Investigation of antitumorigenic effects of food-borne non-pathogenic and pathogenic Salmonella enterica strains on MEF, DU145 and HeLa cell lines

Abstract

Basic applications in cancer therapy may fail to eradicate cancer cells completely, they can show toxic affects to healthy cells and development of resistance to antitumor agents may increase tendency to metastasis. Bacterial therapies have the advantage of specific targetting of tumors by selective toxicity, responsiveness to external signals, self-propelling capacity, and the sense of microenvironment. The most interest on the bacterial cancer therapy is about Salmonella spp. with a special emphasis of S.Typhimurium. The aim of this study was to investigate the antitumorigenic effects of food-borne non-pathogenic and pathogenic Salmonella enterica strains on different cell cultures. Non-pathogenic Salmonella Enteriditis (A17) and pathogenic Salmonella Telaviv (A22) strains isolated from chicken carcasses which were put on the market in Edirne province (located at Thrace region of Turkey), and Salmonella Typhimurium ATCC 14028 strain were used in the study. ATCC-derived MEF (mouse embryonic fibroblasts), DU145 (human prostate cancer cells), and HeLa (human cervical cancer cells) cell lines were cocultivated with Salmonella strains of MOI (Multiplicity of infection; number of bacteria:number of cell) of 1000:1, 100:1, 10:1, 1:1, 0.1:1. The cell viability was measured by colorimetric MTT cytotoxicity assay, the percentage of apoptosis was assessed by Tali® Apoptosis Assay-Annexin V Alexa Fluor® 488 kit (Invitrogen, Molecular Probes, Life Technologies, USA), and the caspase-3 activity was determined by colorimetric protease ApoTarget™ kit (Invitrogen, BioSource International, USA). It was shown that non-pathogenic S.Enteriditis (A17) decreased cell viability approximately to 70%, wheras patogenic S.Telaviv (A22) and standart S.Typhimurium ATCC 14028 strains reduced cell viability approximately to 80%. Adversely, it was also observed that pathogenic S.Telaviv (A22) strain induces apoptosis more effectively than non-pathogenic S.Enteriditis (A17) and S.Typhimurium ATCC 14028 strains. Apoptosis percentage induced by pathogenic S.Telaviv (A22) strain was approximately 15% while 5% for both non-pathogenic S.Enteriditis (A17) and S.Typhimurium ATCC 14028 strains. Similarly, average OD405 values of caspase-3 activity was shown as 0.01 for both non-pathogenic S.Enteriditis (A17) and S.Typhimurium ATCC 14028 strains whereas average OD405 value of caspase-3 activity for pathogenic S.Telaviv (A22) strain was very close to 0.02 and it doubled the value for negative control. Our data are important in terms of the indication of food-borne pathogenic S.Telaviv (A22) strain that enhanced caspase-3 activity and induced apoptosis, and S.Enteriditis (A17) strain that showed selective cytotoxicity on DU145 (human prostate cancer cells).