Natural Compounds as Anticancer Agents Targeting DNA Topoisomerases

Inhibition of DNA Topoisomerase Ι by Flavonoids and Polyacetylenes Isolated from Bidens pilosa L

Human DNA topoisomerase I (Topo I) is an essential enzyme in regulating DNA supercoiling during transcription and replication, and it is an important therapeutic target for anti-tumor agents. Bidens pilosa L. is a medicinal herb that is used as a folk medicine for cancers in China. A new flavonoid (1) and a new polyacetylene (20), along with eighteen flavonoids (2-19) and nine polyacetylenes (21-29), were isolated and identified from the methanol extract of the whole plant of B. pilosa, and some of the compounds (4, 5, 6 and 7) exhibited potent cytotoxicity against a panel of five human cancer cell lines. The DNA relaxation assay revealed that some flavonoids and polyacetylenes exerted inhibitory activities on human DNA Topo I, among them compounds 1, 2, 5, 6, 7, 8, 15, 19, 20, 22, and 24 were the most active ones, with IC50 values of 393.5, 328.98, 145.57, 239.27, 224.38, 189.84, 89.91, 47.5, 301.32, 178.03, and 218.27 μM, respectively. The structure-activity analysis of flavonoids was performed according to the results from the Topo I inhibition assay. The DNA content analysis revealed that 5, 6, and 7 potently arrested cell cycle at the G1/S and G2/M phases in human colon cancer cell DLD-1 depending on the concentration of the inhibitors. The levels of protein expression related to the G1/S and G2/M cell cycle checkpoints were in accordance with the results from the DNA content analysis. These findings suggest that flavonoids are one of the key active ingredients accounting for the anti-tumor effect of B. pilosa.

Targeting the prostate tumor microenvironment by plant-derived natural products

Prostate cancer is among the most common malignancies for men, with limited therapy options for last stages of the tumor. There are some different options for treatment and control of prostate tumor growth. However, targeting some specific molecules and cells within tumors has been attracted interests in recent years. The tumor microenvironment (TME) has an important role in the initiation of various malignancies, which can also expand the progression of tumor and facilitate invasion of malignant cells. By regulating immune responses and distinct changes in the metabolism of cells in the tumor, TME has substantial effects in the resistance of cancer cells to therapy. TME in various solid cancers like prostate cancer includes various cells, including cancer cells, supportive stromal cells, immunosuppressive cells, and anticancer inflammatory cells. Natural products including herbal-derived agents and also other natural compounds have been well studied for their anti-tumor potentials. These compounds may modulate various signaling pathways involved in TME, such as immune responses, the metabolism of cells, epigenetics, angiogenesis, and extracellular matrix (ECM). This paper provides a review of the current knowledge of prostate TME and complex interactions in this environment. Additionally, the potential use of natural products and also nanoparticles loaded with natural products as therapeutic adjuvants on different cells and therapeutic targets within prostate TME will be discussed.

Anticancer Drug Discovery Based on Natural Products: From Computational Approaches to Clinical Studies

Globally, malignancies cause one out of six mortalities, which is a serious health problem. Cancer therapy has always been challenging, apart from major advances in immunotherapies, stem cell transplantation, targeted therapies, hormonal therapies, precision medicine, and palliative care, and traditional therapies such as surgery, radiation therapy, and chemotherapy. Natural products are integral to the development of innovative anticancer drugs in cancer research, offering the scientific community the possibility of exploring novel natural compounds against cancers. The role of natural products like Vincristine and Vinblastine has been thoroughly implicated in the management of leukemia and Hodgkin's disease. The computational method is the initial key approach in drug discovery, among various approaches. This review investigates the synergy between natural products and computational techniques, and highlights their significance in the drug discovery process. The transition from computational to experimental validation has been highlighted through in vitro and in vivo studies, with examples such as betulinic acid and withaferin A. The path toward therapeutic applications have been demonstrated through clinical studies of compounds such as silvestrol and artemisinin, from preclinical investigations to clinical trials. This article also addresses the challenges and limitations in the development of natural products as potential anti-cancer drugs. Moreover, the integration of deep learning and artificial intelligence with traditional computational drug discovery methods may be useful for enhancing the anticancer potential of natural products.

Unveiling the therapeutic potential: Evaluation of anti-inflammatory and antineoplastic activity of Magnolia champaca Linn's stem bark isolate through molecular docking insights

