Targeting apoptosis pathways by natural compounds in cancer: Marine compounds as lead structures and chemical tools for cancer therapy

Modulation of Apoptotic, Cell Cycle, DNA Repair, and Senescence Pathways by Marine Algae Peptides in Cancer Therapy

Marine algae, encompassing both macroalgae and microalgae, have emerged as a promising and prolific source of bioactive compounds with potent anticancer properties. Despite their significant therapeutic potential, the clinical application of these peptides is hindered by challenges such as poor bioavailability and susceptibility to enzymatic degradation. To overcome these limitations, innovative delivery systems, particularly nanocarriers, have been explored. Nanocarriers, including liposomes, nanoparticles, and micelles, have demonstrated remarkable efficacy in enhancing the stability, solubility, and bioavailability of marine algal peptides, ensuring controlled release and prolonged therapeutic effects. Marine algal peptides encapsulated in nanocarriers significantly enhance bioavailability, ensuring more efficient absorption and utilization in the body. Preclinical studies have shown promising results, indicating that nanocarrier-based delivery systems can significantly improve the pharmacokinetic profiles and therapeutic outcomes of marine algal peptides. This review delves into the diverse anticancer mechanisms of marine algal peptides, which include inducing apoptosis, disrupting cell cycle progression, and inhibiting angiogenesis. Further research focused on optimizing nanocarrier formulations, conducting comprehensive clinical trials, and continued exploration of marine algal peptides holds great promise for developing innovative, effective, and sustainable cancer therapies.

Performance of Green Desymmetrization Methods toward Bioactive Cephalostatin Analogues

Since the discovery of cephalostatins, which have shown remarkable activity against human cancer cells, they have attracted the attention of researchers to target the synthesis of such impressive, complicated molecules using the green desymmetrization approach. In the current review, we report the progress in the desymmetrization of symmetrical bis-steroidal pyrazines (BSPs) as an approach toward potentially active anti-- cancer agents, namely cephalostatins/ ritterazines. The achievement of synthesizing a gram-scaled prodrug with comparable activity to the potent natural cephalostatins using green methods is our primary target. These synthetic methods can be scaled up based on the symmetrical coupling (SC) of two steroidal units of the same type. Our secondary target is the discovery of new green pathways that help in structural reconstruction programming toward the total synthesis of at least one potentially active family member. The strategy is based on functional group interconversions with high flexibility and brevity using green selective methods. The introduction of controlling groups using nontrivial reconstruction methodologies forms the backbone of our work. After certain modifications to the symmetrical BSP starting material, the resulting analogs underwent several chemoselective transformations through three main routes in rings F, D, and C. One of these routes is the chemoselective spiroketal opening (ring-F). The second route was the functionalization of the Δ14,15 bond (ring-D), including chlorination/dechlorination, in addition to epoxidation/ oxygenation processes. Finally, the introduction of the C-11 methoxy group as a directing group on ring-C led to several chemoselective transformations. Moreover, certain transformations on C-12 (ring-C), such as methylenation, followed by hydroboration- oxidation, led to a potentially active analog. The alignment of these results directs us toward the targets. Our efforts culminated in preparing effective anti-cancer prodrugs (8, 24, 30, and 31), which are able to overcome cancer drug resistance (chemoresistance) by inducing the atypical endoplasmic reticulum-mediated apoptosis pathway, which works through the release of Smac/Diablo and the activation of caspase-4.

Potentiation of Apoptotic Effect of Combination of Etoposide and Quercetin on HepG2 Liver Cancer Cells

Background: Hepatocellular carcinoma (HCC) is the most common type of liver cancer worldwide. The current remedies for cancer, including chemotherapy and radiation therapy, might damage patients’ organs, sometimes causing death. Etoposide (ETO), as a widely used chemo-drug, possesses the same problems. For years, combinational therapy has been considered a potential adjustor for common treatments, alleviating their side effects. Quercetin (Que), a phytochemical drug, has been used due to its potential against cancer. Objectives: This study explored whether synergy occurs between Que and ETO on the apoptosis of HepG2 HCC cells or not. Methods: The impacts of the drugs on cell growth were assessed through the MTT assay. The apoptotic death rates of treated cells were examined through Annexin/PI double staining and caspase-9 and caspase-3 activities. The relative expression of B-cell lymphoma 2 (Bcl-2) Associated X-protein (Bax), and Bcl-2 genes and proteins were analyzed using quantitative reverse transcription polymerase chain reaction and western blot analysis. Additionally, the levels of p53 protein were determined. Results: Both Que and ETO reduced the cell viability and increased apoptotic rates, caspases activities, Bax gene and protein expression, and the p53 protein levels of HepG2 cells. The combination of Que and ETO showed apparent synergy in terms of cell growth and cell apoptosis. Que significantly enhanced the effects of ETO on caspase activities, Bax and Bcl-2 genes’ expression, and p53 protein levels. Conclusions: The obtained results demonstrated that Que showed synergy when co-treated with ETO on HepG2 cells. Therefore, it is concluded that further studies on the aforementioned combination could lead to a potential anticancer compound against HCC.

Cytotoxic Effects on Breast Cancer Cell Lines of Chalcones Derived from a Natural Precursor and Their Molecular Docking Analysis

This study aimed to determine the in vitro cytotoxicity and understand possible cytotoxic mechanisms via an in silico study of eleven chalcones synthesized from two acetophenones. Five were synthesized from a prenylacetophenone isolated from a plant that grows in the Andean region of the Atacama Desert. The cytotoxic activity of all the synthesized chalcones was tested against breast cancer cell lines using an MTT cell proliferation assay. The results suggest that the prenyl group in the A-ring of the methoxy and hydroxyl substituents of the B-ring appear to be crucial for the cytotoxicity of these compounds. The chalcones 12 and 13 showed significant inhibitory effects against growth in MCF-7 cells (IC₅₀ 4.19 ± 1.04 µM and IC₅₀ 3.30 ± 0.92 µM), ZR-75-1 cells (IC₅₀ 9.40 ± 1.74 µM and IC₅₀ 8.75 ± 2.01µM), and MDA-MB-231 cells (IC₅₀ 6.12 ± 0.84 µM and IC₅₀ 18.10 ± 1.65 µM). Moreover, these chalcones showed differential activity between MCF-10F (IC₅₀ 95.76 ± 1.52 µM and IC₅₀ 95.11 ± 1.97 µM, respectively) and the tumor lines. The in vitro results agree with molecular coupling results, whose affinity energies and binding mode agree with the most active compounds. Thus, compounds 12 and 13 can be considered for further studies and are candidates for developing new antitumor agents. In conclusion, these observations give rise to a new hypothesis for designing chalcones with potential cytotoxicity with high potential for the pharmaceutical industry.

An Updated Review of Tetrodotoxin and Its Peculiarities

Tetrodotoxin (TTX) is a crystalline, weakly basic, colorless organic substance and is one of the most potent marine toxins known. Although TTX was first isolated from pufferfish, it has been found in numerous other marine organisms and a few terrestrial species. Moreover, tetrodotoxication is still an important health problem today, as TTX has no known antidote. TTX poisonings were most commonly reported from Japan, Thailand, and China, but today the risk of TTX poisoning is spreading around the world. Recent studies have shown that TTX-containing fish are being found in other regions of the Pacific and in the Indian Ocean, as well as the Mediterranean Sea. This review aims to summarize pertinent information available to date on the structure, origin, distribution, mechanism of action of TTX and analytical methods used for the detection of TTX, as well as on TTX-containing organisms, symptoms of TTX poisoning, and incidence worldwide.

