Laminarin induces apoptosis of human colon cancer LOVO cells through a mitochondrial pathway

Marine-Derived Anticancer Agents Targeting Apoptotic Pathways: Exploring the Depths for Novel Cancer Therapies

Extensive research has been conducted on the isolation and study of bioactive compounds derived from marine sources. Several natural products have demonstrated potential as inducers of apoptosis and are currently under investigation in clinical trials. These marine-derived compounds selectively interact with extrinsic and intrinsic apoptotic pathways using a variety of molecular mechanisms, resulting in cell shrinkage, chromatin condensation, cytoplasmic blebs, apoptotic bodies, and phagocytosis by adjacent parenchymal cells, neoplastic cells, or macrophages. Numerous marine-derived compounds are currently undergoing rigorous examination for their potential application in cancer therapy. This review examines a total of 21 marine-derived compounds, along with their synthetic derivatives, sourced from marine organisms such as sponges, corals, tunicates, mollusks, ascidians, algae, cyanobacteria, fungi, and actinobacteria. These compounds are currently undergoing preclinical and clinical trials to evaluate their potential as apoptosis inducers for the treatment of different types of cancer. This review further examined the compound's properties and mode of action, preclinical investigations, clinical trial studies on single or combination therapy, and the prospective development of marine-derived anticancer therapies.

In vitro anticancer potential of laminarin and fucoidan from Brown seaweeds

Marine seaweeds are rich source of polysaccharides present in their cell wall and are cultivated and consumed in China, Japan, Korea, and South Asian countries. Brown seaweeds (Phaeophyta) are rich source of polysaccharides such as Laminarin and Fucoidan. In present study, both the laminarin and fucoidan were isolated was yielded higher in PP (Padina pavonica) (4.36%) and STM (Stoechospermum marginatum) (2.32%), respectively. The carbohydrate content in laminarin and fucoidan was 86.91% and 87.36%, whereas the sulphate content in fucoidan was 20.68%. Glucose and mannose were the major monosaccharide units in laminarin (PP), however, fucose, galactose, and xylose in fucoidan (STM). FT-IR down peaks represent the carbohydrate of laminarin and fucoidan except, for 1219 cm-1, and 843 cm-1, illustrating the sulphate groups of fucoidan. The molecular weight of laminarin was 3-5 kDa, and the same for fucoidan was 2-6 kDa, respectively. Both the Fucoidan and Laminarin showed null cytotoxicity on Vero cells. Contrastingly, the fucoidan possess cytotoxic activity on human liver cancer cells (HepG2) (IC50-24.4 ± 1.5 µg/mL). Simultaneously, laminarin also shown cytotoxicity on human colon cancer cells (HT-29) (IC50-57 ± 1.2 µg/mL). The AO/EB (Acriding Orange/Ethidium Bromide) assay significantly resulted in apoptosis and necrosis upon laminarin and fucoidan treatments, respectively. The DNA fragmentation results support necrotic cancer cell death. Therefore, laminarin and fucoidan from PP and STM were potential bioactive compounds for anticancer therapy.

Promising Strategy of mPTP Modulation in Cancer Therapy: An Emerging Progress and Future Insight

