Natural Products as a Vital Source for the Discovery of Cancer Chemotherapeutic and Chemopreventive Agents

Transferrin-bearing liposomes entrapping plumbagin for targeted cancer therapy

The therapeutic potential of plumbagin, a naphthoquinone extracted from the officinal leadwort with anticancer properties, is hampered by its failure to specifically reach tumours at a therapeutic concentration after intravenous administration, without secondary effects on normal tissues. Its use in clinic is further limited by its poor aqueous solubility, its spontaneous sublimation, and its rapid elimination in vivo. We hypothesize that the entrapment of plumbagin within liposomes grafted with transferrin, whose receptors are overexpressed on many cancer cells, could result in a selective delivery to tumours after intravenous administration. The objectives of this study were therefore to prepare and characterize transferrin-targeted liposomes entrapping plumbagin and to evaluate their therapeutic efficacy in vitro and in vivo. The entrapment of plumbagin in transferrin-bearing liposomes led to an increase in plumbagin uptake by cancer cells and improved antiproliferative efficacy and apoptosis activity in B16-F10, A431, and T98G cell lines compared with that observed with the drug solution. In vivo, the intravenous injection of transferrin-bearing liposomes entrapping plumbagin led to tumour suppression for 10% of B16-F10 tumours and tumour regression for a further 10% of the tumours. By contrast, all the tumours treated with plumbagin solution or left untreated were progressive. The animals did not show any signs of toxicity. Transferrin-bearing liposomes entrapping plumbagin are therefore highly promising therapeutic systems that should be further optimized as a therapeutic tool for cancer treatment.

Focus on Formononetin: Anticancer Potential and Molecular Targets

Formononetin, an isoflavone, is extracted from various medicinal plants and herbs, including the red clover (Trifolium pratense) and Chinese medicinal plant Astragalus membranaceus. Formononetin's antioxidant and neuroprotective effects underscore its therapeutic use against Alzheimer's disease. Formononetin has been under intense investigation for the past decade as strong evidence on promoting apoptosis and against proliferation suggests for its use as an anticancer agent against diverse cancers. These anticancer properties are observed in multiple cancer cell models, including breast, colorectal, and prostate cancer. Formononetin also attenuates metastasis and tumor growth in various in vivo studies. The beneficial effects exuded by formononetin can be attributed to its antiproliferative and cell cycle arrest inducing properties. Formononetin regulates various transcription factors and growth-factor-mediated oncogenic pathways, consequently alleviating the possible causes of chronic inflammation that are linked to cancer survival of neoplastic cells and their resistance against chemotherapy. As such, this review summarizes and critically analyzes current evidence on the potential of formononetin for therapy of various malignancies with special emphasis on molecular targets.

Natural compound inducers of immunogenic cell death

Accumulating evidence shows that the anti-cancer potential of the immune response that can be activated by modulation of the immunogenicity of dying cancer cells. This regulated cell death process is called immunogenic cell death (ICD) and constitutes a new innovating anti-cancer strategy with immune-modulatory potential thanks to the release of damage-associated molecular patterns (DAMPs). Some conventional clinically-used chemotherapeutic drugs, as well as preclinically-investigated compounds of natural origins such as anthracyclines, microtubule-destabilizing agents, cardiac glycosides or hypericin derivatives, possess such an immune-stimulatory function by triggering ICD. Here, we discuss the effects of ICD inducers on the release of DAMPs and the activation of corresponding signaling pathways triggering immune recognition. We will discuss potential strategies allowing to overcome resistance mechanisms associated with this treatment approach as well as co-treatment strategies to overcome the immunosuppressive microenvironment. We will highlight the potential role of metronomic immune modulation as well as targeted delivery of ICD-inducing compounds with nanoparticles or liposomal formulations to improving the immunogenicity of ICD inducers aiming at long-term clinical benefits.

Daucosterol induces autophagic-dependent apoptosis in prostate cancer via JNK activation

Plant sterols (phytosterols) have been widely accepted as a natural anti-cancer agent in multiple malignant tumors. This study was designed to investigate the functions of daucosterol in prostate cancer progression and its possible molecular mechanisms. Our results showed that daucosterol inhibited cell proliferation and induced cell cycle arrest. Moreover, daucosterol treatment obviously promoted apoptosis and autophagy. An autophagy inhibitor, 3-methyladenine (3-MA) was proved to counteract daucosterol-triggered autophagy, growth inhibition, and apoptosis, indicating that daucosterol-induced apoptotic response was dependent on autophagy. Additionally, treatment with daucosterol resulted in increased phosphorylation of c-Jun N-terminal kinase (JNK). Furthermore, pre-treatment with a JNK-specific inhibitor SP600125 abated daucosterol-elicited autophagy and apoptotic cell death. Taken together, our findings demonstrated that daucosterol blocked prostate cancer growth at least partly through inducing autophagic-dependent apoptosis via activating JNK signaling, providing a promising candidate for the development of antitumor drugs in prostate cancer treatment.