Quercetin synergistically potentiates the anti-metastatic effect of 5-fluorouracil on the MDA-MB-231 breast cancer cell line

OBJECTIVES

Breast cancer (BC) cells' ability to metastasize to other tissues increases mortality. The Matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) facilitate cancer cell migration. 5-fluorouracil is a frequently applied chemotherapeutic agent in cancer treatment with destructive side effects on normal tissues. Hence, researchers have focused on finding a way to reduce the dose of chemotherapeutic drugs. Quercetin, a natural polyphenolic compound, has inhibitory effects on proliferation and migration of tumor cells. This study evaluated the effect of the combination of Quercetin and 5-fluorouracil on migration of the MDA-MB-231 breast cancer cell line.

MATERIALS AND METHODS

The effect of Quercetin, 5-fluorouracil , and their combination on MDA-MB-231 breast cancer cell proliferation was investigated through MTT assay. Inhibition of tumor cell migration was examined by wound healing assay. Finally, the effect of treatments on gene expression of MMP-2 and MMP-9 was evaluated by quantitative real-time PCR.

RESULTS

The IC50 values for Quercetin and 5-fluorouracil after 48 hr treatment were 295 μM and 525 μM, respectively. The combination index (CI) for Quercetin and 5-fluorouracil was <1, indicating synergy between them. The combination of Quercetin plus 5-fluorouracil resulted in a significant reduction in migration rate and MMP-2 and MMP-9 gene expressions of MDA-MB-231 cancer cells compared with the individual application of 5-FU.

CONCLUSION

Quercetin enhances the suppressory effect of 5-fluorouracil on migration of BC cells. The combination of Quercetin and 5-fluorouracil can be an attractive field for future studies.

Natural Cyclopeptides as Anticancer Agents in the Last 20 Years

Cyclopeptides or cyclic peptides are polypeptides formed by ring closing of terminal amino acids. A large number of natural cyclopeptides have been reported to be highly effective against different cancer cells, some of which are renowned for their clinical uses. Compared to linear peptides, cyclopeptides have absolute advantages of structural rigidity, biochemical stability, binding affinity as well as membrane permeability, which contribute greatly to their anticancer potency. Therefore, the discovery and development of natural cyclopeptides as anticancer agents remains attractive to academic researchers and pharmaceutical companies. Herein, we provide an overview of anticancer cyclopeptides that were discovered in the past 20 years. The present review mainly focuses on the anticancer efficacies, mechanisms of action and chemical structures of cyclopeptides with natural origins. Additionally, studies of the structure-activity relationship, total synthetic strategies as well as bioactivities of natural cyclopeptides are also included in this article. In conclusion, due to their characteristic structural features, natural cyclopeptides have great potential to be developed as anticancer agents. Indeed, they can also serve as excellent scaffolds for the synthesis of novel derivatives for combating cancerous pathologies.

Ganoderma tsugae suppresses the proliferation of endometrial carcinoma cells via Akt signaling pathway

Ganoderma is one of the common medicinal mushrooms in traditional Chinese medicine. Previous researches have unveiled the multifaceted biological activity of Ganoderma extract. Ganoderma tsugae has been investigated the potential on curing prostate, colon, lung, epidermoid, breast and ovarian cancers, but not including endometrial cancer. Endometrial cancer is a gynecological malignant tumor with serious drug resistance problem in clinical cancer treatment. This study aimed to demonstrate the first study of Ganoderma on treating endometrial cancer. The Ganoderma tsugae ethanol extract (GTEE) could suppress the proliferation of endometrial cancer cells HEC-1-A, KLE, and AN3 CA. GTEE also induced G1/S phase arrest and mitochondria-mediated apoptosis in endometrial cancer cells. Furthermore, the Akt signaling pathway could be suppressed by GTEE. Therefore, our results suggest for the first time that GTEE has the potential to be an adjuvant therapeutic agent in the treatment of endometrial cancer.

A novel acid polysaccharide from Boletus edulis: extraction, characteristics and antitumor activities in vitro

A novel cold-water-soluble polysaccharide (BEP), with a molecular weight of 6.0 × 10⁶ Da, was isolated from Boletus edulis. BEP consists of galactose, glucose, xylose, mannose, glucuronic, and galacturonic acid in a ratio of 0.34:0.28:0.28:2.57:1.00:0.44. The IR results showed that BEP was an acid polysaccharide, containing α-type and β-type glucoside bonds. MTT assay showed BEP could inhibit cell proliferation significantly. Morphological observation demonstrated that BEP-treated MDA-MB-231 and Ca761 cells exhibited typical apoptotic morphological features. Flow cytometry analysis revealed that BEP caused mitochondrial membrane potential collapse. Annexin V-FITC/PI staining indicated that BEP induced apoptosis of MDA-MB-231 and Ca761 cells through cell block in S phase and G₀/G₁ phase, respectively. Western blot results showed that BEP could increase the Bax/Bcl-2 ratios, promote the release of cytochrome C, and activate the expression of caspase-3 and caspase-9 in MDA-MB-231 and Ca761 cells. In conclusion, our results demonstrated that BEP could inhibit the proliferation of breast cancer cells and induce apoptosis through mitochondrial pathways.

The natural extract degalactotigonin exerts antitumor effects on renal cell carcinoma cells through repressing YAP

Background

The pervasive progression of renal cell carcinoma (RCC) after treatment demands more effective drugs with few side effects. In the present study, we determined whether degalactotigonin (DGT) extracted from Solanum nigrum L. could exert antitumoral effects on RCC and examined the related molecular mechanisms.

Methods

The effects of DGT on RCC cells were assessed by cell counting kit-8 (CCK-8) assay, flow cytometry, invasion and migration assays and subcutaneous tumor xenograft experiments in nude mice. The related molecular mechanisms were delineated by RNA sequencing (RNA-seq), real-time polymerase chain reaction (PCR), western blotting, coimmunoprecipitation (co-IP) and plasmid transfection.

Results

DGT induced apoptosis and suppressed the proliferation, invasion, migration, and tumorigenicity of RCC cells. Mechanistically, yes-associated protein (YAP) signaling was inactivated, and the expression of YAP and its target genes was reduced in degalactotigonin-treated RCC cells. Additionally, DGT activated phosphorylated large tumor suppressor 1/2 (p-LATS1/2) to phosphorylate YAP, which increased YAP retention in the cytoplasm but decreased the amount of YAP that entered the nuclei of RCC cells. Moreover, DGT impaired the increased aggressive features of RCC cells induced by YAP overexpression.

Conclusions

DGT is an effective therapeutic agent, which facilitates the apoptosis and inhibits the proliferation, invasion, migration, and tumorigenicity of RCC cells in a YAP-dependent manner.