Cancer has been progressively a major global health concern. With this developing global concern, cancer determent is one of the most significant public health challenges of this era. To date, the scientific community undoubtedly highlights mitochondrial dysfunction as a hallmark of cancer cells. Permeabilization of the mitochondrial membranes has been implicated as the most considerable footprint in apoptosis-mediated cancer cell death. Under the condition of mitochondrial calcium overload, exclusively mediated by oxidative stress, an opening of a nonspecific channel with a well-defined diameter in mitochondrial membrane allows free exchange between the mitochondrial matrix and the extra mitochondrial cytosol of solutes and proteins up to 1.5 kDa. Such a channel/nonspecific pore is recognized as the mitochondrial permeability transition pore (mPTP). mPTP has been established for regulating apoptosis-mediated cancer cell death. It has been evident that mPTP is critically linked with the glycolytic enzyme hexokinase II to defend cellular death and reduce cytochrome c release. However, elevated mitochondrial Ca2+ loading, oxidative stress, and mitochondrial depolarization are critical factors leading to mPTP opening/activation. Although the exact mechanism underlying mPTP-mediated cell death remains elusive, mPTP-mediated apoptosis machinery has been considered as an important clamp and plays a critical role in the pathogenesis of several types of cancers. In this review, we focus on structure and regulation of the mPTP complex-mediated apoptosis mechanisms and follow with a comprehensive discussion addressing the development of novel mPTP-targeting drugs/molecules in cancer treatment.

The carboxymethylated derivative of laminaran from brown alga Saccharina cichorioides: Structure, anticancer and anti-invasive activities in 3D cell culture

Polysaccharides' derivatives are promising biologically active compounds for biotechnology, nutrition, industries, and are becoming increasingly important in medicine and pharmacy. Laminaran from brown alga Saccharina cichorioides (ScL) was chemically modified to obtain the carboxymethylated derivative (ScLCM) with improved structure and bioactivity. ScLCM was identified as (1 → 3)-β-D-glucan with -CH2-COOH groups at some positions 2, 4, and 6 of glucose residues. The anticancer activity of ScLCM was studied on the models of viability and invasion of 3D human melanoma SK-MEL-28, breast cancer T-47D, and colorectal carcinoma DLD-1 cells in comparison with native laminaran or its sulfated or aminated derivatives. ScLCM had the highest anticancer and anti-invasive effects among investigated polysaccharides. ScLCM significantly suppressed the viability and invasion of 3D SK-MEL-28 cells via the regulation of the activity of matrix metalloproteinase 9 (MMP 9) and protein kinases of ERK/MAPK signaling pathway. These findings may contribute to the reported anticancer effects of algal polysaccharides' derivatives.

Marine Compounds, Mitochondria, and Malignancy: A Therapeutic Nexus

The marine environment is important yet generally underexplored. It contains new sources of functional constituents that can affect various pathways in food processing, storage, and fortification. Bioactive secondary metabolites produced by marine microorganisms may have significant potential applications for humans. Various components isolated from disparate marine microorganisms, including fungi, microalgae, bacteria, and myxomycetes, showed considerable biological effects, such as anticancer, antioxidant, antiviral, antibacterial, and neuroprotective activities. Growing studies are revealing that potential anticancer effects of marine agents could be achieved through the modulation of several organelles. Mitochondria are known organelles that influence growth, differentiation, and death of cells via influencing the biosynthetic, bioenergetic, and various signaling pathways related to oxidative stress and cellular metabolism. Consequently, mitochondria play an essential role in tumorigenesis and cancer treatments by adapting to alterations in environmental and cellular conditions. The growing interest in marine-derived anticancer agents, combined with the development and progression of novel technology in the extraction and cultures of marine life, led to revelations of new compounds with meaningful pharmacological applications. This is the first critical review on marine-derived anticancer agents that have the potential for targeting mitochondrial function during tumorigenesis. This study aims to provide promising strategies in cancer prevention and treatment.

Anti-colorectal cancer effects of seaweed-derived bioactive compounds

Seaweeds are classified as Chlorophyta, Rhodophyta, and Phaeophyta. They constitute a number of the most significant repositories of new therapeutic compounds for human use. Seaweed has been proven to possess diverse bioactive properties, which include anticancer properties. The present review focuses on colorectal cancer, which is a primary cause of cancer-related mortality in humans. In addition, it discusses various compounds derived from a series of seaweeds that have been shown to eradicate or slow the progression of cancer. Therapeutic compounds extracted from seaweed have shown activity against colorectal cancer. Furthermore, the mechanisms through which these compounds can induce apoptosis in vitro and in vivo were reviewed. This review emphasizes the potential utility of seaweeds as anticancer agents through the consideration of the capability of compounds present in seaweeds to fight against colorectal cancer.

