Immunohistochemical staining revealed that the secondary M4 ovarian cancer cells isolated from tumors of BALB/c nude mice were similar to the primary M4 ovarian cancer cells isolated from the patient, with no expression of WT1 protein, overexpression and diffuse CA125 protein, complete absence of p53, and a high Ki67 protein proliferation index (60%) (Figure 5). The gene discussed is MKI67; the disease is ovarian cancer.