Magnolia champaca Linn. has traditionally been used for medicinal activity in Asia for treating various chronic diseases as well as a source of food, medicines, and other commodities. Due to the long-used history of this plant, the present study was designed to explore the in vitro, in vivo and in silico anti-inflammatory and antineoplastic properties of the methanolic extract and fractions and the pure compound isolated from the most active chloroform fraction (CHF) of the stem bark of the plant. The isolated compound from the most active CHF was characterized and identified as a glycoside, trans-syringin, through chromatographic and spectroscopic (1H-NMR and 13C-NMR) analyses. In the in vitro anti-inflammatory assay, CHF was most effective in inhibiting inflammation and hemolysis of RBCs by 73.91 ± 1.70% and 75.92 ± 0.14%, respectively, induced by heat and hypotonicity compared to standard acetylsalicylic acid. In the egg albumin denaturation assay, CME and CHF showed the highest inhibition by 56.25 ± 0.82% and 65.82 ± 3.52%, respectively, contrasted with acetylsalicylic acid by 80.14 ± 2.44%. In an in vivo anti-inflammatory assay, statistically significant (p < 0.05) decreases in the parameters of inflammation, such as paw edema, leukocyte migration and vascular permeability, were recorded in a dose-dependent manner in the treated groups. In the antineoplastic assay, 45.26 ± 2.24% and 68.31 ± 3.26% inhibition of tumor cell growth for pure compound were observed compared to 73.26 ± 3.41% for standard vincristine. Apoptotic morphologic alterations, such as membrane and nuclear condensation and fragmentation, were also found in EAC cells after treatment with the isolated bioactive pure compound. Such treatment also reversed the increased WBC count and decreased RBC count to normal values compared to the untreated EAC cell-bearing mice and the standard vincristine-treated mice. Subsequently, in silico molecular docking studies substantiated the current findings, and the isolated pure compound and standard vincristine exhibited -6.4 kcal/mol and -7.3 kcal/mol binding affinities with topoisomerase-II. Additionally, isolated pure compound and standard diclofenac showed -8.2 kcal/mol and -7.6 kcal/mol binding affinities with the COX-2 enzyme, respectively. The analysis of this research suggests that the isolated bioactive pure compound possesses moderate to potent anti-inflammatory and antineoplastic activity and justifies the traditional uses of the stem bark of M. champaca. However, further investigations are necessary to analyze its bioactivity, proper mechanism of action and clinical trials for the revelation of new drug formulations.

Evaluation of topotecan and 10-hydroxycamptothecin on Toxoplasma gondii: Implications on baseline DNA damage and repair efficiency

Toxoplasma gondii is an obligate intracellular parasite in the phylum Apicomplexa that causes toxoplasmosis in humans and animals worldwide. Despite its prevalence, there is currently no effective vaccine or treatment for chronic infection. Although there are therapies against the acute stage, prolonged use is toxic and poorly tolerated. This study aims to explore the potential of repurposing topotecan and 10-hydroxycamptothecin (HCPT) as drugs producing double strand breaks (DSBs) in T. gondii. DSBs are mainly repaired by Homologous Recombination Repair (HRR) and Non-Homologous End Joining (NHEJ). Two T. gondii strains, RHΔHXGPRT and RHΔKU80, were used to compare the drug's effects on parasites. RHΔHXGPRT parasites may use both HRR and NHEJ pathways but RHΔKU80 lacks the KU80 protein needed for NHEJ, leaving only the HRR pathway. Here we demonstrate that topotecan and HCPT, both topoisomerase I venoms, affected parasite replication in a concentration-dependent manner. Moreover, variations in fluorescence intensity measurements for the H2A.X phosphorylation mark (γH2A.X), an indicator of DNA damage, were observed in intracellular parasites under drug treatment conditions. Interestingly, intracellular replicative parasites without drug treatment show a strong positive staining for γH2A.X, suggesting inherent DNA damage. Extracellular (non-replicating) parasites did not exhibit γH2A.X staining, indicating that the basal level of DNA damage is likely to be associated with replicative stress. A high rate of DNA replication stress possibly prompted the evolution of an efficient repair machinery in the parasite, making it an attractive target. Our findings show that topoisomerase 1 venoms are effective antiparasitics blocking T. gondii replication.

Nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) with repercussions toward apoptosis, necrosis, and cancer necrosis factor (TNF-α) at nano-biointerfaces

Introduction

Apoptosis, necrosis, and cancer necrosis factor (TNF-a) are all impacted by the nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) at nano-biointerfaces. The creation of multi-functional nanoparticles has had a considerable impact on the transport of drugs and genes, nanotheranostics (in-vivo imaging, concurrent diagnostics), interventions for external healing, the creation of nano-bio interfaces, and the instigation of desired changes in nanotherapeutics.

Objectives

The quantitative structure-activity relationships, chemical transformations, biological interactions as well as toxicological analyses are considered as main objectives. Discrete dimensions of SCoNPs-cell interaction interfaces, their characteristic physical features (size, shape, shell structure, and surface chemistry), impact on cell proliferation and differentiation are the key factors responsible for nanotoxicity.

Methods

The development of multi-functional nanoparticles has been significant in drug/gene delivery, nanotheranostics (in-vivo imaging, coinciding diagnostics), and external healing interventions, designing a nano-bio interface, as well as inciting desired alterations in nanotherapeutics. Every so often, the cellular uptake of multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoONPs) influences cellular mechanics and initiates numerous repercussions (oxidative stress, DNA damage, cytogenotoxicity, and chromosomal damage) in pathways, including the generation of dysregulating factors involved in biochemical transformations.

Results

The concerns and influences of multifunctional SCoNPs on different cell mechanisms (mitochondria impermeability, hydrolysis of ATP, the concentration of Ca2+, impaired calcium clearance, defective autophagy, apoptosis, and necrosis), and interlinked properties (adhesion, motility, and internalization dynamics, role in toxicity, surface hydrophilic and hydrophobicity, biokinetics and biomimetic behaviors of biochemical reactions) have also been summarized. SCoONPs have received a lot of interest among the nanocarriers family because of its advantageous qualities such as biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity.

