The Low Toxicity Of Attenuated Salmonella Typhimurium As A Cancer Gene Therapy Vector And Targeted Research

Objective Study the hypotoxicity and tumor-targeting ability of genetically modified attenuated S.typhymurium VNP20009.Methods Non-tumor-bearing mice were infected intravenously with VNP20009 (case) or wild-type(control).Survival rate was observed;GFP-labeled VNP20009 and MFC murine gastric cancer cell lines labeled with RFP in the cytoplasm and GFP in the nucleus were established.The dual-color MFC cell lines in vitro and tumor-bearing(RFP-labeled MFC gastric cancer cell lines) mice were infected with GFP-labeled VNP20009.Growths of bacteria in vitro were observed under fluorescence microscopy.Growth of bacteria in vivo were observed under fluorescence microscopy to determine the extent of infection and cfu of normal tissues and tumors were determined by harvesting these tissues and homogenizing and planting supernatants on nutrient media.Results All mice infected with wild-type S.typhymurium expired by 4 days.In contrast,all mice infected with VNP20009 survived.The GFP-expressing VNP20009 grew in the cytoplasm of GFP-RFP-labeled MFC cells and caused nuclear destruction. In in vivo experiments,the number of bacteria had markedly regressed in the normal tissue.By day 18,GFP-labeled bacteria could no longer been seen.In contrast,the bacteria grew continuously in the MFC tumor.The tumor/liver bacteria ratios were 224:1 by day 4 and 1020:1 by day 6 after infection.Conclusions The genetically modified attenuated S.typhymurium VNP20009 has the very ability of tumor-targeting and hypotoxicity,which has great potential as a vector for cancer gene therapy.