Gypenoside L Inhibits Proliferation of Liver and Esophageal Cancer Cells by Inducing Senescence

Senescence is an irreversible state of cell cycle arrest that can be triggered by multiple stimuli, such as oxygen reactive species and DNA damage. Growing evidence has proven that senescence is a tumor-suppressive approach in cancer treatment. Therefore, developing novel agents that modulate senescence may be an alternative strategy against cancer. In our study, we investigated the inhibitory effect of gypenoside L (Gyp-L), a saponin isolated from Gynostemma pentaphyllum, on cancer cell growth. We found that Gyp-L increased the SA-β-galactosidase activity, promoted the production of senescence-associated secretory cytokines, and inhibited cell proliferation of human liver and esophageal cancer cells. Moreover, Gyp-L caused cell cycle arrest at S phase, and activated senescence-related cell cycle inhibitor proteins (p21 and p27) and their upstream regulators. In addition, Gyp-L activated p38 and ERK MAPK pathways and NF-κB pathway to induce senescence. Consistently, adding chemical inhibitors efficiently counteracted the Gyp-L-mediated senescence, growth inhibition, and cell cycle arrest in cancer cells. Furthermore, treatment with Gyp-L, enhanced the cytotoxicity of clinic therapeutic drugs, including 5-fluorouracil and cisplatin, on cancer cells. Overall, these results indicate that Gyp-L inhibits proliferation of cancer cells by inducing senescence and renders cancer cells more sensitive to chemotherapy.

Small molecules as therapeutic drugs for Alzheimer's disease

Mitochondrial dysfunction is a central protagonist of Alzheimer's disease (AD) pathogenesis. Mitochondrial dysfunction stems from various factors including mitochondrial DNA damage and oxidative stress from reactive oxygen species, membrane and ionic gradient destabilization, and interaction with toxic proteins such as amyloid beta (Aβ). Therapeutic drugs such as cholinesterase and glutamate inhibitors have proven to improve synaptic neurotransmitters, but do not address mitochondrial dysfunction. Researchers have demonstrated that oxidative damage may be reduced by increasing endogenous antioxidants, and/or increasing exogenous antioxidants such as vitamin C & E, beta-carotene and glutathione. Nonetheless, as AD pathology intensifies, endogenous antioxidants are overwhelmed, and exogenous antioxidants are unable to reach neuronal mitochondria as they are blocked by the blood brain barrier. Current therapeutic methods however include novel usage of lipophilic phosphonium cation bound to antioxidants, to effect neuronal mitochondria targeted activity. Mitochondria targeted MitoQ, MitoVitE, MitoTempo, MitoPBN and MCAT concentrate within mitochondria where they scavenge free-radicals, and augment mitochondrial dysfunction. Additional molecules include Szeto-Schiller (SS) peptides which target stability of the inner mitochondrial membrane, and DDQ molecule capable of improving bioenergetics and reduce mitochondrial fragmentation. This article discusses advantages and disadvantages of small molecules, their ability to mitigate Aβ induced damage, and ability to ameliorate synaptic dysfunction and cognitive loss.

Ursolic Acid Exhibits Potent Anticancer Effects in Human Metastatic Melanoma Cancer Cells (SK-MEL-24) via Apoptosis Induction, Inhibition of Cell Migration and Invasion, Cell Cycle Arrest, and Inhibition of Mitogen-Activated Protein Kinase (MAPK)/ERK Signaling Pathway

BACKGROUND Ursolic acid is an important bioactive triterpenoid that has been reported to be of tremendous pharmacological importance. However, the anticancer potential of ursolic acid has not been examined against metastatic melanoma cells. Therefore, in this study we examined the anticancer potential of ursolic acid and its mode of action. MATERIAL AND METHODS WST-1 and colony formation assays were used for cell viability assessment. Cell cycle analysis was performed by flow cytometry. Apoptosis was detected by AO/EB staining using fluorescence microscopy. Cell migration and invasion were assessed by Boyden chamber assay. Protein expression was checked by Western blotting. RESULTS The results revealed that ursolic acid exerts significant (p<0.01) growth-inhibitory effects on SK-MEL-24 cells. The IC₅₀ of ursolic acid against SK-MEL-24 cells was 25 µM. Our investigation of the underlying mechanism revealed that ursolic acid prompts apoptotic cell death of the SK-MEL-24 cells, which was linked with increased expression of Bax and Caspase 3 and 9, and decreased expression of Bcl-2. Ursolic acid also halted the SK-MEL-24 cells at G0/G1 phase of the cell cycle and also downregulated the expression of Cyclin B1 and Cdc25. Ursolic acid significantly (p<0.01) inhibited the migration and invasion of SK-MEL-2 cells, indicative of its anti-metastatic potential. Finally, ursolic acid inhibited the MAPK/ERK pathway by suppressing the expression of p-P38 and p-ERK. CONCLUSIONS Ursolic acid appears to be a potent molecule for the treatment of melanoma.

