In immune-competent mouse models of melanoma, breast cancer, and colon cancer, PEGylated kynureninase (PEG-KYNase) administration was associated with marked reductions in serum KYN levels and increases in AA levels that were met with concomitant increases in tumor-infiltrating CD8+ T lymphocytes and tumor reduction. This evidence concerns the gene CD8A and malignant colon neoplasm.