12-Deacetyl-12-epi-Scalaradial, a Scalarane Sesterterpenoid from a Marine Sponge Hippospongia sp., Induces HeLa Cells Apoptosis via MAPK/ERK Pathway and Modulates Nuclear Receptor Nur77

12-Deacetyl-12-epi-scalaradial, a scalarane sesterterpenoid from a marine sponge Hippospongia sp, has been reported to possess cytotoxic activity on HepG2, MCF-7, and HCT-116 cells. However, there is no research to indicate that 12-deacetyl-12-epi-scalaradial exhibited anticancer effect on cervical cancer HeLa cells. The aim of this study was to investigate the anticancer activity of 12-deacetyl-12-epi-scalaradial against HeLa cells and to explore the mechanism. The results from a methylthiazolyldiphenyl-tetrazolium (MTT) assay suggested that 12-deacetyl-12-epi-scalaradial suppressed the proliferation of HeLa cells and flow cytometry analysis showed 12-deacetyl-12-epi-scalaradial could induce the apoptosis of HeLa cells in dose- and time-dependent manner. Western blotting analysis demonstrated that 12-deacetyl-12-epi-scalaradial triggered apoptosis via mediating the extrinsic pathway and was found to suppress MAPK/ERK pathway which was associate with cancer cell death. Nur77, a critical number of orphan nuclear receptors, plays diverse roles in tumor development as a transcription factor and has been considered as a promising anticancer drug target. The dual-luciferase reporter assays suggested that 12-deacetyl-12-epi-scalaradial could selectively enhance the trans-activation activity of Nur77. Furthermore, Western blotting analysis and fluorescence quenching showed that 12-deacetyl-12-epi-scalaradial could induce the phosphorylation of Nur77 and interact with the ligand-binding domain (LBD) of Nur77. Our research confirmed 12-deacetyl-12-epi-scalaradial as a potential agent for cervical cancer therapy and provided a view that 12-deacetyl-12-epi-scalaradial may be a modulator of Nur77.

Antitumoral compounds from vertebrate sister group: A review of Mediterranean ascidians

Among the diseases that afflict the human population, cancer is one for which many drug treatments are not yet known or effective. Moreover, the pharmacological treatments used often create serious side effects in sick patients and for this reason, it is essential to find effective and less harmful treatments. To date, marine biodiversity is a real source of metabolites with antitumoral activity and among invertebrates' ascidians have been the main source to obtain them. Mediterranean area is the richest in biodiversity and contains several ascidian species used in drugs development during the years. However, many more Mediterranean ascidian species have not been studied and could be a source of useful bioactive compounds. This review aims to summarize the scientific studies that analyzed the antitumor compounds obtained from different Mediterranean ascidians species, encouraging them to search further compounds in other new species to improve pharmacological treatments and human population life.

Pentadecanoic Acid, an Odd-Chain Fatty Acid, Suppresses the Stemness of MCF-7/SC Human Breast Cancer Stem-Like Cells through JAK2/STAT3 Signaling

Saturated fatty acids possess few health benefits compared to unsaturated fatty acids. However, increasing experimental evidence demonstrates the nutritionally beneficial role of odd-chain saturated fatty acids in human health. In this study, the anti-cancer effects of pentadecanoic acid were evaluated in human breast carcinoma MCF-7/stem-like cells (SC), a cell line with greater mobility, invasiveness, and cancer stem cell properties compared to the parental MCF-7 cells. Pentadecanoic acid exerted selective cytotoxic effects in MCF-7/SC compared to in the parental cells. Moreover, pentadecanoic acid reduced the stemness of MCF-7/SC and suppressed the migratory and invasive ability of MCF-7/SC as evidenced by the results of flow cytometry, a mammosphere formation assay, an aldehyde dehydrogenase activity assay, and Western blot experiments conducted to analyze the expression of cancer stem cell markers—CD44, β-catenin, MDR1, and MRP1—and epithelial–mesenchymal transition (EMT) markers—snail, slug, MMP9, and MMP2. In addition, pentadecanoic acid suppressed interleukin-6 (IL-6)-induced JAK2/STAT3 signaling, induced cell cycle arrest at the sub-G1 phase, and promoted caspase-dependent apoptosis in MCF-7/SC. These findings indicate that pentadecanoic acid can serve as a novel JAK2/STAT3 signaling inhibitor in breast cancer cells and suggest the beneficial effects of pentadecanoic acid-rich food intake during breast cancer treatments.

Induction of programmed necrosis: A novel anti-cancer strategy for natural compounds

Cell death plays a critical role in organism development and the pathogenesis of diseases. Necrosis is considered a non-programmed cell death in an extreme environment. Recent advances have provided solid evidence that necrosis could be programmed and quite a few types of programmed necrosis, such as necroptosis, ferroptosis, pyroptosis, paraptosis, mitochondrial permeability transition-driven necrosis, and oncosis, have been identified. The specific biomarkers, detailed signaling, and precise pathophysiological importance of programmed necrosis are yet to be clarified, but these forms of necrosis provide novel strategies for the treatment of various diseases, including cancer. Natural compounds are a unique source of lead compounds for the discovery of anti-cancer drugs. Natural compounds can induce both apoptosis and programmed necrosis. In this review, we summarized the recent progress of programmed necrosis and introduced their natural inducers. Noptosis, which is a novel type of programmed necrosis that is strictly dependent on NAD(P)H: quinone oxidoreductase 1-derived oxidative stress was proposed. Furthermore, the anti-cancer strategies that take advantage of programmed necrosis and the main concerns from the scientific community in this regard were discussed.

Can marine-derived fungus Neosartorya siamensis KUFA 0017 extract and its secondary metabolites enhance antitumor activity of doxorubicin? An in vitro survey unveils interactions against lung cancer cells

Doxorubicin (Dox) is one of the most successful anticancer drugs in use. However, chemoresistance is one of the main limitations that patients face. Therefore, development of new strategies to improve the efficacy of Dox is needed. Marine-derived fungi are especially promising sources of new anticancer compounds. In this work, antitumor activity of crude ethyl extract of the cultures of the marine-derived fungus Neosartorya siamensis KUFA 0017 (NS), combined with Dox, was evaluated in six cancer cell lines. To evaluate possible mechanisms involved in the eventual improvement of Dox's cytotoxicity by NS extract, effects on DNA damage, cell death, ultrastructural modifications, and intracellular accumulation of Dox were assessed. The NS extract demonstrated a significant enhancement of Dox's cytotoxic activity in A549 cells, inducing DNA damage, cell death, and intracellular accumulation of Dox. Additionally, the cytotoxic effect of eight compounds, isolated from this extract, that is, 2,4-dihydroxy-3-methylacetophenone-(C1), nortryptoquivaline-(C2), chevalone C-(C3), tryptoquivaline H-(C4), fiscalin A-(C5), epi-fiscalin-C (C6), epi-neofiscalin A-(C7), and epi-fiscalin A-(C8), alone and combined with Dox was also evaluated in lung cancer cells. The cytotoxic effect of Dox was potentiated by all the isolated compounds (except C1) in A549 cells. Therefore, we concluded that NS extract potentiated cytotoxicity by inhibiting cell proliferation, increasing intracellular accumulation of Dox, and inducing cell death (possibly by an autophagic process). The isolated compounds also enhanced the activity of Dox, supporting the potential of this sort of combination. These data call for further studies to characterize drug interactions and underlying mechanisms.

