Exopolysaccharides isolated from Rhizopus nigricans induced colon cancer cell apoptosis in vitro and in vivo via activating the AMPK pathway

The Crucial Roles of Diet, Microbiota, and Postbiotics in Colorectal Cancer

PURPOSE OF REVIEW

Colorectal cancer is the second deadliest cancer in the world, and its prevalence has been increasing alarmingly in recent years. After researchers discovered the existence of dysbiosis in colorectal cancer, they considered the use of probiotics in the treatment of colorectal cancer. However, for various reasons, including the low safety profile of probiotics in susceptible and immunocompromised patient5s, and the risk of developing antibiotic resistance, researchers have shifted their focus to non-living cells, their components, and metabolites. This review aims to comprehensively evaluate the literature on the effects of diet, microbiota, and postbiotics on colorectal cancer and the future of postbiotics.

RECENT FINDINGS

The link between diet, gut microbiota, and colorectal cancer has been established primarily as a relationship rather than a cause-effect relationship. The gut microbiota can convert gastrointestinal tract and dietary factors into either onco-metabolites or tumor suppressor metabolites. There is serious dysbiosis in the microbiota in colorectal cancer. Postbiotics appear to be promising agents in the prevention and treatment of colorectal cancer. It has been shown that various postbiotics can selectively induce apoptosis in CRC, inhibit cell proliferation, growth, invasion, and migration, modulate the immune system, suppress carcinogenic signaling pathways, maintain intestinal epithelial integrity, and have a synergistic effect with chemotherapy drugs. However, it is also reported that some postbiotics are ineffective and may be risky in terms of safety profile in some patients. Many issues need to be researched about postbiotics. Large-scale, randomized, double-blind clinical studies are needed.

Targeting lipid metabolism with natural products: A novel strategy for gastrointestinal cancer therapy

Gastrointestinal cancer (GIC), including gastric cancer and colorectal cancer, is a common malignant tumor originating from gastrointestinal epithelial cells. Although the pathogenesis of GIC remains unclear, aberrant lipid metabolism has emerged as a hallmark of cancer. Several enzymes, proteins, and transcription factors are involved in lipid metabolism reprogramming in GIC, and their abnormal expression can promote lipid synthesis and accumulation of lipid droplets through numerous mechanisms, thereby affecting the growth, proliferation, and metastasis of GIC cells. Studies show that some natural compounds, including flavonoids, alkaloids, and saponins, can inhibit the de novo synthesis of lipids in GIC, reduce the level of lipid accumulation, and subsequently, inhibit the occurrence and development of GIC by regulating Sterol regulatory element-binding protein 1 (SREBP-1), adenosine monophosphate-activated protein kinase (AMPK), 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), phosphatidylinositol-3-kinase/Akt and the mammalian target of rapamycin PI3K/Akt/mTOR, amongst other targets and pathways. Therefore, targeting tumor lipid metabolism is the focus of anti-gastrointestinal tumor therapy. Although most natural products require further high-quality studies to firmly establish their clinical efficacy, we review the potential of natural products in the treatment of GIC and summarize the application prospect of lipid metabolism as a new target for the treatment of GIC, hoping to provide a reference for drug development for gastrointestinal tumors.

Suppressive effects of bioactive herbal polysaccharides against different cancers: From mechanisms to translational advancements

BACKGROUND

Fueled by rapidly evolving comprehension of multifaceted nature of cancers, recently emerging preclinical and clinical data have supported researchers in the resolution of knowledge gaps to deepen the understanding of the molecular mechanisms. The extra-ordinary and bewildering chemical diversity encompassed by biologically active natural products continues to be of relevance to drug discovery. Accumulating evidence has spurred a remarkable evolution of concepts related to pharmacological target of oncogenic signaling pathways by polysaccharides in different cancers.

PURPOSE

The objective of the current review is to provide new insights into study progress on anticancer effects of bioactive herbal polysaccharides.

METHODS

PubMed, Scopus, Web of Science, Embase, and other databases were searched for articles related to anticancer effects of polysaccharides. Searches were conducted to locate relevant publications published up to October 2022.

RESULTS

Polysaccharides have been reported to pleiotropically modulate TGF/SMAD, BMP/SMAD, TLR4, mTOR, CXCR4 and VEGF/VEGFR cascades. We have also summarized how different polysaccharides regulated apoptosis and non-coding RNAs. Additionally, this mini-review describes increasingly sophisticated understanding related to polysaccharides mediated tumor suppressive and anti-metastatic effects in tumor-bearing mice. We have also provided an overview of the clinical trials related to chemopreventive role of polysaccharides.

CONCLUSION

Genomic and proteomic findings from these studies will facilitate 'next-generation' clinical initiatives in the prevention/inhibition of cancer.

