Secreting-lux/pT-ClyA engineered bacteria suppresses tumor growth via interleukin-1β in two pathways

Abstract

Engineered Salmonella typhimurium (S.t-ΔpGlux/pT-ClyA) and attenuated Salmonella typhimurium (SL: Salmonella typhimurium with a defect in the synthesis of guanine 5′-diphosphate-3′-diphosphate) exhibit similar tumor targeting capabilities (Kim et al. in Theranostics 5:1328–1342, 2015; Jiang et al. in Mol Ther 18:635–642, 2013), but S.t-ΔpGlux/pT-ClyA exerts superior tumor suppressive effects. The aim of this study was to investigate whether S.t-ΔpGlux/pT-ClyA inhibits colon cancer growth and recurrence by promoting increased IL-1β production. The CT26 tumor mouse model was used, and mice were treated in the following ways: PBS, S.t-ΔpGlux/pT-ClyA(+) + IL-1βAb, SL, S.t-ΔpGlux/pT-ClyA(−), and S.t-ΔpGlux/pT-ClyA(+). Dynamic evaluation of the efficacy of S.t-ΔpGlux/pT-ClyA in the treatment of colon cancer was assessed by MRI. Western blot, immunofluorescence and flow cytometry analysis were used to investigate IL-1β-derived cells and IL-1β expression on tumor cells and immune cells to analyze the regulatory mechanism. IL-1β levels in tumors colonized by S.t-ΔpGlux/pT-ClyA were significantly increased and maintained at high levels compared to control treatments. This increase caused tumors to subside without recurrence. We examined the immune cells mediating S.t-ΔpGlux/pT-ClyA-induced tumor suppression and examined the major cell types producing IL-1β. We found that macrophages and dendritic cells were the primary IL-1β producers. Inhibition of IL-1β in mice treated with S.t-ΔpGlux/pT-ClyA using an IL-1β antibody caused tumor growth to resume. This suggests that IL-1β plays an important role in the treatment of cancer by S.t-ΔpGlux/pT-ClyA. We found that in St-ΔpGlux/pT-ClyA-treated tumors, expression of molecules involved in signaling pathways, such as NLRP3, ASC, Caspase1, TLR4, MyD88, NF-kB and IL-1β, were upregulated, while in ΔppGpp S. typhimurium treated animals, TLR4, MyD88, NF-kB and IL-1β were upregulated with NLRP3, ASC, and Caspase1 being rarely expressed or not expressed at all. Using S.t-ΔpGlux/pT-ClyA may simultaneously activate TLR4 and NLRP3 signaling pathways, which increase IL-1β expression and enhance inhibition of colon cancer growth without tumor recurrence. This study provides a novel platform for treating colon cancer.

Interleukin-1β and Cancer

“…Cancer cell-derived DAMPs (danger-associated molecular patterns) [ 157 ], double-stranded oligodeoxynucleotides [ 158 ], or bacteria [ 159 , 160 ] can be used to activate TLRs and the inflammasome to enable DCs to release IL-1β. For example, Salmonella typhimurium i.v.…”

“…injected into mice can enable DCs to produce IL-1β and enhance inhibition of colon cancer growth. Inhibiting IL-1β restores tumor growth, while local administration of recombinant IL-1β inhibits tumor growth [ 159 , 160 ].…”

Interleukin-1 as Innate Mediator of T Cell Immunity

“…This correlates with an enhanced potential to activate bystander DCs, which in turn cross-present antigen to CD8 + T cells and induce an antigen-specific adaptive immune response ( 281 ). In the CT26 colon carcinoma model, systemic administration of Salmonella typhimurium in mice enhances the release of IL-1β by DCs and inhibits tumor growth, which can be reverted upon treatment with an IL-1β-neutralizing antibody ( 282 , 283 ). Work by Segovia et al demonstrated that mice with a deficiency for the transmembrane protein 176B (TMEM176B), which inhibits activation of the NLRP3 inflammasome by controlling the cellular Ca 2+ flux, efficiently control tumor growth in a caspase 1 and IL-1β-dependent manner.…”

“Trojan Horse” Salmonella Enabling Tumor Homing of Silver Nanoparticles via Neutrophil Infiltration for Synergistic Tumor Therapy and Enhanced Biosafety

“…The Salmonella used in this work was S.t -ΔpG lux (ΔppGpp Salmonella typhimurium with the luciferase gene open luxCDABE). It is a type of avirulent S. typhimurium strain with suppressed endotoxin gene expression achieved by relA and SpoT double mutation to affect ppGpp synthesis, and the biosafety of this attenuated strain has been extensively tested in mice models . Due to the intrinsic expression of the luciferase gene, the bacteria showed strong bioluminescence in both LB broth and LB agar upon excitation (Figure A), which enables its convenient in vivo tracing.…”

“…It is a type of avirulent S. typhimurium strain with suppressed endotoxin gene expression achieved by relA and SpoT double mutation to affect ppGpp synthesis, and the biosafety of this attenuated strain has been extensively tested in mice models. 37 Due to the intrinsic expression of the luciferase gene, the bacteria showed strong bioluminescence in both LB broth and LB agar upon excitation (Figure 3A), which enables its convenient in vivo tracing. From TEM, the S.t-ΔpG lux exhibited a typical ellipsoidal shape with 0.5 μm width and 2 μm length (Figure 3B).…”