Experimental Study Of Silencing MMP-9 Gene On Human Gastric Cancer Xenografts In Nude Mice

Objectives1,To construct nude mice model of gastric cancer , by transplanting the poorly differentiated human gastric cancer BGC-823 cells into nude mice.2,To study the effect of MMP-9 eukaryotic expression vector plasmid on hu-man gastric cancer xenografts growth, volume, weight and MMP-9 protein expres-sion in nude mice.MethodsForty-five nude mice were divided into 5 groups randomly. Human poorly dif-ferentiated gastric cancer cells BGC-823 were injected subcutaneously to the right scapular region of nude mice. Treatment solution was injected directly into the dif-ferent sites of tumor bodies in every other day after forming tumor. The first group was injected with non-specific shRNA coding sequence of the universal negative vector pGenesil-HK, referred as the pGenesil-HK group; second group was injected with opti-MEM medium, referred as the opti-MEM group; third group was injected with pGenensil empty plasmid, referred as the pGenensil empty plasmid group; fourth group was injected with SofastTM liposome, referred as the Sofast group; fifth group was injected with eukaryotic expression vector plasmid pGenesil-MMP-9, re-ferred as the pGenesil-MMP-9 group. We locate pGenesil-HK, opti-MEM, pGenesil empty plasmid and Sofast as control group. The fifth group is experimental group. The nude mice of each group was kept under specific pathogen free (SPF) con-ditions in the animal laboratory. The growth of tumor was observed every other day till all nude mice were euthanized 2 day after the last treatment. Tumor specimens were sectioned on the 4μm thick slices for histopathology analysis by hematox-ylin-eosin and immunohistochemical staining. The mRNA levels of MMP-9 were assessed by Real-time qPCR in a portion of the fresh tumor specimens, which were snap-frozen and stored at a temperature of -80℃.Results1,Human poorly differentiated gastric cancer cells BGC-823 were injected into5 separate groups of nude mice, and formed subcutaneous tumor a week later. The experimental group formed substantially smaller and lighter tumors in nude mice than the other 4 control groups. They were considered statistically significant that the P value was less than 0.05.2,Immunohistochemistry results: MMP-9 protein was weakly positive expres-sion in pGenesil-MMP-9 group. However, it was strongly positive expression in the four control groups, which were injected with pGenesil-HK, pGenesil empty plasmid, Sofast and opti-MEM respectively. There has a statistically significant difference. The P value was less than 0.05.3,The MMP-9 mRNA levels of each group was considered statistically signif-icant. As the result show that the mRNA level of MMP-9 in experimental group lower than control group. The P value was less than 0.05.Conclusions1,We use RT-qPCR and MMP-9 immunohistochemical staining to detect that human poorly differentiated gastric cancer BGC-823 cells express MMP-9 protein.2,In vivo, eukaryotic expression vector plasmid pGenesil-MMP-9 significantly decreased the MMP-9 mRNA transcription and protein expression levels of the gas-tric tumor xenografts in nude mice.3,Vector-mediated gene silencing MMP-9 significantly reduced the volume and weight of gastric cancer tumor xenografts in nude mice.4,RNAi as a means of cancer gene therapy, has a good prospect. MMP-9 is expected to become a new target for treatment of gastric cancer.