Seven OSRGs were included in the OSRG score prognostic model: BDNF, FASLG, KLF2, MMP9, S100A9, SGCB, and TNFRSF1B. Brain-derived neurotrophic factor (BDNF) is a potent neurotrophic factor (Numakawa et al., 2018) that promotes breast cancer cell growth and metastasis (Tajbakhsh et al., 2017). The gene discussed is MMP9; the disease is breast cancer.