Intravenous administration of MIP-1α with intra-tumor injection of P. acnes shows potent anti-tumor effect

Dendritic cells (DCs) play a key role as potent biological adjuvants in anti-tumor host responses. However, DC-based vaccination does not always eradicate tumors effectively. Clinical evidence suggests that a strategy to recruit a substantial number of DCs into the tumor mass might provoke proficient anti-tumor immune responses. Here we describe that myeloid DCs (mDCs) efficiently accumulate in tumor sites after intravenous injection of recombinant macrophage inflammatory protein (MIP)-1α when pretreated locally with adjuvants like Propionibacterium acnes. Combined treatment of tumor-bearing mice with MIP-1α and P. acnes also recruited a large number of natural killer cells (NK cells) to both tumor sites and regional lymph nodes (LNs) and induced a strong T helper 1 immunity at an early time. This early response later led to accumulation of CD8+ T cells, retraction of tumors and survival of animals treated with P. acnes/MIP-1α. In vivo depletion of NK cells or CD8+ T cells impaired anti-tumor effects, suggesting that activation of NK cells and CD8+ T cells contributes to anti-tumor immunity in this model. Therefore, this study provides a novel therapeutic strategy for cancer treatment using MIP-1α and certain adjuvants.