Conclusion

Various applications, such as bio-imaging, cell labeling, gene delivery, enhanced chemical stability, and increased biocompatibility, concerning apoptosis, necrosis, and nano-bio interfaces, along with suitable examples. In this analysis, the multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoNPs) intricacies (cytogenotoxicity, clastogenicity, and immunomodulatory), nanotoxicity, and associated repercussions have been highlighted and explained.

Effects of In Vitro Digestion of Polyphenols from Coffee on Binding Parameters to Human Topoisomerase II α

Type II topoisomerase (TOPII) is an enzyme that influences the topology of DNA. DNA breaks generated by TOPII may result in mutagenic or cytotoxic changes in cancer cells. In this study, we characterized interactions of TOPIIα with coffee extracts and individual chlorogenic acids (CHAs) from the extracts by performing isothermal titration calorimetry (ITC) and molecular docking (MD) simulations. The study showed that the highest affinity to TOPIIα was found in green coffee (ΔG = -38.23 kJ/mol) and monochlorogenic acids fraction of coffee extracts (ΔG = -35.80 kJ/mol), resulting from the high content of polyphenols, such as CHAs, which can bind to the enzyme in the active site. Coffee extracts and their fractions maintained a high affinity for TOPIIα after simulated digestion in the presence of probiotic bacteria. It can be concluded that coffee may be a potential TOPIIα inhibitor considered as a functional food for cancer prevention.

Recent Developments in Combination Chemotherapy for Colorectal and Breast Cancers with Topoisomerase Inhibitors

DNA topoisomerases are important enzymes that stabilize DNA supercoiling and resolve entanglements. There are two main types of topoisomerases in all cells: type I, which causes single-stranded DNA breaks, and type II, which cuts double-stranded DNA. Topoisomerase activity is particularly increased in rapidly dividing cells, such as cancer cells. Topoisomerase inhibitors have been an effective chemotherapeutic option for the treatment of several cancers. In addition, combination cancer therapy with topoisomerase inhibitors may increase therapeutic efficacy and decrease resistance or side effects. Topoisomerase inhibitors are currently being used worldwide, including in the United States, and clinical trials on the combination of topoisomerase inhibitors with other drugs are currently underway. The primary objective of this review was to comprehensively analyze the current clinical landscape concerning the combined application of irinotecan, an extensively investigated type I topoisomerase inhibitor for colorectal cancer, and doxorubicin, an extensively researched type II topoisomerase inhibitor for breast cancer, while presenting a novel approach for cancer therapy.

Chemical Constituents, Anticancer and Anti-Proliferative Potential of Limonium Species: A Systematic Review

Limonium species represent a source of bioactive compounds that have been widely used in folk medicine. This study aimed to synthesize the anticancer and anti-proliferative potential of Limonium species through a systematic review. Searches were performed in the electronic databases PubMed/MEDLINE, Scopus, and Scielo and via a manual search. In vivo or in vitro studies that evaluated the anticancer or anti-proliferative effect of at least one Limonium species were included. In total, 942 studies were identified, with 33 articles read in full and 17 studies included for qualitative synthesis. Of these, 14 (82.35%) refer to in vitro assays, one (5.88%) was in vivo, and two (11.76%) were designed as in vitro and in vivo assays. Different extracts and isolated compounds from Limonium species were evaluated through cytotoxic analysis against various cancer cells lines (especially hepatocellular carcinoma-HepG2; n = 7, 41.18%). Limonium tetragonum was the most evaluated species. The possible cellular mechanism involved in the anticancer activity of some Limonium species included the inhibition of enzymatic activities and expression of matrix metalloproteinases (MMPs), which suggested anti-metastatic effects, anti-melanogenic activity, cell proliferation inhibition pathways, and antioxidant and immunomodulatory effects. The results reinforce the potential of Limonium species as a source for the discovery and development of new potential cytotoxic and anticancer agents. However, further studies and improvements in experimental designs are needed to better demonstrate the mechanism of action of all of these compounds.

Advances in anticancer alkaloid-derived metallo-chemotherapeutic agents in the last decade: Mechanism of action and future prospects

Metal-based complexes have occupied a pioneering niche in the treatment of many chronic diseases, including various types of cancers. Despite the phenomenal success of cisplatin for the treatment of many solid malignancies, a limited number of metallo-drugs are in clinical use against cancer chemotherapy till date. While many other prominent platinum and non‑platinum- based metallo-drugs (e.g. NAMI-A, KP1019, carboplatin, oxaliplatin, titanocene dichloride, casiopeinas® etc) have entered clinical trials, many have failed at later stages of R&D due to deleterious toxic effects, intrinsic resistance and poor pharmacokinetic response and low therapeutic efficacy. Nonetheless, research in the area of medicinal inorganic chemistry has been increasing exponentially over the years, employing novel target based drug design strategies aimed at improving pharmacological outcomes and at the same time mitigating the side-effects of these drug entities. Over the last few decades, natural products became one of the key structural motifs in the anticancer drug development. Many eminent researchers in the area of medicinal chemistry are devoted to develop new 3d-transition metal-based anticancer drugs/repurpose the existing bioactive compounds derived from myriad pharmacophores such as coumarins, flavonoids, chromones, alkaloids etc. Metal complexes of natural alkaloids and their analogs such as luotonin A, jatrorrhizine, berberine, oxoaporphine, 8-oxychinoline etc. have gained prominence in the anticancer drug development process as the naturally occurring alkaloids can be anti-proliferative, induce apoptosis and exhibit inhibition of angiogenesis with better healing effect. While some of them are inhibitors of ERK signal-regulated kinases, others show activity based on cyclooxygenases-2 (COX-2) and telomerase inhibition. However, the targets of these alkaloid complexes are still unclear, though it is well-established that they demonstrate anticancer potency by interfering with multiple pathways of tumorigenesis and tumor progression both in vitro and in vivo. Over the last decade, many significant advances have been made towards the development of natural alkaloid-based metallo-drug therapeutics for intervention in cancer chemotherapy that have been summarized below and reviewed in this article.