Aurone: A biologically attractive scaffold as anticancer agent

Aurones are very simple, promising anticancer lead molecules containing three rings (A, B and C). A very slight structural variation in the aurones elicits diverse affinity and specificity towards different molecular targets. The present review discusses the design, discovery and development of natural and synthetic aurones as small molecule anticancer agents. Detailed structure-activity relationship and intermolecular interactions at different targets are also discussed. Due to their rare occurrence in nature and minimal mention in literature, the anticancer potential of aurones is rather recent but in constant progress.

A Review of Resveratrol as a Potent Chemoprotective and Synergistic Agent in Cancer Chemotherapy

Background: Cancer has become a major disease endangering human health around the world. Conventional chemotherapy suffers from many side effects including pain, cardiotoxicity, hepatotoxicity, and renal toxicity. This review aims to describe a natural product of resveratrol as a chemoprotective and synergistic agent in the modulation of cancer chemotherapy. Methods: The publications were identified by comprehensive searching of SciFinder, PubMed, Web of Science, and our own reference library. Search terms included combinations of "resveratrol," "cancer," "natural products," "chemotherapy," and "side effects." Selection of material focused on resveratrol reducing the side effects on cancer chemotherapy. Results: Thirty one references were referred in this review to outline resveratrol as a potent chemoprotective and synergistic agent in cancer chemotherapy, including 22 papers for describing the chemoprotective effects, and 9 papers for illustrating the synergistic effects. Conclusion: This study provides a systematic summary of resveratrol serving as a potent chemoprotective and synergistic agent to reduce the associated-side effects and enhance the therapeutic outcomes in cancer chemotherapy. Further studies in terms of resveratrol on a large amount of preclinical tests and clinical trials are highly demanded.

Resveratrol: Twenty Years of Growth, Development and Controversy

Resveratrol was first isolated in 1939 by Takaoka from Veratrum grandiflorum O. Loes. Following this discovery, sporadic descriptive reports appeared in the literature. However, spurred by our seminal paper published nearly 60 years later, resveratrol became a household word and the subject of extensive investigation. Now, in addition to appearing in over 20,000 research papers, resveratrol has inspired monographs, conferences, symposia, patents, chemical derivatives, etc. In addition, dietary supplements are marketed under various tradenames. Once resveratrol was brought to the limelight, early research tended to focus on pharmacological activities related to the cardiovascular system, inflammation, and cancer but, over the years, the horizon greatly expanded. Around 130 human clinical trials have been (or are being) conducted with varying results. This may be due to factors such as disparate doses (ca. 5 to 5,000 mg/day) and variable experimental settings. Further, molecular targets are numerous and a dominant mechanism is elusive or nonexistent. In this context, the compound is overtly promiscuous. Nonetheless, since the safety profile is pristine, and use as a dietary supplement is prevalent, these features are not viewed as detrimental. Given the ongoing history of resveratrol, it is reasonable to advocate for additional development and further clinical investigation. Topical preparations seem especially promising, as do conditions that can respond to anti-inflammatory action and/or direct exposure, such as colon cancer prevention. Although the ultimate fate of resveratrol remains an open question, thus far, the compound has inspired innovative scientific concepts and enhanced public awareness of preventative health care.

Induction of Apoptosis by Extract of Persian Gulf Marine Mollusk, Turbo Coronatus through the ROS-Mediated Mitochondrial Targeting on Human Epithelial Ovarian Cancer Cells

Despite recent improvements in treatment, ovarian cancer is still the leading cause of death from gynaecological malignancies. Today, marine mollusks are considered as natural source of new biologically and pharmacologically active compounds by scientists and the pharmaceutical industries. The aim of this study is to investigate the selective apoptotic effects of Turbo coronatus crude extract fractions on human epithelial ovarian cancer (EOC) cells and mitochondria. The cells and mitochondria were isolated from cancerous and non-cancerous ovarian tissues and exposed to IC₅₀ concentration of F1 fraction for evaluation of mitochondrial and cellular parameters. Our results showed that F1 fraction of T. coronatus crude extract significantly induced toxic effects only in the cancerous ovarian mitochondria, including increased reactive oxygen species (ROS) formation, mitochondrial membrane depolarization, mitochondrial swelling, and cytochrome c release.Flow-cytometry analysis demonstrated that F1 fraction of T. coronatus progressively induced apoptosis and necrosis only on EOC but not non-cancerous cells. We eventuallyconcluded that F1 fraction of T. coronatus crude extract selectively induces apoptosis in EOC through a ROS- mediated pathway.

