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

An Electrophilic Deguelin Analogue Inhibits STAT3 Signaling in H-Ras-Transformed Human Mammary Epithelial Cells: The Cysteine 259 Residue as a Potential Target

Signal transducer and activator of transcription 3 (STAT3) is a point of convergence for numerous oncogenic signals that are often constitutively activated in many cancerous or transformed cells and some stromal cells in the tumor microenvironment. Persistent STAT3 activation in malignant cells stimulates proliferation, survival, angiogenesis, invasion, and tumor-promoting inflammation. STAT3 undergoes activation through phosphorylation on tyrosine 705, which facilitates its dimerization. Dimeric STAT3 translocates to the nucleus, where it regulates the transcription of genes involved in cell proliferation, survival, etc. In the present study, a synthetic deguelin analogue SH48, discovered by virtual screening, inhibited the phosphorylation, nuclear translocation, and transcriptional activity of STAT3 in H-ras transformed human mammary epithelial MCF-10A cells (MCF10A-ras). We speculated that SH48 bearing an α,β-unsaturated carbonyl group could interact with a thiol residue of STAT3, thereby inactivating this transcription factor. Non-electrophilic analogues of SH48 failed to inhibit STAT3 activation, lending support to the above supposition. By utilizing a biotinylated SH48, we were able to demonstrate the complex formation between SH48 and STAT3. SH48 treatment to MCF10A-ras cells induced autophagy, which was verified by staining with a fluorescent acidotropic probe, LysoTracker Red, as well as upregulating the expression of LC3II and p62. In conclusion, the electrophilic analogue of deguelin interacts with STAT3 and inhibits its activation in MCF10A-ras cells, which may account for its induction of autophagic death.

Cytotoxicity Potential of Endophytic Fungi Extracts from Terminalia catappa against Human Cervical Cancer Cells

Endophytic fungi are potential sources of novel bioactive metabolites from a natural product drug discovery perspective. This study reports the bioactivity-directed fractionation of the secondary metabolites of the ethyl acetate extract of a fermentation culture of endophytic fungi from Terminalia catappa which were then evaluated for their cytotoxicity against human cervical cancer (HeLa) cells and human foreskin fibroblast (HFF) cells. Furthermore, apoptosis was determined using the Annexin V/propidium iodide (PI) flow cytometry assay. Endophyte extracts N2, N7, N8, N97, N169, and N233 were obtained from Trichoderma sp, Phoma sp, Phomopsis phyllanticola, Fusarium oxyporum, Collectotrichum sp, and Cryptococcus flavescens, respectively. The N97 extract was most active with a 50% inhibitory concentration (IC₅₀) of 33.35 µg/ml. A 50% cytotoxic concentration (CC₅₀) of 268.4 µg/ml was obtained with HFF cells and the selectivity index (SI) was 8.01. The percentages of cell populations were increased at late apoptosis (Annexin+/PI+), with the percentages of 27.4 ± 0.3 and 19.2 ± 0.01 obtained, respectively, for 50 µg/ml and 80 µg/ml of the N97 extract and 2.1 ± 0.1 obtained for the control in late apoptosis (Annexin V+/PI+) . Moreover, a higher reduction in the percentage of viable cells was observed in the HeLa control cells (93.6 ± 0.3), but the percentages of viable HeLa cells were 37 ± 0.05 and 45 ± 0.1, respectively, for the 50 µg/ml and 80 µg/ml treatments with the N97 extract. Also, the percentages of 34.7 ± 0.1 and 33.9 ± 0.4 were, respectively, obtained for 50 µg/ml and 80 µg/ml compared to the control with 4.6 ± 0.2, in early apoptosis (Annexin V+/PI-). These findings highlight the anticancer potential of the N97 extract of endophytic fungi from Terminalia catappa, which is mediated through apoptosis and presumably also attenuation of chemoresistance.

Proanthocyanidins reduce cellular function in the most globally diagnosed cancers in vitro

BACKGROUND

Growing evidence indicates that proanthocyanidins (PACs) may be effective in treating and preventing various cancers. The fundamental mechanism of PACs inhibiting the proliferation at cellular and molecular levels in most of the cancer types remains unclear.

OBJECTIVE

The anticancer efficacy of PACs was investigated in vitro using three human cancer cell lines: human colorectal adenocarcinoma (HT-29), human breast carcinoma (MCF-7), and human prostatic adenocarcinoma (PC-3).

METHODS

Cytotoxicity was evaluated by MTT assay, while cell proliferation was measured by trypan blue exclusion method. Cell migration was measured by wound healing assay, and DAPI staining was used to evaluate apoptotic nucleus morphology. RT-PCR was used to analyze the expression of Bax and Bcl-2, and caspase enzyme activity assay was measured by caspase colorimetric assay.

RESULTS

PACs could inhibit both cellular viability and proliferation in a concentration- and time-dependent fashion in all investigated cells. Further, all tested cells showed similarly decreased migration after 24- and 48-h PAC treatment. We observed increased apoptotic nucleus morphology in treated cells (p ≤ 0.01). BAX expression significantly increased in HT-29 (p < 0.01), PC-3(p < 0.01), and MCF-7 (p < 0.05) cells, while BCL-2 expression significantly declined (p < 0.05). Caspase activities were significantly increased in all tested cancer cell lines after 24-h PAC treatment.

CONCLUSION

PACs may have potential therapeutic properties against colorectal, breast, and prostate cancer.

Withanolide Metabolites Inhibit PI3K/AKT and MAPK Pro-Survival Pathways and Induce Apoptosis in Acute Myeloid Leukemia Cells

Acute myeloid leukemia (AML) is an aggressive disease and, despite advances, its treatment remains challenging. Therefore, it remains important to identify new agents for the management of this disease. Withanolides, a group of steroidal lactones found in Solanaceae plants are of potential interest due to their reported anticancer activities in different settings. In this study we investigated the anti-proliferative effects and mode of action of Solanaceae-derived withanolides in AML cell models; these metabolites include withametelin (WTH) and Coagulansin A (CoA) isolated from Datura innoxia and Withania coagluanse, respectively. Both withanolides inhibited the proliferation of AML cells and induced cell death, with WTH being more potent than CoA in the AML models tested. Quantitative label-free proteomics and phosphoproteomics were employed to define the mechanism of action of the studied withanolides. We identified and quantified 5269 proteins and 17,482 phosphosites in cells treated with WTH, CoA or vehicle control. Withanolides modulated the expression of proteins involved in regulating key cellular processes including cell cycle, metabolism, signaling, protein degradation and gene expression. Enrichment analysis of the phosphoproteomics data against kinase substrates, kinase-kinase relationships and canonical pathways showed that the withanolides decreased the activity of kinases such as phosphoinositide 3-kinase (PI3K), protein kinase B (PKB; also known as RAC-alpha serine/threonine-protein kinase or AKT), mammalian target of rapamycin (mTOR), extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) and the serine/threonine-protein kinase A-Raf (ARAF), while increasing the activation of DNA repair kinases. These results indicate that withanolide metabolites have pleiotropic effects in the modulation of oncogenic pro-survival and pro-apoptotic signaling pathways that regulate the induction of apoptosis. Withanolide mediated apoptosis was confirmed by immunoblotting showing increased expression of cleaved PARP and Caspases 3, 8 and 9 as a result of treatment. Overall, our results suggest that WTH and CoA have therapeutic potential against AML with WTH exhibiting more potent effects and should be explored further.

