Plasmodium infection inhibits triple negative 4T1 breast cancer potentially through induction of CD8 T cell-mediated antitumor responses in mice.

We previously reported that Plasmodium infection promotes antitumor immunity in a murine Lewis lung cancer. In this study, we investigated the effects of Plasmodium infection on the tumor inhibition and antitumor CD8 T cell responses in a murine triple negative breast cancer (TNBCA) model. The results showed that Plasmodium infection significantly inhibited tumor growth, and increased the survival rate of the tumor-bearing mice. Both effector and memory CD8 T cells were increased in peripheral blood and tumor-draining lymph node (DLN) in the infected mice. The co-stimulatory (CD40L, GITR and OX-40) and co-inhibitory (PD-1, CTLA-4, TIM-3, LAG3) immune checkpoints were up-regulated on CD8 T cells in infected mice. Importantly, Py induced remarkable effects on the infiltration of CD8 T cells in the tumor and granzym B CD8 T cells in tumor-bearing mice while not in tumor-free mice. In summary, the results suggested that the effects of Plasmodium infection on murine 4T1 breast cancer might be related to the induction of CD8 T cell-mediated antitumor immune responses. This finding may provide a novel strategy for the treatment of triple negative breast cancer.