Pinostrobin inhibits proliferation and induces apoptosis in cancer stem-like cells through a reactive oxygen species-dependent mechanism

Current treatments and targeted therapies for malignancies are limited due to their severe toxicity and the development of resistance against such treatments, which leads to relapse. Past evidence has indicated that a number of plant-derived dietary agents possess biological activity against highly tumorigenic and resistant cell populations associated with cancer relapse. These subpopulations, termed cancer stem-like cells (CSCs), have been targeted with plant-derived dietary flavonoids. The present study was undertaken to assess the anti-proliferative potential of pinostrobin, a dietary flavonoid, against CSCs. Sphere-forming cells were developed from HeLa cell lines using specific culture conditions. The existence of a CSC population was confirmed by the morphological examination and analysis of surface markers using confocal microscopy and flow cytometry. The effect of pinostrobin on the cell viability of the CSC population, evaluated through MTT reduction assays and the expression levels of surface markers (CD44⁺ and CD24⁺), was studied through various biological assays. HeLa-derived CSCs showed higher CD44⁺ and lower CD24⁺ expression. Pinostrobin inhibited the self-renewal capacity and sphere formation efficiency of CSCs in a dose-dependent manner. Increased ROS production, and decreased mitochondrial membrane potential and CD44⁺ expression indicated that pinostrobin promoted ROS-mediated apoptosis in CSCs. These results thus demonstrate the therapeutic potential and effectiveness of pinostrobin in the chemoprevention and relapse of cancer by targeting the CSC population. Thus, pinostrobin, in combination with currently available chemo and radiation therapies, could possibly be used as a safe strategy to alleviate adverse treatment effects, together with enhancing the efficacy.

The anti-proliferative potential of pinostrobin, a dietary flavonoid, is evaluated against cancer stem-like cells.

Induction of Apoptosis by an Extract of Persian Gulf Marine Mollusc, Turbo Coronatus through the Production of Reactive Oxygen Species in Mouse Melanoma Cells

Objective: A variety of approaches such as surgery, chemotherapy, radiotherapy, hormonal therapy and immunotherapy are used to treat melanomas, but unfortunately in most case, the response is very weak and often side effects are serious. This study concerns selective toxicity of an extract of Turbo coronatus on cells and mitochondria from a syngeneic mouse model of melanoma. Methods: Cells and mitochondria isolated from extra tumoral and melanoma tissues were exposed toa T. coronatus crude extract and fractions obtained by gel-filtration chromatography and assayed for mitochondrial and cellular parameters. Result: Crude extract (375, 750 and 1,500 μg/ml) and fraction 1; F1; (275, 550 and 1100 μg/ml) of T. coronatus extract induced a significant (p<0.05) increase of the reactive oxygen species (ROS) level, swelling of mitochondria, collapse of mitochondrial membrane potential (MMP), release of cytochrome c and caspase-3 activation only in the mitochondria and cells obtained from melanoma but not extra tumoral tissues. In addition, the F1 fraction decreased the percentage of viable cells and induced apoptosis in melanoma cells. Conclusion: For the first time we could demonstrate that the F1 fraction of a T. coronatus extract, selectively induces ROS mediated cytotoxicity by directly targeting mitochondria in melanoma tissues and it may be a suitable candidate for novel drug treatment of malignant melanomas.

Anti-metastatic and anti-proliferative activity of eugenol against triple negative and HER2 positive breast cancer cells

Background

Eugenol is a natural phenolic compound and possesses anticancer and antibacterial activities. Breast cancer is a major global health problem, and most of the chemotherapeutic agents are highly toxic with long-term side effects. Therefore, this study aimed to explore the possibility of using eugenol as an anti-metastatic and anti-proliferative agent against MDA-MB-231 and SK-BR-3 breast cancer cells.

Methods

Breast cancer cell lines MDA-MB-231 and SK-BR-3 were treated with eugenol and cell proliferation was measured using a real-time cell electronic sensing system. Annexin V analysis with flow cytometry was used to detect the effect of eugenol on cell death. In MDA-MB-231 and SK-BR-3 cells, metastatic potential after eugenol treatment was examined using a wound-healing assay. Real-time PCR was used to study the effect of eugenol on the expression of anti-metastatic genes such as MMP2, MMP9, and TIMP-1, and genes involved in apoptosis including Caspase3, Caspase7, and Caspase9.