Ethiopian Medicinal Plants Traditionally Used for the Treatment of Cancer, Part 2: A Review on Cytotoxic, Antiproliferative, and Antitumor Phytochemicals, and Future Perspective

This review provides an overview on the active phytochemical constituents of medicinal plants that are traditionally used to manage cancer in Ethiopia. A total of 119 articles published between 1968 and 2020 have been reviewed, using scientific search engines such as ScienceDirect, PubMed, and Google Scholar. Twenty-seven medicinal plant species that belong to eighteen families are documented along with their botanical sources, potential active constituents, and in vitro and in vivo activities against various cancer cells. The review is compiled and discusses the potential anticancer, antiproliferative, and cytotoxic agents based on the types of secondary metabolites, such as terpenoids, phenolic compounds, alkaloids, steroids, and lignans. Among the anticancer secondary metabolites reported in this review, only few have been isolated from plants that are originated and collected in Ethiopia, and the majority of compounds are reported from plants belonging to different areas of the world. Thus, based on the available bioactivity reports, extensive and more elaborate ethnopharmacology-based bioassay-guided studies have to be conducted on selected traditionally claimed Ethiopian anticancer plants, which inherited from a unique and diverse landscape, with the aim of opening a way forward to conduct anticancer drug discovery program.

Apoptosis in Leukemic Cells Induced by Anti-proliferative Coumarin Isolated from the Stem Bark of Fraxinus rhynchophylla

Esculetin 6-O-β-D-arabinofuranosyl-(1→6)-β-D-glucopyranoside (EAG) is a coumarin glycoside isolated from the stem bark of Fraxinus rhynchophylla. This study scrutinized the anti-proliferative activity of EAG on blood cancer-derived Jurkat leukemic cells. Cell viability assays in leukemic cancer cells determined that EAG possesses potent anti-proliferative effects. Moreover, treatment with EAG increased the proportion of apoptotic cells, resulted in cell cycle arrest being induced at the subG0/ G1 phase, and reduced the proportion of cells present in the S phase. In addition, mitochondrial membrane potential was reduced by EAG in Jurkat cells. Additionally, EAG triggered apoptosis that was mediated by the downregulation of BCL-XL, p-IκBα, and p-p65 expressions in addition to the upregulation of cleaved Caspase 3 and BAX expressions. These findings revealed that the toxic effect of EAG was mediated by intracellular signal transduction pathways that involved a mechanism in which reactive oxygen species (ROS) were upregulated. Thus, this study concludes that EAG could potentially serve as a therapeutic agent for leukemia.

Heterologous Expression of the Unusual Terreazepine Biosynthetic Gene Cluster Reveals a Promising Approach for Identifying New Chemical Scaffolds

Advances in genome sequencing have revitalized natural product discovery efforts, revealing the untapped biosynthetic potential of fungi. While the volume of genomic data continues to expand, discovery efforts are slowed due to the time-consuming nature of experiments required to characterize new molecules. To direct efforts toward uncharacterized biosynthetic gene clusters most likely to encode novel chemical scaffolds, we took advantage of comparative metabolomics and heterologous gene expression using fungal artificial chromosomes (FACs). By linking mass spectral profiles with structural clues provided by FAC-encoded gene clusters, we targeted a compound originating from an unusual gene cluster containing an indoleamine 2,3-dioxygenase (IDO). With this approach, we isolate and characterize R and S forms of the new molecule terreazepine, which contains a novel chemical scaffold resulting from cyclization of the IDO-supplied kynurenine. The discovery of terreazepine illustrates that FAC-based approaches targeting unusual biosynthetic machinery provide a promising avenue forward for targeted discovery of novel scaffolds and their biosynthetic enzymes, and it also represents another example of a biosynthetic gene cluster "repurposing" a primary metabolic enzyme to diversify its secondary metabolite arsenal.IMPORTANCE Here, we provide evidence that Aspergillus terreus encodes a biosynthetic gene cluster containing a repurposed indoleamine 2,3-dioxygenase (IDO) dedicated to secondary metabolite synthesis. The discovery of this neofunctionalized IDO not only enabled discovery of a new compound with an unusual chemical scaffold but also provided insight into the numerous strategies fungi employ for diversifying and protecting themselves against secondary metabolites. The observations in this study set the stage for further in-depth studies into the function of duplicated IDOs present in fungal biosynthetic gene clusters and presents a strategy for accessing the biosynthetic potential of gene clusters containing duplicated primary metabolic genes.

Targeting Multiple Signaling Pathways in Cancer: The Rutin Therapeutic Approach

Multiple dysregulated signaling pathways are implicated in the pathogenesis of cancer. The conventional therapies used in cancer prevention/treatment suffer from low efficacy, considerable toxicity, and high cost. Hence, the discovery and development of novel multi-targeted agents to attenuate the dysregulated signaling in cancer is of great importance. In recent decades, phytochemicals from dietary and medicinal plants have been successfully introduced as alternative anticancer agents due to their ability to modulate numerous oncogenic and oncosuppressive signaling pathways. Rutin (also known as rutoside, quercetin-3-O-rutinoside and sophorin) is an active plant-derived flavonoid that is widely distributed in various vegetables, fruits, and medicinal plants, including asparagus, buckwheat, apricots, apples, cherries, grapes, grapefruit, plums, oranges, and tea. Rutin has been shown to target various inflammatory, apoptotic, autophagic, and angiogenic signaling mediators, including nuclear factor-κB, tumor necrosis factor-α, interleukins, light chain 3/Beclin, B cell lymphoma 2 (Bcl-2), Bcl-2 associated X protein, caspases, and vascular endothelial growth factor. A comprehensive and critical analysis of the anticancer potential of rutin and associated molecular targets amongst various cancer types has not been performed previously. Accordingly, the purpose of this review is to present an up-to-date and critical evaluation of multiple cellular and molecular mechanisms through which the anticancer effects of rutin are known to be exerted. The current challenges and limitations as well as future directions of research are also discussed.

Stable Isotope Tracing Metabolomics to Investigate the Metabolic Activity of Bioactive Compounds for Cancer Prevention and Treatment

A major hallmark of cancer is the metabolic reprogramming of cancer cells to fuel tumor growth and proliferation. Various plant-derived bioactive compounds efficiently target the metabolic vulnerabilities of cancer cells and exhibit potential as emerging therapeutic agents. Due to their safety and common use as dietary components, they are also ideal for cancer prevention. However, to render their use as efficient as possible, the mechanism of action of these phytochemicals needs to be well characterized. Stable isotope tracing is an essential technology to study the molecular mechanisms by which nutraceuticals modulate and target cancer metabolism. The use of positionally labeled tracers as exogenous nutrients and the monitoring of their downstream metabolites labeling patterns enable the analysis of the specific metabolic pathway activity, via the relative production and consumption of the labeled metabolites. Although stable isotope tracing metabolomics is a powerful tool to investigate the molecular activity of bioactive compounds as well as to design synergistic nutraceutical combinations, this methodology is still underutilized. This review aims to investigate the research efforts and potentials surrounding the use of stable isotope tracing metabolomics to examine the metabolic alterations mediated by bioactive compounds in cancer.

