The Structural Analysis Of A Sulfated Galactofucan From Sargassum Fusiforme And Its Anti-Lung Cancer Mechanism

Lung cancer has the highest morbidity and mortality in all kinds of malignant cancers in the world.Chemotherapy along with targeted drugs are the main therapeutic strategies to treat lung cancer.Chemotherapy often have strong side effects and targeted drugs would easily generate drug resistance in clinical trials.Therefore reaearching for some new drugs which have good effects along with low side effects is a direction of developing lung cancer therapies.Polysaccharides derivated from Sargassum fusiforme have many bioactivities such as antihyperlipidemic,anticoauglation,antioxidant,antiviral and immunostimulation.Previous literature reports that polysaccharides derivated from Sargassum fusiforme or other brown seaweeds can induce apopotosis of lung cancer cells along with promoting the effects of chemotherapy drugs.However the anti-lung cancer effects of polysaccharides derivated from Sargassum fusiformeare remains to be exploited.So we carried experiments to do researches.This study made structure analysis of sulfated galactofucan HFSGF extracted from Sargassum fusiforme.Explored its inhibitory effects on the proliferation of A549 cells at different concentrations and times in vitro cell experiment along with its effects on the inhibition of the growth of xenograft tumors in vivo experiment.Researched its effects of A549 cell at transcription and translation level.Main results were as follows:1.The polysaccharide component HFSGF was extracted from Sargassum fusiforme.HFSGF had been treated with cation exchange and alcohol precipitation.The supernate was named HFSGF-S and the precipitate was named HFSGF-C.HFSGF-C was further eluted by p-10 gel column to obtain two downstream components which were named HFSGF-L and HFSGF-H.The chemical components of HFSGF were analyzed and proved it a kind of sulfated galactofucan.All results were summarized and proved HFSGF-L is the branch chain of HFSGF.It has structure of alternating sulfated galactose and sulfated fucose.HFSGF-H is the main chain and fractional branch chain of HFSGF and composed of alternating sulfated mannose and sulfated glucuronic acid.HFSGF is composed of both chains which branch chain’s C1 position of fucose linking with main chain’s C3 position of mannose.2.This experiment explored the inhibition of HFSGF,HFSGF-L and HFSGF-H on the proliferation of A549 cells and the inhibition of HFSGF-L and HFSGF-H on the migration of A549 cells.The cell viability assay demonstrated that HFSGF,HFSGF-L and HFSGF-H can significantly inhibit the proliferation of A549 cells.HFSGF has the highest inhibition rate,HFSGF-H follows and HFSGF-L has the lowest inhibition rate.The results of cell experiment indicated that HFSGF in the three samples might have strong cytotoxic effect due to its impuritiy.So it was not suitable to be used in subsequent experimental exploration.The results of wound healing assay indicated that HFSGF-L and HFSGF-H significantly inhibit the migration of A549 cells at several conditions.3.Subcutaneous injection of A549 cell suspension in nude mice was used to make xenograft tumors model.When solid tumors’ average volume was reached 100 mm3,all nude mice were divided into a model group and two experimental groups.All groups of mice were intraperitoneal injected with the same volume of normal saline,HFSGF-L and HFSGF-H,and the doses of HFSGF-L and HFSGF-H are both 100 mg/kg per day.Then oberved and recorded the variations of weights and tumor volumes of nude mice.Finally weighed the weights of some organs after the dissection of nude mice and calculated organ coefficients.It was found that the inhibition rate of tumor growth of HFSGF-H group were approximately 50% compared with model group.Meanwhile,only spleen coefficients and kidney coefficients have significant differences among two groups and indicate that HFSGFH has no side effects.Due to the results of in vivo xenograft experiment were similar to the results of in vitro cell experiment,HFSGF-H performed well against lung cancer both in vivo and vitro.4.This experiment explored the variations in m RNA and protein expression level of A549 cells after HFSGF-L and HFSGF-H was added to A549 cells at transcription and translation level,respectively.We found that HFSGF-H caused significantly decreasing expression level of FAK,p-AKT and m TOR proteins in A549 cells,which supposed to be one of the mechanisms that HFSGF-H have potent effect on inhibiting the proliferation of lung cancer cell.