The Molecular Mechanisms Of Colorectal Cancer Xenografts Vasculature Decompression In Nude Mice By Gold Nanoparticles

Objective In the colorectal cancer xenograft model,immunohistochemistry and fluorescent labeling combined with enzyme-linked immunosorbent assay were used to detect whether gold nanoparticles could decompress tumor vessels in nude mice and explore its related molecular mechanisms.On this basis,whether gold nanoparticles could further improve the efficacy of cisplatin were investigated.Methods（1）In vitro experiments:Human colorectal cancer cells（sw620）were treated with different concentrations of gold nanoparticles solution and serum-free medium.After 24 hours of treatment,the levels of transforming growth factorβ1（TGF-β1）,connective tissue growth factor（CTGF）and vascular endothelial growth factor（VEGF）in cells and cell culture medium was detected by Western blot and ELISA methods.Meantime,the proliferation of sw620 cells was detected by CCK-8 method.（2）In vivo experiments:1×10⁷ sw620 cells were inoculated into the right hind limb of Balb/c nude mice to establish colorectal cancer xenograft model.Then the nude mice were randomly divided into 4 groups（n=6 per group）:gold nanoparticles treatment group:1.0mg kg^-1 gold nanoparticles;cisplatin treatment group:5.0mg kg^-1 cisplatin;gold nanoparticles combined with cisplatin treatment group:1.0mg kg^-1 gold nanoparticles and 5.0mg kg^-1 cisplatin;Control group:equal dose of saline.Each group was intravenously injected 0.1ml of the corresponding solution every 2 days for 2 weeks.Then the nude mice were sacrificed,the blood samples,tumors and organs were collected for detection:（1）the tumor volume,weight and solid stress.（2）the TGF-β1,CTGF and VEGF levels of serum or tumor.（3）the tumor interstitial collagen I,cancer associated fibroblasts（CAFs）levels,tumor vascular morphology and perfusion.（4）the tumor anoxic area.（5）The cisplatin levels of tumor,liver and kidney.Results The results of in vitro experiments showed that there was no significant difference in the proliferation of sw620 cells（F=0.803,P>0.05）,but gold nanoparticles could inhibit the expression and secretion of TGF-β1（F=23.962,P<0.001）,CTGF（F=214.624,P<0.001）and VEGF（F=214.624,P<0.001）of sw620cells.In vivo experiments:（1）The concentrations of serum TGF-β1 in nude mice were as follows:control group:（1176.31?62.56）pg/ml,gold nanoparticles treatment group:（729.26?108.34）pg/ml,P<0.001.In addition,the effect of gold nanoparticles on serum CTGF and VEGF in nude mice were similar to that of the above results.（2）The positive areas of TGF-β1 in colorectal cancer xenografts of each treatment group were as follows:control group:（14.63?3.01）%,1.0mg/kg gold nanoparticles treatment group:（3.17?0.76）%.Compared with the control group,the area of TGF-β1positive area in colorectal cancer xenografts was significantly reduced in the gold nanoparticles treated group,and the difference was statistically significant（t=9.034,P<0.001）.In addition,the effects of gold nanoparticles on CTGF and VEGF in colorectal cancer xenografts were similar to that of the above results.（3）The tumor solid stress in nude mice was as follows:control group:0.57?0.03,gold nanoparticles treatment group:0.44?0.01,P<0.01.（4）The levels of tumor CAFs in the nude mice were as follows:control group:（3.93?1.90）%,gold nanoparticles treatment group:（0.91?0.24）%,P<0.01.（5）The levels of tumor collagen I in the nude mice were as follows:control group:（42.16?5.14）%,gold nanoparticles treatment group:（11.73?3.97）%,P<0.001.（6）The levels of tumor vascular perfusion in the nude mice were as follows:control group:（12.02?2.64）%,gold nanoparticles treatment group:（35.58?14.26）%,P<0.01.（7）The transplanted tumor hypoxia regions in nude mice were as follows,control group:（37.24?8.08）%,gold nanoparticles treatment group:（11.52?1.83）%,P<0.001.（8）The tumor cisplatin levels in nude mice were as follows:cisplatin treatment group:（16.21?1.28）μg/ml,gold nanoparticles combined with cisplatin treatment group:（25.81?2.04）μg/ml,P<0.01.However,there was no significant difference in the cisplatin level of the liver and kidney between the two treatment groups（P>0.05）.In addition,the transplanted tumor weight and volume in nude mice were statistically different compared with each treatment groups（P<0.01）.Conclusions Gold nanoparticles can inhibit the TGF-β1,CTGF and VEGF expression and secretion of sw620 cells,decrease the levels of serum TGF-β1,CTGF and VEGF in colorectal cancer xenograft nude mice,reduce the levels of tumor collagen I,CAFs and solid stress,decompress tumor vessels,increase tumor vascular perfusion,improve tumor tissue hypoxia,meanwhile,increase tumor cisplatin levels and significantly decrease the volume and weight of lesions.