The Yemeni Brown Algae Dictyota dichotoma Exhibit High In Vitro Anticancer Activity Independent of Its Antioxidant Capability

The aim of this study was to investigate the anticancer and antioxidant activities as well as the safety of the brown algae Dictyota dichotoma of the Western seacoast of Yemen. Cytotoxicity of methanol extract of D. dichotoma and several of its fractions, petroleum ether, chloroform, ethyl acetate, n-butanol, and aqueous extracts against seven different cancer cell lines was determined by crystal violet staining. The antioxidant activity was also assessed using the DPPH radical scavenging assay. Acute toxicity study was performed on rats at increasing doses of the methanol extract. Extracts of D. dichotoma exerted a significant dose-dependent cytotoxicity on the seven tumor cell lines but were generally more selective on MCF-7 and PC-3. Among all fractions, the chloroform fraction of the D. dichotoma displayed the highest cytotoxic activity and was most effective in MCF-7, PC3, and CACO cells (IC50 = 1.93 ± 0.25, 2.2 ± 0.18, and 2.71 ± 0.53 μg/mL, respectively). The petroleum ether fraction was also effective, particularly against MCF-7 and PC-3 (IC50 = 4.77 ± 0.51 and 3.93 ± 0.51 μg/mL, respectively) whereas the activity of the ethyl acetate fraction was more pronounced against HepG2 and CACO (IC50 = 5.06 ± 0.21 and 5.06 ± 0.23 μg/mL, respectively). Of all the extracts tested, the crude methanolic extract of the algae exhibited only a modest antioxidant potential (IC50 = 204.6 ± 8.3 μg/mL). Doses as high as 5000 mg/kg body weight of D. dichotoma methanolic extracts were safe and well tolerated by rats. The overall results showed that D. dichotoma exhibited a significant cytotoxic activity probably due to the occurrence of nonpolar cytotoxic compounds, which is independent of its antioxidant capability.

Elucidation of the Chemopreventive Role of Stigmasterol Against Jab1 in Gall Bladder Carcinoma

BACKGROUND

Plant sterols have proven a potent anti-proliferative and apoptosis inducing agent against several carcinomas including breast and prostate cancers. Jab1 has been reported to be involved in the progression of numerous carcinomas. However, antiproliferative effects of sterols against Jab1 in gall bladder cancer have not been explored yet.

OBJECTIVE

In the current study, we elucidated the mechanism of action of stigmasterol regarding apoptosis induction mediated via downregulation of Jab1 protein in human gall bladder cancer cells.

METHODS

In our study, we performed MTT and Trypan blue assay to assess the effect of stigmasterol on cell proliferation. In addition, RT-PCR and western blotting were performed to identify the effect of stigmasterol on Jab1 and p27 expression in human gall bladder cancer cells. We further performed cell cycle, Caspase-3, Hoechst and FITC-Annexin V analysis, to confirm the apoptosis induction in stigmasterol treated human gall bladder cancer cells.

RESULTS

Our results clearly indicated that stigmasterol has up-regulated the p27 expression and down-regulated Jab1 gene. These modulations of genes might occur via mitochondrial apoptosis signaling pathway. Caspase-3 gets activated with the apoptotic induction. Increase in apoptotic cells and DNA were confirmed through annexin V staining, Hoechst staining, and cell cycle analysis.

CONCLUSION

Thus, these results strongly suggest that stigmasterol has the potential to be considered as an anticancerous therapeutic agent against Jab1 in gall bladder cancer.

Astaxanthin anticancer effects are mediated through multiple molecular mechanisms: A systematic review

During the latest decades, the interest on the effectiveness of natural compounds and their impact on human health constantly increased, especially on those demonstrating to be effective on cancer. Molecules coming from nature are currently used in chemotherapy like Taxol, Vincristine or Vinblastine, and several other natural substances have been showed to be active in reducing cancer cell progression and migration. Among them, astaxanthin, a xanthophyll red colored carotenoid, displayed different biological activities including, antinflammatory, antioxidant, proapoptotic, and anticancer effects. It can induce apoptosis through downregulation of antiapoptotic protein (Bcl-2, p-Bad, and survivin) expression and upregulation of proapoptotic ones (Bax/Bad and PARP). Thanks to these mechanisms, it can exert anticancer effects towards colorectal cancer, melanoma, or gastric carcinoma cell lines. Moreover, it possesses antiproliferative activity in many experimental models and enhances the effectiveness of conventional chemotherapic drugs on tumor cells underling its potential future use. This review provides an overview of the current knowledge on the anticancer potential of astaxanthin by modulating several molecular targets. While it has been clearly demonstrated its multitarget activity in the prevention and regression of malignant cells in in vitro or in preclinical investigations, further clinical studies are needed to assess its real potential as anticancer in humans.

Apoptotic Effects on HL60 Human Leukaemia Cells Induced by Lavandin Essential Oil Treatment

Recent scientific investigations have reported a number of essential oils to interfere with intracellular signalling pathways and to induce apoptosis in different cancer cell types. In this paper, Lavandin Essential Oil (LEO), a natural sterile hybrid obtained by cross-breeding L. angustifolia × L. latifolia, was tested on human leukaemia cells (HL60). Based on the MTT results, the reduced cell viability of HL60 cells was further investigated to determine whether cell death was related to the apoptotic process. HL60 cells treated for 24 h with LEO were processed by flow cytometry, and the presence of Annexin V was measured. The activation of caspases-3 was evaluated by western blot and immunofluorescence techniques. Treated cells were also examined by scanning and transmission electron microscopy to establish the possible occurrence of morphological alterations during the apoptotic process. LEO main compounds, such as linalool, linalyl acetate, 1,8-cineole, and terpinen-4-ol, were also investigated by MTT and flow cytometry analysis. The set of obtained results showed that LEO treatments induced apoptosis in a dose-dependent, but not time-dependent, manner on HL60 cells, while among LEO main compounds, both terpinen-4-ol and linalyl acetate were able to induce apoptosis.

Dihydrochalcone Derivative Induces Breast Cancer Cell Apoptosis via Intrinsic, Extrinsic, and ER Stress Pathways but Abolishes EGFR/MAPK Pathway

Dihydrochalcone derivatives are active compounds that have been purified from the Thai medicinal plant Cyathostemma argenteum. The objectives of this study were to investigate the effects of two dihydrochalcone derivatives on human breast cancer MDA-MB-231 and MCF-7 cell proliferation and to study the relevant mechanisms involved. The two dihydrochalcone derivatives are 4′,6′-dihydroxy-2′,4-dimethoxy-5′-(2″-hydroxybenzyl)dihydrochalcone (compound 1) and calomelanone (2′,6′-dihydroxy-4,4′-dimethoxydihydrochalcone, compound 2), both of which induced cytotoxicity toward both cell lines in a dose-dependent manner by using MTT assay. Treatment with both derivatives induced apoptosis as determined by annexin V-FITC/propidium iodide employing flow cytometry. The reduction of mitochondrial transmembrane potential (staining with 3,3′-dihexyloxacarbocyanine iodide, DiOC₆, employing a flow cytometer) was established in the compound 1-treated cells. Compound 1 induced caspase-3, caspase-8, and caspase-9 activities in both cell lines, as has been determined by specific colorimetric substrates and a spectrophotometric microplate reader which indicated the involvement of both the extrinsic and intrinsic pathways. Calcium ion levels in mitochondrial and cytosolic compartments increased in compound 1-treated cells as detected by Rhod-2AM and Fluo-3AM intensity, respectively, indicating the involvement of the endoplasmic reticulum (ER) stress pathway. Compound 1 induced cell cycle arrest via enhanced atm and atr expressions and by upregulating proapoptotic proteins, namely, Bim, Bad, and tBid. Moreover, compound 1 significantly inhibited the EGFR/MAPK signaling pathway. In conclusion, compound 1 induced MDA-MB-231 and MCF-7 cell apoptosis via intrinsic, extrinsic, and ER stress pathways, whereas it ameliorated the EGFR/MAPK pathway in the MCF-7 cell line. Consequently, it is believed that compound 1 could be effectively developed for cancer treatments.

