Natural polysaccharides and their derivatives targeting the tumor microenvironment: A review

Polysaccharides have gained attention as valuable supplements and natural medicinal resources, particularly for their anti-tumor properties. Their low toxicity and potent anti-tumor effects make them promising candidates for cancer prevention and treatment. The tumor microenvironment is crucial in tumor development and offers potential avenues for novel cancer therapies. Research indicates that polysaccharides can positively influence the tumor microenvironment. However, the structural complexity of most anti-tumor polysaccharides, often heteropolysaccharides, poses challenges for structural analysis. To enhance their pharmacological activity, researchers have modified the structure and properties of natural polysaccharides based on structure-activity relationships, and they have discovered that many polysaccharides exhibit significantly enhanced anti-tumor activity after chemical modification. This article reviews recent strategies for targeting the tumor microenvironment with polysaccharides and briefly discusses the structure-activity relationships of anti-tumor polysaccharides. It also summarises the main chemical modification methods of polysaccharides and discusses the impact of chemical modifications on the anti-tumor activity of polysaccharides. The review aims to lay a theoretical foundation for the development of anti-tumor polysaccharides and their derivatives.

Sulfated Galactans from Agarophytes: Review of Extraction Methods, Structural Features, and Biological Activities

Agarophytes are important seaweeds of the Rhodophyta type, which have been highly exploited for industrial use as sources of a widely consumed polysaccharide of agar. In addition to that, sulfated galactans (SGs) from agarophytes, which consist of various functional sulfate groups, have attracted the attention of scientists in current studies. SGs possess various biological activities, such as anti-tumor, anticoagulant, anti-inflammatory, antioxidant, anti-obesity, anti-diabetic, anti-microbial, anti-diarrhea, and gut microbiota regulation properties. Meanwhile, the taxonomy, ecological factors, i.e., environmental factors, and harvest period, as well as preparation methods, i.e., the pretreatment, extraction, and purification conditions, have been found to influence the chemical compositions and fine structures of SGs, which have, further, been shown to have an impact on their biological activities. However, the gaps in the knowledge of the properties of SGs due to the above complex factors have hindered their industrial application. The aim of this paper is to collect and systematically review the scientific evidence about SGs and, thus, to pave the way for broader and otherwise valuable industrial applications of agarophytes for human enterprise. In the future, this harvested biomass could be sustainably used not only as a source of agar production but also as natural materials in functional food and pharmaceutical industries.

Sulfated Galactans from Gracilaria fisheri with Supplementation of Octanoyl Promote Wound Healing Activity In Vitro and In Vivo

Sulfated galactans (SG) isolated from Gracilaria fisheri is partially degraded (DSG), and subsequentially supplemented with octanoyl (DSGO) and sulfate (DSGS) groups. The molecular weights of DSG, DSGO, and DSGS are 7.87, 152.79, and 97.07 kDa, respectively. The modification is confirmed using FTIR and NMR, while in vitro wound healing activity is assessed using scratched wound fibroblasts. The results reveal that DSGO exhibits highest percentage of wound closure in scratched fibroblast L929 cells. Furthermore, DSGO is able to promote proliferation and accelerate migration of scratched fibroblasts, which correspond to the regulation of proteins and mRNA (Ki67, p-FAK, vimentin, and E-cadherin) determined by Western blotting and qPCR analysis. The superior wound healing activity of DSGO is also confirmed in excision wound of rats. The results demonstrate that DSGO significantly enhances the percentage of wound closure, re-epithelialization, and collagen arrangement, increases α-smoth muscle actin (α-SMA) and vimentin expression, and decreases that of tumor necrosis factor-α (TNF-α) at the wound site. The results suggest that degraded SG supplemented with medium-chain fatty acids of octanoyl group may pass through the membrane, subsequently activating the mediators associated with proliferation and migration of fibroblasts, which can potentially lead to the promotion of wound healing activity.

Structural characterization, antioxidant activity, and protective effect against hydrogen peroxide-induced oxidative stress of chemically degraded Gracilaria fisheri sulfated galactans

Sulfated polysaccharides (SPs) possess an extensive range of biological activities, such as the inhibition of oxidation, correlated with their molecular weight (MW) and chemical structure. In this study, we used the trifluoroacetic acid (TFA) controlled degradation method to degrade sulfated galactans (SG) isolated from Gracilaria fisheri and evaluated the antioxidant and protective effects of the low molecular weight SG (LMSG) against H₂O₂ on fibroblast cells for the first time. Degradation of native SG (NSG) with an initial MW of 217.45 kDa using different concentrations of TFA resulted in five degraded NSG with MW of 97.23, 62.26, 30.74, 2.63, and 2.59 kDa. The reduction in MW was positively correlated with TFA concentrations. Chemical structure analyses using FTIR and NMR indicated that the TFA degradation process did not significantly change the LMSG polysaccharide main chain but did change the functional groups. LMSG exhibited higher scavenging activities and enhanced the cellular activities of GSH, CAT, and SOD enzymes. Moreover, LMSG activated Nrf-2/ARE signaling and increased expression of antioxidant genes CAT and SOD, which corresponded to increase protective effects against H₂O₂-induced ROS generation in fibroblast cells. The study reveals modification of NSG by acid TFA degradation resulted in the creation of LMSG, which showed greater antioxidant activity.

