Salmonella Promoters Preferentially Activated Inside Tumors

Abstract

Salmonella enterica and avirulent derivatives prefer solid tumors over normal tissue in animal models. The identification of endogenous Salmonella promoters that are preferentially activated in tumors could further our understanding of this phenomenon. Toward this goal, a random library of S. enterica typhimurium 14028 genomic DNA was cloned upstream of a promoterless gene encoding the green fluorescent protein (GFP) TurboGFP. A population of Salmonella containing this library was injected i.v. into tumor-free nude mice and into human PC3 prostate tumors growing subcutaneously in nude mice. After 2 days, fluorescence-activated cell sorting was used to enrich for bacterial clones expressing GFP from spleens or tumors. The resulting libraries were hybridized to an oligonucleotide tiling array of the Salmonella genome. Eighty-six intergenic regions were found to be enriched in tumor samples but not in spleen. Twenty of these candidate promoters were also detected in the sequences of 100 random clones from a library enriched for expression in bacteria growing in tumors. Three candidate promoter clones were individually tested in vivo, and enhanced GFP expression in bacteria growing in tumor relative to spleen was confirmed. Two of the three clones (pflE and ansB promoter regions) are known to be induced in hypoxic conditions that pertain to many tumors. For many of the other candidate promoters preferentially induced in bacteria growing in tumors, regulatory mechanisms may not be related to hypoxia. The expression of therapeutics in Salmonella under the regulation of one or more promoters that are activated preferentially in tumors has the potential to improve the targeting of drug delivery. [Cancer Res 2008;68(12):4827–32]

Gene therapy for cancer: bacteria-mediated anti-angiogenesis therapy

“…However, further research is needed to fully delineate the most effective way to target angiogenesis for cancer treatment. The application of new approaches using bacteria for the transfer of therapeutic genes or the Loeffler et al 53 Loeffler et al 54 Loeffler Bacteria in cancer gene therapy R Gardlik et al production of therapeutic protein or small RNAs has the potential to significantly advance cancer gene therapy. Recent studies indicate that treatments targeting a single molecule/pathway, even if it has pleiotropic effects, are unlikely to be able to completely eradicate tumors; however, if the natural anti-tumor activity inherent to some anaerobic bacteria strains can be successfully combined with their ability to deliver agents targeting tumor angiogenesis, apoptosis or the immune system, this will represent a significant step toward reaching this important goal.…”

“…51,52 A subset of promoters preferentially activated inside tumors has been identified recently, suggesting that there are additional regulatory mechanisms beside those hypoxia-related. 53 This is particularly interesting in light of recent findings regarding the ability of tumor-targeting bacteria to colonize both the necrotic and well-perfused areas of tumors. 6,54 These results further enhance the potential of using bacteria for anti-tumor gene therapy, by providing a wider variety of promoters capable of tumor targeting and regulated gene expression.…”

Salmonella Utilizes D-Glucosaminate via a Mannose Family Phosphotransferase System Permease and Associated Enzymes

“…We are unaware, though, of any reports of D-glucosaminate in the intestinal tract contents of any animal. There have been numerous studies in which the Salmonella transcriptome has been analyzed by use of bacteria grown in vivo (e.g., during infection of macrophage-like cells or epithelial cells or isolated from the intestinal tract), cultured under different conditions, or exposed to various chemical stimuli (53)(54)(55)(56)(57)(58)(59)(60)(61). In addition, there are several reports on how the loss of known global regulators affects the Salmonella transcriptome (62)(63)(64).…”

Influence of Salmonella enterica Serovar Typhimurium ssrB on Colonization of Eastern Oysters (Crassostrea virginica) as Revealed by a Promoter Probe Screen

“…The previously constructed Salmonella promoter probe library consisted of random small fragments of the S. enterica 14028 genome cloned upstream of the promoterless gfp obtained by removing the Tn5 promoter from the commercial pTurboGFP-B reporter plasmid (26). A negative control, pGFP-OFF, was created by self-ligating the promoterless pTurboGFP-B.…”