In the tumor-bearing mice infected with P. yoelii, we found an increased proportion of TUNEL-positive cells, upregulated expression of proapoptotic factors including Bax, caspase-9, and cleaved caspase-3, and downregulated expression of antiapoptotic factor Bcl-2 in colon cancer tissues, indicating that Plasmodium infection promoted mitochondria-mediated apoptosis. The gene discussed is CASP9; the disease is infection.