Penicamide A, A Unique N,N'-Ketal Quinazolinone Alkaloid from Ascidian-Derived Fungus Penicillium sp. 4829

Previously unreported N,N′-ketal quinazolinone enantiomers [(−)-1 and (+)-1] and a new biogenetically related compound (2), along with six known compounds, 2-pyrovoylaminobenzamide (3), N-(2-hydroxypropanoyl)-2 amino benzoic acid amide (4), pseurotin A (5), niacinamide (6), citreohybridonol (7), citreohybridone C (8) were isolated from the ascidian-derived fungus Penicillium sp. 4829 in wheat solid-substrate medium culture. Their structures were elucidated by a combination of spectroscopic analyses (1D and 2D NMR and Electron Circular Dichroism data) and X-ray crystallography. The enantiomeric pair of 1 is the first example of naturally occurring N,N′-ketal quinazolinone possessing a unique tetracyclic system having 4-quinazolinone fused with tetrahydroisoquinoline moiety. The enantiomeric mixtures of 1 displayed an inhibitory effect on NO production in lipopolysaccharide-activated RAW264.7 cells, while the optically pure (–)-1 showed better inhibitory effect than (+)-1.

Bursopentin (BP5) induces G1 phase cell cycle arrest and endoplasmic reticulum stress/mitochondria-mediated caspase-dependent apoptosis in human colon cancer HCT116 cells

Background

Bursopentin (BP5) is a multifunctional pentapeptide found in the chicken bursa of Fabricius. Recent study indicated that BP5 significantly stimulates expression of p53 protein in colon cancer HCT116 cells. However, the effects and underlying mechanisms of BP5 on HCT116 cell proliferation remain largely unclear.

Methods

Analyses of cell viability, cell cycle arrest as well as apoptosis were performed to study the actions of BP5 on HCT116 cells. Western blot analyse was assayed to measure the cell cycle-related and apoptosis-related proteins. Specific siRNAs targeting IRE1, ATF-6, and PERK were used for IRE1, ATF-6, and PERK knockdown, respectively. Cellular reactive oxygen species (ROS) were detected using a H₂DCF-DA green fluorescence probe. Cytosolic free Ca²⁺ concentrations and mitochondrial membrane potential (ΔΨm) were measured using Fluo-3 AM and JC-1 stains, respectively.

Results

BP5 possessed strong inhibitory effects on the cell growth and induced apoptosis in HCT116 cells. Mechanistically, BP5 arrested the cell cycle at G1 phase by increasing p53 and p21 expression and decreasing cyclin E1-CDK2 complex expression. BP5 treatment dramatically activated the endoplasmic reticulum (ER) stress-mediated apoptotic pathway, as revealed by the significantly enhanced expression of unfolded protein response (UPR) sensors (IRE1α, ATF6, PERK) as well as downstream signaling molecules (XBP-1s, eIF2α, ATF4 and CHOP), and by the significantly altered the BP5-induced phenotypic changes in IRE1, ATF6, and PERK knockdown cells. Additionally, BP5-induced ER stress was accompanied by the accumulation of cytosolic free Ca²⁺ and intracellular ROS. Furthermore, BP5 treatment resulted in the increase of Bax expression, the decrease of Bcl-2 expression and the reduction of ΔΨm, subsequently causing a release of cytochrome c from the mitochondria into the cytoplasm and finally enhancing the activities of caspase-9 and -3. In addition, z-VAD-fmk, a pan-caspase inhibitor, markedly rescued BP5-induced cell viability reduction and reduced BP5-induced apoptosis.

Conclusions

Our present results suggest that BP5 has an anticancer capacity to arrest cell cycle at G1 phase and to trigger ER stress/mitochondria-mediated caspase-dependent apoptosis in HCT116 cells. Therefore, our findings provide insight into further investigations of the anticancer activities of BP5.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0849-3) contains supplementary material, which is available to authorized users.

Apoptotic effects of hsian-tsao (Mesona procumbens Hemsley) on hepatic stellate cells mediated by reactive oxygen species and ERK, JNK, and caspase-3 pathways

The activation of hepatic stellate cells (HSCs) is an important step in the progress of liver fibrosis. Fibrosis can be impeded by HSC reversion to a quiescent state or HSC clearance through apoptosis. To investigate the apoptotic effects of hsian-tsao (Mesona procumbens Hemsl) on human HSCs, the expression levels of cleaved caspase-3, p38, and c-Jun N-terminal kinase (JNK) were assessed using Western blotting, and the caspase-3 activity was measured using caspase-3/CPP32 colorimetric assay kit. Hsian-tsao extract (HTE) increased the activity of caspase-3 and the level of activated caspase-3, indicating the activation of apoptosis. The intracellular reactive oxygen species (ROS) level increased in a dose-dependent manner. This increase was prevented by an antioxidant, suggesting that HTE induces ROS accumulation. In addition, we found that HTE induced the phosphorylation of the mitogen-activated protein kinases JNK and p38. These collective data indicate that HTE induces apoptosis via ROS production through the p38, JNK, and caspase-3-dependent pathways. HTE may decrease HSC activation in liver fibrosis and may have a therapeutic potential.

Biosynthesis, characterization, and anticancer effect of plant-mediated silver nanoparticles using Coptis chinensis

Background

Tremendous growth in nanotechnology has opened up new frontiers in fundamental and applied aspects, including the synthesis of nanoscale matter and understanding/utilizing its exotic physicochemical and optoelectronic properties. Green-synthesis methods employing either biological microorganisms or plant extracts have emerged as a simple and alternative to chemical synthesis.

Methods

In our present study, we aimed to synthesize silver nanoparticles (AgNPs) in combination with an aqueous extract of Coptis chinensis (CC) using a suitable ecofriendly green-synthesis way.

Results

In our results, ultraviolet-visible spectroscopy revealed a near-absorbance peak at 450 nm, which confirmed the AgNP synthesis. The crystalline nature of the AgNPs was revealed with X-ray diffraction. Transmission electron-microscopy analysis showed spherically dispersed nanoparticles of 6–45 nm diameter. We analyzed the elementary mechanism across A549 lung carcinoma cells ahead of treatment with doses of CC-AgNPs (10 µg/mL and 25 µg/mL). The antiproliferative effect of CC-AgNPs revealed a significant decline in cell viability. Antibacterial assays with both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria exhibited a higher zone of inhibition against S. aureus.

Conclusion

Furthermore, CC-AgNPs regulated apoptosis using the intrinsic pathway to inhibit A549-cell proliferation. Proliferation migration and invasion were notably inhibited by CC-AgNPs, which promoted apoptosis in lung adenocarcinoma cells by regulating the apoptotic pathway.

Regulated Cell Death Signaling Pathways and Marine Natural Products That Target Them

Our understanding of cell death used to consist in necrosis, an unregulated form, and apoptosis, regulated cell death. That understanding expanded to acknowledge that apoptosis happens through the intrinsic or extrinsic pathways. Actually, many other regulated cell death processes exist, including necroptosis, a regulated form of necrosis, and autophagy-dependent cell death. We also understand that apoptosis occurs beyond the intrinsic and extrinsic pathways with caspase independent forms of apoptosis existing. Our knowledge of the signaling continues to grow, and with that, so does our ability to target different parts of the pathways with small molecules. Marine natural products co-evolve with their targets, and these unique molecules have complex structures with exquisite biological activities and specificities. This article offers a review of our current understanding of the signaling pathways regulating cell death, and highlights marine natural products that can affect these signaling pathways.