Natural products and their derivatives: Promising modulators of tumor immunotherapy

A wealth of evidence supports the role of tumor immunotherapy as a vital therapeutic option in cancer. In recent decades, accumulated studies have revealed the anticancer activities of natural products and their derivatives. Increasing interest has been driven toward finding novel potential modulators of tumor immunotherapy from natural products, a hot research topic worldwide. These works of research mainly focused on natural products, including polyphenols (e.g., curcumin, resveratrol), cardiotonic steroids (e.g., bufalin and digoxin), terpenoids (e.g., paclitaxel and artemisinins), and polysaccharide extracts (e.g., lentinan). Compelling data highlight that natural products have a promising future in tumor immunotherapy. Considering the importance and significance of this topic, we initially discussed the integrated research progress of natural products and their derivatives, including target T cells, macrophages, B cells, NKs, regulatory T cells, myeloid‐derived suppressor cells, inflammatory cytokines and chemokines, immunogenic cell death, and immune checkpoints. Furthermore, these natural compounds inactivate several key pathways, including NF‐κB, PI3K/Akt, MAPK, and JAK/STAT pathways. Here, we performed a deep generalization, analysis, and summarization of the previous achievements, recent progress, and the bottlenecks in the development of natural products as tumor immunotherapy. We expect this review to provide some insight for guiding future research.

Hemocyanins from Helix and Rapana Snails Exhibit in Vitro Antitumor Effects in Human Colorectal Adenocarcinoma

Hemocyanins are oxygen-transporting glycoproteins in the hemolymph of arthropods and mollusks that attract scientific interest with their diverse biological activities and potential applications in pharmacy and medicine. The aim of the present study was to assess the in vitro antitumor activity of hemocyanins isolated from marine snail Rapana venosa (RvH) and garden snails Helix lucorum (HlH) and Helix aspersa (HaH), as well the mucus of H. aspersa snails, in the HT-29 human colorectal carcinoma cell line. The effects of the hemocyanins on the cell viability and proliferation were analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the alterations in the tumor cell morphology were examined by fluorescent and transmission electron microscopy. The results of the MTT assay showed that the mucus and α-subunit of hemocyanin from the snail H. aspersa had the most significant antiproliferative activity of the tested samples. Cytomorphological analysis revealed that the observed antitumor effects were associated with induction of apoptosis in the tumor cells. The presented data indicate that hemocyanins and mucus from H. aspersa have an antineoplastic activity and potential for development of novel therapeutics for treatment of colorectal carcinoma.

6H2L, a novel synthetic derivative of bifendate, induces apoptosis in hepatoma cells via mitochondrial and MAPK pathway

Hepatocellular carcinoma (HCC) is a major cause of cancer-related death worldwide. Our previous study indicated that 6H2L, a novel synthetic bifendate derivative, shows multidrug resistance reversal activity, while its antitumor effect has not been revealed. Here, the potent antitumor effects of 6H2L on hepatoma cells both in vitro and in vivo were investigated. 6H2L inhibited cell viability of HepG2 and SMMC-7721 cells with less sensitivity to normal human liver L-02 cells. 6H2L induced apoptosis in hepatoma cells. It upregulated Bax expression, while simultaneously decreasing Bcl-2 expression. Further elucidation of the mechanism revealed that 6H2L induced mitochondrial dysfunction, with transmitochondrial membrane potential collapse and cytochrome c release, which activated caspase-9 and caspase-3 and subsequently cleaved PARP, suggesting that 6H2L induced apoptosis via triggering mitochondrial pathway. Moreover, 6H2L decreased the phosphorylation of ERK1/2, whereas it increased the expression of p-JNK and p-p38. Then, specific inhibitors of the mitogen-activated protein kinase (MAPK) pathway were employed to confirm the roles of the MAPK pathway in the apoptosis-inducing effects of 6H2L. Additionally, 6H2L obviously inhibited the tumor growth in H22-bearing ICR mice. Meanwhile, 6H2L remarkably up-regulated Bax while suppressing Bcl-2 in tumors. Importantly, neither significant weight loss, white blood cell (WBC) count, nor histopathological abnormalities of major organs were observed in the mice receiving 6H2L treatment, indicating that 6H2L exerted strong anticancer activities with low toxicity in vivo. In contrast, fluorouracil inhibited tumor growth with significant decreased body weight and WBC count. Taken together, these results suggested 6H2L is a potential therapeutic candidate for HCC.

Exploring the Mechanism of Flaccidoxide-13-Acetate in Suppressing Cell Metastasis of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common liver or hepatic cancer, accounting for 80% of all cases. The majority of this cancer mortality is due to metastases, rather than orthotopic tumors. Therefore, the inhibition of tumor metastasis is widely recognized as the key strategy for successful intervention. A cembrane-type diterpene, flaccidoxide-13-acetate, isolated from marine soft coral Sinularia gibberosa, has been reported to have inhibitory effects against RT4 and T24 human bladder cancer invasion and cell migration. In this study, we investigated its suppression effects on tumor growth and metastasis of human HCC, conducting Boyden chamber and Transwell assays using HA22T and HepG2 human HCC cell lines to evaluate invasion and cell migration. We utilized gelatin zymography to determine the enzyme activities of matrix metalloproteinases MMP-2 and MMP-9. We also analyzed the expression levels of MMP-2 and MMP-9. Additionally, assays of tissue inhibitors of metalloproteinase-1/2 (TIMP-1/2), the focal adhesion kinase (FAK)/phosphatidylinositide-3 kinases (PI3K)/Akt/mammalian target of the rapamycin (mTOR) signaling pathway, and the epithelial-mesenchymal transition (EMT) process were performed. We observed that flaccidoxide-13-acetate could potentially inhibit HCC cell migration and invasion. We postulated that, by inhibiting the FAK/PI3K/Akt/mTOR signaling pathway, MMP-2 and MMP-9 expressions were suppressed, resulting in HCC cell metastasis. Flaccidoxide-13-acetate was found to inhibit EMT in HA22T and HepG2 HCC cells. Our study results suggested the potential of flaccidoxide-13-acetate as a chemotherapeutic candidate; however, its clinical application for the management of HCC in humans requires further research.