Targeting DNA Topoisomerase II in Antifungal Chemotherapy

Topoisomerase inhibitors have been in use clinically for the treatment of several diseases for decades. Although those enzymes are significant molecular targets in antibacterial and anticancer chemotherapy very little is known about the possibilities to target fungal topoisomerase II (topo II). Raising concern for the fungal infections, lack of effective drugs and a phenomenon of multidrug resistance underlie a strong need to expand the range of therapeutic options. In this review paper, we discussed the usefulness of fungal topo II as a molecular target for new drug discovery. On the basis of previously published data, we described structural and biochemical differences between fungal and human enzymes as well as a molecular basis of differential sensitivity to known anticancer drugs targeting the latter. This review focuses especially on highlighting the differences that may underlie the selectivity of action of new inhibitors. Distinct sites within fungal topo II in comparison with human counterparts are observed and should be further studied to understand the significance of those sites and their possible usage in design of new drugs.

The efficacy of irinotecan supplementation for colorectal cancer: A meta-analysis of randomized controlled studies

BACKGROUND

The efficacy of irinotecan as the adjunctive therapy to fluorouracil and leucovorin remains controversial in patients with colorectal cancer. We conduct this meta-analysis to explore the efficacy of irinotecan supplementation for colorectal cancer.

METHODS

We have searched PubMed, EMBASE, Web of science, EBSCO, and Cochrane library databases through March 19, 2020, and included randomized controlled trials assessing the efficacy of irinotecan plus fluorouracil and leucovorin for colorectal cancer.

RESULTS

Five randomized controlled trials were included in the meta-analysis. Compared with fluorouracil and leucovorin for colorectal cancer, irinotecan supplementation could significantly improve progression-free survival rate (hazard ratio = 0.72; 95% confidence interval [CI] = 0.58-0.90; P = .003), median progression-free survival (standard mean difference = -0.30; 95% CI = -0.44 to -0.15; P < .0001), overall survival rate (hazard ratio = 0.77; 95% CI = 0.66-0.90; P = .001), and objective response (risk ratio [RR] = 0.57; 95% CI = 0.49-0.66; P < .00001) and decrease progressive disease (RR = 2.10; 95% CI = 1.40-3.14; P = .0003), but revealed no obvious effect on complete response (RR = 0.88; 95% CI = 0.33-2.29; P = .79). The incidence of grade ≥3 adverse events in irinotecan supplementation group was increased compared to control group (RR = 0.67; 95% CI = 0.57-0.79; P < .00001).

CONCLUSIONS

Irinotecan as the adjunctive therapy to fluorouracil and leucovorin can increase the survival and objective response of patients with colorectal cancer, but the incidence of grade ≥3 adverse events is found to be increased after irinotecan supplementation.

The DNA-topoisomerase Inhibitors in Cancer Therapy

DNA-topoisomerases are ubiquitous enzymes essential for major cellular processes. In recent years, interest in DNA-topoisomerases has increased not only because of their crucial role in promoting DNA replication and transcription processes, but also because they are the target of numerous active ingredients. The possibility of exploiting for therapeutic purposes the blocking of the activity of these enzymes has led to the development of a new class of anticancer agents capable of inducing apoptosis of tumor cells following DNA damage and its failure to repair.

From Antarctica to cancer research: a novel human DNA topoisomerase 1B inhibitor from Antarctic sponge Dendrilla antarctica

Nature has been always a great source of possible lead compounds to develop new drugs against several diseases. Here we report the identification of a natural compound, membranoid G, derived from the Antarctic sponge Dendrilla antarctica displaying an in vitro inhibitory activity against human DNA topoisomerase 1B. The experiments indicate that membranoid G, when pre-incubated with the enzyme, strongly and irreversibly inhibits the relaxation of supercoiled DNA. This compound completely inhibits the cleavage step of the enzyme catalytic mechanism by preventing protein binding to the DNA. Membranoid G displays also a cytotoxic effect on tumour cell lines, suggesting its use as a possible lead compound to develop new anticancer drugs.

Antiviral, Anticancer and Hypotensive Potential of Diphyllin Glycosides and their Mechanisms of Action

Diphyllin glycosides (DG) are the type of arylnaphthalene lignans isolated from different plants and their synthetic derivatives have shown effective antiviral, cytotoxic, hypotensive and diuretic effects at very low concentrations similar to standard drugs that are under clinical use. The biological activities of the DG interfere with signaling pathways of viral infection and cancer induction. The sugar moieties of DG enhance bioavailability and pharmacological activities. The promising results of DG at nanomolar concentrations under in vitro and in vivo conditions should be explored further with clinical trials to determine its toxic effects, pharmacokinetics and pharmacodynamics. This may identify suitable antiviral and anticancer drugs in the near future. Considering all these activities, the present review is focused on the chemical aspects of DG with a detailed account on the mechanisms of action of DG. An attempt is also made to comment on the status of clinical trials of DG along with the possible limitations in studies based on available literature through September 2020.