Separation and Structural Characterization of a Novel Exopolysaccharide from Rhizopus nigricans

The present study aims to analyze the structural characterization and antioxidant activity of a novel exopolysaccharide from Rhizopus nigricans (EPS2-1). For this purpose, EPS2-1 was purified through DEAE-52, Sephadex G-100, and Sephadex G-75 chromatography. The structural characterization of EPS2-1 was analyzed using high-performance gel permeation chromatography (HPGPC), Fourier transform infrared spectroscopy (FT-IR), methylation analysis, nuclear magnetic resonance (NMR) spectra, transmission electron microscope (TEM), and atomic force microscope (AFM). The results revealed that EPS2-1 is composed of mannose (Man), galactose (Gal), glucose (Glc), arabinose (Ara), and Fucose (Fuc), and possesses a molecular weight of 32.803 kDa. The backbone of EPS2-1 comprised →2)-α-D-Manp-(1→ and →3)-β-D-Galp-(1→, linked with the O-6 position of (→2,6)-α-D-Manp-(1→) of the main chain is branch α-D-Manp-(1→6)-α-D-Manp-(1→, linked with the O-6 positions of (→3)-β-D-Galp-(1→) of the main chain are branches →4)-β-D-Glcp-(1→ and →3)-β-D-Galp-(1→, respectively. Finally, we demonstrated that EPS2-1 also shows free radical scavenging activity and iron ion reducing ability. At the same time, EPS2-1 could inhibit the proliferation of MFC cells and increase the cell viability of RAW264.7 cells. Our results suggested that EPS2-1 is a novel polysaccharide, and EPS2-1 has antioxidant activity. In addition, EPS2-1 may possess potential immunomodulatory and antitumor activities. This study promoted the application of EPS2-1 as the functional ingredients in the pharmaceutical and food industries.

[Assessment of biological activities of exopolysaccharides with different relative molecular masses extracted from Rhizopus nigricans]

OBJECTIVE

To evaluate the antioxidant, anti-tumor and immunomodulatory activities of exopolysaccharides with different molecular masses isolated from Rhizopus nigricans.

METHODS

Three polysaccharides with different molecular masses, namely RPS-1, RPS-2 and RPS-3, were separated from the fermentation broth of Rhizopus nigricans by fractional ethanol precipitation, and their capacity for scavenging DPPH, ABTS, and hydroxyl radicals was assessed. Cell counting kit-8 was used to analyze the changes in the viability of MFC, A549 and RAW 264.7 cells following treatments with the 3 polysaccharides; The level of nitric oxide in the supernatant of RAW 264.7 cells was detected using a nitric oxide detection kit, and the apoptosis rate of A549 cells was analyzed with flow cytometry.

RESULTS

All the 3 polysaccharides had good antioxidant activities, and among them RPS-1 with a medium molecular mass exhibited the strongest scavenging capacity for DPPH and ABTS radicals (P < 0.05) while RPS-3 with the lowest molecular mass had the best scavenging activity for hydroxyl radicals (P < 0.01). All the 3 polysaccharides were capable of inhibiting the proliferation of MFC cells and A549 cells, activating the macrophages RAW 264.7 cells, and inducing apoptosis of A549 cells. RPS-2 with the highest molecular mass showed the strongest inhibitory effects against MFC and A549 cells (P > 0.05), and RPS-2 had the strongest activity for inducing apoptosis in A549 cells (P < 0.05). Compared with the other two polysaccharides, RPS-2 more strongly promoted the proliferation of RAW 264.7 cells and enhanced NO release from the cells (P < 0.05).

CONCLUSION

The 3 polysaccharides all have antioxidant, anti-tumor and immunomodulatory activities, and among them RPS-1 and RPS-3 have better antioxidant activities, and RPS-2 has stronger anti-tumor and immunomodulatory activities.

Effects of Rhizopus Nigricans Exopolysaccharide on Proliferation, Apoptosis, and Migration of Breast Cancer MCF-7 Cells and Akt Signaling Pathway

Objective. To study the effect of Rhizopus nigricans exopolysaccharide EPS1-1 on the proliferation, apoptosis, and migration of breast cancer MCF-7 cells. Methods. Human breast cancer MCF-7 cells were cultured in vitro and treated with different concentrations of EPS1-1. The effect of EPS1-1 on cell proliferation was tested by the CCK-8 experiment, and the effect of EPS1-1 on cell apoptosis was determined by flow cytometry. And the scratch test was used to detect the impact of EPS1-1 on cell migration. Western blot then was used to measure the expression changes of related proteins in the Akt signaling pathway. Results. Compared with the control group, treatment with EPS1-1 significantly reduced the proliferation, migration, and invasion ability of MCF-7 cells and promoted the apoptosis of MCF-7 cells in a dose-dependent manner. In terms of the underlying mechanism, EPS1-1 can significantly inhibit the phosphorylation of Akt at threonine 308 and serine 473 and cause the expression changes of downstream proliferation-related genes CCND1 and p21, apoptosis-related genes Bcl-2 and Bax, and migration-related genes Vimentin and E-cadherin in terms of their protein levels. Conclusion. EPS1-1 can inhibit the proliferation, migration, and invasion of breast cancer MCF-7 cells and promote the apoptosis of MCF-7 cells by inhibiting the activation of the Akt signaling pathway. Therefore, EPS1-1 can be used as a potential new drug or adjuvant drug for the treatment of breast cancer.