Mango (Mangifera indica L.): a magnificent plant with cancer preventive and anticancer therapeutic potential

Mangifera indica L. (mango), a long-living evergreen plant belonging to the Anacardiaceae family, has been cultivated for thousands of years in the Indian subcontinent for its excellent fruits which represent a rich source of fiber, vitamin A and C, essential amino acids, and a plethora of phytochemicals. M. indica is extensively used in various traditional systems of medicine to prevent and treat several diseases. The health-promoting and disease-preventing effects of M. indica are attributed to a number of bioactive phytochemicals, including polyphenols, terpenoids, carotenoid and phytosterols, found in the leaf, bark, edible flesh, peel, and seed. M. indica has been shown to exhibit various biological and pharmacological activities, such as antioxidant, anti-inflammatory, immunomodulatory, antimicrobial, antidiabetic, antiobesity, and anticancer effects. There are a few studies conducted that have indicated the nontoxic nature of mango constituents. However, while there are numerous individual studies investigating anticancer effects of various constituents from the mango tree, an up-to-date, comprehensive and critical review of available research data has not been performed according to our knowledge. The purpose of this review is to present a comprehensive and critical evaluation of cancer preventive and anticancer therapeutic potential of M. indica and its phytochemicals with special focus on the cellular and molecular mechanisms of action. The bioavailability, pharmacokinetics, and safety profile of individual phytocomponents of M. indica as well as current limitations, challenges, and future directions of research have also been discussed.

Anticancer and Antiangiogenic Activities of Novel α-Mangostin Glycosides in Human Hepatocellular Carcinoma Cells via Downregulation of c-Met and HIF-1α

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and is a leading cause of cancer-related death worldwide. Therefore, exploring effective anticancer agents and their modes of action is essential for the prevention and treatment of HCC. Glycosylation can significantly improve the physicochemical and biological properties of small molecules, such as high solubility, stability increase, and lower toxicity. In the present study, for the first time, we evaluated the anticancer and antiangiogenic activities of α-mangostin-3-O-β-D-2-deoxyglucopyranoside (Man-3DG) and α-mangostin 6-O-β-D-2-deoxyglucopyranoside (Man-6DG), glycosides of α-mangostin, against human HCC cells. Our results demonstrated that Man-3DG and Man-6DG significantly suppressed the growth of three different HCC cells (Hep3B, Huh7, and HepG2) as well as the migration of Hep3B cells. Furthermore, they induced cell cycle arrest in the G0/G1 phases and apoptotic cell death by regulating apoptosis-related proteins of mitochondria in Hep3B cells. Noticeably, Man-3DG and Man-6DG also caused autophagy, while co-treatment of the α-mangostin glycosides with an autophagy inhibitor 3-MA enhanced the inhibitory effect on Hep3B cell growth in comparison to single agent treatment. Moreover, Man-3DG and Man-6DG inhibited the c-Met signaling pathway that plays a critical role in the pathogenesis of HCC. Furthermore, the α-mangostin glycosides decreased Hep3B cell-induced angiogenesis in vitro through the downregulation of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF). Notably, Man-6DG more effectively inhibited the growth, tumorsphere formation, and expression of cancer stemness regulators compared to α-mangostin and Man-3DG in 3D spheroid-cultured Hep3B cells. These findings suggest that the α-mangostin glycosides might be promising anticancer agents for HCC treatment with superior pharmacological properties than the parent molecule α-mangostin.

Periplocin mediates TRAIL-induced apoptosis and cell cycle arrest in human myxofibrosarcoma cells via the ERK/p38/JNK pathway

BACKGROUND

Periploca sepium is traditionally used in Chinese medicine to treat particularly rheumatic disorders and as a tonic. Periplocin was found as the most cytotoxic compound of its root bark and induced death receptor mediated apoptosis in liposarcoma cells. Sarcomas are a rare type of cancer with only a few treatment options. The five-year survival rate of advanced tumors is low.

PURPOSE

In this study, we investigated the effects of periplocin in two myxofibrosarcoma (MFS)cell lines, MUG-Myx2a and MUG-Myx2b, which are subclones of the same tumor and reflect the tumor´s heterogeneity, and in T60 primary myxofibrosarcoma cells.

METHODS

The xCELLigence system and the CellTiter 96® AQueous assay were used for studying cell viability. FACS and Western blot experiments were used to investigate the effects of periplocin on apoptosis induction, cell cycle distribution, and the expression of cleaved PARP, caspase 3, p53, phospho-histone γH2AX, ERK/phospho ERK, p38/phospho p38, and, finally, JNK/phospho JNK. Additionally, the expression of the apoptotic markers Bim, NOXA, Bak, Bcl-2, Bcl-xl, and the death receptors IGFR, FADD, TRADD, TNFR1A, TRAIL-R1, and TRAIL-R2 were evaluated using reversed real-time PCR.

RESULTS

Periplocin decreased dose-dependently the viability of all MFS cell lines and was more effective than the standard chemotherapeutic doxorubicin. It arrested the cells in the G2/M phase and led to caspase activation. Moreover, periplocin increased the mRNA expression of NOXA, Bak, Bcl-2, and death receptors such as TRAIL-R1 and TRAIL-R2 and the protein expression of ERK/phospho ERK, p38/phospho p38, and JNK/phospho JNK. In all cases, differences in the effects in the different subclones were observed.

CONCLUSION

Periplocin showed promising effects in MFS cells. The higher effectiveness compared to doxorubicin is an important aspect for further research with regard as a treatment option. The different effects of periplocin in the two subclones showed the great importance of intratumoral heterogeneity in MFS therapy.

The role of natural products in revealing NRF2 function

Covering: up to 2020The transcription factor NRF2 is one of the body's major defense mechanisms, driving transcription of >300 antioxidant response element (ARE)-regulated genes that are involved in many critical cellular processes including redox regulation, proteostasis, xenobiotic detoxification, and primary metabolism. The transcription factor NRF2 and natural products have an intimately entwined history, as the discovery of NRF2 and much of its rich biology were revealed using natural products both intentionally and unintentionally. In addition, in the last decade a more sinister aspect of NRF2 biology has been revealed. NRF2 is normally present at very low cellular levels and only activated when needed, however, it has been recently revealed that chronic, high levels of NRF2 can lead to diseases such as diabetes and cancer, and may play a role in other diseases. Again, this "dark side" of NRF2 was revealed and studied largely using a natural product, the quassinoid, brusatol. In the present review, we provide an overview of NRF2 structure and function to orient the general reader, we will discuss the history of NRF2 and NRF2-activating compounds and the biology these have revealed, and we will delve into the dark side of NRF2 and contemporary issues related to the dark side biology and the role of natural products in dissecting this biology.

Annona muricata L.-Derived Polysaccharides as a Potential Adjuvant to a Dendritic Cell-Based Vaccine in a Thymoma-Bearing Model

Dendritic cells (DCs) are powerful antigen-presenting cells that are often used to evaluate adjuvants, particularly for adjuvant selection for various vaccines. Here, polysaccharides (named ALP) isolated from leaves of Annona muricata L., which are used in traditional medicine such as for bacterial infections and inflammatory diseases, were evaluated as an adjuvant candidate that can induce anti-tumor activity. We first confirmed the phenotypic (surface molecules, cytokines, antigen uptake, and antigen-presenting ability) and functional alterations (T cell proliferation/activation) of DCs in vitro. We also confirmed the adjuvant effect by evaluating anti-tumor activity and immunity using an ALP-treated DC-immunized mouse model. ALP functionally induced DC maturation by up-regulating the secretion of Th1-polarizing pro-inflammatory cytokines, the expression of surface molecules, and antigen-presenting ability. ALP triggered DC maturation, which is dependent on the activation of the MAPK and NF-κB signaling pathways. ALP-activated DCs showed an ample capacity to differentiate naive T cells to Th1 and activated CD8⁺ T cells effectively. The systemic administration of DCs that pulse ALP and ovalbumin peptides strongly increased cytotoxic T lymphocyte (CTL) activity (by 9.5% compared to that in the control vaccine groups), the generation of CD107a-producing multifunctional T cells, and Th1-mediated humoral immunity, and caused a significant reduction (increased protection by 29% over that in control vaccine groups) in tumor growth. ALP, which triggers the Th1 and CTL response, provides a basis for a new adjuvant for various vaccines.

