Salmonella‐mediated tumor‐targeting TRAIL gene therapy significantly suppresses melanoma growth in mouse model

Abstract

Attenuated Salmonella typhimurium (S. typhimurium) strains can selectively grow and express exogenous genes in tumors for targeted therapy. We engineered S. typhimurium strain VNP20009 to secrete tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) under the control of a hypoxia-induced nirB promoter and examined the efficacy of Salmonella-mediated targeted expression of TRAIL in mice bearing melanoma tumor and in TRAIL-resistant RM-1 tumor. We found that VNP preferentially accumulated in tumor tissues and the nirB promoter effectively drove targeted expression of TRAIL. Compared with recombinant TRAIL protein and VNP20009 combination therapy, VNP20009 expressing TRAIL significantly suppressed melanoma growth but failed to suppress RM-1 tumor growth. Furthermore, we confirmed that VNP20009 expressing TRAIL yielded its antitumor effect by inducing melanoma apoptosis. Our findings indicate that Salmonella-mediated tumor-targeted therapy with TRAIL could reduce tumor growth and extend host survival. (Cancer Sci 2012; 103: 325-333) T umor tissues consume a greater amount of oxygen than that supplied by the tumor-feeding blood vessels.(1) Normal tissues typically have median oxygen tensions of 40-70 mmHg, whereas that of most solid tumors is <10 mmHg. Clinically, poor oxygenation is a major indicator of adverse prognosis for solid tumors, which frequently contain large regions with low oxygen concentrations.(2-6) One contributing factor to the adverse outcome is the inadequate distribution of antitumor agents to the hypoxic areas of a tumor where blood flow is sluggish or highly irregular.(2) Strategies for improving tumor oxygenation have met with rather limited success.(7) Specific killing of hypoxic tumor cells by hypoxia-selective tumoricidal agents or modalities offers a separate strategy that views the presence of hypoxia in tumors not only as a determinant for poor prognosis but also as an opportunity for tumor-specific treatment.Selective targeting of tumors where hypoxia exists enhances targeted concentration of therapeutic agents of interest in cancer cells while minimizing damage to the normal tissues, regardless of whether these therapeutic agents are chemotherapeutic drugs or recombinant proteins or ectopic genes. Attenuated Salmonella typhimurium (S. typhimurium) strains have been shown to selectively grow and express exogenous genes in tumors for targeted therapy. (8)(9)(10)(11)(12) We have previously shown that the facultative anaerobe S. typhimurium strain VNP20009 can replicate in hypoxic tumors (13)(14)(15)(16) and is synergistic with cyclophosphamide against melanoma in a mouse tumor model. (17) Because the bacteria could preferentially accumulate in the hypoxic tumor microenvironment, there have been attempts to engineer controllable expression of therapeutic molecules such as prodrugconverting enzymes and antigens. (18)(19)(20)(21) Tumor necrosis factor-related apoptosis-inducing ligand can selectively induce apoptosis in cancer cells and is effective against many cancers, includin...

Anti-cancer activity of Annexin V in murine melanoma model by suppressing tumor angiogenesis

“…For every experiment, the mice were randomized into 4 groups (8 mice per group) and intraperitoneally injected with PBS, 5.0 mg/kg Annexin V, 10.0 mg/kg Annexin V, 40.0 mg/kg dacarbazine (DTIC, for positive control) daily for continuous 13 days. Tumor volume was measured every day after the initial injection with calipers and determined asmm3 using the equation: A×B 2 ×0.52 [29, 30], where A was the length (mm) and B was the width (mm). Tumor doubling time refers to the time for a tumor to double in volume and tumor growth delay time is the time interval to reach 1000 mm 3 compared with the PBS control group [17].…”

Bacterial Carriers for Glioblastoma Therapy

“…S. typhimurium is a known intracellular pathogen, and in particular, the VNP strain has been shown to express proteins in host tissues53, 58, 59 (also observed in Figure 3). Once a VNP carrier invades the host cell, it can express Azurin, which gets secreted outside the bacterial cell into the host cytosol (due to its N-terminal secretion signal sequence) where it can exert its apoptotic activity or protect endogenously synthesized or bacterially expressed p53.…”

Therapeutic benefit of Salmonella attributed to LPS and TNF-α is exhaustible and dictated by tumor susceptibility

“…Not surprising, these stimulants are in focus as potential therapeutic adjuvants or as molecular targets for immune modulation in BMTT [30, 60–62]. However, one should keep in mind their naturally detrimental effect.…”