Potential mechanism of mycelium polysaccharide from Pholiota dinghuensis Bi in regulating the proliferation and apoptosis of human breast cancer MCF-7 cells through p38/MAPK pathway

Polysaccharide-Based Stimulus-Responsive Nanomedicines for Combination Cancer Immunotherapy

Cancer immunotherapy is a promising antitumor approach, whereas nontherapeutic side effects, tumor microenvironment (TME) intricacy, and low tumor immunogenicity limit its therapeutic efficacy. In recent years, combination immunotherapy with other therapies has been proven to considerably increase antitumor efficacy. However, achieving codelivery of the drugs to the tumor site remains a major challenge. Stimulus-responsive nanodelivery systems show controlled drug delivery and precise drug release. Polysaccharides, a family of potential biomaterials, are widely used in the development of stimulus-responsive nanomedicines due to their unique physicochemical properties, biocompatibility, and modifiability. Here, the antitumor activity of polysaccharides and several combined immunotherapy strategies (e.g., immunotherapy combined with chemotherapy, photodynamic therapy, or photothermal therapy) are summarized. More importantly, the recent progress of polysaccharide-based stimulus-responsive nanomedicines for combination cancer immunotherapy is discussed, with the focus on construction of nanomedicine, targeted delivery, drug release, and enhanced antitumor effects. Finally, the limitations and application prospects of this new field are discussed.

Cefotetan-bound human RKIP involves in Ras/Raf1/MEK/ERK signaling pathway

Cefotetan is widely used to treat bacterial infections in the clinic owing to its broad spectrum of antibacterial activity. In the present study, we demonstrate that cefotetan can bind to the conserved ligand-binding pocket of human Raf1 kinase inhibitory protein (hRKIP), which acts as a negative regulator of the Ras/Raf1/MEK/ERK signaling pathway. The cefotetan-bound hRKIP adopts a rigid structure with insufficient space for binding Raf1 kinase, thereby reliving the inhibitory activity of hRKIP in the Ras/Raf1/MEK/ERK signaling pathway and enhancing the phosphorylation level of ERK. Both NMR titration and molecular docking approaches show that several residues (P74, Y81, W84, P111, P112, K113, S142, G143, D144, W173, P178, Y181 and L184) play crucial roles in hRKIP binding cefotetan. NMR dynamics analysis reveals that the binding of cefotetan with hRKIP promotes ps-ns internal motion but reduces μs-ms conformational exchange for residues in the cefotetan-binding pocket of hRKIP. Our results not only disclose the structural basis of cefotetan upregulating the Ras/Raf1/MEK/ERK signaling pathway but also benefit developing novel drugs against diseases caused by the impaired Ras/Raf1/MEK/ERK pathway.

Advances in the regulation of natural polysaccharides on human health: The role of apoptosis/autophagy pathway

Due to the multiple biological activities of polysaccharides, their great potential as "natural drugs" for many diseases has been the subject of continuous exploration in the field of food and nutrition. Apoptosis and autophagy play a key role in mammalian growth, development and maintenance of cellular homeostasis. Recent studies suggest that apoptosis/autophagy may be the key regulatory target for the beneficial effects of polysaccharides. However, the regulation of apoptosis and autophagy by polysaccharides is not consistent in different disease models. Therefore, this review outlined the relationship between apoptosis/autophagy and some common human diseases, then discussed the role of apoptosis/autophagy pathway in the regulation of human health by polysaccharides, Furthermore, the application of visualization, imaging and multi-omics techniques was proposed in the future trend. The present review may be beneficial to accelerate our understanding of the anti-disease mechanisms of polysaccharides, and promote the development and utilization of polysaccharides.

Polysaccharides with Antitumor Effect in Breast Cancer: A Systematic Review of Non-Clinical Studies

Purpose: To review the effects of polysaccharides and their proposed mechanisms of action in breast cancer experimental models. Data sources, selection, and extraction: Articles were selected by using PubMed, ScienceDirect, Scopus, and Medline, assessed from 1 May 2019 to 1 July 2020. The systematic review was registered in the International Prospective Register of Systematic Reviews (Prospero) under the number CRD42020169103. Results: Most of the studies explore algae polysaccharides (43.2%), followed by mushrooms (13.5%), plants (13.5%), fruits (10.8%), fungus (2.7%), bacteria, (2.7%), and sea animals (2.7%). A total of 8.1% investigated only in vitro models, 62.1% evaluated only in vivo models, and 29.7% evaluated in vitro and in vivo models. The mechanism of action involves apoptosis, inhibition of cellular proliferation, angiogenesis, and antimetastatic effects through multiple pathways. Conclusions: Findings included here support further investigations on the anti-tumor effect of polysaccharides. Some polysaccharides, such as fucoidan and β-glucans, deserve detailed and structured studies aiming at translational research on breast tumors, since they are already used in the clinical practice of other proposals of human health.

