Except for the diagnostic value, miR-21 affects the proliferation and apoptosis of ovarian cancer cells by regulating the PTEN/PI3K/AKT pathway 4 and the jagged-1 pathway 8, and it regulates ovarian cancer cell invasion, migration, and colony formation through the Wnt/CD44v6 pathway 9. The gene discussed is PTEN; the disease is ovarian cancer.