In preclinical mouse models of MC38 (colorectal cancer), B16 (melanoma), CT26 (colorectal cancer), and 4T1 (breast cancer), ProIL-2 has been shown to preferentially activate and expand antigen-specific CD8+ T cells intra-tumorally, significantly reducing IL-2 toxicity and mortality without compromising antitumor efficacy (153). The gene discussed is CD8A; the disease is melanoma.