KLF4 inhibition in several cancer types, including prostate cancer, may contribute to cellular hyperproliferation and malignant transformation.4, 5, 21, 30, 31 Our previous report showed that KLF4 is a direct transcriptional inhibitor of SLUG expression in prostate cancer cells,2 suggesting a role of KLF4 in inhibiting cell migration and invasion in prostate cancer. This evidence concerns the gene KLF4 and prostate cancer.