Spatial distribution of tumor vaccine improves efficacy

Objectives: Genetically engineered tumor cells were used as a vaccine in a murine model to compare tumor formation after inoculating multiple sites versus a single site. The effect of vaccinating draining lymph node basins was evaluated. Study Design: Mice were vaccinated in either the floor of the mouth, the draining nodes of the front legs, the hind leg, or a combination of sites. Seven days later, the mice were challenged with parental tumor cells in the floor of the mouth and followed for tumor growth. Methods: A retroviral vector was used to transduce the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene into SCCFVII/SF tumor cells, which were then irradiated to prevent replication in vivo. Syngeneic C3H/HeJ mice were vaccinated with 1 × 10⁶ cells in various sites, then challenged with 1 × 10⁵ parental cells after 7 days. Results: Animals vaccinated in multiple sites had better protection from later tumor challenge than those receiving single vaccinations. Of the animals receiving vaccination at multiple sites, those vaccinated in the site of tumor challenge (floor of the mouth) had more protection than those not vaccinated at the site. Conclusions: Mice vaccinated at multiple draining lymph node sites were better primed against tumor challenge than mice receiving single inoculations. Vaccination strategies that included the challenge site (floor of the mouth) and the nodes near this site were optimal.