Bioactive polysaccharides from red seaweed as potent food supplements: a systematic review of their extraction, purification, and biological activities

Most marine macroalgae such as red seaweeds are potential alternative sources of useful bioactive compounds. Beside serving as food source, recent studies have shown that red seaweeds are rich sources of bioactive polysaccharides. Red seaweed polysaccharides (RSPs) have various physiological and biological activities, which allow them to be used as immunomodulators, anti-obesity agents, and prebiotic ingredients. Lack of summary information and human clinical trials on the various polysaccharides from red seaweeds, however limits industrial-scale utilization of RSPs in functional foods. This review summarizes recent information on the approaches used for RSPs extraction and purification, mechanistic investigations of their biological activities, and related molecular principles behind their purported ability to prevent diseases. The information here also provides a theoretical foundation for further research into the structure and mechanism of action of RSPs and their potential applications in functional foods.

Probing the Anti-Cancer Potency of Sulfated Galactans on Cholangiocarcinoma Cells Using Synchrotron FTIR Microspectroscopy, Molecular Docking, and In Vitro Studies

Sulfated galactans (SG) isolated from red alga Gracilaria fisheri have been reported to inhibit the growth of cholangiocarcinoma (CCA) cells, which was similar to the epidermal growth factor receptor (EGFR)-targeted drug, cetuximab. Herein, we studied the anti-cancer potency of SG compared to cetuximab. Biological studies demonstrated SG and cetuximab had similar inhibition mechanisms in CCA cells by down-regulating EGFR/ERK pathway, and the combined treatment induced a greater inhibition effect. The molecular docking study revealed that SG binds to the dimerization domain of EGFR, and this was confirmed by dimerization assay, which showed that SG inhibited ligand-induced EGFR dimer formation. Synchrotron FTIR microspectroscopy was employed to examine alterations in cellular macromolecules after drug treatment. The SR-FTIR-MS elicited similar spectral signatures of SG and cetuximab, pointing towards the bands of RNA/DNA, lipids, and amide I vibrations, which were inconsistent with the changes of signaling proteins in CCA cells after drug treatment. Thus, this study demonstrates the underlined anti-cancer mechanism of SG by interfering with EGFR dimerization. In addition, we reveal that FTIR signature spectra offer a useful tool for screening anti-cancer drugs’ effect.

Mitogen-Activated Protein Kinases (MAPKs) and Cholangiocarcinoma: The Missing Link

In recent years, the incidence of both liver and biliary tract cancer has increased. Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) are the two most common types of hepatic malignancies. Whereas HCC is the fifth most common malignant tumor in Western countries, the prevalence of CCA has taken an alarming increase from 0.3 to 2.1 cases per 100,000 people. The lack of specific biomarkers makes diagnosis very difficult in the early stages of this fatal cancer. Thus, the prognosis of CCA is dismal and surgery is the only effective treatment, whilst recurrence after resection is common. Even though chemotherapy and radiotherapy may prolong survival in patients with CCA, the 5-year survival rate is still very low-a significant global problem in clinical diagnosis and therapy. The mitogen-activated protein kinase (MAPK) pathway plays an important role in signal transduction by converting extracellular stimuli into a wide range of cellular responses including inflammatory response, stress response, differentiation, survival, and tumorigenesis. Dysregulation of the MAPK cascade involves key signaling components and phosphorylation events that play an important role in tumorigenesis. In this review, we discuss the pathophysiological role of MAPK, current therapeutic options, and the current situation of MAPK-targeted therapies in CCA.

β-Pentagalloyl-Glucose Sabotages Pancreatic Cancer Cells and Ameliorates Cachexia in Tumor-Bearing Mice