Results

Treatment with 4 μM and 8 μM eugenol for 48 h significantly inhibited cell proliferation of MDA-MB-231, with an inhibition rate of 76.4%, whereas 5 μM and 10 μM of eugenol for 48 h significantly inhibited the proliferation of SK-BR-3 cells with an inhibition rate of 68.1%. Eugenol-treated cells showed significantly decreased MMP2 and MMP9 expression and an insignificant increase in TIMP1 expression in HER2 positive and triple negative breast cancer cells. Eugenol significantly increased the proportion of MDA-MB-231 and SK-BR-3 cells in late apoptosis and increased the expression of Caspase3, Caspase7, and Caspase9.

Conclusion

To the best of our knowledge, this is the first study to describe the anti-metastatic effect of eugenol against MDA-MB-231 and SK-BR-3 breast cancer cell lines.

Autophagy plays a protective role against apoptosis induced by toxicarioside N via the Akt/mTOR pathway in human gastric cancer SGC-7901 cells

Toxicarioside N (Tox N), a natural product extract from Antiaris toxicaria, has been reported to induce apoptosis in human gastric cancer cells. However, the mechanism and actual role of autophagy in Tox N-induced apoptosis of human gastric cancer cells remains poorly understood. In the current study, we demonstrated that Tox N could induce autophagy by inhibiting the Akt/mTOR signaling pathway in SGC-7901 cells. Moreover, we found that the inhibition of autophagy by 3-methyladenine, an autophagy inhibitor, enhanced Tox N-induced apoptotic cell death. However, the stimulation of autophagy by rapamycin, an autophagy activator, remarkably suppressed Tox N-induced apoptosis, suggesting that autophagy plays a protective role in Tox N-induced apoptosis. Thus, the results from this study suggested that Tox N combination with an autophagy inhibitor might be a promising strategy to enhance the anticancer activity of Tox N for the treatment of human gastric cancer.

Chemical constituents and cytotoxic activity from the wood-decaying fungus Xylaria sp. SWUF08-37

A new cyclic pentapeptide, pentaminolarin (1), and a new cytochalasin, xylochalasin (2), along with thirteen known compounds (3-15) were isolated from the wood-decaying fungus Xylaria sp. SWUF08-37. The absolute configurations of 1 were determined by a combination of Marfey's method and TDDFT ECD calculation and the absolute configurations of 2 were established by TDDFT ECD calculation. Compound 12 showed moderate cytotoxicity against HeLa (IC₅₀ = 19.60 µg/mL), HT29 (IC₅₀ = 17.31 µg/mL), HCT116 (IC₅₀ = 14.28 µg/mL), MCF-7 (IC₅₀ = 15.38 µg/mL), and Vero (IC₅₀ = 24.97 µg/mL) cell lines by MTT assay. Compounds 1 and 2 showed slight cytotoxicity against all tested cancer cell lines.

What Has Come out from Phytomedicines and Herbal Edibles for the Treatment of Cancer?

Several modern treatment strategies have been adopted to combat cancer with the aim of minimizing toxicity. Medicinal plant-based compounds with the potential to treat cancer have been widely studied in preclinical research and have elicited many innovations in cutting-edge clinical research. In parallel, researchers have eagerly tried to decrease the toxicity of current chemotherapeutic agents either by combining them with herbals or in using herbals alone. The aim of this article is to present an update of medicinal plants and their bioactive compounds, or mere changes in the bioactive compounds, along with herbal edibles, which display efficacy against diverse cancer cells and in anticancer therapy. It describes the basic mechanism(s) of action of phytochemicals used either alone or in combination therapy with other phytochemicals or herbal edibles. This review also highlights the remarkable synergistic effects that arise between certain herbals and chemotherapeutic agents used in oncology. The anticancer phytochemicals used in clinical research are also described; furthermore, we discuss our own experience related to semisynthetic derivatives, which are developed based on phytochemicals. Overall, this compilation is intended to facilitate research and development projects on phytopharmaceuticals for successful anticancer drug discovery.

Thymoquinone loaded in nanostructured lipid carrier showed enhanced anticancer activity in 4T1 tumor-bearing mice

Aim: To investigate the enhancement of anticancer activity of thymoquinone (TQ) by the use of nanostructured lipid carrier (NLC) in 4T1 tumor-bearing female BALB/c mice. Material & methods: TQ was incorporated into NLC (TQNLC) by using high pressure homogenization. TQNLC and TQ were orally administered to the mice. Results & conclusion: TQNLC and TQ are potential chemotherapeutic drugs as they exhibited anticancer activity. The use of NLC as a carrier has enhanced the therapeutic property of TQ by increasing the survival rate of mice. The antimetastasis effect of TQNLC and TQ to the lungs was evidence by downregulation of MMP-2. TQNLC and TQ induced apoptosis via modulation of Bcl-2 and caspase-8 in the intrinsic apoptotic pathway.