Betulinic Acid and Brosimine B Hybrid Derivatives as Potential Agents against Female Cancers

Background:

Cancer is a multifactorial disease, representing one of the leading causes of death worldwide. On a global estimate, breast cancer is the most frequently occurring cancer in women and cervical cancer, the fourth most common. Both types of cancer remain the major cause of cancer-related mortality in developing countries. A strategy for rational drug design is hybridization, which aims to bring together in one molecule, two or more pharmacophores in order to reach several biological targets.

Objective:

The objective of this work was to develop new hybrids based on natural pharmacophores: Betulinic acid (1) and brosimine b (2), active in female cancer cell lines.

Methods:

The coupling reactions were carried out by Steglich esterification. Different compounds were designed for the complete and simplified structural hybridization of molecules. The anticancer activities of the compounds were evaluated in human cervical adenocarcinoma (HeLa), human cervical metastatic epidermoid carcinoma (ME-180), and human breast adenocarcinoma (MCF-7) cell lines.

Results:

Hybrid 3 presented higher potency (IC50 = 9.2 ± 0.5μM) and SI (43.5) selectively in MCF-7 cells (in relation to Vero cells) with its cytotoxic effect occurring via apoptosis. In addition, compound 6 showed activity in MCF-7 and HeLa cells with intermediate potency, but with high efficacy, acting via apoptosis as well.

Conclusion:

In this context, we showed that the combination of two complex structures generated the development of hybrids with differing inhibitory profiles and apoptotic modes of action, thus representing potential alternatives in female cancer treatment.

Effects of an ethyl acetate extract of Daphne altaica stem bark on the cell cycle, apoptosis and expression of PPARγ in Eca‑109 human esophageal carcinoma cells

Daphne altaica Pall. (D. altaica; Thymelaeaceae) has long been used in traditional Kazakh medicine for the treatment of cancer and respiratory diseases. Previous studies have demonstrated the in vitro anticancer effects of D. altaica extract and its constituents in certain cancer cell lines; however, the underlying molecular mechanisms are not completely understooD. The present study aimed to investigate the molecular mechanisms underlying the activity of an ethyl acetate extract of D. altaica (Da‑Ea) by assessing its effects on cell morphology, cell apoptosis, cell cycle progression and the expression levels of peroxisome proliferator‑activated receptor γ (PPARγ) in Eca‑109 cells. Cell morphology was observed under a phase contrast microscope. Cell apoptosis and cell cycle progression were assessed by flow cytometry following Annexin V/propidium iodide (PI) double staining and PI single staining, respectively. The mRNA and protein expression levels of PPARγ were determined by reverse transcription‑quantitative PCR and western blotting, respectively. Compared with the control group, the percentage of apoptotic cells, cell cycle arrest at S phase and apoptotic morphological cell characteristics were increased in Da‑Ea‑treated Eca‑109 cells. Furthermore, Da‑Ea treatment upregulated the mRNA and protein expression levels of PPARγ compared with the control cells. High‑performance liquid chromatography with diode‑array detection indicated that daphnetin‑7‑O‑β‑D‑glucoside, daphnetin, demethyldaphnoretin‑7‑O‑β‑D‑glucopyranoside and genkwanol A were the main constituents of Da‑Ea. Collectively, the results suggested that Da‑Ea displayed antiproliferative activities in Eca‑109 cells by inducing apoptosis and S phase cell cycle arrest, as well as upregulating PPARγ expression levels.

Heterologous Biosynthesis of Type II Polyketide Products Using E. coli

The heterologous biosynthesis of complex natural products has enabled access to polyketide, nonribosomal peptide, isoprenoid, and other compounds with wide-spanning societal value. Though several surrogate host systems exist, Escherichia coli is often a preferred choice due to its rapid growth kinetics and extensive molecular biology protocols. However, a persistent challenge to the utilization of E. coli has been the successful in vivo reconstitution of type II polyketide synthase (PKS) systems. In particular, gene expression of the ketosynthase (KS) components of the minimal PKS has consistently yielded insoluble protein products. In the following report, two type II PKS systems were functionally reconstituted in E. coli. The approach to do so relied upon the utilization of the native transcriptional coupling between the dimeric KS subunits, leading to soluble recombinant protein products and successful polyketide biosynthesis. Resulting strains produced 10 mg/L TW95c and 25 mg/L dehydrorabelomycin. Hence, the strategy offers a new option in the biosynthetic engineering efforts for the heterologous production of type II polyketide products using E. coli.

22β-hydroxytingenone reduces proliferation and invasion of human melanoma cells

Melanoma is a skin cancer with high invasive potential and high lethality. Considering that quinonemethide triterpenes are described as promising anticancer agents, the aim of this study was to evaluate the effect of 22β-hydroxytingenone (22-HTG) against human melanoma cells. Alamar blue assay was performed in order to evaluate its cytotoxic effect. Thus, subtoxic concentrations (1.0, 2.0, and 2.5 μM) were used to evaluate the effect of this compound on proliferation, migration, metabolism, and invasion. IC₅₀ value against SK-MEL-28 cell line was 4.35, 3.72, and 3.29 μM after 24, 48, and 72 h of incubation, respectively. 22-HTG reduced proliferation, migration and invasion by melanoma cells, with decreased activity of metalloproteinases (MMP-2 and MMP-9). Futhermore, 22-HTG decreased expression of lactate dehydrogenase (LDHA), an enzyme associated with cell metabolism. Howerver, the small reduction in LDHA enzyme activity must have occurred by the cytotoxic effect of 22-HTG. According to the results, 22-HTG interferes with important characteristics of cancer, with anti-proliferative, and anti-invasive effect against melanoma cells. The data suggest that 22-HTG is an effective substance against melanoma cells and it should be considered as a potential anticancer agent.

