Abstract: Objective To investigate the effect of Gastrodia elata polysaccharide via microRNA-27a-3p（miR-27a-3p）/ homolog 3（B7-H3） on the proliferation,invasion and apoptosis of colon cancer cells exposed to arsenic. Methods The colon cancer cells were divided into SW480 cell group,arsenic（As） exposure group（500 μg/mL As₂O₃ treatment）,low-dose Gastrodia elata polysaccharide group（500 μg/mL As₂O₃ and 500 μmol/mL Gastrodia elata polysaccharide treatment）,and high-dose Gastrodia elata polysaccharide group（500 μg/mL As₂O₃ and 1 000 μmol/mL Gastrodia elata polysaccharide treatment）,the cells of the above groups were set up in six duplicate wells,and the culture time was 72 hours. After the experiment,3-（4,5）-dimethylthiahiazo（-z-y1）-3,5-di-phenytetrazoliumromide（MTT） method was used to measure the proliferation of cancer cells in each group,the transwell method and wound healing test were used to measure the invasion and migration of cancer cells in each group,the flow cytometry was used to measure the apoptosis level of cancer cells in each group,the reverse transcription quantitative polymerase chain reaction（RT-qPCR） and Western blotting method were used to determine the levels of miR-27a-3p and B7-H3 in cancer cells of each group. Results Compared with the SW480 cell group,the OD value（0.66±0.03 vs 0.95±0.04）,the survival rate level [（60.01±5.50）% vs（89.74±6.07）%],the number of monoclonal formation（126.69±39.65 vs 1 985.36±398.52）,the number of transmembrane（256.68±86.21 vs 2 472.57±186.52）,migration distance[（256.68±86.21）vs（2 472.57±196.52）μm] and B7-H3 mRNA protein expression level（0.64±0.27 vs 2.89±0.23,0.23±0.28 vs 1.27±0.23） in As exposure group significantly increased,while the apoptosis rate[（20.30±5.89）% vs（3.40±0.97）%] and the expression level of miR-27a-3p mRNA（3.39±0.41 vs 0.66±0.43） significantly decreased（all P<0.01）. Compared with the As exposure group,the OD value（0.95±0.04 vs 0.84±0.03,0.76±0.03）,the survival rate level[（89.74±3.07）% vs（81.03±3.04）%,（63.56±5.05）%],the number of monoclonal formation（1 985.36±398.52 vs 1 025.63±325.66,562.96±105.59）,the number of transmembrane（2 472.57±186.52 vs 1 842.36±165.52,635.20±189.36）,migration distance[（2 472.57±196.52） vs（1 842.36±165.52）,（1 235.20±189.36）μm] and B7-H3 mRNA protein expression level（2.89±0.23 vs 2.01±0.26,1.53±0.24;1.27±0.23 vs 0.89±0.25,0.53±0.24） in low-and high-dose Gastrodia elata polysaccharide group significantly decreased,while the apoptosis rate[（3.40±0.97）% vs（12.30±1.58）（17.70±0.98）%] and the expression level of miR-27a-3p mRNA（0.66±0.43 vs 1.73±0.36,2.65±0.39）significantly increased（all P<0.01）. And OD value,the survival rate level,the number of monoclonal formation,the number of transmembrane,migration distance and B7-H3 mRNA protein expression level in the high-dose Gastrodia elata polysaccharide group were significantly lower than those in the low-dose Gastrodia elata polysaccharide group,while the apoptosis rate and miR-27a-3p mRNA expression level were significantly higher than those in the low-dose Gastrodia elata polysaccharide group（all P<0.05）. Conclusion The Gastrodia elata polysaccharide can inhibit the proliferation and invasion of colon cancer cells colon cancer cells exposed to arsenic and promote their apoptosis,and the mechanism may be related to the fact that Gastrodia elata polysaccharide promotes the expression of miR-27a-3p and then inhibits the expression of B7-H3.

Key words: Gastrodia elata polysaccharide, Arsenic, miR-27a-3p, B7-H3, Colon cancer