Plasmodium infection simultaneously upregulates the expression levels of co-stimulatory (such as CD40L, OX-40, GITR) and co-inhibitory checkpoint molecules (such as PD-1, CTLA-4, TIM-3) on CD8+ T cells in tumor-bearing mice, but these CD8+ T cells express high levels of effector molecules (such as perforin and granzyme B) at the same time, representing the increase of their cytotoxicity. This evidence concerns the gene PRF1 and neoplasm.