Potential Antimicrobial and Anticancer Activities of an Ethanol Extract from Bouea macrophylla

Bouea macrophylla is a tree widely grown throughout South East Asia. It is used in folk medicine for the treatment of various illnesses. The present study aimed to identify the chemical constituents and to test the antimicrobial and anticancer activities of an ethanol extract from B. macrophylla leaves. The extract exhibited excellent antibacterial properties against 9 out of 10 target microorganisms. including four Gram-negative bacteria (Escherichia coli, Shigella flexneri, Vibrio cholera, and Pseudomonas aeruginosa) and four Gram-positive bacteria (Staphylococcus aureus, Listeria monocytogenes, Enterococcus faecalis, and Bacillus cereus), as well as a fungus (Candida albicans). In addition, the extract was also tested on HeLa and human colorectal carcinoma (HCT116) cells to evaluate its cytostatic effects. The ethanol extract was able to inhibit the proliferation of HeLa and HCT116 cells, showing IC₅₀ = 24 ± 0.8 and 28 ± 0.9 µg/mL, respectively, whereas the IC₅₀ values of doxorubicin (standard) were 13.6 ± 1.3 and 15.8 ± 1.1 µg/mL respectively. Also, we identified various bioactive compounds in the extract such as polyphenols, flavonoids, caryophyllene, phytol, and trans-geranylgeraniol by GC-MS, which could contribute to the extract's biological activities. Therefore, our findings strongly indicate that the constituents of the B. macrophylla ethanol extract could be active against the tested bacteria and fungi as well as cancer cells. Further investigation is needed to understand the mechanisms mediating the antimicrobial and anticancer effects and identify signaling pathways that could be targeted for therapeutic application.

Cancer prevention and treatment using combination therapy with natural compounds

Introduction: Naturally occurring compounds play an essential role in the prevention and treatment of various cancers. There are more than 100 plant and animal based natural compounds currently in clinical use.Areas covered: 1) The importance of natural products combinations in the prevention and treatment of cancer, 2) the need to maximize efficacy while minimizing side effects when using natural product combinations, and 3) specifics related to plant and animal derived natural products, as well as agents derived from natural products. Therapies using natural compounds that have been investigated, their rationale, mechanism of action and findings are reviewed. When the data warrant it, combined interventions that appear to increase efficacy (compared with monotherapy) while minimizing toxicity have been highlighted. Pubmed was used to search for relevant publications.Expert opinion: Combination therapy with natural compounds has the potential to be more effective than single agent therapy. Similar to pharmacologic agents, the goal is to maximize efficacy while mimimizing potential side effects. There is an increasing research focus on the development of agents derived from natural products, with notable successes already achieved from the effort.

Effects of Glycyrrhetic Acid on Human Chronic Myelogenous Leukemia Cells

Objectives

Chronic myelogenous leukemia (CML) is a type of blood cancer that is initially treated with imatinib (first Abl kinase inhibitor). However, some patients with CML develop imatinib resistance. Several new generation drugs have been developed, but do not overcome this problem. Glycyrrhetic acid (GA) is a plant-derived pentacyclic triterpenoid that exhibits multiple pharmacological properties for the treatment of cancers. The current study aimed to investigate the effects of GA on the K562 cell line (Bcr-Abl positive leukemia).

Materials and Methods

The MTT cell proliferation assay was employed to evaluate the cytotoxic effect of GA compared with imatinib (positive control) against leukemia and normal blood cells. For detection of cell death, an apoptotic/necrotic/healthy assay was performed against the K562 cell line. To investigate the kinase inhibitory activity of GA, the Abl1 kinase profiling assay and a molecular docking study were performed.

Results

GA showed Abl kinase inhibitory activity with an IC₅₀ value of 29.2 μM and induced apoptosis in the K562 cell line after 6 h of treatment.

Conclusion

The current findings indicate that this class of plant extract could be a potential candidate for treatment of CML.

Helix Self-Assembly Behavior of Amino Acid-Modified Camptothecin Prodrugs and Its Antitumor Effect

For effective antitumor treatment, it is important to increase the water solubility of hydrophobic antitumor drugs and improve their cell absorption efficiency and nuclear transmission capacity. Here, we use endogenous hydrophilic arginine to modify camptothecin (CPT) to increase its water solubility. Surprisingly, the modified CPT can self-assemble into helical nanofibers through intermolecular π-π stacking and hydrophilic-hydrophobic interactions. Prodrug-based nanofibers were better endocytosed into the nucleus than their nonassembled CPT. Moreover, in vivo, such nanofibers had a longer blood circulation time and a better ability to accumulate in the tumor site. Further, we found that the cationic nanofibers can be combined with the anionic cisplatin-polyglutamic acid through electrostatic interaction to achieve a combined antitumor effect. This provides a new idea for achieving more effective cancer chemotherapy effects.

The Cytoprotective and Anti-cancer Potential of Bisbenzylisoquinoline Alkaloids from Nelumbo nucifera

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Natural product therapy has been gaining therapeutic importance against various diseases, including cancer. The failure of chemotherapy due to its associated adverse effects promoted adjunct therapy with natural products. Phytochemicals exert anti-carcinogenic activities through the regulation of various cell signaling pathways such as cell survival, inflammation, apoptosis, autophagy and metastasis. The ‘small molecule-chemosensitizing agents’ from plants induce apoptosis in drug-resistant and host-immune resistant cancer cells in in vitro as well as in vivo models. For example, alkaloids from Nelumbo nucifera, liensinine, isoliensinine and neferine exert the anticancer activity through enhanced ROS generation, activation of MAP kinases, followed by induction of autophagy and apoptotic cell death. Likewise, these alkaloids also exert their cytoprotective action against cerebrovascular stroke/ischemic stroke, diabetes, and chemotherapy-induced cytotoxicity. Therefore, the present review elucidates the pharmacological activities of these bisbenzylisoquinoline alkaloids which include the cytoprotective, anticancer and chemosensitizing abilities against various diseases such as cardiovascular diseases, neurological diseases and cancer.

6-O-(3″, 4″-di-O-trans-cinnamoyl)-α-l-rhamnopyranosylcatalpol and verbascoside: Cytotoxicity, cell cycle kinetics, apoptosis, and ROS production evaluation in tumor cells

The aim of this study was to evaluate the impact that 6-O-(3″, 4″-di-O-trans-cinnamoyl)-α- l-rhamnopyranosylcatalpol (Dicinn) and verbascoside (Verb), two compounds simultaneously reported in Verbascum ovalifolium, have on tumor cell viability, apoptosis, cell cycle kinetics, and intracellular reactive oxygen species (ROS) level. At 100 µg/mL and 48 hours incubation time, Dicinn and Verb produced good cytotoxic effects in A549, HT-29, and MCF-7 cells. Dicinn induced cell-cycle arrest at the G₀ /G₁ phase and apoptosis, whereas Verb increased the population of subG₁ cells and cell apoptosis rates. Furthermore, the two compounds exhibited time-dependent ROS generating effects in tumor cells (1-24 hours). Importantly, no cytotoxic effects were induced in nontumor MCF-10A cells by the two compounds up to 100 µg/mL. Overall, the effects exhibited by Verb in tumor cells were more potent, which can be correlated with its structural features, such as the presence of phenolic hydroxyl groups.