Molecular Mechanisms of Anticancer Activity of N-Glycosides of Indolocarbazoles LCS-1208 and LCS-1269

Novel indolocarbazole derivatives named LCS were synthesized by our research group. Two of them were selected as the most active anticancer agents in vivo. We studied the mechanisms of anticancer activity in accordance with the previously described effects of indolocarbazoles. Cytotoxicity was estimated by MTT assay. We analyzed LCS-DNA interactions by circular dichroism in cholesteric liquid crystals and fluorescent indicator displacement assay. The effect on the activity of topoisomerases I and II was studied by DNA relaxation assay. Expression of interferon signaling target genes was estimated by RT-PCR. Chromatin remodeling was analyzed–the effect on histone H1 localization and reactivation of epigenetically silenced genes. LCS-induced change in the expression of a wide gene set was counted by means of PCR array. Our study revealed the cytotoxic activity of the compounds against 11 cancer cell lines and it was higher than in immortalized cells. Both compounds bind DNA; binding constants were estimated—LCS-1208 demonstrated higher affinity than LCS-1269; it was shown that LCS-1208 intercalates into DNA that is typical for rebeccamycin derivatives. LCS-1208 also inhibits topoisomerases I and IIα. Being a strong intercalator and topoisomerase inhibitor, LCS-1208 upregulates the expression of interferon-induced genes. In view of LCSs binding to DNA we analyzed their influence on chromatin stability and revealed that LCS-1269 displaces histone H1. Our analysis of chromatin remodeling also included a wide set of epigenetic experiments in which LCS-1269 demonstrated complex epigenetic activity. Finally, we revealed that the antitumor effect of the compounds is based not only on binding to DNA and chromatin remodeling but also on alternative mechanisms. Both compounds induce expression changes in genes involved in neoplastic transformation and target genes of the signaling pathways in cancer cells. Despite of being structurally similar, each compound has unique biological activities. The effects of LCS-1208 are associated with intercalation. The mechanisms of LCS-1269 include influence on higher levels such as chromatin remodeling and epigenetic effects.

Characterization of Oligomeric Proanthocyanidin-Enriched Fractions from Aronia melanocarpa (Michx.) Elliott via High-Resolution Mass Spectrometry and Investigations on Their Inhibitory Potential on Human Topoisomerases

Aronia melanocarpa (MICHX.) ELLIOTT, which belongs to the Rosaceae family, has increasingly come into focus of research due to the high content of polyphenols. In addition to antioxidative properties, further health-promoting effects of these polyphenols are still of interest. Especially, the proanthocyanidins offer thereby huge opportunities due to their high structural heterogeneity. Therefore, the present study focuses on the topoisomerase inhibiting effects of oligomeric proanthocyanidins (PACs), which are potentially depended on their degree of polymerization. The investigated PACs isolated from Aronia berries were characterized by chromatographic techniques and liquid chromatography-high-resolution mass spectrometry. Four PAC enriched fractions were obtained from Aronia pomace containing 47 PACs with a degree of polymerization from three to six. Due to the low yield of hexamers, the potential inhibiting effects against human topoisomerase were investigated for the trimer to pentamer fractions. The relaxation and decatenation assays were performed to examine the inhibiting effect on topoisomerases under cell-free conditions. Moreover, rapid isolation of topoisomerase cleavage complexes in human colon carcinoma HT29 cells was performed to evaluate the effect on topoisomerases in a cell-based system. The fractions demonstrated inhibitory potential on topoisomerases I and II. In sum, an increasing effect strength depending on the degree of polymerization was shown.

Evaluation of the target-specific therapeutic potential of herbal compounds for the treatment of cancer

Cancer is among one of the most fatal diseases leading to millions of death around the globe. Chemotherapy is the most popular conventional approach for the treatment of cancer. However, this is usually associated with various side effects and puts the patients under extreme physical and mental stress. Besides, there are increasing concerns about drug resistance. Thus, to surmount these limitations, there is a need to explore some alternative treatments. Studies related to plant-derived compounds are crucial in the search for safer and more efficient treatments. Plants and their associated secondary metabolites have been a revolutionary approach in the field of cancer treatment, as they give answers to almost all the constraints faced by synthetic drugs. Various plants and associated secondary metabolites display a great prospective as cytotoxic anticancer agents due to their specific interference with validated drug targets, such as inhibitors of mitosis, topoisomerase I and II inhibitor, DNA interactive agent, protein kinase inhibitors, inhibitors of DNA synthesis. In this review, the therapeutic potential of various natural compounds and their derivatives are presented based on their molecular targets. These herbal compounds and their derivatives could provide a rich resource for novel anticancer drug development.

