In the study, large (2-5 cm) intrahepatic tumors of 5 woodchucks were injected with a single dose of 1 × 10 9 PFU AdV expressing IL-12 and B7.1 molecule (AdIL-12/B7.1). The B7.1 molecule (also known as a CD80) is naturally expressed on the professional APCs and provides the synergistic effect in the tumor regression [181, 186, 187] . In 4 out of 5 animals, AdIL-12/B7.1 was delivered by laparotomy into the three HCC nodules and three nodules were injected with a vector expressing GFP as a control. Animals were sacrificed 7-14 days later and the tumor volumes were assessed. On average, treated tumors showed an 80% reduction in the volume whereas the size of the AdGFP-injected nodules increased. Remission of the tumors was associated with CD4 + and CD8 + T cell infiltration into the tumor tissue and increased local IFNγ levels after AdIL-12/B7.1 injection. One of the treated woodchucks received the intratumoral injection by magnetic resonance imaging (MRI) guidance and was monitored for 7 weeks. During this period the tumor size decreased from 8,6 cm 3 to 0,5 cm 3 [168] . This observation shows that administration of AdIL-12/B7.1 during MRI guidance, with therapeutic effect similar to laparotomy, could prevent the animals from harmful consequences of the surgery.