Suramin Targets the Conserved Ligand-Binding Pocket of Human Raf1 Kinase Inhibitory Protein

Suramin was initially used to treat African sleeping sickness and has been clinically tested to treat human cancers and HIV infection in the recent years. However, the therapeutic index is low with numerous clinical side-effects, attributed to its diverse interactions with multiple biological macromolecules. Here, we report a novel binding target of suramin, human Raf1 kinase inhibitory protein (hRKIP), which is an important regulatory protein involved in the Ras/Raf1/MEK/ERK (MAPK) signal pathway. Biolayer interference technology showed that suramin had an intermediate affinity for binding hRKIP with a dissociation constant of 23.8 µM. Both nuclear magnetic resonance technology and molecular docking analysis revealed that suramin bound to the conserved ligand-binding pocket of hRKIP, and that residues K113, W173, and Y181 play crucial roles in hRKIP binding suramin. Furthermore, suramin treatment at 160 µM could profoundly increase the ERK phosphorylation level by around 3 times. Our results indicate that suramin binds to hRKIP and prevents hRKIP from binding with hRaf1, thus promoting the MAPK pathway. This work is beneficial to both mechanistically understanding the side-effects of suramin and efficiently improving the clinical applications of suramin.

Anti-inflammatory effects of dicaffeoylquinic acids from Ilex kudingcha on lipopolysaccharide-treated RAW264.7 macrophages and potential mechanisms

Increasing evidence has shown that dicaffeoylquinic acids (DiCQAs) have anti-inflammatory activity. However, the underlying molecular mechanisms of the anti-inflammatory effects of DiCQAs are still unclear. In the present study, the anti-inflammatory effects of DiCQAs from the leaves of Ilex kudingcha and the potential molecular mechanisms on LPS-induced inflammatory responses in RAW264.7 macrophage cells were investigated. The results showed that pretreatment with DiCQAs could suppress the production of NO, PGE₂ and also pro-inflammatory cytokines TNF-α, IL-1β and IL-6, and the mRNA expression of two major inflammatory mediators of COX-2 and iNOS. The phosphorylated IκBα, ERK, JNK and p38 proteins in LPS-treated cells were significantly increased, which could be reversed by pretreatment with DiCQAs in a concentration-dependent manner. Taken together, the results suggest that DiCQAs from I. kudingcha have potent anti-inflammatory effects on LPS-induced inflammatory responses by inhibiting the NF-κB and MAPKs pathways and may be a prophylactic for inflammation.

Antiproliferative Activity of Combined Biochanin A and Ginsenoside Rh₂ on MDA-MB-231 and MCF-7 Human Breast Cancer Cells

Breast cancer is the most frequently diagnosed cancer in women worldwide. The antiproliferative activities of biochanin A (BA) and ginsenoside Rh₂ were determined by evaluating their inhibitory effect on MDA-MB-231 human breast cancer cell proliferation. The combination of BA with Rh₂ was also assessed. In MDA cells, combination treatment led to a decrease in the EC₅₀ values of BA and Rh₂ to 25.20 μM and 22.75 μM, respectively. In MCF-7 cells, the EC₅₀ values of combined BA and Rh₂ decreased to 27.68 μM and 25.41 μM, respectively. BA combined with Rh₂ also improved the inhibition of MDA-MB-231 and MCF-7 cell migration and invasion compared to the individual compounds. Western blot analysis demonstrated upregulation in p-p53, p-p38, and p-ASK1 proteins while levels of TRAF2 were downregulated. These results suggest that BA combined with Rh₂ exhibits synergistic effects against MDA-MB-231 and MCF-7 cell proliferation.

Purification, partial characterization and inducing tumor cell apoptosis activity of a polysaccharide from Ganoderma applanatum

In this study, a homogeneous polysaccharide (designated as GAP-3S) with an average molecular weight of 6.82×10⁵ Da was purified from Ganoderma applanatum. GAP-3S was composed of glucose, galactose, fucose and xylose in the molar ratio of 7.1:2.6:1.1:1. It could significantly inhibit the proliferation of MCF-7 cells in a dose- and time-dependent manner. Flow cytometry analysis indicated that GAP-3S could also induce cell apoptosis. Treatment of MCF-7 cells with GAP-3S lead to the collapse of mitochondrial membrane potential and the accumulation of ROS, up-regulated expression of Bax, cleavage of PARP, p-p38 and p-JNK, and the down-regulated expression of Bcl-2, PARP and p-ERK. The activities of caspase-3 and caspase-9 were also increased in GAP-3S-treated MCF-7 cells compared to untreated cells. These findings suggested that GAP-3S probably induced apoptosis in MCF-7 cells through intrinsic mitochondrial apoptosis and MAPK signaling pathways.

Optimization of extraction, characterization and antioxidant activity of polysaccharides from Brassica rapa L

The root of Brassica rapa L. has been traditionally used as a Uyghur folk medicine to cure cough and asthma by Uyghur nationality in Xinjiang Uygur Autonomous Region of China. In the present study, therefore, extraction optimization, characterization and antioxidant activity in vitro of polysaccharides from the root of B. rapa L. (BRP) were investigated. The optimal extraction conditions with an extraction yield of 21.48 ± 0.41% for crude BRP were obtained as follows: extraction temperature 93°C, extraction time 4.3h and ratio of extraction solvent (water) to raw material 75 mL/g. The crude BRP was purified by chromatographic columns of DEAE-52 cellulose and Sephadex G-100, affording three purified fractions of BRP-1-1, BRP-2-1 and BRP-2-2 with average molecular weight of 1510, 1110 and 838 kDa, respectively. Monosaccharide composition analysis indicated that BRP-1-1 was composed of mannose, rhamnose, glucose, galactose and arabinose, BRP-2-1 was composed of rhamnose, galacturonic acid, galactose and arabinose, and BRP-2-2 was composed of rhamnose and galacturonic acid in a molar ratio of 1.27: 54.92. Furthermore, the crude BRP exhibited relatively higher antioxidant activity in vitro than purified fractions; hence, it could be used as a natural antioxidant in functional foods or medicines.