Pancreatic cancer cells overexpress the insulin receptor (IR) and the insulin-like growth factor-1 receptor (IGF1R). Activating these receptors, insulin and insulin-like growth factor-1 increase the growth and glycolysis of pancreatic cancer cells. The high glycolysis in pancreatic cancer cells increases whole-body energy expenditure and is therefore involved in the pathogenesis of cancer cachexia. The antagonism of IR and IGF1R may sabotage pancreatic cancer cells and attenuate cancer cachexia. Previous studies have shown that the intracellular regulating system of IR/IGF1R may be functionally interrelated to another intracellular system whose master regulator is hypoxia-inducible factor-1 (HIF-1). In this study, we investigated how the IR/IGF1R and HIF-1 systems are interrelated in pancreatic cancer cells. We also investigated whether a phytochemical, penta-O-galloyl- β -D-glucose ( β -PGG), antagonizes IR/IGF1R, sabotages pancreatic cancer cells and alleviates cancer cachexia. We found in MiaPaCa2 pancreatic cancer cells that IR/IGF1R activation increased both the α -subunit of HIF-1 and caveolin-1. This result suggests that IR/IGF1R, HIF-1 α , and caveolin-1 may constitute a feed-forward loop to mediate the effect of IR/IGF1R activation. β -PGG inhibited IR/IGF1R activity and decreased glycolytic enzymes in MiaPaCa2 and Panc-1 pancreatic cancer cells. When MiaPaCa2 cells were transplanted in athymic mice, their growth was inhibited by β -PGG or by a HIF-1 α inhibitor, rhein. β -PGG and rhein also decreased glycolytic enzymes in the tumor grafts and reduced liver gluconeogenesis, skeletal-muscle proteolysis and fat lipolysis in the tumor carriers. Cancer-induced body-weight loss, however, was prevented by β -PGG but not rhein. In conclusion, β -PGG combats pancreatic cancer cells and cures cancer cachexia.

Overexpressed long noncoding RNA Sox2ot predicts poor prognosis for cholangiocarcinoma and promotes cell proliferation and invasion

SOX2 overlapping transcript (Sox2ot), a long noncoding RNA (lncRNA), was initially found a close concomitant expression pattern of SOX2 gene. Multiple studies have demonstrated that the relatively upregulated Sox2ot could be observed in different types of cancer tissues and effectively promotes cell proliferation, invasion, and tumorigenesis in vitro. In the present study, we aimed to detect the crucial prognostic role of Sox2ot in cholangiocarcinoma (CCA) patients' clinicopathologic features and evaluated the correlation between Sox2ot expression and CCA patients overall survival. 58 CCA patients who underwent surgical treatment were recruited for the investigation. Sox2ot expression levels estimated by the quantitative real-time PCR (qRT-PCR) showed that both clinical tissues and cell lines possessed the overexpressed states and the upregulation of Sox2ot significantly associated with lymph node invasion (p=0.0308), TNM stage (p=0.0072) and postoperative recurrence (p=0.0019). The Kaplan-Meier curve showed a strong association between Sox2ot and overall survival (OS) and multivariate analysis confirmed this finding. Furthermore, the proliferation, migration and invasion assays were carried out with RBE and QBC939 cell lines and the knockdown of Sox2ot in all experiments could remarkably decrease malignant biological behaviors. Taken together, lncRNA Sox2ot indicates an unfavorable prognostic biomarker and potential therapeutics target for CCA patients.

Sulfated galactans from the red seaweed Gracilaria fisheri exerts anti-migration effect on cholangiocarcinoma cells

BACKGROUND

Seaweeds have a long history of use in Asian countries as functional foods, medicinal herbs, and the treatment of cancer. Polysaccharides from various seaweeds have shown anti-tumor activity. Cholangiocarcinoma (CCA), often with metastatic disease, is highly prevalent in Thailand as a consequence of liver fluke infection. Recently, we extracted sulfated galactans (SG) from Gracilaria fisheri (G. fisheri), a south east Asian seaweed, and found it exhibited anti-proliferation effect on CCA cells.

PURPOSE

In the present study, we evaluated the anti-migration activity of SG on CCA cells and its underlined mechanism.

METHODS

CCA cells were treated with SG alone or drugs targeting to epidermal growth factor (EGF) receptor (EGFR) or pretreated with SG prior to incubation with EGF. Anti-migration activity was determined using a scratch wound-healing assay and zymography. Immunofluorescence staining and western blotting were used to investigate EGFR signaling mediators.

RESULTS

Under basal condition, SG reduced the migration rate of CCA, which was correlated with a decrease in the active-form of matrix metalloproteinases-9. SG decreased expression of phosphorylated focal adhesion kinase (FAK), but increased expression of E-cadherin to promote cells stasis. Moreover, phosphorylation of EGFR and extracellular signal-regulated kinases (ERK), known to stimulate growth of cancer cells, was blocked in a comparable way to EGFR inhibitors Cetuximab and Erlotinib. Pretreatment cells with SG attenuated EGF induced phosphorylation of EGFR, ERK and FAK.

CONCLUSION

This study reveals that SG from G. fisheri retards migration of CCA cells, and its mechanism of inhibition is mediated, to some extent, by inhibitory effects on MAPK/ERK signal transduction pathway. Our findings suggest that there may be a therapeutic potential of SG in CCA treatment.