To determine the bacterial biodistribution and analyze the capability of NirB promoter to express exogenous proteins in hypoxic tumor regions, the recombinant strains VNP, VNP-pN, VNP-pN-FADD and VNP-pN-N-FADD were injected into mice bearing B16F10 melanoma xenograft respectively. Here, FADD is linked to melanoma.