Nutrient Deprivation Coupled with High Light Exposure for Bioactive Chrysolaminarin Production in the Marine Microalga Isochrysis zhangjiangensis

Chrysolaminarin, a kind of water-soluble bioactive β-glucan produced by certain microalgae, is a potential candidate for food/pharmaceutical applications. This study identified a marine microalga Isochrysis zhangjiangensis, in which chrysolaminarin production was investigated via nutrient (nitrogen, phosphorus, or sulfur) deprivations (-N, -P, or -S conditions) along with an increase in light intensity. A characterization of the antioxidant activities of the chrysolaminarin produced under each condition was also conducted. The results showed that nutrient deprivation caused a significant increase in chrysolaminarin accumulation, though this was accompanied by diminished biomass production and photosynthetic activity. -S was the best strategy to induce chrysolaminarin accumulation. An increase in light intensity from 80 (LL) to 150 (HL) µE·m⁻²·s⁻¹ further enhanced chrysolaminarin production. Compared with -N, -S caused more suitable stress and reduced carbon allocation toward neutral lipid production, which enabled a higher chrysolaminarin accumulation capacity. The highest chrysolaminarin content and concentration reached 41.7% of dry weight (%DW) and 632.2 mg/L, respectively, under HL-S, with a corresponding productivity of 155.1 mg/L/day achieved, which exceeds most of the photoautotrophic microalgae previously reported. The chrysolaminarin produced under HL-N (Iz-N) had a relatively competitive hydroxyl radical scavenging activity at low concentrations, while the chrysolaminarin produced under HL-S (Iz-S) exhibited an overall better activity, comparable to the commercial yeast β-glucan, demonstrating I. zhangjiangensis as a promising bioactive chrysolaminarin producer from CO₂.

Applications of algae to obtain healthier meat products: A critical review on nutrients, acceptability and quality

Meat constitutes one the main protein sources worldwide. However, ethical and health concerns have limited its consumption over the last years. To overcome this negative impact, new ingredients from natural sources are being applied to meat products to obtain healthier proteinaceous meat products. Algae is a good source of unsaturated fatty acids, proteins, essential amino acids, and vitamins, which can nutritionally enrich several foods. On this basis, algae have been applied to meat products as a functional ingredient to obtain healthier meat-based products. This paper mainly reviews the bioactive compounds in algae and their application in meat products. The bioactive ingredients present in algae can give meat products functional properties such as antioxidant, neuroprotective, antigenotoxic, resulting in healthier foods. At the same time, algae addition to foods can also contribute to delay microbial spoilage extending shelf-life. Additionally, other algae-based applications such as for packaging materials for meat products are being explored. However, consumers' acceptance for new products (particularly in Western countries), namely those containing algae, not only depends on their knowledge, but also on their eating habits. Therefore, it is necessary to further explore the nutritional properties of algae-containing meat products to overcome the gap between new meat products and traditional products, so that healthier algae-containing meat can occupy a significant place in the market.

Brown Algae Carbohydrates: Structures, Pharmaceutical Properties, and Research Challenges

Brown algae (Phaeophyceae) have been consumed by humans for hundreds of years. Current studies have shown that brown algae are rich sources of bioactive compounds with excellent nutritional value, and are considered functional foods with health benefits. Polysaccharides are the main constituents of brown algae; their diverse structures allow many unique physical and chemical properties that help to moderate a wide range of biological activities, including immunomodulation, antibacterial, antioxidant, prebiotic, antihypertensive, antidiabetic, antitumor, and anticoagulant activities. In this review, we focus on the major polysaccharide components in brown algae: the alginate, laminarin, and fucoidan. We explore how their structure leads to their health benefits, and their application prospects in functional foods and pharmaceuticals. Finally, we summarize the latest developments in applied research on brown algae polysaccharides.

