As IRF-7 and STAT-3 were also expressed by host cells, it could be hypothesized that transfer of VACV from cancer cells to host cells infiltrating the xenografts reproduced patterns observed in human cancer cells, while host's immune cells followed the classical up-regulation of pro-inflammatory pathways through STAT-1, IRF-1 signaling [18,42,51]. This evidence concerns the gene STAT3 and cancer.