Antitumor effects of melanin from Lachnum YM226 and its derivative in H22 tumor-bearing mice

In the present study, we investigated the anti-tumor activities of the intracellular homogeneous melanin (LM) of Lachnum YM226 and its derivative (ALM) on liver cancer using murine H22 hepatocarcinoma model. The results showed that LM and ALM (50 and 200 mg kg-1) could effectively inhibit tumor growth of H22 tumour-bearing mice. The body weight, liver, spleen and thymus indices also improved in the LM and ALM treated groups. Moreover, the levels of alanine aminotransferase (ALT), aspartate aminotransaminase (AST), alkaline phosphatase (ALP), creatinine (CRE), blood urea nitrogen (BUN) and uric acid (UA) were lowered. Serum cytokines of interleukin-2 (IL-2), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) were increased on LM and ALM administration, while LM and ALM significantly decreased the vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) levels. The H&E staining indicated that LM and ALM exhibited antitumor activity in vivo by promoting apoptosis and inhibiting angiogenesis. The anti-tumor effect of ALM was more significant than that of LM for the same dose. In summary, the findings demonstrated that LM and ALM might be promising candidates for the prevention and treatment of HCC.

Isothiocyanates: An Overview of Their Antimicrobial Activity against Human Infections

The use of plant-derived products as antimicrobial agents has been investigated in depth. Isothiocyanates (ITCs) are bioactive products resulting from enzymatic hydrolysis of glucosinolates (GLs), the most abundant secondary metabolites in the botanical order Brassicales. Although the antimicrobial activity of ITCs against foodborne and plant pathogens has been well documented, little is known about their antimicrobial properties against human pathogens. This review collects studies that focus on this topic. Particular focus will be put on ITCs’ antimicrobial properties and their mechanism of action against human pathogens for which the current therapeutic solutions are deficient and therefore of prime importance for public health. Our purpose was the evaluation of the potential use of ITCs to replace or support the common antibiotics. Even though ITCs appear to be effective against the most important human pathogens, including bacteria with resistant phenotypes, the majority of the studies did not show comparable results and thus it is very difficult to compare the antimicrobial activity of the different ITCs. For this reason, a standard method should be used and further studies are needed.

Effects of ursolic and oleanolic on SK‑MEL‑2 melanoma cells: In vitro and in vivo assays

Among the triterpenoids, oleanolic acid (OA) and its isomer, ursolic acid (UA) are promising therapeutic candidates, with potential benefits in the management of melanoma. In this study, we aimed to examine the in vitro and in vivo anti‑invasive and anti‑metastatic activity of OA and UA to determine their possible usefulness as chemopreventive or chemotherapeutic agents in melanoma. For the in vitro experiments, the anti‑proliferative activity of the triterpenic compounds on SK‑MEL‑2 melanoma cells was examined. The anti‑invasive potential was assessed by testing the effects of the active compound on vascular cell adhesion molecule (VCAM) and intercellular adhesion molecule (ICAM) adhesion to melanoma cells. Normal and tumor angiogenesis were evaluated in vivo by chicken embryo chorioallantoic membrane (CAM) assay. The two test triterpenoid acids, UA and OA, exerted differential effects in vitro and in vivo on the SK‑MEL‑2 melanoma cells. UA exerted a significant and dose‑dependent anti‑proliferative effect in vitro, compared to OA. The cytotoxic effects in vitro on the melanoma cells were determined by the examining alterations in the cell cycle phases induced by UA that lead to cell arrest in the S phase. Moreover, UA was found to affect SK‑MEL‑2 melanoma cell invasiveness by limiting the cell adhesion capacity to ICAM molecules, but not influencing their adhesion to VCAM molecules. On the whole, in this study, by assessing the effects of the two triterpenoids in vivo, our results revealed that OA had a greater potential to impair the invasive capacity and tumor angiogenesis compared with UA.

Therapeutic effects of the euglenoid ichthyotoxin, euglenophycin, in colon cancer

