequivocal evidence on the effects of sympathetic innervation on the cell content of bone marrow.

Identification of NCK1 as a novel downstream effector of STAT3 in colorectal cancer metastasis and angiogenesis

Signal transducer and activator of transcription 3 (STAT3) is known to activate targets associated with invasion, proliferation, and angiogenesis in a wide variety of cancers. The adaptor protein NCK1 is involved in cytoskeletal movement and was identified as a STAT3-associated target in human tumors. However, the underlying molecular mechanism associated with colorectal cancer (CRC) metastasis is not yet completely understood. In this study, we report a novel STAT3 to NCK1 signaling pathway in colorectal cancer (CRC). We investigated the expression of NCK1 and its potential clinical and biological significance in CRC. NCK1 was noticeably up-regulated in human CRC tissues. NCK1 was also significantly associated with serosal invasion, lymph metastasis, and tumor-node-metastasis classification but was inversely correlated with differentiation. Gain-of-function and loss-of-function studies have shown that ectopic expression of NCK1 enhanced metastasis and angiogenesis in CRC cells. By gene expression analyses, we revealed a high co-overexpression of STAT3 and NCK1 in CRC tissues. Ectopic overexpression of STAT3 in CRC cells induced the expression of NCK1, whereas STAT3 knockdown decreased the expression of NCK1. Promoter activation and binding analyses demonstrated that STAT3 promoted the expression of NCK1 via direct action on the NCK1 promoter. The knock down of NCK1 partially reduced the CRC cell metastasis and angiogenesis promoted by STAT3. Additionally, by co-immunoprecipitation assays, we verified that NCK1 interacted with PAK1, which resulted in the activation of the PAK1/ERK pathway. STAT3 induced the transcription of NCK1 and triggered a PAK1/ERK cascade in CRC. These findings suggest a novel STAT3 to NCK1 to PAK1/ERK signaling mechanism that is potentially critical for CRC metastasis and angiogenesis.