Combined Anticancer Effect of Sulfated Laminaran from the Brown Alga Alaria angusta and Polyhydroxysteroid Glycosides from the Starfish Protoreaster lincki on 3D Colorectal Carcinoma HCT 116 Cell Line

Colorectal cancer is one of the most frequent types of malignancy in the world. The search for new approaches of increasing the efficacy of cancer therapy is relevant. This work was aimed to study individual, combined anticancer effects, and molecular mechanism of action of sulfated laminaran AaLs of the brown alga Alaria angusta and protolinckiosides A (PL1), B (PL2), and linckoside L1 (L1) of the starfish Protoreaster lincki using a 3D cell culture model. The 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), soft agar, 3D spheroids invasion, and Western blotting assays were performed to determine the effect and mechanism of the action of investigated compounds or their combinations on proliferation, colony formation, and the invasion of 3D HCT 116 spheroids. AaLs, PL1, PL2, and L1 individually inhibited viability, colony growth, and the invasion of 3D HCT 116 spheroids in a variable degree with greater activity of linckoside L1. AaLs in combination with L1 exerted synergism of a combined anticancer effect through the inactivation of protein kinase B (AKT) kinase and, consequently, the induction of apoptosis via the regulation of proapoptotic/antiapoptotic proteins balance. The obtained data about the efficacy of the combined anticancer effect of a laminaran derivative of brown algae and polyhydroxysteroid glycosides of starfish open up prospects for the development of new therapeutic approaches for colorectal cancer treatment.

Laminarans and 1,3-β-D-glucanases

The laminarans are biologically active water-soluble polysaccharide (1,3;1,6-β-D-glucans) of brown algae. These polysaccharides are an attractive object for research due to its relatively simple structure, low toxicity, and various biological effects. 1,3-β-D-glucanases are an effective tool for studying the structure of laminarans, and can also be used to obtain new biologically active derivatives. This review is to outline what is currently known about laminarans and enzymes that catalyze of their transformation. We focused on information about sources, structure and properties of laminarans and 1,3-β-D-glucanases, methods of obtaining and structural elucidation of laminarans, and biological activity of laminarans and products of their enzymatic transformation. It has an increased focus on the immunomodulating and anticancer activity of laminarans and their derivatives.

Marine Cyanobacteria and Microalgae Metabolites-A Rich Source of Potential Anticancer Drugs

Cancer is at present one of the utmost deadly diseases worldwide. Past efforts in cancer research have focused on natural medicinal products. Over the past decades, a great deal of initiatives was invested towards isolating and identifying new marine metabolites via pharmaceutical companies, and research institutions in general. Secondary marine metabolites are looked at as a favorable source of potentially new pharmaceutically active compounds, having a vast structural diversity and diverse biological activities; therefore, this is an astonishing source of potentially new anticancer therapy. This review contains an extensive critical discussion on the potential of marine microbial compounds and marine microalgae metabolites as anticancer drugs, highlighting their chemical structure and exploring the underlying mechanisms of action. Current limitation, challenges, and future research pathways were also presented.

Laminarin from Seaweed (Laminaria japonica) Inhibits Hepatocellular Carcinoma Through Upregulating Senescence Marker Protein-30

Objective: This study aimed at investigating the specific roles of laminarin from seaweed (Laminaria japonica) in hepatocellular carcinoma (HCC) and its potential mechanisms related to senescence marker protein-30 (SMP-30).

Materials and Methods: Human HCC cell lines, including Bel-7404 and HepG2, were incubated with different concentrations of laminarin (0, 5, 15, 25, 35, and 45 mg/mL). The cell viability and apoptosis rates were detected by WST-8 cell proliferation assay and flow cytometry, respectively. Hepa 1–6 tumor-bearing mice were injected with different concentrations of laminarin (400, 800, and 1200 mg/kg·d), and tumor volume and weight were measured. The expression of SMP-30 was detected in laminarin-treated Bel-7404 and HepG2 HCC cells and LO2 normal liver cells by quantitative real-time PCR and Western blotting.

