Tryptanthrin effectively inhibited tumor growth in 4 T1 murine breast cancer model; modulated expression levels of nitric oxide synthase 1 (NOS1), COX-2, and nuclear factor kappa-B (NF-κB) in mouse tumor tissues; and regulated some factors such as IL-2, IL-10, and TNF-α in mice (Zeng et al., 2021). Here, NOS1 is linked to breast cancer.