Colorectal cancer (CRC) remains one of the most commonly diagnosed cancers and the 3^rd leading cause of cancer-related mortality. The emergence of drug resistance poses a major challenge in CRC care or treatment. This can be addressed by determining cancer mechanisms, discovery of druggable targets, and development of new drugs. In search for novel agents, aquatic microorganisms offer a vastly untapped pharmacological source that can be developed for cancer therapeutics. In this study, we characterized the anti-colorectal cancer potential of euglenophycin, a microalgal toxin from Euglena sanguinea. The toxin (49.1-114.6 μM) demonstrated cytotoxic, anti-proliferative, anti-clonogenic, and anti-migration effects against HCT116, HT29, and SW620 CRC cells. We identified G1 cell cycle arrest and cell type - dependent modulation of autophagy as mechanisms of growth inhibition. We validated euglenophycin’s anti-tumorigenic activity in vivo using CRL:Nu(NCr)Foxn1^nu athymic nude mouse CRC xenograft models. Intraperitoneal toxin administration (100 mg/kg; 5 days) decreased HCT116 and HT29 xenograft tumor volumes (n=10 each). Tumor inhibition was associated with reduced expression of autophagy negative regulator mechanistic target of rapamycin (mTOR) and decreased trend of serum pro-inflammatory cytokines. Together, these results provide compelling evidence that euglenophycin can be a promising anti-colorectal cancer agent targeting multiple cancer-promoting processes. Furthermore, this study supports expanding natural products drug discovery to freshwater niches as prospective sources of anti-cancer compounds.

Moringa isothiocyanate complexed with α-cyclodextrin: a new perspective in neuroblastoma treatment

BACKGROUND

Several lines of evidence suggest the consume of natural products for cancer prevention or treatment. In particular, isothiocyanates (ITCs) exerting anti-cancer properties, have received great interest as potential chemotherapeutic agents. This study was designed to assess the anti-proliferative activities of a new preparation of Moringa oleifera-derived 4-(α-L-rhamnopyranosyloxy)benzyl ITC (moringin) complexed with alpha-cyclodextrin (moringin + α-CD; MAC) on SH-SY5Y human neuroblastoma cells. This new formulation arises in the attempt to overcome the poor solubility and stability of moringin alone in aqueous media.

METHODS

SH-SY5Y cells were cultured and exposed to increasing concentrations of MAC (1.0, 2.5 and 5.0 μg). Cell proliferation was examined by MTT and cell count assays. The cytotoxic activity of the MAC complex was assessed by lactate dehydrogenase (LDH) assay and trypan blue exclusion test. In addition, western blotting analyses for the main apoptosis-related proteins were performed.

RESULTS

Treatment of SH-SY5Y cells with the MAC complex reduced cell growth in concentration dependent manner. Specifically, MAC exhibited a potent action in inhibiting the PI3K/Akt/mTOR pathway, whose aberrant activation was found in many types of cancer. MAC was also found to induce the nuclear factor-κB (NF-κB) p65 activation by phosphorylation and its translocation into the nucleus. Moreover, treatment with MAC was able to down-regulate MAPK pathway (results focused on JNK and p38 expression). Finally, MAC was found to trigger apoptotic death pathway (based on expression levels of cleaved-caspase 3, Bax/Bcl-2 balance, p53 and p21).

CONCLUSION

These findings suggest that use of MAC complex may open novel perspectives to improve the poor prognosis of patients with neuroblastoma.

A Flavone Constituent from Myoporum bontioides Induces M-Phase Cell Cycle Arrest of MCF-7 Breast Cancer Cells

Myoporum bontioides is a traditional medicinal plant in Asia with various biological activities, including anti-inflammatory and anti-bacterial characteristics. To identify the bioactive constituents from M. bontioides, a newly-identified flavone, 3,4'-dimethoxy-3',5,7-trihydroxyflavone (compound 1), along with eight known compounds, were investigated in human MCF-7 breast cancer, SCC4 oral cancer, and THP-1 monocytic leukemia cells. Among these compounds, compound 1 exhibited the strongest antiproliferative activity with half-maximal inhibitory concentration (IC₅₀) values ranging from 3.3 μM (MCF-7) to 8.6 μM (SCC4). Flow cytometric analysis indicated that compound 1 induced G2/M cell cycle arrest in MCF-7 cells. Mechanistic evidence suggests that the G2/M arrest could be attributable to compound 1's modulatory effects on the phosphorylation and expression of numerous key signaling effectors, including cell division cycle 2 (CDC2), CDC25C, and p53. Notably, compound 1 downregulated the expression of histone deacetylase 2 (HDAC2) and HDAC4, leading to increased histone H3 acetylation and p21 upregulation. Together, these findings suggest the translational potential of compound 1 as a breast cancer treatment.

Marine Antibody-Drug Conjugates: Design Strategies and Research Progress

Antibody-drug conjugates (ADCs), constructed with monoclonal antibodies (mAbs), linkers, and natural cytotoxins, are innovative drugs developed for oncotherapy. Owing to the distinctive advantages of both chemotherapy drugs and antibody drugs, ADCs have obtained enormous success during the past several years. The development of highly specific antibodies, novel marine toxins' applications, and innovative linker technologies all accelerate the rapid R&D of ADCs. Meanwhile, some challenges remain to be solved for future ADCs. For instance, varieties of site-specific conjugation have been proposed for solving the inhomogeneity of DARs (Drug Antibody Ratios). In this review, the usages of various natural toxins, especially marine cytotoxins, and the development strategies for ADCs in the past decade are summarized. Representative ADCs with marine cytotoxins in the pipeline are introduced and characterized with their new features, while perspective comments for future ADCs are proposed.