Results: The treatment with laminarin (48 h) significantly decreased the viability and increased the apoptosis rates of Bel-7404 and HepG2 cells in a dose-dependent manner. The injection of laminarin also significantly decreased the tumor volumes (beginning on the 10th day) and tumor weights (30 d post-injection) of mice in a dose-dependent manner. In addition, the treatment with laminarin (35 mg/mL for 48 h) significantly upregulated SMP-30 in Bel-7404 and HepG2 cells but not in LO2 cells.

Conclusion: Laminarin inhibited the proliferation of Bel-7404 and HepG2 cells and inhibited the growth of tumors in Hepa 1–6 tumor-bearing mice by upregulating SMP-30.

Laminarin-Derived from Brown Algae Suppresses the Growth of Ovarian Cancer Cells via Mitochondrial Dysfunction and ER Stress

Ovarian cancer (OC) is difficult to diagnose at an early stage and leads to the high mortality rate reported in the United States. Standard treatment for OC includes maximal cytoreductive surgery followed by platinum-based chemotherapy. However, relapse due to chemoresistance is common in advanced OC patients. Therefore, it is necessary to develop new anticancer drugs to suppress OC progression. Recently, the anticancer effects of laminarin, a beta-1,3-glucan derived from brown algae, have been reported in hepatocellular carcinoma, colon cancer, leukemia, and melanoma. However, its effects in OC are not reported. We confirmed that laminarin decreases cell growth and cell cycle progression of OC cells through the regulation of intracellular signaling. Moreover, laminarin induced cell death through DNA fragmentation, reactive oxygen species generation, induction of apoptotic signals and endoplasmic reticulum (ER) stress, regulation of calcium levels, and alteration of the ER-mitochondria axis. Laminarin was not cytotoxic in a zebrafish model, while in a zebrafish xenograft model, it inhibited OC cell growth. These results suggest that laminarin may be successfully used as a novel OC suppressor.

Biomedical applications of laminarin

The ocean is par excellence a fertile territory of biodiversity on our planet. Marine-derived polysaccharides have been applied as functional materials in biomedicine due to their attractive bioactive properties, safety, high availability and low-cost production. Laminarin (or laminaran), a low molecular weight β-glucan storage polysaccharide present in brown algae, can be (bio-) chemically modified to enhance its biological activity and employed in cancer therapies, drug/gene delivery, tissue engineering, antioxidant and anti-inflammatory functions. This review provides a brief overview on laminarin characteristics, modification strategies and highlights its pivotal biomedical applications.

Bioactive compounds in seaweeds: An overview of their biological properties and safety

Seaweeds are among the significant currently exploited marine plant resources which are gaining full applications in culinary, cosmetic, pharmaceutical, and biotechnological processes. Much attention has been devoted to seaweeds based on their proven health benefits and is considered as a rich source of structurally different bioactive metabolites for the discovery of novel functional food-based pharmacophores/drugs. Nonetheless, there is still a dearth of updated compilation and analysis of the in-depth pharmacological activities of these compounds. This review, therefore, aims to provide a piece of up-to-date detailed information on the major compounds isolated from various seaweed species together with their in-vitro and in-vivo biological properties. These compounds were found to possess broad pharmacological properties and inhibitory enzyme activities against critical enzymes involved in the aetiology of noncommunicable diseases. However, their toxicity, clinical efficacy, mechanisms of action, and interaction with conventional foods, are still less explored and require more attention in future studies.

