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Tumor-targeting Salmonella typhimurium, a natural tool for activation of prodrug 6MePdR and their combination therapy in murine melanoma model
Ist Teil von
Applied microbiology and biotechnology, 2013-05, Vol.97 (10), p.4393-4401
Ort / Verlag
Berlin/Heidelberg: Springer-Verlag
Erscheinungsjahr
2013
Quelle
MEDLINE
Beschreibungen/Notizen
The PNP/6-methylpurine 2′-deoxyriboside (6MePdR) system is an efficient gene-directed enzyme prodrug therapy system with significant antitumor activities. In this system,
Escherichia coli
purine nucleoside phosphorylase (ePNP) activates nontoxic 6MePdR into potent antitumor drug 6-methylpurine (6MeP). The
Salmonella typhimurium
PNP (sPNP) gene has a 96-% sequence homology in comparison with ePNP and also has the ability to convert 6MePdR to 6MeP. In this study, we used tumor-targeting
S. typhimurium
VNP20009 expressing endogenous PNP gene constitutively to activate 6MePdR and a combination treatment of bacteria and prodrug in B16F10 melanoma model. The conversion of 6MePdR to 6MeP by
S. typhimurium
was analyzed by HPLC and the enzyme activity of sPNP was confirmed by in vitro (tetrazolium-based colorimetric assay) MTT cytotoxicity assay. After systemic administration of VNP20009 to mice, the bacteria largely accumulated and specifically delivered endogenous sPNP in the tumor. In comparison with VNP20009 or 6MePdR treatment alone, combined administration of VNP20009 followed by 6MePdR treatment significantly delayed the growth of B16F10 tumor and increased the CD8
+
T-cell infiltration. In summary, our results demonstrated that the combination therapy of
S. typhimurium
and prodrug 6MePdR is a promising strategy for cancer therapy.