Subsequent in vitro experiments confirmed that Huaier, by downregulating proteins associated with cell cycle regulation in MCF-7 and MDA-MB-468 breast cancer cells, induced G0/G1 arrest, prolonged the duration of γ-H2Ax foci after radiotherapy, and increased the radiosensitivity of breast cancer cells by downregulating RAD51, disrupting the homologous recombination (HR) pathway for DNA repair (122). The gene discussed is RAD51; the disease is breast cancer.