New Drugs from the Sea: Pro-Apoptotic Activity of Sponges and Algae Derived Compounds

Natural compounds derived from marine organisms exhibit a wide variety of biological activities. Over the last decades, a great interest has been focused on the anti-tumour role of sponges and algae that constitute the major source of these bioactive metabolites. A substantial number of chemically different structures from different species have demonstrated inhibition of tumour growth and progression by inducing apoptosis in several types of human cancer. The molecular mechanisms by which marine natural products activate apoptosis mainly include (1) a dysregulation of the mitochondrial pathway; (2) the activation of caspases; and/or (3) increase of death signals through transmembrane death receptors. This great variety of mechanisms of action may help to overcome the multitude of resistances exhibited by different tumour specimens. Therefore, products from marine organisms and their synthetic derivates might represent promising sources for new anticancer drugs, both as single agents or as co-adjuvants with other chemotherapeutics. This review will focus on some selected bioactive molecules from sponges and algae with pro-apoptotic potential in tumour cells.

Phycochemical Constituents and Biological Activities of Fucus spp

Seaweeds are known to be a good supply of key nutrients including carbohydrates, protein, minerals, polyunsaturated lipids, as well as several other health-promoting compounds capable of acting on a wide spectrum of disorders and/or diseases. While these marine macroalgae are deeply rooted in the East Asian culture and dietary habits, their major application in Western countries has been in the phycocolloid industry. This scenario has however been gradually changing, since seaweed consumption is becoming more common worldwide. Among the numerous edible seaweeds, members of the genus Fucus have a high nutritional value and are considered good sources of dietary fibers and minerals, especially iodine. Additionally, their wealth of bioactive compounds such as fucoidan, phlorotannins, fucoxanthin and others make them strong candidates for multiple therapeutic applications (e.g., antioxidant, anti-inflammatory, anti-tumor, anti-obesity, anti-coagulant, anti-diabetes and others). This review presents an overview of the nutritional and phytochemical composition of Fucus spp., and their claimed biological activities, as well as the beneficial effects associated to their consumption. Furthermore, the use of Fucus seaweeds and/or their components as functional ingredients for formulation of novel and enhanced foods is also discussed.

p38 inhibitor inhibits the apoptosis of cowanin-treated human colorectal adenocarcinoma cells

Colorectal cancer, which is the third most common type of cancer diagnosed in both men and women, is the leading cause of cancer-related deaths worldwide. Cowanin is a pure compound extracted from Garcinia cowa Roxb., a tree species present in Thailand, Malaysia and Myanmar. The crude extract has been demonstrated to have antitumor activity, inflammation induction, antibacterial activity, anti-inflammatory activity and antimalarial activity. In the present study, the effects of cowanin on apoptosis induction and on the apoptosis-related and mitogen-activated protein kinase (MAPK) pathways were investigated in the LoVo human colorectal cancer cell line. The cytotoxicity of cowanin in LoVo cells was determined by MTT assay. Hoechst 33342 and JC‑1 staining were used to determine nuclear morphological changes and mitochondrial membrane potential, respectively. The expression levels of BCL2 apoptosis regulator (Bcl‑2) family, MAPK and AKT serine/threonine kinase 1 (Akt) pathway proteins following cowanin treatment were determined by western blot analysis. The results demonstrated that cowanin inhibited cell proliferation and induced cell death via the apoptosis pathway. Cowanin treatment increased BCL2 associated X (Bax) and decreased Bcl‑2 expression. In addition, cowanin activated caspase‑9, -7 and poly-ADP-ribose-polymerase expression. Furthermore, cowanin decreased the levels of phosphorylated extracellular signal-regulated kinase (p‑ERK), p‑Akt, p‑3‑phosphoinositide‑dependent protein kinase‑1, while it increased p‑p38 expression, thus resulting in the induction of apoptosis. In conclusion, cowanin inhibited cell proliferation and induced apoptosis of LoVo cells via the MAPK and Akt signaling pathways. Notably, inhibition of p38 by using a p38 inhibitor (SB203580) prevented the cowanin-induced apoptosis in LoVo cells. These results suggested that cowanin may be a potential candidate for the treatment of colorectal cancer and provided important information on the molecular mechanisms underlying its antitumor activity.