Dehydrocrenatidine extracted from Picrasma quassioides induces the apoptosis of nasopharyngeal carcinoma cells through the JNK and ERK signaling pathways

Nasopharyngeal carcinoma (NPC) is an indicator disease in Asia due to its unique geographical and ethnic distribution. Dehydrocrenatidine (DC) is a β-carboline alkaloid abundantly present in Picrasma quassioides (D. Don) Benn, a deciduous shrub or small tree native to temperate regions of southern Asia, and β-carboline alkaloids play anti-inflammatory and antiproliferative roles in various cancers. However, the mechanism and function of DC in human NPC cells remain only partially explored. The present study aimed to examine the cytotoxicity and biochemical role of DC in human NPC cells. The MTT method, cell cycle analysis, DAPI determination, Annexin V/PI double staining, and mitochondrial membrane potential examination were performed to evaluate the effects of DC treatment on human NPC cell lines. In addition, western blotting analysis was used to explore the effect of DC on apoptosis and signaling pathways in related proteins. The analysis results confirmed that DC significantly reduced the viability of NPC cell lines in a dose- and time-dependent manner and induced apoptosis through internal and external apoptotic pathways (including cell cycle arrest, altered mitochondrial membrane potential, and activated death receptors). Western blot analysis illustrated that DC's effect on related proteins in the mitogen-activated protein kinase pathway can induce apoptosis by enhancing ERK phosphorylation and inhibiting Janus kinase (JNK) phosphorylation. Notably, DC induced apoptosis by affecting the phosphorylation of JNK and ERK, and DC and inhibitors (SP600125 and U0126) in combination restored the overexpression of p-JNK and p-ERK. To date, this is the first study to confirm the apoptosis pathway induced by DC phosphorylation of p-JNK and p-REK in human NPC. On the basis of evidence obtained from this study, DC targeting the inhibition of NPC cell lines may be a promising future strategy for NPC treatment.

The Use of Bio-Active Compounds of Citrus Fruits as Chemopreventive Agents and Inhibitor of Cancer Cells Viability

Common therapy of cancer, such as chemotherapy, has various side effects for the patients. In recent studies, new therapeutic approaches in cancer treatment are adjuvant therapy, along with a reduction in side effects of chemotherapy drugs. Treatment by herbal medicines may have some advantages over treatment with single purified chemicals, also in terms of side effects, the use of plants in cancer treatment is a more secure method. Citrus fruits are one of the most consumed natural products in the world due to the presence of various metabolites and bioactive compounds, such as phenols, flavonoids and, carotenoids. Bioactive compounds of citrus modulate signaling pathways and interact with signaling molecules such as apoptotic and cell cycle (P53, P21, etc.) and thus have a wide range of pharmacological activities, including anti-inflammatory, anti-cancer and oxidative stress. The findings discussed in this review strongly support their potential as anti-cancer agents. Therefore, the purpose of this review was to examine the effects of active compounds in citrus as a therapy agent in cancer treatment.

Antifungal Activity and DNA Topoisomerase Inhibition of Hydrolysable Tannins from Punica granatum L

Punica granatum L. (pomegranate) fruit is known to be an important source of bioactive phenolic compounds belonging to hydrolysable tannins. Pomegranate extracts have shown antifungal activity, but the compounds responsible for this activity and their mechanism/s of action have not been completely elucidated up to now. The aim of the present study was the investigation of the inhibition ability of a selection of pomegranate phenolic compounds (i.e., punicalagin, punicalin, ellagic acid, gallic acid) on both plant and human fungal pathogens. In addition, the biological target of punicalagin was identified here for the first time. The antifungal activity of pomegranate phenolics was evaluated by means of Agar Disk Diffusion Assay and minimum inhibitory concentration (MIC) evaluation. A chemoinformatic analysis predicted for the first time topoisomerases I and II as potential biological targets of punicalagin, and this prediction was confirmed by in vitro inhibition assays. Concerning phytopathogens, all the tested compounds were effective, often similarly to the fungicide imazalil at the label dose. Particularly, punicalagin showed the lowest MIC for Alternaria alternata and Botrytis cinerea, whereas punicalin was the most active compound in terms of growth control extent. As for human pathogens, punicalagin was the most active compound among the tested ones against Candida albicans reference strains, as well as against the clinically isolates. UHPLC coupled with HRMS indicated that C. albicans, similarly to the phytopathogen Coniella granati, is able to hydrolyze both punicalagin and punicalin as a response to the fungal attack. Punicalagin showed a strong inhibitory activity, with IC₅₀ values of 9.0 and 4.6 µM against C. albicans topoisomerases I and II, respectively. Altogether, the results provide evidence that punicalagin is a valuable candidate to be further exploited as an antifungal agent in particular against human fungal infections.

Natural Compounds as Therapeutic Agents: The Case of Human Topoisomerase IB

Natural products are widely used as source for drugs development. An interesting example is represented by natural drugs developed against human topoisomerase IB, a ubiquitous enzyme involved in many cellular processes where several topological problems occur due the formation of supercoiled DNA. Human topoisomerase IB, involved in the solution of such problems relaxing the DNA cleaving and religating a single DNA strand, represents an important target in anticancer therapy. Several natural compounds inhibiting or poisoning this enzyme are under investigation as possible new drugs. This review summarizes the natural products that target human topoisomerase IB that may be used as the lead compounds to develop new anticancer drugs. Moreover, the natural compounds and their derivatives that are in clinical trial are also commented on.

