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Antitumor immunity of alcohol-soluble polysaccharide from Nostoc sphaeroides in non-small cell lung cancer
Aobo Wu1, Yanxia Jin1, Yang Chen2
1Hubei Key Laboratory of Edible Wild Plants Conservation and Utilization, College of Life Sciences, Hubei Normal University, Huangshi 435002, China.
Background:
Nostoc sphaeroides is a species of edible blue-green alga (cyanobacterium) that forms large, spherical colonies and has been used for centuries as a food. Alcohol-soluble polysaccharides exhibit diverse bioactivities such as antitumor, immunomodulatory, and antioxidant effects. However, their extraction and functions in N. sphaeroides remain unreported.
Purpose:
To extract alcohol-soluble polysaccharides from N. sphaeroides and explore its antitumor effect and potential mechanism on lung cancer.
Method:
The alcohol-soluble polysaccharide named NSAP was isolated from N. sphaeroides using hot water extraction, enzymatic hydrolysis, and 80 % ethanol precipitation followed by purification with a DEAE-Sepharose A25 dextran gel chromatography column. Subsequently, its structural characterizations were explored and anti-lung cancer effects were evaluated in vitro and in vivo experiments.
Results:
Structural characterization revealed that NSAP is an acidic polysaccharide with a molecular weight ranging from 7 × 104-3 × 105 Da, which mainly composed of glucose, galactose, mannose, xylose, glucuronic acid, and rhamnose. Methylation analysis indicated that the glycosidic linkages were 4-linked glucose (4-Glc(p), 21.62 %), 3,4-linked glucuronic acid (3,4-Glc(p)-UA, 15.55 %), 4-linked mannose (4-Man(p), 7.81 %), and 4,6-linked galactose (4,6-Gal(p), 11.74 %). Functionally, NSAP suppressed cell viability, DNA replication, and cell migration, while inducing apoptosis and lactose dehydrogenase release in H157 and A549 lung cancer cells, without affecting normal BEAS-2B and NIH/3T3 cells. NSAP also promoted cytokine secretion from RAW264.7 macrophages and splenic lymphocytes, and enhanced macrophage phagocytosis in zebrafish. In vivo, NSAP inhibited tumor growth and infiltration in lung cancer-bearing mice. Mechanistically, NSAP exerted antitumor immunity by upregulating NFKBIZ expression and inhibiting the NF-κB/PD-L1 pathway. Moreover, NSAP could overcome resistance in osimertinib-resistant lung cancer cells.
Conclusion:
This study identifies NSAP as a novel alcohol-soluble polysaccharide from N. sphaeroides, with potential as a therapeutic agent for lung cancer via modulation of the NFKBIZ/NF-κB/PD-L1 pathway.