Anti-glioma trichobamide A with an unprecedented tetrahydro-5H-furo[2,3-b]pyrrol-5-one functionality from ascidian-derived fungus Trichobotrys effuse 4729

Trichobamide A (1), a novel pyrrocidine alkaloid with an unprecedented tetrahydro-5H-furo[2,3-b]pyrrol-5-one moiety, was isolated from the ascidian-derived fungus Trichobotrys effuse 4729.

Curcuminoids Induce Reactive Oxygen Species and Autophagy to Enhance Apoptosis in Human Oral Cancer Cells

Numerous studies support the use of herbal medicine or natural products for chemotherapy in human cancers. Reports have associated curcumin (CUR), dimethoxy curcumin (DMC) and bisdemethoxycurcumin (BDMC) with numerous biological activities including anticancer activities, but no available information have shown that these induced apoptotic cell death and autophagy in human oral cancer cells. In the present study, we investigated the effect of CUR, DMC and BDMC on the cell viability, apoptotic cell death, reactive oxygen species (ROS), Ca[Formula: see text], mitochondria membrane potential (MMP) and caspase activities using flow cytometry assay and autophagy by monodansylcadaverine (MDC) and acridine orange (AO) staining in human oral cancer SAS cells. Results indicated that CUR, DMC and BDMC decreased total viable cell number through the induction of cell autophagy and apoptosis in SAS cells. Cells were pretreated with N-acetyl-cysteine (NAC), 3-methyladenine (3MA), rapamycin and carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoro-methylketone (Z-VAD-fmk) and then were treated with CUR, DMC and BDMC that led to increased total viable cell number when compared to CUR, DMC and BDMC treatments only. Results indicated induced apoptotic cell death through ROS, mitochondria-dependent pathway and induction of cell autophagy. Based on those observations, we suggest that CUR, DMC and BDMC could be used as a potential anticancer agent in human oral cancer.

Antitumour bioactive peptides isolated from marine organisms

Marine organisms are an important source of antitumour active substances. Thus, pharmaceutical research in recent years has focused on exploring new antitumour drugs derived from marine organisms, and, many peptide drugs with strong antitumour activities have been successfully extracted. Based on different mechanisms, this paper reviews the research on several typical antitumour bioactive peptides in marine drugs and the latest progress therein. Additionally, the development prospects for these antitumour bioactive peptide-based drugs are discussed so as to provide a reference for future research in this field.

Curcuminoids combined with gefitinib mediated apoptosis and autophagy of human oral cancer SAS cells in vitro and reduced tumor of SAS cell xenograft mice in vivo

Gefitinib has been used for cancer patients and curcumin (CUR), demethoxycurcumin (DMC), or bisdemethoxycurcumin (BDMC) also shown to induce cancer cell apoptosis. However, no report shows the combination of gefitinib with, CUR, DMC, or BDMC induce cell apoptosis and autophagy in human oral cancer cells. In this study, we investigated the effects of gefitinib with or without CUR, DMC, or BDMC co-treatment on the cell viability, apoptotic cell death, autophagy, mitochondria membrane potential (MMP), and caspase-3 activities by flow cytometry assay and autophagy by acridine orange (AO) staining in human oral cancer SAS cells. Results indicated that gefitinib co-treated with CUR, DMC, or BDMC decreased total viable cell number through the induction of cell apoptosis and autophagy and decreased the levels of MMP and increased caspase-3 activities in SAS cells. Western blotting indicated that gefitinib combined with CUR, DMC, or BDMC led to decrease Bcl-2 protein expression which is an antiapoptotic protein and to increase ATG5, Beclin 1, p62/SQSTM1, and LC3 expression that associated with cell autophagy in SAS cells. Gefitinib combined with CUR and DMC led to significantly reduce the tumor weights and volumes in SAS cell xenograft nude mice but did not affect the total body weights. Based on those observations, we suggest that the combination of gefitinib with CUR, DMC, and BDMC can be a potential anticancer agent for human oral cancer in future.

Coralyne, a protoberberine alkaloid, causes robust photosenstization of cancer cells through ATR-p38 MAPK-BAX and JAK2-STAT1-BAX pathways

Photodynamic therapy (PDT) provides an effective cancer treatment option but it requires sufficient cellular oxygen concentration to exert its photosensitizing effects. Due to hypoxic nature of most tumors, widespread clinical application of PDT is restricted and warrants development of photosensitizers which can kill cancer cells in ROS independent manner. Previously, we reported significant enhancement of the anti-cancer property of coralyne in presence of ultraviolet-A (UVA) light exposure against several human carcinoma cell lines. This study aimed at unravelling molecular cascades of events in CUVA treatment (coralyne and UVA light)-mediated photosensitization of human skin cancer. The CUVA-treatment caused robust apoptosis of A431 cancer cells, primarily through mitochondrial and lysosomal dysfunctions. Silencing of BAX conferred a significant protection against CUVA-induced apoptosis. Both lysosomal proteases and caspase-8 activation contributed to BID cleavage. Further, our results revealed that a dual signaling axis e.g., ATR-p38 MAPK and JAK2-STAT1 pathways functioned upstream of BAX activation in apoptosis response. Moreover, transient silencing of ATR and pharmacological inhibition of p38-MAPK or JAK2 significantly abolished the effect of CUVA treatment induced BAX expression and cell death, linking the extrinsic and intrinsic pathways with the observed cell death. Our data suggest that coralyne, which is known topoisomerase-I inhibitor, may be an attractive agent for photo-chemotherapeutic treatment of human skin cancers.

Toward aplyronine payloads for antibody–drug conjugates: total synthesis of aplyronines A and D

We report an expedient total synthesis of aplyronines A and D, together with a linker-modified analogue for bioconjugation studies.

Noninvasive bioluminescence imaging of the dynamics of sanguinarine induced apoptosis via activation of reactive oxygen species

Most chemotherapeutic drugs exert their anti-tumor effects primarily by triggering a final pathway leading to apoptosis. Noninvasive imaging of apoptotic events in preclinical models would greatly facilitate the development of apoptosis-inducing compounds and evaluation of their therapeutic efficacy. Here we employed a cyclic firefly luciferase (cFluc) reporter to screen potential pro-apoptotic compounds from a number of natural agents. We demonstrated that sanguinarine (SANG) could induce apoptosis in a dose- and time-dependent manner in UM-SCC-22B head and neck cancer cells. Moreover, SANG-induced apoptosis was associated with the generation of reactive oxygen species (ROS) and activation of c-Jun-N-terminal kinase (JNK) and nuclear factor-kappaB (NF-κB) signal pathways. After intravenous administration with SANG in 22B-cFluc xenograft models, a dramatic increase of luminescence signal can be detected as early as 48 h post-treatment, as revealed by longitudinal bioluminescence imaging in vivo. Remarkable apoptotic cells reflected from ex vivo TUNEL staining confirmed the imaging results. Importantly, SANG treatment caused distinct tumor growth retardation in mice compared with the vehicle-treated group. Taken together, our results showed that SANG is a candidate anti-tumor drug and noninvasive imaging of apoptosis using cFluc reporter could provide a valuable tool for drug development and therapeutic efficacy evaluation.