Harnessing Plant Biodiversity for the Discovery of Novel Anticancer Drugs Targeting Microtubules

The microtubule cytoskeleton plays a critical role in a wide range of cellular activities and has been shown to be a highly effective target for the treatment of human malignancies. Despite the recent focus on proteomics and high-throughput profiling, it is clear that analysis of plant extracts has yielded several highly efficacious microtubule-targeting agents (MTAs) currently in clinical use, as well as agents in the current pipeline with promising efficacy. To date, a large proportion of the world's plant biodiversity remains untapped by the pharmaceutical industry, presenting a major opportunity for the discovery of novel pharmacologically active lead compounds. Because plants contain an astonishing array of structurally diverse molecules, they represent an ideal source for the discovery of novel MTA leads. To demonstrate the importance of searching for novel bioactive compounds across the plant kingdom, herein, we summarize the discovery and development of plant-derived MTAs and discuss the challenges associated with searching for novel bioactive compounds from plants. We propose potential solutions to these problems with the aim of facilitating further exploration and identification of novel MTAs from plant biodiversity.

Endophytic fungi associated with Taxus fuana (West Himalayan Yew) of Pakistan: potential bio-resources for cancer chemopreventive agents

CONTEXT

Endophytic fungi, being a prolific source of bioactive secondary metabolites, are of great interest for natural product discovery.

OBJECTIVE

Isolation and partial characterization of endophytic fungi inhabiting the leaves and woody parts of Taxus fuana Nan Li & R.R. Mill. (Taxaceae) and evaluation of biological activity.

MATERIALS AND METHODS

Endophytic fungal isolates were identified by molecular analysis of internal transcribed spacer (ITS) regions of 18S rDNA. Extracts of the endophytic fungi cultured on potato dextrose agar and modified medium were evaluated using cancer chemoprevention bioassays [inhibition of TNF-α-induced NFκB, aromatase and inducible nitric oxide synthase (iNOS); induction of quinone reductase 1 (QR1)] and growth inhibition with MCF-7 cells.

RESULTS

Nine of 15 fungal isolates were identified as belonging to Epicoccum, Mucor, Penicillium, Chaetomium, Paraconiothriym, Plectania or Trichoderma. Five of the 15 extracts inhibited NFκB activity (IC₅₀ values ranging between 0.18 and 17 μg/mL) and five inhibited iNOS (IC₅₀ values ranging between 0.32 and 12.9 μg/mL). In the aromatase assay, only two isolates mediated inhibition (IC₅₀ values 12.2 and 10.5 μg/mL). With QR1 induction, three extracts exhibited significant activity (concentrations to double activity values ranging between 0.20 and 5.5 μg/mL), and five extracts inhibited the growth of MCF-7 cells (IC₅₀ values ranging from 0.56 to 17.5 μg/mL). Six active cultures were derived from woody parts of the plant material.

CONCLUSION

The endophytic fungi studied are capable of producing pharmacologically active natural compounds. In particular, isolates derived from the wood of Taxus fuana should be prioritized for the isolation and characterization of bioactive constituents.

Dietary flavonoid fisetin for cancer prevention and treatment

Cancer remains a major public health concern and a significant cause of death worldwide. Identification of bioactive molecules that have the potential to inhibit carcinogenesis continues to garner interest among the scientific community. In particular, flavonoids from dietary sources are the most sought after because of their safety, cost-effectiveness, and feasibility of oral administration. Emerging data have provided newer insights into understanding the molecular mechanisms that are essential to identify novel mechanism-based strategies for cancer prevention and treatment. Dietary flavonoid fisetin (3,3',4',7-tetrahydroxyflavone) found in many fruits and vegetables has been shown in preclinical studies to inhibit cancer growth through alteration of cell cycle, inducing apoptosis, angiogenesis, invasion, and metastasis without causing any toxicity to normal cells. Although data from in-vitro and in-vivo studies look convincing, well-designed clinical trials in humans are needed to conclusively determine the efficacy across various cancers. This review highlights the chemopreventive and therapeutic effects, molecular targets, and mechanisms that contribute to the observed anticancer activity of fisetin against various cancers.

Self-assembling nanowires of an amphiphilic camptothecin prodrug derived from homologous derivative conjugation

A novel amphiphilic camptothecin prodrug, CPT-ss-Ir, was synthesized and used to construct self-assembled nanowires, which could release active CPT and Ir species upon intracellular triggering.