Kaempferol and Its Glycoside Derivatives as Modulators of Etoposide Activity in HL-60 Cells

Kaempferol is a polyphenol found in a variety of plants. Kaempferol exerts antitumor properties by affecting proliferation and apoptosis of cancer cells. We investigated whether kaempferol and its glycoside derivatives-kaempferol 3-O-[(6-O-E-caffeoyl)-β-D-glucopyranosyl-(1→2)]-β-D-galactopyranoside-7-O-β-D-glucuropyranoside (P2), kaempferol 3-O-[(6-O-E-p-coumaroyl)-β-D-glucopyranosyl-(1→2)]-β-D-galactopyranoside-7-O-β-D-glucuropyranoside (P5) and kaempferol 3-O-[(6-O-E-feruloyl)-β-D-glucopyranosyl-(1→2)]-β-D-galactopyranoside-7-O-β-D-glucuropyranoside (P7), isolated from aerial parts of Lens culinaris Medik.-affect the antitumor activity of etoposide in human promyelocytic leukemia (HL-60) cells. We analyzed the effect of kaempferol and its derivatives on cytotoxicity, DNA damage, apoptosis, cell cycle progression and free radicals induced by etoposide. We demonstrated that kaempferol increases the sensitivity of HL-60 cells to etoposide but does not affect apoptosis induced by this drug. Kaempferol also reduces the level of free radicals generated by etoposide. Unlike kaempferol, some of its derivatives reduce the apoptosis of HL-60 cells (P2 and P7) and increase the level of free radicals (P2 and P5) induced by etoposide. Our results indicate that kaempferol and its glycoside derivatives can modulate the activity of etoposide in HL-60 cells and affect its antitumor efficacy in this way. Kaempferol derivatives may have the opposite effect on the action of etoposide in HL-60 cells compared to kaempferol.

DNA topoisomerases as molecular targets for anticancer drugs

The significant role of topoisomerases in the control of DNA chain topology has been confirmed in numerous research conducted worldwide. The prevalence of these enzymes, as well as the key importance of topoisomerase in the proper functioning of cells, have made them the target of many scientific studies conducted all over the world. This article is a comprehensive review of knowledge about topoisomerases and their inhibitors collected over the years. Studies on the structure-activity relationship and molecular docking are one of the key elements driving drug development. In addition to information on molecular targets, this article contains details on the structure-activity relationship of described classes of compounds. Moreover, the work also includes details about the structure of the compounds that drive the mode of action of topoisomerase inhibitors. Finally, selected topoisomerases inhibitors at the stage of clinical trials and their potential application in the chemotherapy of various cancers are described.

Emerging Therapeutic Targets Against Toxoplasma gondii: Update on DNA Repair Response Inhibitors and Genotoxic Drugs

Toxoplasma gondii is the causative agent of toxoplasmosis in animals and humans. This infection is transmitted to humans through oocysts released in the feces of the felines into the environment or by ingestion of undercooked meat. This implies that toxoplasmosis is a zoonotic disease and T. gondii is a foodborne pathogen. In addition, chronic toxoplasmosis in goats and sheep is the cause of recurrent abortions with economic losses in the sector. It is also a health problem in pets such as cats and dogs. Although there are therapies against this infection in its acute stage, they are not able to permanently eliminate the parasite and sometimes they are not well tolerated. To develop better, safer drugs, we need to elucidate key aspects of the biology of T. gondii. In this review, we will discuss the importance of the homologous recombination repair (HRR) pathway in the parasite's lytic cycle and how components of these processes can be potential molecular targets for new drug development programs. In that sense, the effect of different DNA damage agents or HHR inhibitors on the growth and replication of T. gondii will be described. Multitarget drugs that were either associated with other targets or were part of general screenings are included in the list, providing a thorough revision of the drugs that can be tested in other scenarios.

A novel topoisomerase I inhibitor DIA-001 induces DNA damage mediated cell cycle arrest and apoptosis in cancer cell

Background

DNA topoisomerase enzyme plays an essential role in controlling the DNA topology structure by binding to DNA and cutting the phosphate backbone of either one or both of the DNA strands. Here, we have identified a small molecule inhibitor, DIA-001, that directly binds to Topoisomerase 1 (Topo I) and promotes the Topo I-DNA adducts.

Methods

In this study, we investigated the antitumor effects of DIA-001 using MTS assay and colony formation. We examined cell cycle of tumor cells with DIA-001 treatment in vitro by flow cytometry. And we investigated DNA damage and cell cycle marker protein after treatment with DIA-001 at different concentration and time point by western blot. Immunofluorescence was performance to detect the nuclear foci. The effects of DIA-001 on Topo I and Topo II activities were examined by DNA relaxation assays.

Results

We demonstrate that DIA-001 inhibit DNA replication and arrest cell cycle progression at the G2/M phase by directly binds to Topo I and promotes the Topo I-DNA adducts. In addition, DIA-001 can activate the DNA damage response signaling cascade, resulting in apoptosis in treated cells.

Conclusions

Our findings show a novel compound for treatment of cancer cells with the potential as a chemotherapy candidate that is less toxic to normal cells.