Blocking autophagy enhances the pro-apoptotic effect of bufalin on human gastric cancer cells through endoplasmic reticulum stress

Bufalin has been used to treat cancer for several years. However, the molecular mechanisms for its anti-tumor function are not fully understood. This work aimed to investigate the effect of bufalin on the proliferation and apoptosis of human gastric cancer (HGC) cells and the roles of endoplasmic reticulum (ER) stress and autophagy in bufalin-induced apoptosis. HGC cell lines, SGC7901 and BGC823, were treated with different concentrations of bufalin or 80 nmol/l bufalin for 1, 2, 3 and 4 days. Cell counting kit-8 (CCK-8) assay and direct cell counting method were used to detect proliferation. Cell cycle arrest and apoptosis was detected using flow cytometry. Protein levels of caspase-3, -8, Bax/Bcl-2, Beclin-1, LC3, inositol-requiring enzyme 1 (IRE1) and C/EBP homologous protein (CHOP) were determined using western blotting. Autophagy was blocked using 3-methyladenine (3MA) or Atg5 siRNA to evaluate the effect of autophagy on bufalin-induced apoptosis. The IRE1 and CHOP were knocked down using specific siRNA to determine the pathway involved in bufalin-induced autophagy. It was found that bufalin significantly suppressed proliferation of SGC7901 and BGC823 cells and induced apoptosis in a time- and dose-dependent manner. The mechanism responsible for bufalin-induced apoptosis was the formation of ER stress via the IRE1-JNK pathway. Moreover, autophagy was activated during ER stress, and blocking autophagy significantly exacerbated bufalin-induced apoptosis.

Summary: Bufalin suppressed human gastric cancer cells and induced apoptosis. The mechanism was related to ER stress formation via the IRE1-JNK pathway. Blocking autophagy exacerbated bufalin-induced apoptosis.

Synthesis and bioactivity of bis-steroidal pyrazine 23-deoxy-25-epi ritterostatin GN1N

Cephalostatins, ritterazines and their hybrid bis-steroidal pyrazine analogs such as 25-epi-rittereostatin G_N1_N show unusually high potency against a wide range of cancer cell lines. Herein, we report the synthesis and bioactivity of 23-deoxy-25-epi ritterostatin G_N1_N, which lacks the 23-hydroxyl group of 25-epi rittereostatin G_N1_N. The less oxygenated bis-steroidal pyrazine was ∼50- to 1000-fold less potent than 25-epi ritterostatin G_N1_N, highlighting the importance of the 23-hydroxyl group for the antiproliferative activity of the cephalostatin/ritterazine class of drugs.

The therapeutic effects of Longikaurin A, a natural ent-kauranoid, in esophageal squamous cell carcinoma depend on ROS accumulation and JNK/p38 MAPK activation

Effective treatments for esophageal squamous cell carcinoma (ESCC), one of the most common cancers in China, are lacking. Longikaurin A (LK-A), an ent-kauranoid diterpenoid isolated from Isodon ternifolius, has been shown to have potent cytotoxic effects on ESCC cells both in vivo and in vitro, mainly by inducing apoptosis. In this study, LK-A inhibited ESCC cells viability and induced G2/M cell cycle arrest. Moreover, LK-A was also highly effective in a KYSE-30 xenograft nude mouse model. Treatment with Z-VAD(OMe)-FMK partially attenuated LK-A-induced apoptosis. LK-A significantly induced reactive oxygen species (ROS) production in ESCC cells, and LK-A-induced apoptosis was attenuated by the ROS scavenger N-acetyl cysteine (NAC). Furthermore, we found that treatment with LK-A activated both the JNK and p38 MAPK signaling pathways, resulting in increases in ROS levels and apoptosis induction. Taken together, these findings indicate that LK-A exerts novel anti-tumor effects in ESCC cells by activating the JNK and p38 MAPK pathways and inducing increases in ROS production, which suggest that the compound may have potential as a clinical therapeutic agent.

High-Throughput Identification of miR-596 Inducing p53-Mediated Apoptosis in HeLa and HCT116 Cells Using Cell Microarray

miRNAs play a key role in the regulation of gene networks in mammalian cells. However, little is known about their roles and functions in the apoptosis pathway. Here, we conducted a whole-genome miRNA screening for apoptosis and identified more than 100 miRNAs as apoptosis inducers. To further explain the roles of these mRNAs in apoptosis, a second round of screening was conducted between p53 +/+ and -/- cells. Among the hits, miR-596 was identified as a regulator of p53. The overexpression of miR-596 significantly increased p53 at the protein level, thereby inducing apoptosis. We also demonstrated that Smurf1 was the direct target of miR-596. Previously, Smurf1 was reported to attenuate the level of p53 through binding and stabilizing MDM2, a p53 inhibitor. Consequently, by targeting Smurf1, miR-596 indirectly increased the p53 level in mammalian cells. Moreover, our study demonstrated that miR-596 had other antitumor characteristics, such as inhibiting migration and proliferation. The data from the GEO dataset revealed that the high expression of miR-596 contributed to survival benefits among cancer patients. These results make miR-596 a potential antitumor factor for future biomedical applications.

Mertensene, a Halogenated Monoterpene, Induces G2/M Cell Cycle Arrest and Caspase Dependent Apoptosis of Human Colon Adenocarcinoma HT29 Cell Line through the Modulation of ERK-1/-2, AKT and NF-κB Signaling

Conventional treatment of advanced colorectal cancer is associated with tumor resistance and toxicity towards normal tissues. Therefore, development of effective anticancer therapeutic alternatives is still urgently required. Nowadays, marine secondary metabolites have been extensively investigated due to the fact that they frequently exhibit anti-tumor properties. However, little attention has been given to terpenoids isolated from seaweeds. In this study, we isolated the halogenated monoterpene mertensene from the red alga Pterocladiella capillacea (S.G. Gmelin) Santelices and Hommersand and we highlight its inhibitory effect on the viability of two human colorectal adenocarcinoma cell lines HT29 and LS174. Interestingly, exposure of HT29 cells to different concentrations of mertensene correlated with the activation of MAPK ERK-1/-2, Akt and NF-κB pathways. Moreover, mertensene-induced G2/M cell cycle arrest was associated with a decrease in the phosphorylated forms of the anti-tumor transcription factor p53, retinoblastoma protein (Rb), cdc2 and chkp2. Indeed, a reduction of the cellular level of cyclin-dependent kinases CDK2 and CDK4 was observed in mertensene-treated cells. We also demonstrated that mertensene triggers a caspase-dependent apoptosis in HT29 cancer cells characterized by the activation of caspase-3 and the cleavage of poly (ADP-ribose) polymerase (PARP). Besides, the level of death receptor-associated protein TRADD increased significantly in a concentration-dependent manner. Taken together, these results demonstrate the potential of mertensene as a drug candidate for the treatment of colon cancer.

