Human responses against HER-2-positive cancer cells in human immune system-engrafted mice

Background: Human immune system (HIS)-engrafted mice are new tools to investigate human immune responses. Here, we used HIS mice to study human immune responses against human HER-2-positive cancer cells and their ability to control tumour growth and metastasis. Methods: BALB/c Rag2^-/-, Il2rg^-/- mice were engrafted with CD34⁺ or CD133 ⁺ human cord blood hematopoietic stem cells (HSC) and vaccinated with human HER-2-positive cancer cells SK-OV-3 combined to human IL-12. Results: Both CD34⁺ or CD133⁺ human HSC gave long-term engraftment and differentiation, both in peripheral blood and in lymphoid organs, and production of human antibodies. Vaccinated mice produced specific anti-HER-2 human IgG. An s.c. SK-OV-3 challenge was significantly inhibited (but not abolished) in both vaccinated and non-vaccinated HIS mice. Tumours were heavily infiltrated with human and murine cells, mice showed NK cells and production of human interferon-γ, that could contribute to tumour growth inhibition. Vaccinated HIS mice showed significantly inhibited lung metastases when compared with non-vaccinated HIS mice and to non-HIS mice, along with higher levels of tumour-infiltrating human dendritic cells. Conclusion: Anti-HER-2 responses were elicited through an adjuvanted allogeneic cancer cell vaccine in HIS mice. Human immune responses elicited in HIS mice effectively inhibited lung metastases.