A new insight into the apoptotic effect of nitidine chloride targeting Checkpoint kinase 2 in human cervical cancer in vitro

Nitidine chloride (NC), a natural, bioactive, phytochemical alkaloid derived from the roots of Zanthoxylum nitidum, has been reported to exhibit anti-tumor activity against various types of cancer. However, the potential therapeutic role of NC in human cervical cancer has not yet been studied. We are the first to report that NC acts as a potential apoptosis-inducing agent for human cervical cancer in vitro. NC treatment of human cervical cancer cell lines induced caspase-mediated apoptosis, thereby reducing cell viability. Phospho-kinase proteome profiling using a human phospho-kinase array revealed that NC treatment phosphorylated Checkpoint kinase 2 (Chk2) at Thr68, which activates Chk2 in both cell lines. We also found that NC significantly affected the p53/Bim signaling axis, which was accompanied by mitochondrial membrane depolarization and cytochrome c release from the mitochondria into the cytosol. In addition, NC profoundly increased phosphorylation of the histone variant H2AX at Ser139, a typical marker of DNA damage. Taken together, these results provide in vitro evidence that NC can increase Chk2 activation, thereby acting as an attractive cell death inducer for treatment of human cervical cancer.

DNA Damage by an essential enzyme: A delicate balance act on the tightrope

DNA topoisomerases are essential for DNA metabolic processes such as replication and transcription. Since DNA is double stranded, the unwinding needed for these processes results in DNA supercoiling and catenation of replicated molecules. Changing the topology of DNA molecules to relieve supercoiling or resolve catenanes requires that DNA be transiently cut. While topoisomerases carry out these processes in ways that minimize the likelihood of genome instability, there are several ways that topoisomerases may fail. Topoisomerases can be induced to fail by therapeutic small molecules such as by fluoroquinolones that target bacterial topoisomerases, or a variety of anti-cancer agents that target the eukaryotic enzymes. Increasingly, there have been a large number of agents and processes, including natural products and their metabolites, DNA damage, and the intrinsic properties of the enzymes that can lead to long-lasting DNA breaks that subsequently lead to genome instability, cancer, and other diseases. Understanding the processes that can interfere with topoisomerases and how cells respond when topoisomerases fail will be important in minimizing the consequences when enzymes need to transiently interfere with DNA integrity.

Marine bromophenols as an effective inhibitor of virulent proteins (peptidyl arginine deiminase, gingipain R and hemagglutinin A) in Porphyromas gingivalis

OBJECTIVES

Porphyromonas gingivalis, is one of the major oral pathogen that produce virulent proteins which mediate periodontal tissue inflammation and infection. Marine algae have recently gained popularity for its bioactive molecules and their oral applications. Marine bromophenols (MBs) is abundant in red algae which are reported to have wide medicinal properties. The current research primarily focuses to elucidate the bioactivity of MBs against the virulent proteins produced by P. gingivalis.

MATERIALS AND METHODS

Potent MBs which effectively binds and inhibits the virulent proteins peptidyl arginine deiminase (PPAD), gingipain R (Rgp) and hemagglutinin A (HgA) was identified through molecular docking and molecular simulation approach. MBs were extracted from Kappaphycus alvarezii (KAB), marine red algae found in India. The efficacy of this MB was studied against P. gingivalis by employing antibacterial activity assays, gingipain assay, hemagglutination inhibition assay (HIA) and mRNA expression analysis (q RT PCR).

RESULTS

MBs with benzene, methyl and glycosyl substitutions demonstrated significant docking score, with good stability and pharmacokinetic properties. In addition to the antibacterial activities against P. gingivalis, KAB was also found to inhibit the gingipain and hemagglutination activities. Exposure of KAB to the virulent genes in P. gingivalis resulted in low mRNA levels of these genes, which suggested the down regulation functions induced by the MBs.

CONCLUSION

Biochemical investigations revealed that KAB is a potent natural metabolite that can inhibit and control the virulent proteins produced by P. gingivalis. This study recommends future research to direct towards applicability of MBs in commercial dental products.

Novel therapeutic roles of MC-4 in combination with everolimus against advanced renal cell carcinoma by dual targeting of Akt/pyruvate kinase muscle isozyme M2 and mechanistic target of rapamycin complex 1 pathways

Current clinical trials of new anticancer therapies against metastatic renal cell carcinoma (RCC), including molecular-targeted therapies, have not shown promise. The purpose of this study was to preclinically assess the antitumor effects of MC-4, a partially purified material of Artemisia annua L., as a monotherapy or in combination with the known mechanistic target of rapamycin complex 1 (mTORC1) inhibitor, everolimus, against Caki-1 (Von Hippel-Lindau (VHL)+/+) and 786-O (VHL-/-) human RCC cells. MC-4 monotherapy significantly increased tumor growth inhibition and autophagic cell death in RCC cells in vitro and in vivo. Everolimus led to compensatory Akt activation by inhibiting only mTORC1 signaling pathway. In contrast to everolimus, MC-4 enhanced phosphatase and tensin homolog expression and reduced its downstream effector, Akt/pyruvate kinase muscle isozyme M2 (PKM2), leading to decreased expression of glucose transporter 1, which is associated with cancer cell metabolism. The synergistic antitumor and anti-metastatic effects induced by co-administration of MC-4 and everolimus involve cell growth inhibition and autophagic cell death via dual targeting of phosphatidylinositol 3-kinase (PI3K)/Akt/PKM2 and mTORC1. These findings suggest that MC-4 is a novel Akt/PKM2 inhibitor that can overcome the limitation of existing mTOR inhibitors and can be considered a novel strategy to treat patients with rapidly progressing advanced RCC.