Structure and anticancer activity of native and modified polysaccharides from brown alga Dictyota dichotoma

The laminaran DdL and fucoidan DdF were obtained from the brown alga Dictyota dichotoma. DdF was a sulfated (28.9%) and acetylated heteropolysaccharide containing fucose, galactose, mannose and glucose (57.9, 20.4, 12.4 and 9.2mol%, respectively). DdL was a 1,3;1,6-β-d-glucan with the main chain built from 1,3-linked glucose residues and single glucose residue in branches at C6 (one branch on three glucose residues of the main chain). Sulfated (43.7%) laminaran DdLs was obtained from DdL by sulfation. It was determined that sulfates occur at C2, C4 and C6 of glucose residues. The anticancer effect of DdF, DdL, and DdLs (200μg/mL) was studied in vitro on colon cancer cells HCT-116, HT-29, and DLD-1. The effect of polysaccharides (40μg/mL) on colony formation of DLD-1 cancer cells after irradiation (4Gy) was investigated first. All polysaccharides showed a synergistic effect with X-ray irradiation against cancer cells, decreasing the amount and size of cancer cells colonies.

Polysaccharides from the Marine Environment with Pharmacological, Cosmeceutical and Nutraceutical Potential

Carbohydrates, also called saccharides, are molecules composed of carbon, hydrogen, and oxygen. They are the most abundant biomolecules and essential components of many natural products and have attracted the attention of researchers because of their numerous human health benefits. Among carbohydrates the polysaccharides represent some of the most abundant bioactive substances in marine organisms. In fact, many marine macro- and microorganisms are good resources of carbohydrates with diverse applications due to their biofunctional properties. By acting on cell proliferation and cycle, and by modulating different metabolic pathways, marine polysaccharides (including mainly chitin, chitosan, fucoidan, carrageenan and alginate) also have numerous pharmaceutical activities, such as antioxidative, antibacterial, antiviral, immuno-stimulatory, anticoagulant and anticancer effects. Moreover, these polysaccharides have many general beneficial effects for human health, and have therefore been developed into potential cosmeceuticals and nutraceuticals. In this review we describe current advances in the development of marine polysaccharides for nutraceutical, cosmeceutical and pharmacological applications. Research in this field is opening new doors for harnessing the potential of marine natural products.

A Survey of Marine Natural Compounds and Their Derivatives with Anti-cancer Activity Reported in 2012

Although considerable effort and progress has been made in the search for new anticancer drugs and treatments in the last several decades, cancer remains a major public health problem and one of the major causes of death worldwide. Many sources, including plants, animals, and minerals, are of interest in cancer research because of the possibility of identifying novel molecular therapeutics. Moreover, structure-activity-relationship (SAR) investigations have become a common way to develop naturally derived or semi-synthetic molecular analogues with improved efficacy and decreased toxicity. In 2012, approximately 138 molecules from marine sources, including isolated compounds and their associated analogues, were shown to be promising anticancer drugs. Among these, 62% are novel compounds. In this report, we review the marine compounds identified in 2012 that may serve as novel anticancer drugs.