Antitumor agent 25-epi Ritterostatin GN1N induces endoplasmic reticulum stress and autophagy mediated cell death in melanoma cells

Metastatic melanoma is the most aggressive of all skin cancers and is associated with poor prognosis owing to lack of effective treatments. 25-epi Ritterostatin G_N1_N is a novel antitumor agent with yet undefined mechanisms of action. We sought to delineate the antitumor mechanisms of 25-epi Ritterostatin G_N1_N in melanoma cells to determine the potential of this compound as a treatment for melanoma. Activation of the endoplasmic reticulum (ER) stress protein glucose-regulated protein 78 (GRP78) has been associated with increased melanoma progression, oncogenic signaling, drug resistance, and suppression of cell death. We found that 25-epi Ritterostatin G_N1_N induced cell death in melanoma cells at nanomolar concentrations, and this cell death was characterized by inhibition of GRP78 expression, increased expression of the ER stress marker CHOP, loss of mitochondrial membrane potential, and lipidation of the autophagy marker protein LC3B. Importantly, normal melanocytes exhibited limited sensitivity to 25-epi Ritterostatin G_N1_N. Subsequent in vivo results demonstrated that 25-epi Ritterostatin G_N1_N reduced melanoma growth in mouse tumor xenografts and did not affect body weight, suggesting minimal toxicity. In summary, our findings indicate that 25-epi Ritterostatin G_N1_N causes ER stress and massive autophagy, leading to collapse of mitochondrial membrane potential and cell death in melanoma cells, with minimal effects in normal melanocytes. Thus, 25-epi Ritterostatin G_N1_N is a promising anticancer agent that warrants further investigation.

Activation of AIFM2 enhances apoptosis of human lung cancer cells undergoing toxicological stress

Application of cisplatin (DDP) for treating lung cancer is restricted due to its toxicity and lung cancer's drug resistance. In this study, we examined the effect of Jinfukang (JFK), an effective herbal medicine against lung cancer, on DDP-induced cytotoxicity in lung cancer cells. Morphologically, we observed that JFK increases DDP-induced pro-apoptosis in A549 cells in a synergistic manner. Transcriptome profiling analysis indicated that the combination of JFK and DDP regulates genes involved in apoptosis-related signaling pathways. Moreover, we found that the combination of JFK and DDP produces synergistic pro-apoptosis effect in other lung cancer cell lines, such as NCI-H1975, NCI-H1650, and NCI-H2228. Particularly, we demonstrated that AIFM2 is activated by the combined treatment of JFK and DDP and partially mediates the synergistic pro-apoptosis effect. Collectively, this study not only offered the first evidence that JFK promotes DDP-induced cytotoxicity, and activation of AIFM2 enhances apoptosis of human lung cancer cells undergoing toxicological stress, but also provided a novel insight for improving cytotoxicity by combining JFK with DDP to treat lung cancer cells.

Macroalgae of Izmir Gulf: Dictyotaceae exhibit high in vitro anti-cancer activity independent from their antioxidant capabilities

In this study, 24 marine macroalgae collected from the coastline of Izmir Gulf were examined for their antioxidant activities and their effects on cell proliferation. Crude extracts were obtained from samples with cold methanol extraction. Antioxidant activity was evaluated as 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging activity and total phenolic content (TPC); growth inhibitory effects of the extracts were determined by using WST-8. Amongst the species, Polysiphonia denuata (Rhodophyta) and Cystoseira species (Phaeophyceae) have been noticed by their high DPPH radical scavenging activities and TPCs. As expected, there was a strong correlation between these tests. Dictyota dichotoma (Phaeophyceae) showed the highest anti-cancer activity on MCF-7 cells with an IC₅₀ of 17.2 ng mL^-1. Flow cytometry analyses demonstrated that D. dichotoma methanolic extract strongly induced apoptosis. This extract exhibited moderate viability inhibition on MCF10A cells (IC₅₀: 49.3 ng mL^-1), suggesting a potential use of the extracts or its compounds for cancer therapy. There was no correlation between anti-cancer potential and antioxidant content of the extracts.

Stellettin B Induces G1 Arrest, Apoptosis and Autophagy in Human Non-small Cell Lung Cancer A549 Cells via Blocking PI3K/Akt/mTOR Pathway

Until now, there is not yet antitumor drug with dramatically improved efficacy on non-small cell lung cancer (NSCLC). Marine organisms are rich source of novel compounds with various activities. We isolated stellettin B (Stel B) from marine sponge Jaspis stellifera, and demonstrated that it induced G1 arrest, apoptosis and autophagy at low concentrations in human NSCLC A549 cells. G1 arrest by Stel B might be attributed to the reduction of cyclin D1 and enhancement of p27 expression. The apoptosis induction might be related to the cleavage of PARP and increase of ROS generation. Moreover, we demonstrated that Stel B induced autophagy in A549 cells by use of various assays including monodansylcadaverine (MDC) staining, transmission electron microscopy (TEM), tandem mRFP-GFP-LC3 fluorescence microscopy, and western blot detection of the autophagy markers of LC3B, p62 and Atg5. Meanwhile, Stel B inhibited the expression of PI3K-p110, and the phosphorylation of PDK1, Akt, mTOR, p70S6K as well as GSK-3β, suggesting the correlation of blocking PI3K/Akt/mTOR pathway with the above antitumor activities. Together, our findings indicate the antitumor potential of Stel B for NSCLC by targeting PI3K/Akt/mTOR pathway.

In vitro anticancer properties and biological evaluation of novel natural alkaloid jerantinine B

Natural products play a pivotal role in medicine especially in the cancer arena. Many drugs that are currently used in cancer chemotherapy originated from or were inspired by nature. Jerantinine B (JB) is one of seven novel Aspidosperma indole alkaloids isolated from the leaf extract of Tabernaemontana corymbosa. Preliminary antiproliferative assays revealed that JB and JB acetate significantly inhibited growth and colony formation, accompanied by time- and dose-dependent apoptosis induction in human cancer cell lines. JB significantly arrested cells at the G2/M cell cycle phase, potently inhibiting tubulin polymerisation. Polo-like kinase 1 (PLK1; an early trigger for the G2/M transition) was also dose-dependently inhibited by JB (IC50 1.5 µM). Furthermore, JB provoked significant increases in reactive oxygen species (ROS). Annexin V+ cell populations, dose-dependent accumulation of cleaved-PARP and caspase 3/7 activation, and reduced Bcl-2 and Mcl-1 expression confirm apoptosis induction. Preclinical in silico biopharmaceutical assessment of JB calculated rapid absorption and bioavailability >70%. Doses of 8-16 mg/kg JB were predicted to maintain unbound plasma concentrations >GI50 values in mice during efficacy studies. These findings advocate continued development of JB as a potential chemotherapeutic agent.

The synthesis and evaluation of new benzophenone derivatives as tubulin polymerization inhibitors

Inspired by the potent inhibition activity of phenstatin and millepachine against cancer cell growth, a series of new benzophenone derivatives were synthesized and evaluated as tubulin polymerization inhibitors.

Recent Advances in Drug Discovery from South African Marine Invertebrates

Recent developments in marine drug discovery from three South African marine invertebrates, the tube worm Cephalodiscus gilchristi, the ascidian Lissoclinum sp. and the sponge Topsentia pachastrelloides, are presented. Recent reports of the bioactivity and synthesis of the anti-cancer secondary metabolites cephalostatin and mandelalides (from C. gilchristi and Lissoclinum sp., respectively) and various analogues are presented. The threat of drug-resistant pathogens, e.g., methicillin-resistant Staphylococcus aureus (MRSA), is assuming greater global significance, and medicinal chemistry strategies to exploit the potent MRSA PK inhibition, first revealed by two marine secondary metabolites, cis-3,4-dihydrohamacanthin B and bromodeoxytopsentin from T. pachastrelloides, are compared.