Antiproliferative activities of tricyclic amides derived from β-caryophyllene via the Ritter reaction against MDA-MB-231 breast cancer cells

A library of novel tricyclic amides has been synthesised via the Ritter reaction from β-caryophyllene 1 and its monoepoxy derivative 4. The compounds were assessed for antiproliferative activities against the aggressive MDA-MB-231 breast cancer cell line. Of the synthesised compounds, eight were active. 3c and 6b were the most potent and inhibited proliferation with IC₅₀ of 9.7 and 8.2 μM, respectively. Mechanistic studies revealed differences in their antiproliferative actions. 6b inhibited cell cycle progression and induced predominantly apoptotic cell death. In contrast, 3c did not affect cell cycle kinetics and favoured necrotic over apoptotic pathways. Screening against mammalian cells (VERO cells) indicates that 3c and 6b were more active towards MDA-MB-231 cells than noncancerous cells. Facile synthesis and biological results suggest that these caryophyllene derived amides are viable lead compounds for further development.

Current status and contemporary approaches to the discovery of antitumor agents from higher plants

Higher plant constituents have afforded clinically available anticancer drugs. These include both chemically unmodified small molecules and their synthetic derivatives currently used or those in clinical trials as antineoplastic agents, and an updated summary is provided. In addition, botanical dietary supplements, exemplified by mangosteen and noni constituents, are also covered as potential cancer chemotherapeutic agents. Approaches to metabolite purification, rapid dereplication, and biological evaluation including analytical hyphenated techniques, molecular networking, and advanced cellular and animal models are discussed. Further, enhanced and targeted drug delivery systems for phytochemicals, including micelles, nanoparticles and antibody drug conjugates (ADCs) are described herein.

Antitumor bioactivity of porphyran extracted from Pyropia yezoensis Chonsoo2 on human cancer cell lines

BACKGROUND

Pyropia yezoensis, rich in porphyran, is a medicine-edible red alga. In the present study, the physicochemical characteristics, conformational states and antitumor activities of a novel porphyran extracted from the high-yield algal strain Pyropia yezoensis Chonsoo2 and its two degraded derivatives by gamma irradiation were investigated.

RESULTS

Pyropia yezoensis porphyran is a water-soluble, triple-helical sulfated hetero-galactopyranose, named PYP. PYP was degraded by gamma irradiation at 20 kGy and 50 kGy, giving two low molecular weight derivatives comprising PYP-20 and PYP-50, respectively. PYP with a higher molecular weight has a solution conformation different from PYP-20 and PYP-50. Three porphyrans had no toxicity in normal human liver cells (HL-7702) and showed antitumor effects on Hep3B, HeLa and MDA-MB-231. They had better antitumor against HeLa cells, exhibiting a similar inhibition ratio compared to 5-fluorouracil, with PYP especially exhibiting a higher inhibition ratio than 5-fluorouracil. With respect to HeLa cells, the different antitumor activities might be related to porphyran molecular weight and solution conformation. Furthermore, the HeLa cell cycle was blocked in the G2/M phase after PYP treatment, leading to cell proliferation inhibition. The induction of cell cycle arrest was related to the changes in the expression of p21, p53, Cyclin B1 and cyclin-dependent kinase 1.

CONCLUSION

Pyropia yezoensis porphyran, as applied to medicine and functional food, could potentially be used as a non-toxic natural adjuvant in cancer therapy. © 2019 Society of Chemical Industry.

Semi-Synthetic Ingenol Derivative from Euphorbia tirucalli Inhibits Protein Kinase C Isotypes and Promotes Autophagy and S-phase Arrest on Glioma Cell Lines

The identification of signaling pathways that are involved in gliomagenesis is crucial for targeted therapy design. In this study we assessed the biological and therapeutic effect of ingenol-3-dodecanoate (IngC) on glioma. IngC exhibited dose-time-dependent cytotoxic effects on large panel of glioma cell lines (adult, pediatric cancer cells, and primary cultures), as well as, effectively reduced colonies formation. Nevertheless, it was not been able to attenuate cell migration, invasion, and promote apoptotic effects when administered alone. IngC exposure promoted S-phase arrest associated with p21CIP/WAF1 overexpression and regulated a broad range of signaling effectors related to survival and cell cycle regulation. Moreover, IngC led glioma cells to autophagy by LC3B-II accumulation and exhibited increased cytotoxic sensitivity when combined to a specific autophagic inhibitor, bafilomycin A1. In comparison with temozolomide, IngC showed a mean increase of 106-fold in efficacy, with no synergistic effect when they were both combined. When compared with a known compound of the same class, namely ingenol-3-angelate (I3A, Picato^®), IngC showed a mean 9.46-fold higher efficacy. Furthermore, IngC acted as a potent inhibitor of protein kinase C (PKC) activity, an emerging therapeutic target in glioma cells, showing differential actions against various PKC isotypes. These findings identify IngC as a promising lead compound for the development of new cancer therapy and they may guide the search for additional PKC inhibitors.

In depth natural product discovery - Myxobacterial strains that provided multiple secondary metabolites

In recognition of many microorganisms ability to produce a variety of secondary metabolites in parallel, Zeeck and coworkers introduced the term "OSMAC" (one strain many compounds) around the turn of the century. Since then, additional efforts focused on the systematic characterization of a single bacterial species ability to form multiple secondary metabolite scaffolds. With the beginning of the genomic era mainly initiated by a dramatic reduction of sequencing costs, investigations of the genome encoded biosynthetic potential and especially the exploitation of biosynthetic gene clusters of undefined function gained attention. This was seen as a novel means to extend range and diversity of bacterial secondary metabolites. Genome analyses showed that even for well-studied bacterial strains, like the myxobacterium Myxococcus xanthus DK1622, many biosynthetic gene clusters are not yet assigned to their corresponding hypothetical secondary metabolites. In contrast to the results from emerging genome and metabolome mining techniques that show the large untapped biosynthetic potential per strain, many newly isolated bacterial species are still used for the isolation of only one target compound class and successively abandoned in the sense that no follow up studies are published from the same species. This work provides an overview about myxobacterial bacterial strains, from which not just one but multiple different secondary metabolite classes were successfully isolated. The underlying methods used for strain prioritization and natural product discovery such as biological characterization of crude extracts against a panel of pathogens, in-silico prediction of secondary metabolite abundance from genome data and state of the art instrumental analytics required for new natural product scaffold discovery in comparative settings are summarized and classified according to their output. Furthermore, for each approach selected studies performed with actinobacteria are shown to underline especially innovative methods used for natural product discovery.

Psorachromene Suppresses Oral Squamous Cell Carcinoma Progression by Inhibiting Long Non-coding RNA GAS5 Mediated Epithelial-Mesenchymal Transition

The extract of the seeds of Psoralea corylifolia Linn. (P. corylifolia) have been shown to display anti-tumor activity. However, the prospects of the active compounds from this plant in the treatment of oral squamous cell carcinoma (OSCC) remains unclear. In the present study, the antitumor effects of psorachromene, a flavonoid extracted from the seeds of P. corylifolia, were investigated using cells and animal models of OSCC; the downstream regulatory mechanisms were also elucidated. The results showed that psorachromene significantly repressed cell proliferation, migration, and invasiveness and increased the toxic effects of chemotherapeutic agents against OSCC cells. The repressive effects of psorachromene were attributable to the inhibition of EGFR-Slug signaling, and the induction of G2/M arrest and apoptosis in the OSCC cells. Additionally, we found that psorachromene induced the expression of tumor suppressor long non-coding ribonucleic acid (RNA) growth arrest-specific transcript 5 (GAS5) and the activation of its downstream anticancer mechanisms. Animal experiments also showed noticeable inhibition of tumor growth, without significant physiological toxicity. The findings indicate that psorachromene displays anti-tumor activity in OSCC, and warrants further investigation as a potential agent for clinical application.