Apoptosis of human gastric cancer SGC-7901 cells induced by podophyllotoxin

Numerous studies have demonstrated that podophyllotoxin and its derivatives exhibit antitumor effects. The aim of the present study was to investigate SGC-7901 cell apoptosis and the underlying mechanism induced by podophyllotoxin. SGC-7901 cells were treated with varying concentrations of podophyllotoxin. MTT assays and flow cytometry were used to evaluate the effects of podophyllotoxin on the proliferation and apoptosis of SGC-7901 cells, while fluorescence inverted microscopy was used to observe the morphology of SGC-7901 cells that had been dyed with Hoechst 33258. In addition, laser scanning confocal microscopy was used to analyze the mitochondrial membrane potential (MMP) of SGC-7901 cells dyed with Rhodamine 123. Western blotting was performed to analyze the expression levels of cytochrome c (cyt-c), caspase-9 and caspase-3 in the SGC-7901 cells. The results indicated that podophyllotoxin was capable of inhibiting growth and inducing the apoptosis of SGC-7901 cells in a dose-dependent manner, causing cell cycle arrest at the G₂/M phase. After 48 h of treatment, the apoptotic morphology of SGC-7901 cells was clear, exhibiting cell protuberance, concentrated cytoplasms and apoptotic bodies. Following 24 h of treatment, the MMP of the SGC-7901 cells decreased. In addition, after 48 h, the expression of cyt-c was shown to be upregulated, while the expression levels of pro-caspase-9 and pro-caspase-3 in the SGC-7901 cells were shown to be downregulated. In conclusion, apoptosis can be induced in SGC-7901 cells by podophyllotoxin, potentially via a mitochondrial pathway, indicating that podophyllotoxin may be a potent agent for cancer treatment.

Laminarin-induced apoptosis in human colon cancer LoVo cells

A number of scientific studies have revealed that laminarin has antitumor effects. Therefore, the aim of the present study was to investigate the apoptosis of LoVo cells and the underlying mechanisms induced by laminarin. LoVo cells were treated with various concentrations of laminarin and fluorescence-inverted microscopy was used to observe the morphology of LoVo cells treated with laminarin. In addition, western blotting was performed to analyze the expression levels of death receptor (DR)4, DR5, TNF-related apoptosis-inducing ligand (TRAIL), Fas-associated protein with death domain (FADD), caspase-8, caspase-3, Bid and tBid. Flow cytometry was conducted to analyze the expressions of Bcl-2 and Bax, and spectrophotometry was performed to quantify the activity of caspases-8, -3, -6 and -7. Following the treatment of LoVo cells with laminarin for 24 h, the expression levels of DR4, DR5, TRAIL, FADD, Bid, tBid and Bax were observed to be upregulated, whereas the expression levels of pro-caspase-8, pro-caspase-3 and Bcl-2 were downregulated. In addition, the activities of casapse-8, -3, -6 and -7 were observed to increase, which was a significant difference when compared with those of the control group. Therefore, laminarin is considered to induce the apoptosis of LoVo cells, which may occur via a DR pathway, suggesting that laminarin may be a potent agent for cancer treatment.

Sulfated modification and anti-tumor activity of laminarin

The aim of this study was to investigate the sulfated modification of laminarin and the changes in structure and antitumor activity. The chlorosulfonic acid-pyridine method was applied for sulfated modification. The molecular weights of laminarin and laminarin sulfate (LAMS) were measured by high-performance liquid chromatography (HPLC), and IR and NMR spectra were also recorded. The surface conformations of laminarin and LAMS were observed with a scanning electron microscope. The antitumor activities of the two polysaccharides were also evaluated using an MTT assay. LAMS with a sulfate content of 45.92% and a molecular weight of 16,000 was synthesized. The IR spectra of laminarin and LAMS showed the characteristic absorption peaks of a polysaccharide, and LAMS also had the characteristic absorption peaks of sulfate moieties. The NMR spectra showed that laminarin and LAMS had β-(1→3) glycosidic bonds forming the main chain, and sulfate substitution was at the hydroxyl groups of C₂ and C₆. Under the scanning electron microscope, there were clear differences in surface conformation between laminarin and LAMS; laminarin was cloud-like and spongy, while LAMS was block-like and flaky. The MTT results showed that laminarin and LAMS had inhibitory effects on LoVo cell growth, and the antitumor activity of LAMS was higher than that of laminarin at the same concentration. This suggests that sulfated modification was able to change the laminarin structure and markedly enhance the antitumor activity.