Bright Spots in The Darkness of Cancer: A Review of Starfishes-Derived Compounds and Their Anti-Tumor Action

The fight against cancer represents a great challenge for researchers and, for this reason, the search for new promising drugs to improve cancer treatments has become inevitable. Oceans, due to their wide diversity of marine species and environmental conditions have proven to be precious sources of potential natural drugs with active properties. As an example, in this context several studies performed on sponges, tunicates, mollusks, and soft corals have brought evidence of the interesting biological activities of the molecules derived from these species. Also, echinoderms constitute an important phylum, whose members produce a huge number of compounds with diverse biological activities. In particular, this review is the first attempt to summarize the knowledge about starfishes and their secondary metabolites that exhibited a significant anticancer effect against different human tumor cell lines. For each species of starfish, the extracted molecules, their effects, and mechanisms of action are described.

Overview of the Anticancer Profile of Avenanthramides from Oat

Cancer represents one of the leading causes of death worldwide. Progresses in treatment of cancer have continued at a rapid pace. However, undesirable side effects and drug resistance remain major challenges for therapeutic success. Natural products represent a valuable starting point to develop new anticancer strategies. Polyphenols, well-known as antioxidant, exert anticancer effects through the modulation of multiple pathways and mechanisms. Oat (Avena sativa L., Poaceae) is a unique source of avenanthramides (AVAs), a group of polyphenolic alkaloids, considered as its signature compounds. The present review aims to offer a comprehensive and critical perspective on the chemopreventive and chemotherapeutic potential of AVAs. AVAs prevent cancer mainly by blocking reactive species. Moreover, they exhibit potential therapeutic activity through the modulation of different pathways including the activation of apoptosis and senescence, the block of cell proliferation, and the inhibition of epithelial mesenchymal transition and metastatization. AVAs are promising chemopreventive and anticancer phytochemicals, which need further clinical trials and toxicological studies to define their efficacy in preventing and reducing the burden of cancer diseases.

Anti-inflammatory and cytotoxic agents from Xylaria sp. SWUF09-62 fungus

The ongoing search for anti-cancer agents from microorganisms led to the isolation of four new compounds including 6-ethyl-8-hydroxy-4H-chromen-4-one (1), 6-ethyl-7,8-dihydroxy-4H-chromen-4-one (2), (3S)-3,4-dihydro-8-hydroxy-7-methoxy-3-methylisocoumarin (3) and (3S)-3,4-dihydro-5,7,8-trihydroxy-3-methylisocoumarin (4), together with eleven known compounds (5-15) from Xylaria sp. SWUF09-62 fungus. The chemical structures were deduced from IR, 1D and 2D NMR, and MS data. The absolute configurations of 3 and 4 were determined by ECD experiment. Compounds 2 and 4 indicated possible chemo-prevention and chemo-therapeutic properties, exhibited anti-inflammatory properties by reducing nitric oxide production in LPS-stimulated RAW264.7 cells (IC₅₀ = 1.57 ± 0.25 and 3.02 ± 0.27 μg/mL) and cytotoxicity against HT29 cells (IC₅₀ = 16.46 ± 0.48 and 97.78 ± 7.14 μg/mL).

Fucosterol exerts antiproliferative effects on human lung cancer cells by inducing apoptosis, cell cycle arrest and targeting of Raf/MEK/ERK signalling pathway

BACKGROUND

Phytochemicals have attained tremendous attention as the chemo-preventive and chemotheruptic agents. Fucosterol is a phytosterol that in prevalently found in marine algae and many other plant species. Previous studies have indicated the potential of fucosterol as an anticancer agent. However, the information on the anticancer activity of fucosterol against lung cancer as well as several other types of cancers is scantly.

PURPOSE

The present study was designed to investigate the anticancer activity of fucosterol against a panel of lung cancer cell lines.

METHODS

MTT and colony formation assays were used to determine the cell viability. DAPI and annexin V/PI staining assays were used for the detection of apoptosis. Cell cycle analysis was performed by flow cytometery. Boyden chamber assay was used to monitor cell migration and western blot analysis was used to determine the protein expression. In vivo evaluation was carried out in xenografted mice models.

RESULTS

The results indicated that fucosterol inhibits the growth of the lung cancer cell lines. However, the anticancer effects were more profound against the A549 and SK-LU-1 cancer cells (IC_50, 15 µM). In contrast, the anticancer effects of fucosterol on the non-cancerous lung cell lines were minimal. Further investigation revealed that the anticancer effects of fucosterol on the A549 and SK-LU-1 cells are due to the induction of apoptosis. Fucosterol significantly enhanced the expression of Bax and cleaved caspase-3 which was concomitant with decline in the expression of Bcl-2. Fucosterol also triggered G₂/M cell cycle arrest of the A549 and SK-LU-1 cells which was associated with decrease in the expression of Cdc2, Cyclin A, Cyclin B1 and upregulation of the negative regulators of cell cycle progression (p21^Cip1, and p27^Kip1). Moreover, fucosterol could also inhibit the invasion of A549 and SK-LU-1 cells. Finally fucosterol could also inhibit the growth of xenografted tumours in mice.

CONCLUSION

Taken together, fucosterol inhibits the growth of lung cancer cells and may prove to be a lead molecule for the treatment of lung cancer.

The Role of Polyphenol (Flavonoids) Compounds in the Treatment of Cancer Cells

Cancer remains a second leading cause of deaths and major public health problem. It occurs due to extensive DNA damage caused by ultraviolet radiations, ionizing radiations, environmental agents, therapeutic agents, etc. Among all cancers, the most frequently diagnosed cancers are lung (12.7%), breast (10.9%), colorectal (9.7%), and gastric cancer (7.81%). Natural compounds are most favorable against cancer on the count of their anti-cancerous ability, easy to avail and efficient. Among natural compounds, polyphenols (flavonoids, catechin, hesperetin, flavones, quercetin, phenolic acids, ellagic acid, lignans, stilbenes, etc.) represent a large and diverse group used in the prevention and treatment of cancer. Natural flavonoids are derived from different plant sources and from various medicinal plants including Petroselinum crispum, Apium graveolens, Flemingia vestita, Phyllanthus emblica, etc. Natural flavonoids possess antioxidant, anti-inflammation, as well as anti-cancerous activities through multiple pathways, they induce apoptosis in breast, colorectal, and prostate cancers, lower the nucleoside diphosphate kinase-B activity in lung, bladder and colon cancers, inhibit cell-proliferation and cell cycle arrest by suppressing the NF-kB pathway in various cancers, etc. The current review summarized the anticancer activities of natural polyphenols and their mechanisms of action.